2020-09-28 11:35:11

by Alan Maguire

Subject: [PATCH v7 bpf-next 0/8] bpf: add helpers to support BTF-based kernel data display

This series attempts to provide a simple way for BPF programs (and in
future other consumers) to utilize BPF Type Format (BTF) information
to display kernel data structures in-kernel. The use case this
functionality is applied to here is to support a snprintf()-like
helper to copy a BTF representation of kernel data to a string,
and a BPF seq file helper to display BTF data for an iterator.

There is already support in kernel/bpf/btf.c for "show" functionality;
the changes here generalize that support from seq-file specific
verifier display to the more generic case and add another specific
use case; rather than seq_printf()ing the show data, it is copied
to a supplied string using a snprintf()-like function. Other future
consumers of the show functionality could include a bpf_printk_btf()
function which printk()ed the data instead. Oops messaging in
particular would be an interesting application for such functionality.

The above potential use case hints at a potential reply to
a reasonable objection that such typed display should be
solved by tracing programs, where the in-kernel tracing records
data and the userspace program prints it out. While this
is certainly the recommended approach for most cases, I
believe having an in-kernel mechanism would be valuable
also. Critically in BPF programs it greatly simplifies
debugging and tracing of such data to invoking a simple
helper.

One challenge raised in an earlier iteration of this work -
where the BTF printing was implemented as a printk() format
specifier - was that the amount of data printed per
printk() was large, and other format specifiers were far
simpler. Here we sidestep that concern by printing
components of the BTF representation as we go for the
seq file case, and in the string case the snprintf()-like
operation is intended to be a basis for perf event or
ringbuf output. The reasons for avoiding bpf_trace_printk
are that

1. bpf_trace_printk() strings are restricted in size and
cannot display anything beyond trivial data structures; and
2. bpf_trace_printk() is for debugging purposes only.

As Alexei suggested, a bpf_trace_puts() helper could solve
this in the future but it still would be limited by the
1000 byte limit for traced strings.

Default output for an sk_buff looks like this (zeroed fields
are omitted):

(struct sk_buff){
.transport_header = (__u16)65535,
.mac_header = (__u16)65535,
.end = (sk_buff_data_t)192,
.head = (unsigned char *)0x000000007524fd8b,
.data = (unsigned char *)0x000000007524fd8b,
.truesize = (unsigned int)768,
.users = (refcount_t){
.refs = (atomic_t){
.counter = (int)1,
},
},
}

Flags can modify aspects of output format; see patch 3
for more details.

Changes since v6:

- Updated safe data size to 32, object name size to 80.
This increases the number of safe copies done, but performance is
not a key goal here. WRT name size the largest type name length
in bpf-next according to "pahole -s" is 64 bytes, so that still gives
room for additional type qualifiers, parens etc within the name limit
(Alexei, patch 2)
- Remove inlines and converted as many #defines to functions as was
possible. In a few cases - btf_show_type_value[s]() specifically -
I left these as macros as btf_show_type_value[s]() prepends and
appends format strings to the format specifier (in order to include
indentation, delimiters etc so a macro makes that simpler (Alexei,
patch 2)
- Handle btf_resolve_size() error in btf_show_obj_safe() (Alexei, patch 2)
- Removed clang loop unroll in BTF snprintf test (Alexei)
- switched to using bpf_core_type_id_kernel(type) as suggested by Andrii,
and Alexei noted that __builtin_btf_type_id(,1) should be used (patch 4)
- Added skip logic if __builtin_btf_type_id is not available (patches 4,8)
- Bumped limits on bpf iters to support printing larger structures (Alexei,
patch 5)
- Updated overflow bpf_iter tests to reflect new iter max size (patch 6)
- Updated seq helper to use type id only (Alexei, patch 7)
- Updated BTF task iter test to use task struct instead of struct fs_struct
since new limits allow a task_struct to be displayed (patch 8)
- Fixed E2BIG handling in iter task (Alexei, patch 8)

Changes since v5:

- Moved btf print prepare into patch 3, type show seq
with flags into patch 2 (Alexei, patches 2,3)
- Fixed build bot warnings around static declarations
and printf attributes
- Renamed functions to snprintf_btf/seq_printf_btf
(Alexei, patches 3-6)

Changes since v4:

- Changed approach from a BPF trace event-centric design to one
utilizing a snprintf()-like helper and an iter helper (Alexei,
patches 3,5)
- Added tests to verify BTF output (patch 4)
- Added support to tests for verifying BTF type_id-based display
as well as type name via __builtin_btf_type_id (Andrii, patch 4).
- Augmented task iter tests to cover the BTF-based seq helper.
Because a task_struct's BTF-based representation would overflow
the PAGE_SIZE limit on iterator data, the "struct fs_struct"
(task->fs) is displayed for each task instead (Alexei, patch 6).

Changes since v3:

- Moved to RFC since the approach is different (and bpf-next is
closed)
- Rather than using a printk() format specifier as the means
of invoking BTF-enabled display, a dedicated BPF helper is
used. This solves the issue of printk() having to output
large amounts of data using a complex mechanism such as
BTF traversal, but still provides a way for the display of
such data to be achieved via BPF programs. Future work could
include a bpf_printk_btf() function to invoke display via
printk() where the elements of a data structure are printk()ed
one at a time. Thanks to Petr Mladek, Andy Shevchenko and
Rasmus Villemoes who took time to look at the earlier printk()
format-specifier-focused version of this and provided feedback
clarifying the problems with that approach.
- Added trace id to the bpf_trace_printk events as a means of
separating output from standard bpf_trace_printk() events,
ensuring it can be easily parsed by the reader.
- Added bpf_trace_btf() helper tests which do simple verification
of the various display options.

Changes since v2:

- Alexei and Yonghong suggested it would be good to use
probe_kernel_read() on to-be-shown data to ensure safety
during operation. Safe copy via probe_kernel_read() to a
buffer object in "struct btf_show" is used to support
this. A few different approaches were explored
including dynamic allocation and per-cpu buffers. The
downside of dynamic allocation is that it would be done
during BPF program execution for bpf_trace_printk()s using
%pT format specifiers. The problem with per-cpu buffers
is we'd have to manage preemption and since the display
of an object occurs over an extended period and in printk
context where we'd rather not change preemption status,
it seemed tricky to manage buffer safety while considering
preemption. The approach of utilizing stack buffer space
via the "struct btf_show" seemed like the simplest approach.
The stack size of the associated functions which have a
"struct btf_show" on their stack to support show operation
(btf_type_snprintf_show() and btf_type_seq_show()) stays
under 500 bytes. The compromise here is the safe buffer we
use is small - 256 bytes - and as a result multiple
probe_kernel_read()s are needed for larger objects. Most
objects of interest are smaller than this (e.g.
"struct sk_buff" is 224 bytes), and while task_struct is a
notable exception at ~8K, performance is not the priority for
BTF-based display. (Alexei and Yonghong, patch 2).
- safe buffer use is the default behaviour (and is mandatory
for BPF) but unsafe display - meaning no safe copy is done
and we operate on the object itself - is supported via a
'u' option.
- pointers are prefixed with 0x for clarity (Alexei, patch 2)
- added additional comments and explanations around BTF show
code, especially around determining whether objects such
zeroed. Also tried to comment safe object scheme used. (Yonghong,
patch 2)
- added late_initcall() to initialize vmlinux BTF so that it would
not have to be initialized during printk operation (Alexei,
patch 5)
- removed CONFIG_BTF_PRINTF config option as it is not needed;
CONFIG_DEBUG_INFO_BTF can be used to gate test behaviour and
determining behaviour of type-based printk can be done via
retrieval of BTF data; if it's not there BTF was unavailable
or broken (Alexei, patches 4,6)
- fix bpf_trace_printk test to use vmlinux.h and globals via
skeleton infrastructure, removing need for perf events
(Andrii, patch 8)

Changes since v1:

- changed format to be more drgn-like, rendering indented type info
along with type names by default (Alexei)
- zeroed values are omitted (Arnaldo) by default unless the '0'
modifier is specified (Alexei)
- added an option to print pointer values without obfuscation.
The reason to do this is the sysctls controlling pointer display
are likely to be irrelevant in many if not most tracing contexts.
Some questions on this in the outstanding questions section below...
- reworked printk format specifer so that we no longer rely on format
%pT<type> but instead use a struct * which contains type information
(Rasmus). This simplifies the printk parsing, makes use more dynamic
and also allows specification by BTF id as well as name.
- removed incorrect patch which tried to fix dereferencing of resolved
BTF info for vmlinux; instead we skip modifiers for the relevant
case (array element type determination) (Alexei).
- fixed issues with negative snprintf format length (Rasmus)
- added test cases for various data structure formats; base types,
typedefs, structs, etc.
- tests now iterate through all typedef, enum, struct and unions
defined for vmlinux BTF and render a version of the target dummy
value which is either all zeros or all 0xff values; the idea is this
exercises the "skip if zero" and "print everything" cases.
- added support in BPF for using the %pT format specifier in
bpf_trace_printk()
- added BPF tests which ensure %pT format specifier use works (Alexei).

Alan Maguire (8):
bpf: provide function to get vmlinux BTF information
bpf: move to generic BTF show support, apply it to seq files/strings
bpf: add bpf_snprintf_btf helper
selftests/bpf: add bpf_snprintf_btf helper tests
bpf: bump iter seq size to support BTF representation of large data
structures
selftests/bpf: fix overflow tests to reflect iter size increase
bpf: add bpf_seq_printf_btf helper
selftests/bpf: add test for bpf_seq_printf_btf helper

include/linux/bpf.h | 3 +
include/linux/btf.h | 39 +
include/uapi/linux/bpf.h | 76 ++
kernel/bpf/bpf_iter.c | 4 +-
kernel/bpf/btf.c | 1007 ++++++++++++++++++--
kernel/bpf/core.c | 2 +
kernel/bpf/helpers.c | 4 +
kernel/bpf/verifier.c | 18 +-
kernel/trace/bpf_trace.c | 98 ++
scripts/bpf_helpers_doc.py | 2 +
tools/include/uapi/linux/bpf.h | 76 ++
tools/testing/selftests/bpf/prog_tests/bpf_iter.c | 88 +-
.../selftests/bpf/prog_tests/snprintf_btf.c | 60 ++
.../selftests/bpf/progs/bpf_iter_task_btf.c | 50 +
.../selftests/bpf/progs/netif_receive_skb.c | 249 +++++
15 files changed, 1659 insertions(+), 117 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/snprintf_btf.c
create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_task_btf.c
create mode 100644 tools/testing/selftests/bpf/progs/netif_receive_skb.c

--
1.8.3.1

2020-09-28 11:35:36

by Alan Maguire

Subject: [PATCH v7 bpf-next 2/8] bpf: move to generic BTF show support, apply it to seq files/strings

generalize the "seq_show" seq file support in btf.c to support
a generic show callback of which we support two instances; the
current seq file show, and a show with snprintf() behaviour which
instead writes the type data to a supplied string.

Both classes of show function call btf_type_show() with different
targets; the seq file or the string to be written. In the string
case we need to track additional data - length left in string to write
and length to return that we would have written (a la snprintf).

By default show will display type information, field members and
their types and values etc, and the information is indented
based upon structure depth. Zeroed fields are omitted.

Show however supports flags which modify its behaviour:

BTF_SHOW_COMPACT - suppress newline/indent.
BTF_SHOW_NONAME - suppress show of type and member names.
BTF_SHOW_PTR_RAW - do not obfuscate pointer values.
BTF_SHOW_UNSAFE - do not copy data to safe buffer before display.
BTF_SHOW_ZERO - show zeroed values (by default they are not shown).

Signed-off-by: Alan Maguire <[email protected]>
---
include/linux/btf.h | 36 ++
kernel/bpf/btf.c | 1007 +++++++++++++++++++++++++++++++++++++++++++++------
2 files changed, 941 insertions(+), 102 deletions(-)

diff --git a/include/linux/btf.h b/include/linux/btf.h
index a9af5e7..d0f5d3c 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -13,6 +13,7 @@
struct btf_member;
struct btf_type;
union bpf_attr;
+struct btf_show;

extern const struct file_operations btf_fops;

@@ -46,8 +47,43 @@ int btf_get_info_by_fd(const struct btf *btf,
const struct btf_type *btf_type_id_size(const struct btf *btf,
u32 *type_id,
u32 *ret_size);
+
+/*
+ * Options to control show behaviour.
+ * - BTF_SHOW_COMPACT: no formatting around type information
+ * - BTF_SHOW_NONAME: no struct/union member names/types
+ * - BTF_SHOW_PTR_RAW: show raw (unobfuscated) pointer values;
+ * equivalent to %px.
+ * - BTF_SHOW_ZERO: show zero-valued struct/union members; they
+ * are not displayed by default
+ * - BTF_SHOW_UNSAFE: skip use of bpf_probe_read() to safely read
+ * data before displaying it.
+ */
+#define BTF_SHOW_COMPACT (1ULL << 0)
+#define BTF_SHOW_NONAME (1ULL << 1)
+#define BTF_SHOW_PTR_RAW (1ULL << 2)
+#define BTF_SHOW_ZERO (1ULL << 3)
+#define BTF_SHOW_UNSAFE (1ULL << 4)
+
void btf_type_seq_show(const struct btf *btf, u32 type_id, void *obj,
struct seq_file *m);
+
+/*
+ * Copy len bytes of string representation of obj of BTF type_id into buf.
+ *
+ * @btf: struct btf object
+ * @type_id: type id of type obj points to
+ * @obj: pointer to typed data
+ * @buf: buffer to write to
+ * @len: maximum length to write to buf
+ * @flags: show options (see above)
+ *
+ * Return: length that would have been/was copied as per snprintf, or
+ * negative error.
+ */
+int btf_type_snprintf_show(const struct btf *btf, u32 type_id, void *obj,
+ char *buf, int len, u64 flags);
+
int btf_get_fd_by_id(u32 id);
u32 btf_id(const struct btf *btf);
bool btf_member_is_reg_int(const struct btf *btf, const struct btf_type *s,
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 5d3c36e..be5acf6 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -284,6 +284,91 @@ static const char *btf_type_str(const struct btf_type *t)
return btf_kind_str[BTF_INFO_KIND(t->info)];
}

+/* Chunk size we use in safe copy of data to be shown. */
+#define BTF_SHOW_OBJ_SAFE_SIZE 32
+
+/*
+ * This is the maximum size of a base type value (equivalent to a
+ * 128-bit int); if we are at the end of our safe buffer and have
+ * less than 16 bytes space we can't be assured of being able
+ * to copy the next type safely, so in such cases we will initiate
+ * a new copy.
+ */
+#define BTF_SHOW_OBJ_BASE_TYPE_SIZE 16
+
+/* Type name size */
+#define BTF_SHOW_NAME_SIZE 80
+
+/*
+ * Common data to all BTF show operations. Private show functions can add
+ * their own data to a structure containing a struct btf_show and consult it
+ * in the show callback. See btf_type_show() below.
+ *
+ * One challenge with showing nested data is we want to skip 0-valued
+ * data, but in order to figure out whether a nested object is all zeros
+ * we need to walk through it. As a result, we need to make two passes
+ * when handling structs, unions and arrays; the first path simply looks
+ * for nonzero data, while the second actually does the display. The first
+ * pass is signalled by show->state.depth_check being set, and if we
+ * encounter a non-zero value we set show->state.depth_to_show to
+ * the depth at which we encountered it. When we have completed the
+ * first pass, we will know if anything needs to be displayed if
+ * depth_to_show > depth. See btf_[struct,array]_show() for the
+ * implementation of this.
+ *
+ * Another problem is we want to ensure the data for display is safe to
+ * access. To support this, the anonymous "struct {} obj" tracks the data
+ * object and our safe copy of it. We copy portions of the data needed
+ * to the object "copy" buffer, but because its size is limited to
+ * BTF_SHOW_OBJ_COPY_LEN bytes, multiple copies may be required as we
+ * traverse larger objects for display.
+ *
+ * The various data type show functions all start with a call to
+ * btf_show_start_type() which returns a pointer to the safe copy
+ * of the data needed (or if BTF_SHOW_UNSAFE is specified, to the
+ * raw data itself). btf_show_obj_safe() is responsible for
+ * using copy_from_kernel_nofault() to update the safe data if necessary
+ * as we traverse the object's data. skbuff-like semantics are
+ * used:
+ *
+ * - obj.head points to the start of the toplevel object for display
+ * - obj.size is the size of the toplevel object
+ * - obj.data points to the current point in the original data at
+ * which our safe data starts. obj.data will advance as we copy
+ * portions of the data.
+ *
+ * In most cases a single copy will suffice, but larger data structures
+ * such as "struct task_struct" will require many copies. The logic in
+ * btf_show_obj_safe() handles the logic that determines if a new
+ * copy_from_kernel_nofault() is needed.
+ */
+struct btf_show {
+ u64 flags;
+ void *target; /* target of show operation (seq file, buffer) */
+ void (*showfn)(struct btf_show *show, const char *fmt, va_list args);
+ const struct btf *btf;
+ /* below are used during iteration */
+ struct {
+ u8 depth;
+ u8 depth_to_show;
+ u8 depth_check;
+ u8 array_member:1,
+ array_terminated:1;
+ u16 array_encoding;
+ u32 type_id;
+ int status; /* non-zero for error */
+ const struct btf_type *type;
+ const struct btf_member *member;
+ char name[BTF_SHOW_NAME_SIZE]; /* space for member name/type */
+ } state;
+ struct {
+ u32 size;
+ void *head;
+ void *data;
+ u8 safe[BTF_SHOW_OBJ_SAFE_SIZE];
+ } obj;
+};
+
struct btf_kind_operations {
s32 (*check_meta)(struct btf_verifier_env *env,
const struct btf_type *t,
@@ -300,9 +385,9 @@ struct btf_kind_operations {
const struct btf_type *member_type);
void (*log_details)(struct btf_verifier_env *env,
const struct btf_type *t);
- void (*seq_show)(const struct btf *btf, const struct btf_type *t,
+ void (*show)(const struct btf *btf, const struct btf_type *t,
u32 type_id, void *data, u8 bits_offsets,
- struct seq_file *m);
+ struct btf_show *show);
};

static const struct btf_kind_operations * const kind_ops[NR_BTF_KINDS];
@@ -679,6 +764,488 @@ bool btf_member_is_reg_int(const struct btf *btf, const struct btf_type *s,
return true;
}

+/* Similar to btf_type_skip_modifiers() but does not skip typedefs. */
+static const struct btf_type *btf_type_skip_qualifiers(const struct btf *btf,
+ u32 id)
+{
+ const struct btf_type *t = btf_type_by_id(btf, id);
+
+ while (btf_type_is_modifier(t) &&
+ BTF_INFO_KIND(t->info) != BTF_KIND_TYPEDEF) {
+ id = t->type;
+ t = btf_type_by_id(btf, t->type);
+ }
+
+ return t;
+}
+
+#define BTF_SHOW_MAX_ITER 10
+
+#define BTF_KIND_BIT(kind) (1ULL << kind)
+
+/*
+ * Populate show->state.name with type name information.
+ * Format of type name is
+ *
+ * [.member_name = ] (type_name)
+ */
+static const char *btf_show_name(struct btf_show *show)
+{
+ /* BTF_MAX_ITER array suffixes "[]" */
+ const char *array_suffixes = "[][][][][][][][][][]";
+ const char *array_suffix = &array_suffixes[strlen(array_suffixes)];
+ /* BTF_MAX_ITER pointer suffixes "*" */
+ const char *ptr_suffixes = "**********";
+ const char *ptr_suffix = &ptr_suffixes[strlen(ptr_suffixes)];
+ const char *name = NULL, *prefix = "", *parens = "";
+ const struct btf_member *m = show->state.member;
+ const struct btf_type *t = show->state.type;
+ const struct btf_array *array;
+ u32 id = show->state.type_id;
+ const char *member = NULL;
+ bool show_member = false;
+ u64 kinds = 0;
+ int i;
+
+ show->state.name[0] = '\0';
+
+ /*
+ * Don't show type name if we're showing an array member;
+ * in that case we show the array type so don't need to repeat
+ * ourselves for each member.
+ */
+ if (show->state.array_member)
+ return "";
+
+ /* Retrieve member name, if any. */
+ if (m) {
+ member = btf_name_by_offset(show->btf, m->name_off);
+ show_member = strlen(member) > 0;
+ id = m->type;
+ }
+
+ /*
+ * Start with type_id, as we have resolved the struct btf_type *
+ * via btf_modifier_show() past the parent typedef to the child
+ * struct, int etc it is defined as. In such cases, the type_id
+ * still represents the starting type while the struct btf_type *
+ * in our show->state points at the resolved type of the typedef.
+ */
+ t = btf_type_by_id(show->btf, id);
+ if (!t)
+ return "";
+
+ /*
+ * The goal here is to build up the right number of pointer and
+ * array suffixes while ensuring the type name for a typedef
+ * is represented. Along the way we accumulate a list of
+ * BTF kinds we have encountered, since these will inform later
+ * display; for example, pointer types will not require an
+ * opening "{" for struct, we will just display the pointer value.
+ *
+ * We also want to accumulate the right number of pointer or array
+ * indices in the format string while iterating until we get to
+ * the typedef/pointee/array member target type.
+ *
+ * We start by pointing at the end of pointer and array suffix
+ * strings; as we accumulate pointers and arrays we move the pointer
+ * or array string backwards so it will show the expected number of
+ * '*' or '[]' for the type. BTF_SHOW_MAX_ITER of nesting of pointers
+ * and/or arrays and typedefs are supported as a precaution.
+ *
+ * We also want to get typedef name while proceeding to resolve
+ * type it points to so that we can add parentheses if it is a
+ * "typedef struct" etc.
+ */
+ for (i = 0; i < BTF_SHOW_MAX_ITER; i++) {
+
+ switch (BTF_INFO_KIND(t->info)) {
+ case BTF_KIND_TYPEDEF:
+ if (!name)
+ name = btf_name_by_offset(show->btf,
+ t->name_off);
+ kinds |= BTF_KIND_BIT(BTF_KIND_TYPEDEF);
+ id = t->type;
+ break;
+ case BTF_KIND_ARRAY:
+ kinds |= BTF_KIND_BIT(BTF_KIND_ARRAY);
+ parens = "[";
+ if (!t)
+ return "";
+ array = btf_type_array(t);
+ if (array_suffix > array_suffixes)
+ array_suffix -= 2;
+ id = array->type;
+ break;
+ case BTF_KIND_PTR:
+ kinds |= BTF_KIND_BIT(BTF_KIND_PTR);
+ if (ptr_suffix > ptr_suffixes)
+ ptr_suffix -= 1;
+ id = t->type;
+ break;
+ default:
+ id = 0;
+ break;
+ }
+ if (!id)
+ break;
+ t = btf_type_skip_qualifiers(show->btf, id);
+ }
+ /* We may not be able to represent this type; bail to be safe */
+ if (i == BTF_SHOW_MAX_ITER)
+ return "";
+
+ if (!name)
+ name = btf_name_by_offset(show->btf, t->name_off);
+
+ switch (BTF_INFO_KIND(t->info)) {
+ case BTF_KIND_STRUCT:
+ case BTF_KIND_UNION:
+ prefix = BTF_INFO_KIND(t->info) == BTF_KIND_STRUCT ?
+ "struct" : "union";
+ /* if it's an array of struct/union, parens is already set */
+ if (!(kinds & (BTF_KIND_BIT(BTF_KIND_ARRAY))))
+ parens = "{";
+ break;
+ case BTF_KIND_ENUM:
+ prefix = "enum";
+ break;
+ default:
+ break;
+ }
+
+ /* pointer does not require parens */
+ if (kinds & BTF_KIND_BIT(BTF_KIND_PTR))
+ parens = "";
+ /* typedef does not require struct/union/enum prefix */
+ if (kinds & BTF_KIND_BIT(BTF_KIND_TYPEDEF))
+ prefix = "";
+
+ if (!name)
+ name = "";
+
+ /* Even if we don't want type name info, we want parentheses etc */
+ if (show->flags & BTF_SHOW_NONAME)
+ snprintf(show->state.name, sizeof(show->state.name), "%s",
+ parens);
+ else
+ snprintf(show->state.name, sizeof(show->state.name),
+ "%s%s%s(%s%s%s%s%s%s)%s",
+ /* first 3 strings comprise ".member = " */
+ show_member ? "." : "",
+ show_member ? member : "",
+ show_member ? " = " : "",
+ /* ...next is our prefix (struct, enum, etc) */
+ prefix,
+ strlen(prefix) > 0 && strlen(name) > 0 ? " " : "",
+ /* ...this is the type name itself */
+ name,
+ /* ...suffixed by the appropriate '*', '[]' suffixes */
+ strlen(ptr_suffix) > 0 ? " " : "", ptr_suffix,
+ array_suffix, parens);
+
+ return show->state.name;
+}
+
+static const char *__btf_show_indent(struct btf_show *show)
+{
+ const char *indents = " ";
+ const char *indent = &indents[strlen(indents)];
+
+ if ((indent - show->state.depth) >= indents)
+ return indent - show->state.depth;
+ return indents;
+}
+
+static const char *btf_show_indent(struct btf_show *show)
+{
+ return show->flags & BTF_SHOW_COMPACT ? "" : __btf_show_indent(show);
+}
+
+static const char *btf_show_newline(struct btf_show *show)
+{
+ return show->flags & BTF_SHOW_COMPACT ? "" : "\n";
+}
+
+static const char *btf_show_delim(struct btf_show *show)
+{
+ if (show->state.depth == 0)
+ return "";
+
+ if ((show->flags & BTF_SHOW_COMPACT) && show->state.type &&
+ BTF_INFO_KIND(show->state.type->info) == BTF_KIND_UNION)
+ return "|";
+
+ return ",";
+}
+
+__printf(2, 3) static void btf_show(struct btf_show *show, const char *fmt, ...)
+{
+ va_list args;
+
+ if (!show->state.depth_check) {
+ va_start(args, fmt);
+ show->showfn(show, fmt, args);
+ va_end(args);
+ }
+}
+
+/* Macros are used here as btf_show_type_value[s]() prepends and appends
+ * format specifiers to the format specifier passed in; these do the work of
+ * adding indentation, delimiters etc while the caller simply has to specify
+ * the type value(s) in the format specifier + value(s).
+ */
+#define btf_show_type_value(show, fmt, value) \
+ do { \
+ if ((value) != 0 || (show->flags & BTF_SHOW_ZERO) || \
+ show->state.depth == 0) { \
+ btf_show(show, "%s%s" fmt "%s%s", \
+ btf_show_indent(show), \
+ btf_show_name(show), \
+ value, btf_show_delim(show), \
+ btf_show_newline(show)); \
+ if (show->state.depth > show->state.depth_to_show) \
+ show->state.depth_to_show = show->state.depth; \
+ } \
+ } while (0)
+
+#define btf_show_type_values(show, fmt, ...) \
+ do { \
+ btf_show(show, "%s%s" fmt "%s%s", btf_show_indent(show), \
+ btf_show_name(show), \
+ __VA_ARGS__, btf_show_delim(show), \
+ btf_show_newline(show)); \
+ if (show->state.depth > show->state.depth_to_show) \
+ show->state.depth_to_show = show->state.depth; \
+ } while (0)
+
+/* How much is left to copy to safe buffer after @data? */
+static int btf_show_obj_size_left(struct btf_show *show, void *data)
+{
+ return show->obj.head + show->obj.size - data;
+}
+
+/* Is object pointed to by @data of @size already copied to our safe buffer? */
+static bool btf_show_obj_is_safe(struct btf_show *show, void *data, int size)
+{
+ return data >= show->obj.data &&
+ (data + size) < (show->obj.data + BTF_SHOW_OBJ_SAFE_SIZE);
+}
+
+/*
+ * If object pointed to by @data of @size falls within our safe buffer, return
+ * the equivalent pointer to the same safe data. Assumes
+ * copy_from_kernel_nofault() has already happened and our safe buffer is
+ * populated.
+ */
+static void *__btf_show_obj_safe(struct btf_show *show, void *data, int size)
+{
+ if (btf_show_obj_is_safe(show, data, size))
+ return show->obj.safe + (data - show->obj.data);
+ return NULL;
+}
+
+/*
+ * Return a safe-to-access version of data pointed to by @data.
+ * We do this by copying the relevant amount of information
+ * to the struct btf_show obj.safe buffer using copy_from_kernel_nofault().
+ *
+ * If BTF_SHOW_UNSAFE is specified, just return data as-is; no
+ * safe copy is needed.
+ *
+ * Otherwise we need to determine if we have the required amount
+ * of data (determined by the @data pointer and the size of the
+ * largest base type we can encounter (represented by
+ * BTF_SHOW_OBJ_BASE_TYPE_SIZE). Having that much data ensures
+ * that we will be able to print some of the current object,
+ * and if more is needed a copy will be triggered.
+ * Some objects such as structs will not fit into the buffer;
+ * in such cases additional copies when we iterate over their
+ * members may be needed.
+ *
+ * btf_show_obj_safe() is used to return a safe buffer for
+ * btf_show_start_type(); this ensures that as we recurse into
+ * nested types we always have safe data for the given type.
+ * This approach is somewhat wasteful; it's possible for example
+ * that when iterating over a large union we'll end up copying the
+ * same data repeatedly, but the goal is safety not performance.
+ * We use stack data as opposed to per-CPU buffers because the
+ * iteration over a type can take some time, and preemption handling
+ * would greatly complicate use of the safe buffer.
+ */
+static void *btf_show_obj_safe(struct btf_show *show,
+ const struct btf_type *t,
+ void *data)
+{
+ const struct btf_type *rt;
+ int size_left, size;
+ void *safe = NULL;
+
+ if (show->flags & BTF_SHOW_UNSAFE)
+ return data;
+
+ rt = btf_resolve_size(show->btf, t, &size);
+ if (IS_ERR(rt)) {
+ show->state.status = PTR_ERR(rt);
+ return NULL;
+ }
+
+ /*
+ * Is this toplevel object? If so, set total object size and
+ * initialize pointers. Otherwise check if we still fall within
+ * our safe object data.
+ */
+ if (show->state.depth == 0) {
+ show->obj.size = size;
+ show->obj.head = data;
+ } else {
+ /*
+ * If the size of the current object is > our remaining
+ * safe buffer we _may_ need to do a new copy. However
+ * consider the case of a nested struct; it's size pushes
+ * us over the safe buffer limit, but showing any individual
+ * struct members does not. In such cases, we don't need
+ * to initiate a fresh copy yet; however we definitely need
+ * at least BTF_SHOW_OBJ_BASE_TYPE_SIZE bytes left
+ * in our buffer, regardless of the current object size.
+ * The logic here is that as we resolve types we will
+ * hit a base type at some point, and we need to be sure
+ * the next chunk of data is safely available to display
+ * that type info safely. We cannot rely on the size of
+ * the current object here because it may be much larger
+ * than our current buffer (e.g. task_struct is 8k).
+ * All we want to do here is ensure that we can print the
+ * next basic type, which we can if either
+ * - the current type size is within the safe buffer; or
+ * - at least BTF_SHOW_OBJ_BASE_TYPE_SIZE bytes are left in
+ * the safe buffer.
+ */
+ safe = __btf_show_obj_safe(show, data,
+ min(size,
+ BTF_SHOW_OBJ_BASE_TYPE_SIZE));
+ }
+
+ /*
+ * We need a new copy to our safe object, either because we haven't
+ * yet copied and are intializing safe data, or because the data
+ * we want falls outside the boundaries of the safe object.
+ */
+ if (!safe) {
+ size_left = btf_show_obj_size_left(show, data);
+ if (size_left > BTF_SHOW_OBJ_SAFE_SIZE)
+ size_left = BTF_SHOW_OBJ_SAFE_SIZE;
+ show->state.status = copy_from_kernel_nofault(show->obj.safe,
+ data, size_left);
+ if (!show->state.status) {
+ show->obj.data = data;
+ safe = show->obj.safe;
+ }
+ }
+
+ return safe;
+}
+
+/*
+ * Set the type we are starting to show and return a safe data pointer
+ * to be used for showing the associated data.
+ */
+static void *btf_show_start_type(struct btf_show *show,
+ const struct btf_type *t,
+ u32 type_id, void *data)
+{
+ show->state.type = t;
+ show->state.type_id = type_id;
+ show->state.name[0] = '\0';
+
+ return btf_show_obj_safe(show, t, data);
+}
+
+static void btf_show_end_type(struct btf_show *show)
+{
+ show->state.type = NULL;
+ show->state.type_id = 0;
+ show->state.name[0] = '\0';
+}
+
+static void *btf_show_start_aggr_type(struct btf_show *show,
+ const struct btf_type *t,
+ u32 type_id, void *data)
+{
+ void *safe_data = btf_show_start_type(show, t, type_id, data);
+
+ if (!safe_data)
+ return safe_data;
+
+ btf_show(show, "%s%s%s", btf_show_indent(show),
+ btf_show_name(show),
+ btf_show_newline(show));
+ show->state.depth++;
+ return safe_data;
+}
+
+static void btf_show_end_aggr_type(struct btf_show *show,
+ const char *suffix)
+{
+ show->state.depth--;
+ btf_show(show, "%s%s%s%s", btf_show_indent(show), suffix,
+ btf_show_delim(show), btf_show_newline(show));
+ btf_show_end_type(show);
+}
+
+static void btf_show_start_member(struct btf_show *show,
+ const struct btf_member *m)
+{
+ show->state.member = m;
+}
+
+static void btf_show_start_array_member(struct btf_show *show)
+{
+ show->state.array_member = 1;
+ btf_show_start_member(show, NULL);
+}
+
+static void btf_show_end_member(struct btf_show *show)
+{
+ show->state.member = NULL;
+}
+
+static void btf_show_end_array_member(struct btf_show *show)
+{
+ show->state.array_member = 0;
+ btf_show_end_member(show);
+}
+
+static void *btf_show_start_array_type(struct btf_show *show,
+ const struct btf_type *t,
+ u32 type_id,
+ u16 array_encoding,
+ void *data)
+{
+ show->state.array_encoding = array_encoding;
+ show->state.array_terminated = 0;
+ return btf_show_start_aggr_type(show, t, type_id, data);
+}
+
+static void btf_show_end_array_type(struct btf_show *show)
+{
+ show->state.array_encoding = 0;
+ show->state.array_terminated = 0;
+ btf_show_end_aggr_type(show, "]");
+}
+
+static void *btf_show_start_struct_type(struct btf_show *show,
+ const struct btf_type *t,
+ u32 type_id,
+ void *data)
+{
+ return btf_show_start_aggr_type(show, t, type_id, data);
+}
+
+static void btf_show_end_struct_type(struct btf_show *show)
+{
+ btf_show_end_aggr_type(show, "}");
+}
+
__printf(2, 3) static void __btf_verifier_log(struct bpf_verifier_log *log,
const char *fmt, ...)
{
@@ -1268,11 +1835,11 @@ static int btf_df_resolve(struct btf_verifier_env *env,
return -EINVAL;
}

-static void btf_df_seq_show(const struct btf *btf, const struct btf_type *t,
- u32 type_id, void *data, u8 bits_offsets,
- struct seq_file *m)
+static void btf_df_show(const struct btf *btf, const struct btf_type *t,
+ u32 type_id, void *data, u8 bits_offsets,
+ struct btf_show *show)
{
- seq_printf(m, "<unsupported kind:%u>", BTF_INFO_KIND(t->info));
+ btf_show(show, "<unsupported kind:%u>", BTF_INFO_KIND(t->info));
}

static int btf_int_check_member(struct btf_verifier_env *env,
@@ -1445,7 +2012,7 @@ static void btf_int_log(struct btf_verifier_env *env,
btf_int_encoding_str(BTF_INT_ENCODING(int_data)));
}

-static void btf_int128_print(struct seq_file *m, void *data)
+static void btf_int128_print(struct btf_show *show, void *data)
{
/* data points to a __int128 number.
* Suppose
@@ -1464,9 +2031,10 @@ static void btf_int128_print(struct seq_file *m, void *data)
lower_num = *(u64 *)data;
#endif
if (upper_num == 0)
- seq_printf(m, "0x%llx", lower_num);
+ btf_show_type_value(show, "0x%llx", lower_num);
else
- seq_printf(m, "0x%llx%016llx", upper_num, lower_num);
+ btf_show_type_values(show, "0x%llx%016llx", upper_num,
+ lower_num);
}

static void btf_int128_shift(u64 *print_num, u16 left_shift_bits,
@@ -1510,8 +2078,8 @@ static void btf_int128_shift(u64 *print_num, u16 left_shift_bits,
#endif
}

-static void btf_bitfield_seq_show(void *data, u8 bits_offset,
- u8 nr_bits, struct seq_file *m)
+static void btf_bitfield_show(void *data, u8 bits_offset,
+ u8 nr_bits, struct btf_show *show)
{
u16 left_shift_bits, right_shift_bits;
u8 nr_copy_bytes;
@@ -1531,14 +2099,14 @@ static void btf_bitfield_seq_show(void *data, u8 bits_offset,
right_shift_bits = BITS_PER_U128 - nr_bits;

btf_int128_shift(print_num, left_shift_bits, right_shift_bits);
- btf_int128_print(m, print_num);
+ btf_int128_print(show, print_num);
}


-static void btf_int_bits_seq_show(const struct btf *btf,
- const struct btf_type *t,
- void *data, u8 bits_offset,
- struct seq_file *m)
+static void btf_int_bits_show(const struct btf *btf,
+ const struct btf_type *t,
+ void *data, u8 bits_offset,
+ struct btf_show *show)
{
u32 int_data = btf_type_int(t);
u8 nr_bits = BTF_INT_BITS(int_data);
@@ -1551,55 +2119,77 @@ static void btf_int_bits_seq_show(const struct btf *btf,
total_bits_offset = bits_offset + BTF_INT_OFFSET(int_data);
data += BITS_ROUNDDOWN_BYTES(total_bits_offset);
bits_offset = BITS_PER_BYTE_MASKED(total_bits_offset);
- btf_bitfield_seq_show(data, bits_offset, nr_bits, m);
+ btf_bitfield_show(data, bits_offset, nr_bits, show);
}

-static void btf_int_seq_show(const struct btf *btf, const struct btf_type *t,
- u32 type_id, void *data, u8 bits_offset,
- struct seq_file *m)
+static void btf_int_show(const struct btf *btf, const struct btf_type *t,
+ u32 type_id, void *data, u8 bits_offset,
+ struct btf_show *show)
{
u32 int_data = btf_type_int(t);
u8 encoding = BTF_INT_ENCODING(int_data);
bool sign = encoding & BTF_INT_SIGNED;
u8 nr_bits = BTF_INT_BITS(int_data);
+ void *safe_data;
+
+ safe_data = btf_show_start_type(show, t, type_id, data);
+ if (!safe_data)
+ return;

if (bits_offset || BTF_INT_OFFSET(int_data) ||
BITS_PER_BYTE_MASKED(nr_bits)) {
- btf_int_bits_seq_show(btf, t, data, bits_offset, m);
- return;
+ btf_int_bits_show(btf, t, safe_data, bits_offset, show);
+ goto out;
}

switch (nr_bits) {
case 128:
- btf_int128_print(m, data);
+ btf_int128_print(show, safe_data);
break;
case 64:
if (sign)
- seq_printf(m, "%lld", *(s64 *)data);
+ btf_show_type_value(show, "%lld", *(s64 *)safe_data);
else
- seq_printf(m, "%llu", *(u64 *)data);
+ btf_show_type_value(show, "%llu", *(u64 *)safe_data);
break;
case 32:
if (sign)
- seq_printf(m, "%d", *(s32 *)data);
+ btf_show_type_value(show, "%d", *(s32 *)safe_data);
else
- seq_printf(m, "%u", *(u32 *)data);
+ btf_show_type_value(show, "%u", *(u32 *)safe_data);
break;
case 16:
if (sign)
- seq_printf(m, "%d", *(s16 *)data);
+ btf_show_type_value(show, "%d", *(s16 *)safe_data);
else
- seq_printf(m, "%u", *(u16 *)data);
+ btf_show_type_value(show, "%u", *(u16 *)safe_data);
break;
case 8:
+ if (show->state.array_encoding == BTF_INT_CHAR) {
+ /* check for null terminator */
+ if (show->state.array_terminated)
+ break;
+ if (*(char *)data == '\0') {
+ show->state.array_terminated = 1;
+ break;
+ }
+ if (isprint(*(char *)data)) {
+ btf_show_type_value(show, "'%c'",
+ *(char *)safe_data);
+ break;
+ }
+ }
if (sign)
- seq_printf(m, "%d", *(s8 *)data);
+ btf_show_type_value(show, "%d", *(s8 *)safe_data);
else
- seq_printf(m, "%u", *(u8 *)data);
+ btf_show_type_value(show, "%u", *(u8 *)safe_data);
break;
default:
- btf_int_bits_seq_show(btf, t, data, bits_offset, m);
+ btf_int_bits_show(btf, t, safe_data, bits_offset, show);
+ break;
}
+out:
+ btf_show_end_type(show);
}

static const struct btf_kind_operations int_ops = {
@@ -1608,7 +2198,7 @@ static void btf_int_seq_show(const struct btf *btf, const struct btf_type *t,
.check_member = btf_int_check_member,
.check_kflag_member = btf_int_check_kflag_member,
.log_details = btf_int_log,
- .seq_show = btf_int_seq_show,
+ .show = btf_int_show,
};

static int btf_modifier_check_member(struct btf_verifier_env *env,
@@ -1872,34 +2462,44 @@ static int btf_ptr_resolve(struct btf_verifier_env *env,
return 0;
}

-static void btf_modifier_seq_show(const struct btf *btf,
- const struct btf_type *t,
- u32 type_id, void *data,
- u8 bits_offset, struct seq_file *m)
+static void btf_modifier_show(const struct btf *btf,
+ const struct btf_type *t,
+ u32 type_id, void *data,
+ u8 bits_offset, struct btf_show *show)
{
if (btf->resolved_ids)
t = btf_type_id_resolve(btf, &type_id);
else
t = btf_type_skip_modifiers(btf, type_id, NULL);

- btf_type_ops(t)->seq_show(btf, t, type_id, data, bits_offset, m);
+ btf_type_ops(t)->show(btf, t, type_id, data, bits_offset, show);
}

-static void btf_var_seq_show(const struct btf *btf, const struct btf_type *t,
- u32 type_id, void *data, u8 bits_offset,
- struct seq_file *m)
+static void btf_var_show(const struct btf *btf, const struct btf_type *t,
+ u32 type_id, void *data, u8 bits_offset,
+ struct btf_show *show)
{
t = btf_type_id_resolve(btf, &type_id);

- btf_type_ops(t)->seq_show(btf, t, type_id, data, bits_offset, m);
+ btf_type_ops(t)->show(btf, t, type_id, data, bits_offset, show);
}

-static void btf_ptr_seq_show(const struct btf *btf, const struct btf_type *t,
- u32 type_id, void *data, u8 bits_offset,
- struct seq_file *m)
+static void btf_ptr_show(const struct btf *btf, const struct btf_type *t,
+ u32 type_id, void *data, u8 bits_offset,
+ struct btf_show *show)
{
- /* It is a hashed value */
- seq_printf(m, "%p", *(void **)data);
+ void *safe_data;
+
+ safe_data = btf_show_start_type(show, t, type_id, data);
+ if (!safe_data)
+ return;
+
+ /* It is a hashed value unless BTF_SHOW_PTR_RAW is specified */
+ if (show->flags & BTF_SHOW_PTR_RAW)
+ btf_show_type_value(show, "0x%px", *(void **)safe_data);
+ else
+ btf_show_type_value(show, "0x%p", *(void **)safe_data);
+ btf_show_end_type(show);
}

static void btf_ref_type_log(struct btf_verifier_env *env,
@@ -1914,7 +2514,7 @@ static void btf_ref_type_log(struct btf_verifier_env *env,
.check_member = btf_modifier_check_member,
.check_kflag_member = btf_modifier_check_kflag_member,
.log_details = btf_ref_type_log,
- .seq_show = btf_modifier_seq_show,
+ .show = btf_modifier_show,
};

static struct btf_kind_operations ptr_ops = {
@@ -1923,7 +2523,7 @@ static void btf_ref_type_log(struct btf_verifier_env *env,
.check_member = btf_ptr_check_member,
.check_kflag_member = btf_generic_check_kflag_member,
.log_details = btf_ref_type_log,
- .seq_show = btf_ptr_seq_show,
+ .show = btf_ptr_show,
};

static s32 btf_fwd_check_meta(struct btf_verifier_env *env,
@@ -1964,7 +2564,7 @@ static void btf_fwd_type_log(struct btf_verifier_env *env,
.check_member = btf_df_check_member,
.check_kflag_member = btf_df_check_kflag_member,
.log_details = btf_fwd_type_log,
- .seq_show = btf_df_seq_show,
+ .show = btf_df_show,
};

static int btf_array_check_member(struct btf_verifier_env *env,
@@ -2123,28 +2723,90 @@ static void btf_array_log(struct btf_verifier_env *env,
array->type, array->index_type, array->nelems);
}

-static void btf_array_seq_show(const struct btf *btf, const struct btf_type *t,
- u32 type_id, void *data, u8 bits_offset,
- struct seq_file *m)
+static void __btf_array_show(const struct btf *btf, const struct btf_type *t,
+ u32 type_id, void *data, u8 bits_offset,
+ struct btf_show *show)
{
const struct btf_array *array = btf_type_array(t);
const struct btf_kind_operations *elem_ops;
const struct btf_type *elem_type;
- u32 i, elem_size, elem_type_id;
+ u32 i, elem_size = 0, elem_type_id;
+ u16 encoding = 0;

elem_type_id = array->type;
- elem_type = btf_type_id_size(btf, &elem_type_id, &elem_size);
+ elem_type = btf_type_skip_modifiers(btf, elem_type_id, NULL);
+ if (elem_type && btf_type_has_size(elem_type))
+ elem_size = elem_type->size;
+
+ if (elem_type && btf_type_is_int(elem_type)) {
+ u32 int_type = btf_type_int(elem_type);
+
+ encoding = BTF_INT_ENCODING(int_type);
+
+ /*
+ * BTF_INT_CHAR encoding never seems to be set for
+ * char arrays, so if size is 1 and element is
+ * printable as a char, we'll do that.
+ */
+ if (elem_size == 1)
+ encoding = BTF_INT_CHAR;
+ }
+
+ if (!btf_show_start_array_type(show, t, type_id, encoding, data))
+ return;
+
+ if (!elem_type)
+ goto out;
elem_ops = btf_type_ops(elem_type);
- seq_puts(m, "[");
+
for (i = 0; i < array->nelems; i++) {
- if (i)
- seq_puts(m, ",");

- elem_ops->seq_show(btf, elem_type, elem_type_id, data,
- bits_offset, m);
+ btf_show_start_array_member(show);
+
+ elem_ops->show(btf, elem_type, elem_type_id, data,
+ bits_offset, show);
data += elem_size;
+
+ btf_show_end_array_member(show);
+
+ if (show->state.array_terminated)
+ break;
}
- seq_puts(m, "]");
+out:
+ btf_show_end_array_type(show);
+}
+
+static void btf_array_show(const struct btf *btf, const struct btf_type *t,
+ u32 type_id, void *data, u8 bits_offset,
+ struct btf_show *show)
+{
+ const struct btf_member *m = show->state.member;
+
+ /*
+ * First check if any members would be shown (are non-zero).
+ * See comments above "struct btf_show" definition for more
+ * details on how this works at a high-level.
+ */
+ if (show->state.depth > 0 && !(show->flags & BTF_SHOW_ZERO)) {
+ if (!show->state.depth_check) {
+ show->state.depth_check = show->state.depth + 1;
+ show->state.depth_to_show = 0;
+ }
+ __btf_array_show(btf, t, type_id, data, bits_offset, show);
+ show->state.member = m;
+
+ if (show->state.depth_check != show->state.depth + 1)
+ return;
+ show->state.depth_check = 0;
+
+ if (show->state.depth_to_show <= show->state.depth)
+ return;
+ /*
+ * Reaching here indicates we have recursed and found
+ * non-zero array member(s).
+ */
+ }
+ __btf_array_show(btf, t, type_id, data, bits_offset, show);
}

static struct btf_kind_operations array_ops = {
@@ -2153,7 +2815,7 @@ static void btf_array_seq_show(const struct btf *btf, const struct btf_type *t,
.check_member = btf_array_check_member,
.check_kflag_member = btf_generic_check_kflag_member,
.log_details = btf_array_log,
- .seq_show = btf_array_seq_show,
+ .show = btf_array_show,
};

static int btf_struct_check_member(struct btf_verifier_env *env,
@@ -2376,15 +3038,18 @@ int btf_find_spin_lock(const struct btf *btf, const struct btf_type *t)
return off;
}

-static void btf_struct_seq_show(const struct btf *btf, const struct btf_type *t,
- u32 type_id, void *data, u8 bits_offset,
- struct seq_file *m)
+static void __btf_struct_show(const struct btf *btf, const struct btf_type *t,
+ u32 type_id, void *data, u8 bits_offset,
+ struct btf_show *show)
{
- const char *seq = BTF_INFO_KIND(t->info) == BTF_KIND_UNION ? "|" : ",";
const struct btf_member *member;
+ void *safe_data;
u32 i;

- seq_puts(m, "{");
+ safe_data = btf_show_start_struct_type(show, t, type_id, data);
+ if (!safe_data)
+ return;
+
for_each_member(i, t, member) {
const struct btf_type *member_type = btf_type_by_id(btf,
member->type);
@@ -2393,23 +3058,65 @@ static void btf_struct_seq_show(const struct btf *btf, const struct btf_type *t,
u32 bytes_offset;
u8 bits8_offset;

- if (i)
- seq_puts(m, seq);
+ btf_show_start_member(show, member);

member_offset = btf_member_bit_offset(t, member);
bitfield_size = btf_member_bitfield_size(t, member);
bytes_offset = BITS_ROUNDDOWN_BYTES(member_offset);
bits8_offset = BITS_PER_BYTE_MASKED(member_offset);
if (bitfield_size) {
- btf_bitfield_seq_show(data + bytes_offset, bits8_offset,
- bitfield_size, m);
+ safe_data = btf_show_start_type(show, member_type,
+ member->type,
+ data + bytes_offset);
+ if (safe_data)
+ btf_bitfield_show(safe_data,
+ bits8_offset,
+ bitfield_size, show);
+ btf_show_end_type(show);
} else {
ops = btf_type_ops(member_type);
- ops->seq_show(btf, member_type, member->type,
- data + bytes_offset, bits8_offset, m);
+ ops->show(btf, member_type, member->type,
+ data + bytes_offset, bits8_offset, show);
}
+
+ btf_show_end_member(show);
}
- seq_puts(m, "}");
+
+ btf_show_end_struct_type(show);
+}
+
+static void btf_struct_show(const struct btf *btf, const struct btf_type *t,
+ u32 type_id, void *data, u8 bits_offset,
+ struct btf_show *show)
+{
+ const struct btf_member *m = show->state.member;
+
+ /*
+ * First check if any members would be shown (are non-zero).
+ * See comments above "struct btf_show" definition for more
+ * details on how this works at a high-level.
+ */
+ if (show->state.depth > 0 && !(show->flags & BTF_SHOW_ZERO)) {
+ if (!show->state.depth_check) {
+ show->state.depth_check = show->state.depth + 1;
+ show->state.depth_to_show = 0;
+ }
+ __btf_struct_show(btf, t, type_id, data, bits_offset, show);
+ /* Restore saved member data here */
+ show->state.member = m;
+ if (show->state.depth_check != show->state.depth + 1)
+ return;
+ show->state.depth_check = 0;
+
+ if (show->state.depth_to_show <= show->state.depth)
+ return;
+ /*
+ * Reaching here indicates we have recursed and found
+ * non-zero child values.
+ */
+ }
+
+ __btf_struct_show(btf, t, type_id, data, bits_offset, show);
}

static struct btf_kind_operations struct_ops = {
@@ -2418,7 +3125,7 @@ static void btf_struct_seq_show(const struct btf *btf, const struct btf_type *t,
.check_member = btf_struct_check_member,
.check_kflag_member = btf_generic_check_kflag_member,
.log_details = btf_struct_log,
- .seq_show = btf_struct_seq_show,
+ .show = btf_struct_show,
};

static int btf_enum_check_member(struct btf_verifier_env *env,
@@ -2549,24 +3256,35 @@ static void btf_enum_log(struct btf_verifier_env *env,
btf_verifier_log(env, "size=%u vlen=%u", t->size, btf_type_vlen(t));
}

-static void btf_enum_seq_show(const struct btf *btf, const struct btf_type *t,
- u32 type_id, void *data, u8 bits_offset,
- struct seq_file *m)
+static void btf_enum_show(const struct btf *btf, const struct btf_type *t,
+ u32 type_id, void *data, u8 bits_offset,
+ struct btf_show *show)
{
const struct btf_enum *enums = btf_type_enum(t);
u32 i, nr_enums = btf_type_vlen(t);
- int v = *(int *)data;
+ void *safe_data;
+ int v;
+
+ safe_data = btf_show_start_type(show, t, type_id, data);
+ if (!safe_data)
+ return;
+
+ v = *(int *)safe_data;

for (i = 0; i < nr_enums; i++) {
- if (v == enums[i].val) {
- seq_printf(m, "%s",
- __btf_name_by_offset(btf,
- enums[i].name_off));
- return;
- }
+ if (v != enums[i].val)
+ continue;
+
+ btf_show_type_value(show, "%s",
+ __btf_name_by_offset(btf,
+ enums[i].name_off));
+
+ btf_show_end_type(show);
+ return;
}

- seq_printf(m, "%d", v);
+ btf_show_type_value(show, "%d", v);
+ btf_show_end_type(show);
}

static struct btf_kind_operations enum_ops = {
@@ -2575,7 +3293,7 @@ static void btf_enum_seq_show(const struct btf *btf, const struct btf_type *t,
.check_member = btf_enum_check_member,
.check_kflag_member = btf_enum_check_kflag_member,
.log_details = btf_enum_log,
- .seq_show = btf_enum_seq_show,
+ .show = btf_enum_show,
};

static s32 btf_func_proto_check_meta(struct btf_verifier_env *env,
@@ -2662,7 +3380,7 @@ static void btf_func_proto_log(struct btf_verifier_env *env,
.check_member = btf_df_check_member,
.check_kflag_member = btf_df_check_kflag_member,
.log_details = btf_func_proto_log,
- .seq_show = btf_df_seq_show,
+ .show = btf_df_show,
};

static s32 btf_func_check_meta(struct btf_verifier_env *env,
@@ -2696,7 +3414,7 @@ static s32 btf_func_check_meta(struct btf_verifier_env *env,
.check_member = btf_df_check_member,
.check_kflag_member = btf_df_check_kflag_member,
.log_details = btf_ref_type_log,
- .seq_show = btf_df_seq_show,
+ .show = btf_df_show,
};

static s32 btf_var_check_meta(struct btf_verifier_env *env,
@@ -2760,7 +3478,7 @@ static void btf_var_log(struct btf_verifier_env *env, const struct btf_type *t)
.check_member = btf_df_check_member,
.check_kflag_member = btf_df_check_kflag_member,
.log_details = btf_var_log,
- .seq_show = btf_var_seq_show,
+ .show = btf_var_show,
};

static s32 btf_datasec_check_meta(struct btf_verifier_env *env,
@@ -2886,24 +3604,28 @@ static void btf_datasec_log(struct btf_verifier_env *env,
btf_verifier_log(env, "size=%u vlen=%u", t->size, btf_type_vlen(t));
}

-static void btf_datasec_seq_show(const struct btf *btf,
- const struct btf_type *t, u32 type_id,
- void *data, u8 bits_offset,
- struct seq_file *m)
+static void btf_datasec_show(const struct btf *btf,
+ const struct btf_type *t, u32 type_id,
+ void *data, u8 bits_offset,
+ struct btf_show *show)
{
const struct btf_var_secinfo *vsi;
const struct btf_type *var;
u32 i;

- seq_printf(m, "section (\"%s\") = {", __btf_name_by_offset(btf, t->name_off));
+ if (!btf_show_start_type(show, t, type_id, data))
+ return;
+
+ btf_show_type_value(show, "section (\"%s\") = {",
+ __btf_name_by_offset(btf, t->name_off));
for_each_vsi(i, t, vsi) {
var = btf_type_by_id(btf, vsi->type);
if (i)
- seq_puts(m, ",");
- btf_type_ops(var)->seq_show(btf, var, vsi->type,
- data + vsi->offset, bits_offset, m);
+ btf_show(show, ",");
+ btf_type_ops(var)->show(btf, var, vsi->type,
+ data + vsi->offset, bits_offset, show);
}
- seq_puts(m, "}");
+ btf_show_end_type(show);
}

static const struct btf_kind_operations datasec_ops = {
@@ -2912,7 +3634,7 @@ static void btf_datasec_seq_show(const struct btf *btf,
.check_member = btf_df_check_member,
.check_kflag_member = btf_df_check_kflag_member,
.log_details = btf_datasec_log,
- .seq_show = btf_datasec_seq_show,
+ .show = btf_datasec_show,
};

static int btf_func_proto_check(struct btf_verifier_env *env,
@@ -4606,12 +5328,93 @@ int btf_prepare_func_args(struct bpf_verifier_env *env, int subprog,
return 0;
}

+static void btf_type_show(const struct btf *btf, u32 type_id, void *obj,
+ struct btf_show *show)
+{
+ const struct btf_type *t = btf_type_by_id(btf, type_id);
+
+ show->btf = btf;
+ memset(&show->state, 0, sizeof(show->state));
+ memset(&show->obj, 0, sizeof(show->obj));
+
+ btf_type_ops(t)->show(btf, t, type_id, obj, 0, show);
+}
+
+static void btf_seq_show(struct btf_show *show, const char *fmt,
+ va_list args)
+{
+ seq_vprintf((struct seq_file *)show->target, fmt, args);
+}
+
+static int btf_type_seq_show_flags(const struct btf *btf, u32 type_id,
+ void *obj, struct seq_file *m, u64 flags)
+{
+ struct btf_show sseq;
+
+ sseq.target = m;
+ sseq.showfn = btf_seq_show;
+ sseq.flags = flags;
+
+ btf_type_show(btf, type_id, obj, &sseq);
+
+ return sseq.state.status;
+}
+
void btf_type_seq_show(const struct btf *btf, u32 type_id, void *obj,
struct seq_file *m)
{
- const struct btf_type *t = btf_type_by_id(btf, type_id);
+ (void) btf_type_seq_show_flags(btf, type_id, obj, m,
+ BTF_SHOW_NONAME | BTF_SHOW_COMPACT |
+ BTF_SHOW_ZERO | BTF_SHOW_UNSAFE);
+}
+
+struct btf_show_snprintf {
+ struct btf_show show;
+ int len_left; /* space left in string */
+ int len; /* length we would have written */
+};
+
+static void btf_snprintf_show(struct btf_show *show, const char *fmt,
+ va_list args)
+{
+ struct btf_show_snprintf *ssnprintf = (struct btf_show_snprintf *)show;
+ int len;
+
+ len = vsnprintf(show->target, ssnprintf->len_left, fmt, args);
+
+ if (len < 0) {
+ ssnprintf->len_left = 0;
+ ssnprintf->len = len;
+ } else if (len > ssnprintf->len_left) {
+ /* no space, drive on to get length we would have written */
+ ssnprintf->len_left = 0;
+ ssnprintf->len += len;
+ } else {
+ ssnprintf->len_left -= len;
+ ssnprintf->len += len;
+ show->target += len;
+ }
+}
+
+int btf_type_snprintf_show(const struct btf *btf, u32 type_id, void *obj,
+ char *buf, int len, u64 flags)
+{
+ struct btf_show_snprintf ssnprintf;
+
+ ssnprintf.show.target = buf;
+ ssnprintf.show.flags = flags;
+ ssnprintf.show.showfn = btf_snprintf_show;
+ ssnprintf.len_left = len;
+ ssnprintf.len = 0;
+
+ btf_type_show(btf, type_id, obj, (struct btf_show *)&ssnprintf);
+
+ /* If we encontered an error, return it. */
+ if (ssnprintf.show.state.status)
+ return ssnprintf.show.state.status;

- btf_type_ops(t)->seq_show(btf, t, type_id, obj, 0, m);
+ /* Otherwise return length we would have written */
+ return ssnprintf.len;
}

#ifdef CONFIG_PROC_FS
--
1.8.3.1

2020-09-28 11:36:27

by Alan Maguire

Subject: [PATCH v7 bpf-next 1/8] bpf: provide function to get vmlinux BTF information

It will be used later for BPF structure display support

Signed-off-by: Alan Maguire <[email protected]>
---
include/linux/bpf.h | 2 ++
kernel/bpf/verifier.c | 18 ++++++++++++------
2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 7990232..2eae3f3 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1355,6 +1355,8 @@ int bpf_check(struct bpf_prog **fp, union bpf_attr *attr,
union bpf_attr __user *uattr);
void bpf_patch_call_args(struct bpf_insn *insn, u32 stack_depth);

+struct btf *bpf_get_btf_vmlinux(void);
+
/* Map specifics */
struct xdp_buff;
struct sk_buff;
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index b25ba98..686f6a9 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -11517,6 +11517,17 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
}
}

+struct btf *bpf_get_btf_vmlinux(void)
+{
+ if (!btf_vmlinux && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) {
+ mutex_lock(&bpf_verifier_lock);
+ if (!btf_vmlinux)
+ btf_vmlinux = btf_parse_vmlinux();
+ mutex_unlock(&bpf_verifier_lock);
+ }
+ return btf_vmlinux;
+}
+
int bpf_check(struct bpf_prog **prog, union bpf_attr *attr,
union bpf_attr __user *uattr)
{
@@ -11550,12 +11561,7 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr,
env->ops = bpf_verifier_ops[env->prog->type];
is_priv = bpf_capable();

- if (!btf_vmlinux && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) {
- mutex_lock(&bpf_verifier_lock);
- if (!btf_vmlinux)
- btf_vmlinux = btf_parse_vmlinux();
- mutex_unlock(&bpf_verifier_lock);
- }
+ bpf_get_btf_vmlinux();

/* grab the mutex to protect few globals used by verifier */
if (!is_priv)
--
1.8.3.1

2020-09-28 11:36:27

by Alan Maguire

Subject: [PATCH v7 bpf-next 7/8] bpf: add bpf_seq_printf_btf helper

A helper is added to allow seq file writing of kernel data
structures using vmlinux BTF. Its signature is

long bpf_seq_printf_btf(struct seq_file *m, struct btf_ptr *ptr,
u32 btf_ptr_size, u64 flags);

Flags and struct btf_ptr definitions/use are identical to the
bpf_snprintf_btf helper, and the helper returns 0 on success
or a negative error value.

Suggested-by: Alexei Starovoitov <[email protected]>
Signed-off-by: Alan Maguire <[email protected]>
---
include/linux/btf.h | 2 ++
include/uapi/linux/bpf.h | 9 +++++++++
kernel/bpf/btf.c | 4 ++--
kernel/bpf/core.c | 1 +
kernel/trace/bpf_trace.c | 33 +++++++++++++++++++++++++++++++++
tools/include/uapi/linux/bpf.h | 9 +++++++++
6 files changed, 56 insertions(+), 2 deletions(-)

diff --git a/include/linux/btf.h b/include/linux/btf.h
index 3e5cdc2..024e16f 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -68,6 +68,8 @@ const struct btf_type *btf_type_id_size(const struct btf *btf,

void btf_type_seq_show(const struct btf *btf, u32 type_id, void *obj,
struct seq_file *m);
+int btf_type_seq_show_flags(const struct btf *btf, u32 type_id, void *obj,
+ struct seq_file *m, u64 flags);

/*
* Copy len bytes of string representation of obj of BTF type_id into buf.
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index fcafe80..82817c4 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3623,6 +3623,14 @@ struct bpf_stack_build_id {
* The number of bytes that were written (or would have been
* written if output had to be truncated due to string size),
* or a negative error in cases of failure.
+ *
+ * long bpf_seq_printf_btf(struct seq_file *m, struct btf_ptr *ptr, u32 ptr_size, u64 flags)
+ * Description
+ * Use BTF to write to seq_write a string representation of
+ * *ptr*->ptr, using *ptr*->type_id as per bpf_snprintf_btf().
+ * *flags* are identical to those used for bpf_snprintf_btf.
+ * Return
+ * 0 on success or a negative error in case of failure.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3775,6 +3783,7 @@ struct bpf_stack_build_id {
FN(d_path), \
FN(copy_from_user), \
FN(snprintf_btf), \
+ FN(seq_printf_btf), \
/* */

/* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index be5acf6..99e307a 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5346,8 +5346,8 @@ static void btf_seq_show(struct btf_show *show, const char *fmt,
seq_vprintf((struct seq_file *)show->target, fmt, args);
}

-static int btf_type_seq_show_flags(const struct btf *btf, u32 type_id,
- void *obj, struct seq_file *m, u64 flags)
+int btf_type_seq_show_flags(const struct btf *btf, u32 type_id,
+ void *obj, struct seq_file *m, u64 flags)
{
struct btf_show sseq;

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 403fb23..c4ba45f 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2217,6 +2217,7 @@ void bpf_user_rnd_init_once(void)
const struct bpf_func_proto bpf_get_local_storage_proto __weak;
const struct bpf_func_proto bpf_get_ns_current_pid_tgid_proto __weak;
const struct bpf_func_proto bpf_snprintf_btf_proto __weak;
+const struct bpf_func_proto bpf_seq_printf_btf_proto __weak;

const struct bpf_func_proto * __weak bpf_get_trace_printk_proto(void)
{
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 983cbd3..6ac254e 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -71,6 +71,10 @@ static struct bpf_raw_event_map *bpf_get_raw_tracepoint_module(const char *name)
u64 bpf_get_stackid(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
u64 bpf_get_stack(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);

+static int bpf_btf_printf_prepare(struct btf_ptr *ptr, u32 btf_ptr_size,
+ u64 flags, const struct btf **btf,
+ s32 *btf_id);
+
/**
* trace_call_bpf - invoke BPF program
* @call: tracepoint event
@@ -776,6 +780,31 @@ struct bpf_seq_printf_buf {
.arg3_type = ARG_CONST_SIZE_OR_ZERO,
};

+BPF_CALL_4(bpf_seq_printf_btf, struct seq_file *, m, struct btf_ptr *, ptr,
+ u32, btf_ptr_size, u64, flags)
+{
+ const struct btf *btf;
+ s32 btf_id;
+ int ret;
+
+ ret = bpf_btf_printf_prepare(ptr, btf_ptr_size, flags, &btf, &btf_id);
+ if (ret)
+ return ret;
+
+ return btf_type_seq_show_flags(btf, btf_id, ptr->ptr, m, flags);
+}
+
+static const struct bpf_func_proto bpf_seq_printf_btf_proto = {
+ .func = bpf_seq_printf_btf,
+ .gpl_only = true,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_BTF_ID,
+ .arg1_btf_id = &btf_seq_file_ids[0],
+ .arg2_type = ARG_PTR_TO_MEM,
+ .arg3_type = ARG_CONST_SIZE_OR_ZERO,
+ .arg4_type = ARG_ANYTHING,
+};
+
static __always_inline int
get_map_perf_counter(struct bpf_map *map, u64 flags,
u64 *value, u64 *enabled, u64 *running)
@@ -1695,6 +1724,10 @@ static void put_bpf_raw_tp_regs(void)
return prog->expected_attach_type == BPF_TRACE_ITER ?
&bpf_seq_write_proto :
NULL;
+ case BPF_FUNC_seq_printf_btf:
+ return prog->expected_attach_type == BPF_TRACE_ITER ?
+ &bpf_seq_printf_btf_proto :
+ NULL;
case BPF_FUNC_d_path:
return &bpf_d_path_proto;
default:
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index fcafe80..82817c4 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3623,6 +3623,14 @@ struct bpf_stack_build_id {
* The number of bytes that were written (or would have been
* written if output had to be truncated due to string size),
* or a negative error in cases of failure.
+ *
+ * long bpf_seq_printf_btf(struct seq_file *m, struct btf_ptr *ptr, u32 ptr_size, u64 flags)
+ * Description
+ * Use BTF to write to seq_write a string representation of
+ * *ptr*->ptr, using *ptr*->type_id as per bpf_snprintf_btf().
+ * *flags* are identical to those used for bpf_snprintf_btf.
+ * Return
+ * 0 on success or a negative error in case of failure.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3775,6 +3783,7 @@ struct bpf_stack_build_id {
FN(d_path), \
FN(copy_from_user), \
FN(snprintf_btf), \
+ FN(seq_printf_btf), \
/* */

/* integer value in 'imm' field of BPF_CALL instruction selects which helper
--
1.8.3.1

2020-09-28 11:36:48

by Alan Maguire

Subject: [PATCH v7 bpf-next 4/8] selftests/bpf: add bpf_snprintf_btf helper tests

Tests verifying snprintf()ing of various data structures,
flags combinations using a tp_btf program. Tests are skipped
if __builtin_btf_type_id is not available to retrieve BTF
type ids.

Signed-off-by: Alan Maguire <[email protected]>
---
.../selftests/bpf/prog_tests/snprintf_btf.c | 60 +++++
.../selftests/bpf/progs/netif_receive_skb.c | 249 +++++++++++++++++++++
2 files changed, 309 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/snprintf_btf.c
create mode 100644 tools/testing/selftests/bpf/progs/netif_receive_skb.c

diff --git a/tools/testing/selftests/bpf/prog_tests/snprintf_btf.c b/tools/testing/selftests/bpf/prog_tests/snprintf_btf.c
new file mode 100644
index 0000000..3a8ecf8
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/snprintf_btf.c
@@ -0,0 +1,60 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <test_progs.h>
+#include <linux/btf.h>
+#include "netif_receive_skb.skel.h"
+
+/* Demonstrate that bpf_snprintf_btf succeeds and that various data types
+ * are formatted correctly.
+ */
+void test_snprintf_btf(void)
+{
+ struct netif_receive_skb *skel;
+ struct netif_receive_skb__bss *bss;
+ int err, duration = 0;
+
+ skel = netif_receive_skb__open();
+ if (CHECK(!skel, "skel_open", "failed to open skeleton\n"))
+ return;
+
+ err = netif_receive_skb__load(skel);
+ if (CHECK(err, "skel_load", "failed to load skeleton: %d\n", err))
+ goto cleanup;
+
+ bss = skel->bss;
+
+ err = netif_receive_skb__attach(skel);
+ if (CHECK(err, "skel_attach", "skeleton attach failed: %d\n", err))
+ goto cleanup;
+
+ /* generate receive event */
+ system("ping -c 1 127.0.0.1 > /dev/null");
+
+ if (bss->skip) {
+ printf("%s:SKIP:no __builtin_btf_type_id\n", __func__);
+ test__skip();
+ goto cleanup;
+ }
+
+ /*
+ * Make sure netif_receive_skb program was triggered
+ * and it set expected return values from bpf_trace_printk()s
+ * and all tests ran.
+ */
+ if (CHECK(bss->ret <= 0,
+ "bpf_snprintf_btf: got return value",
+ "ret <= 0 %ld test %d\n", bss->ret, bss->ran_subtests))
+ goto cleanup;
+
+ if (CHECK(bss->ran_subtests == 0, "check if subtests ran",
+ "no subtests ran, did BPF program run?"))
+ goto cleanup;
+
+ if (CHECK(bss->num_subtests != bss->ran_subtests,
+ "check all subtests ran",
+ "only ran %d of %d tests\n", bss->num_subtests,
+ bss->ran_subtests))
+ goto cleanup;
+
+cleanup:
+ netif_receive_skb__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/progs/netif_receive_skb.c b/tools/testing/selftests/bpf/progs/netif_receive_skb.c
new file mode 100644
index 0000000..b873d80
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/netif_receive_skb.c
@@ -0,0 +1,249 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020, Oracle and/or its affiliates. */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_core_read.h>
+
+#include <errno.h>
+
+long ret = 0;
+int num_subtests = 0;
+int ran_subtests = 0;
+bool skip = false;
+
+#define STRSIZE 2048
+#define EXPECTED_STRSIZE 256
+
+#ifndef ARRAY_SIZE
+#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
+#endif
+
+struct {
+ __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+ __uint(max_entries, 1);
+ __type(key, __u32);
+ __type(value, char[STRSIZE]);
+} strdata SEC(".maps");
+
+static int __strncmp(const void *m1, const void *m2, size_t len)
+{
+ const unsigned char *s1 = m1;
+ const unsigned char *s2 = m2;
+ int i, delta = 0;
+
+ for (i = 0; i < len; i++) {
+ delta = s1[i] - s2[i];
+ if (delta || s1[i] == 0 || s2[i] == 0)
+ break;
+ }
+ return delta;
+}
+
+#if __has_builtin(__builtin_btf_type_id)
+#define TEST_BTF(_str, _type, _flags, _expected, ...) \
+ do { \
+ static const char _expectedval[EXPECTED_STRSIZE] = \
+ _expected; \
+ static const char _ptrtype[64] = #_type; \
+ __u64 _hflags = _flags | BTF_F_COMPACT; \
+ static _type _ptrdata = __VA_ARGS__; \
+ static struct btf_ptr _ptr = { }; \
+ int _cmp; \
+ \
+ ++num_subtests; \
+ if (ret < 0) \
+ break; \
+ ++ran_subtests; \
+ _ptr.ptr = &_ptrdata; \
+ _ptr.type_id = bpf_core_type_id_kernel(_type); \
+ if (_ptr.type_id <= 0) { \
+ ret = -EINVAL; \
+ break; \
+ } \
+ ret = bpf_snprintf_btf(_str, STRSIZE, \
+ &_ptr, sizeof(_ptr), _hflags); \
+ if (ret) \
+ break; \
+ _cmp = __strncmp(_str, _expectedval, EXPECTED_STRSIZE); \
+ if (_cmp != 0) { \
+ bpf_printk("(%d) got %s", _cmp, _str); \
+ bpf_printk("(%d) expected %s", _cmp, \
+ _expectedval); \
+ ret = -EBADMSG; \
+ break; \
+ } \
+ } while (0)
+#endif
+
+/* Use where expected data string matches its stringified declaration */
+#define TEST_BTF_C(_str, _type, _flags, ...) \
+ TEST_BTF(_str, _type, _flags, "(" #_type ")" #__VA_ARGS__, \
+ __VA_ARGS__)
+
+/* TRACE_EVENT(netif_receive_skb,
+ * TP_PROTO(struct sk_buff *skb),
+ */
+SEC("tp_btf/netif_receive_skb")
+int BPF_PROG(trace_netif_receive_skb, struct sk_buff *skb)
+{
+ static __u64 flags[] = { 0, BTF_F_COMPACT, BTF_F_ZERO, BTF_F_PTR_RAW,
+ BTF_F_NONAME, BTF_F_COMPACT | BTF_F_ZERO |
+ BTF_F_PTR_RAW | BTF_F_NONAME };
+ static struct btf_ptr p = { };
+ __u32 key = 0;
+ int i, __ret;
+ char *str;
+
+#if __has_builtin(__builtin_btf_type_id)
+ str = bpf_map_lookup_elem(&strdata, &key);
+ if (!str)
+ return 0;
+
+ /* Ensure we can write skb string representation */
+ p.type_id = bpf_core_type_id_kernel(struct sk_buff);
+ p.ptr = skb;
+ for (i = 0; i < ARRAY_SIZE(flags); i++) {
+ ++num_subtests;
+ ret = bpf_snprintf_btf(str, STRSIZE, &p, sizeof(p), 0);
+ if (ret < 0)
+ bpf_printk("returned %d when writing skb", ret);
+ ++ran_subtests;
+ }
+
+ /* Check invalid ptr value */
+ p.ptr = 0;
+ __ret = bpf_snprintf_btf(str, STRSIZE, &p, sizeof(p), 0);
+ if (__ret >= 0) {
+ bpf_printk("printing NULL should generate error, got (%d)",
+ __ret);
+ ret = -ERANGE;
+ }
+
+ /* Verify type display for various types. */
+
+ /* simple int */
+ TEST_BTF_C(str, int, 0, 1234);
+ TEST_BTF(str, int, BTF_F_NONAME, "1234", 1234);
+ /* zero value should be printed at toplevel */
+ TEST_BTF(str, int, 0, "(int)0", 0);
+ TEST_BTF(str, int, BTF_F_NONAME, "0", 0);
+ TEST_BTF(str, int, BTF_F_ZERO, "(int)0", 0);
+ TEST_BTF(str, int, BTF_F_NONAME | BTF_F_ZERO, "0", 0);
+ TEST_BTF_C(str, int, 0, -4567);
+ TEST_BTF(str, int, BTF_F_NONAME, "-4567", -4567);
+
+ /* simple char */
+ TEST_BTF_C(str, char, 0, 100);
+ TEST_BTF(str, char, BTF_F_NONAME, "100", 100);
+ /* zero value should be printed at toplevel */
+ TEST_BTF(str, char, 0, "(char)0", 0);
+ TEST_BTF(str, char, BTF_F_NONAME, "0", 0);
+ TEST_BTF(str, char, BTF_F_ZERO, "(char)0", 0);
+ TEST_BTF(str, char, BTF_F_NONAME | BTF_F_ZERO, "0", 0);
+
+ /* simple typedef */
+ TEST_BTF_C(str, uint64_t, 0, 100);
+ TEST_BTF(str, u64, BTF_F_NONAME, "1", 1);
+ /* zero value should be printed at toplevel */
+ TEST_BTF(str, u64, 0, "(u64)0", 0);
+ TEST_BTF(str, u64, BTF_F_NONAME, "0", 0);
+ TEST_BTF(str, u64, BTF_F_ZERO, "(u64)0", 0);
+ TEST_BTF(str, u64, BTF_F_NONAME|BTF_F_ZERO, "0", 0);
+
+ /* typedef struct */
+ TEST_BTF_C(str, atomic_t, 0, {.counter = (int)1,});
+ TEST_BTF(str, atomic_t, BTF_F_NONAME, "{1,}", {.counter = 1,});
+ /* typedef with 0 value should be printed at toplevel */
+ TEST_BTF(str, atomic_t, 0, "(atomic_t){}", {.counter = 0,});
+ TEST_BTF(str, atomic_t, BTF_F_NONAME, "{}", {.counter = 0,});
+ TEST_BTF(str, atomic_t, BTF_F_ZERO, "(atomic_t){.counter = (int)0,}",
+ {.counter = 0,});
+ TEST_BTF(str, atomic_t, BTF_F_NONAME|BTF_F_ZERO,
+ "{0,}", {.counter = 0,});
+
+ /* enum where enum value does (and does not) exist */
+ TEST_BTF_C(str, enum bpf_cmd, 0, BPF_MAP_CREATE);
+ TEST_BTF(str, enum bpf_cmd, 0, "(enum bpf_cmd)BPF_MAP_CREATE", 0);
+ TEST_BTF(str, enum bpf_cmd, BTF_F_NONAME, "BPF_MAP_CREATE",
+ BPF_MAP_CREATE);
+ TEST_BTF(str, enum bpf_cmd, BTF_F_NONAME|BTF_F_ZERO,
+ "BPF_MAP_CREATE", 0);
+
+ TEST_BTF(str, enum bpf_cmd, BTF_F_ZERO, "(enum bpf_cmd)BPF_MAP_CREATE",
+ BPF_MAP_CREATE);
+ TEST_BTF(str, enum bpf_cmd, BTF_F_NONAME|BTF_F_ZERO,
+ "BPF_MAP_CREATE", BPF_MAP_CREATE);
+ TEST_BTF_C(str, enum bpf_cmd, 0, 2000);
+ TEST_BTF(str, enum bpf_cmd, BTF_F_NONAME, "2000", 2000);
+
+ /* simple struct */
+ TEST_BTF_C(str, struct btf_enum, 0,
+ {.name_off = (__u32)3,.val = (__s32)-1,});
+ TEST_BTF(str, struct btf_enum, BTF_F_NONAME, "{3,-1,}",
+ { .name_off = 3, .val = -1,});
+ TEST_BTF(str, struct btf_enum, BTF_F_NONAME, "{-1,}",
+ { .name_off = 0, .val = -1,});
+ TEST_BTF(str, struct btf_enum, BTF_F_NONAME|BTF_F_ZERO, "{0,-1,}",
+ { .name_off = 0, .val = -1,});
+ /* empty struct should be printed */
+ TEST_BTF(str, struct btf_enum, 0, "(struct btf_enum){}",
+ { .name_off = 0, .val = 0,});
+ TEST_BTF(str, struct btf_enum, BTF_F_NONAME, "{}",
+ { .name_off = 0, .val = 0,});
+ TEST_BTF(str, struct btf_enum, BTF_F_ZERO,
+ "(struct btf_enum){.name_off = (__u32)0,.val = (__s32)0,}",
+ { .name_off = 0, .val = 0,});
+
+ /* struct with pointers */
+ TEST_BTF(str, struct list_head, BTF_F_PTR_RAW,
+ "(struct list_head){.next = (struct list_head *)0x0000000000000001,}",
+ { .next = (struct list_head *)1 });
+ /* NULL pointer should not be displayed */
+ TEST_BTF(str, struct list_head, BTF_F_PTR_RAW,
+ "(struct list_head){}",
+ { .next = (struct list_head *)0 });
+
+ /* struct with char array */
+ TEST_BTF(str, struct bpf_prog_info, 0,
+ "(struct bpf_prog_info){.name = (char[])['f','o','o',],}",
+ { .name = "foo",});
+ TEST_BTF(str, struct bpf_prog_info, BTF_F_NONAME,
+ "{['f','o','o',],}",
+ {.name = "foo",});
+ /* leading null char means do not display string */
+ TEST_BTF(str, struct bpf_prog_info, 0,
+ "(struct bpf_prog_info){}",
+ {.name = {'\0', 'f', 'o', 'o'}});
+ /* handle non-printable characters */
+ TEST_BTF(str, struct bpf_prog_info, 0,
+ "(struct bpf_prog_info){.name = (char[])[1,2,3,],}",
+ { .name = {1, 2, 3, 0}});
+
+ /* struct with non-char array */
+ TEST_BTF(str, struct __sk_buff, 0,
+ "(struct __sk_buff){.cb = (__u32[])[1,2,3,4,5,],}",
+ { .cb = {1, 2, 3, 4, 5,},});
+ TEST_BTF(str, struct __sk_buff, BTF_F_NONAME,
+ "{[1,2,3,4,5,],}",
+ { .cb = { 1, 2, 3, 4, 5},});
+ /* For non-char, arrays, show non-zero values only */
+ TEST_BTF(str, struct __sk_buff, 0,
+ "(struct __sk_buff){.cb = (__u32[])[1,],}",
+ { .cb = { 0, 0, 1, 0, 0},});
+
+ /* struct with bitfields */
+ TEST_BTF_C(str, struct bpf_insn, 0,
+ {.code = (__u8)1,.dst_reg = (__u8)0x2,.src_reg = (__u8)0x3,.off = (__s16)4,.imm = (__s32)5,});
+ TEST_BTF(str, struct bpf_insn, BTF_F_NONAME, "{1,0x2,0x3,4,5,}",
+ {.code = 1, .dst_reg = 0x2, .src_reg = 0x3, .off = 4,
+ .imm = 5,});
+#else
+ skip = true;
+#endif
+
+ return 0;
+}
+
+char _license[] SEC("license") = "GPL";
--
1.8.3.1

2020-09-28 11:37:18

by Alan Maguire

Subject: [PATCH v7 bpf-next 5/8] bpf: bump iter seq size to support BTF representation of large data structures

BPF iter size is limited to PAGE_SIZE; if we wish to display BTF-based
representations of larger kernel data structures such as task_struct,
this will be insufficient.

Suggested-by: Alexei Starovoitov <[email protected]>
Signed-off-by: Alan Maguire <[email protected]>
---
kernel/bpf/bpf_iter.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c
index 30833bb..8f10e30 100644
--- a/kernel/bpf/bpf_iter.c
+++ b/kernel/bpf/bpf_iter.c
@@ -88,8 +88,8 @@ static ssize_t bpf_seq_read(struct file *file, char __user *buf, size_t size,
mutex_lock(&seq->lock);

if (!seq->buf) {
- seq->size = PAGE_SIZE;
- seq->buf = kmalloc(seq->size, GFP_KERNEL);
+ seq->size = PAGE_SIZE << 3;
+ seq->buf = kvmalloc(seq->size, GFP_KERNEL);
if (!seq->buf) {
err = -ENOMEM;
goto done;
--
1.8.3.1

2020-09-28 11:37:30

by Alan Maguire

Subject: [PATCH v7 bpf-next 3/8] bpf: add bpf_snprintf_btf helper

A helper is added to support tracing kernel type information in BPF
using the BPF Type Format (BTF). Its signature is

long bpf_snprintf_btf(char *str, u32 str_size, struct btf_ptr *ptr,
u32 btf_ptr_size, u64 flags);

struct btf_ptr * specifies

- a pointer to the data to be traced
- the BTF id of the type of data pointed to
- a flags field is provided for future use; these flags
are not to be confused with the BTF_F_* flags
below that control how the btf_ptr is displayed; the
flags member of the struct btf_ptr may be used to
disambiguate types in kernel versus module BTF, etc;
the main distinction is the flags relate to the type
and information needed in identifying it; not how it
is displayed.

For example a BPF program with a struct sk_buff *skb
could do the following:

static struct btf_ptr b = { };

b.ptr = skb;
b.type_id = __builtin_btf_type_id(struct sk_buff, 1);
bpf_snprintf_btf(str, sizeof(str), &b, sizeof(b), 0, 0);

Default output looks like this:

(struct sk_buff){
.transport_header = (__u16)65535,
.mac_header = (__u16)65535,
.end = (sk_buff_data_t)192,
.head = (unsigned char *)0x000000007524fd8b,
.data = (unsigned char *)0x000000007524fd8b,
.truesize = (unsigned int)768,
.users = (refcount_t){
.refs = (atomic_t){
.counter = (int)1,
},
},
}

Flags modifying display are as follows:

- BTF_F_COMPACT: no formatting around type information
- BTF_F_NONAME: no struct/union member names/types
- BTF_F_PTR_RAW: show raw (unobfuscated) pointer values;
equivalent to %px.
- BTF_F_ZERO: show zero-valued struct/union members;
they are not displayed by default

Signed-off-by: Alan Maguire <[email protected]>
---
include/linux/bpf.h | 1 +
include/linux/btf.h | 9 +++---
include/uapi/linux/bpf.h | 67 ++++++++++++++++++++++++++++++++++++++++++
kernel/bpf/core.c | 1 +
kernel/bpf/helpers.c | 4 +++
kernel/trace/bpf_trace.c | 65 ++++++++++++++++++++++++++++++++++++++++
scripts/bpf_helpers_doc.py | 2 ++
tools/include/uapi/linux/bpf.h | 67 ++++++++++++++++++++++++++++++++++++++++++
8 files changed, 212 insertions(+), 4 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 2eae3f3..1d020d8 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1810,6 +1810,7 @@ static inline int bpf_fd_reuseport_array_update_elem(struct bpf_map *map,
extern const struct bpf_func_proto bpf_skc_to_tcp_request_sock_proto;
extern const struct bpf_func_proto bpf_skc_to_udp6_sock_proto;
extern const struct bpf_func_proto bpf_copy_from_user_proto;
+extern const struct bpf_func_proto bpf_snprintf_btf_proto;

const struct bpf_func_proto *bpf_tracing_func_proto(
enum bpf_func_id func_id, const struct bpf_prog *prog);
diff --git a/include/linux/btf.h b/include/linux/btf.h
index d0f5d3c..3e5cdc2 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -6,6 +6,7 @@

#include <linux/types.h>
#include <uapi/linux/btf.h>
+#include <uapi/linux/bpf.h>

#define BTF_TYPE_EMIT(type) ((void)(type *)0)

@@ -59,10 +60,10 @@ const struct btf_type *btf_type_id_size(const struct btf *btf,
* - BTF_SHOW_UNSAFE: skip use of bpf_probe_read() to safely read
* data before displaying it.
*/
-#define BTF_SHOW_COMPACT (1ULL << 0)
-#define BTF_SHOW_NONAME (1ULL << 1)
-#define BTF_SHOW_PTR_RAW (1ULL << 2)
-#define BTF_SHOW_ZERO (1ULL << 3)
+#define BTF_SHOW_COMPACT BTF_F_COMPACT
+#define BTF_SHOW_NONAME BTF_F_NONAME
+#define BTF_SHOW_PTR_RAW BTF_F_PTR_RAW
+#define BTF_SHOW_ZERO BTF_F_ZERO
#define BTF_SHOW_UNSAFE (1ULL << 4)

void btf_type_seq_show(const struct btf *btf, u32 type_id, void *obj,
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 2d6519a..fcafe80 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3587,6 +3587,42 @@ struct bpf_stack_build_id {
* the data in *dst*. This is a wrapper of **copy_from_user**\ ().
* Return
* 0 on success, or a negative error in case of failure.
+ *
+ * long bpf_snprintf_btf(char *str, u32 str_size, struct btf_ptr *ptr, u32 btf_ptr_size, u64 flags)
+ * Description
+ * Use BTF to store a string representation of *ptr*->ptr in *str*,
+ * using *ptr*->type_id. This value should specify the type
+ * that *ptr*->ptr points to. LLVM __builtin_btf_type_id(type, 1)
+ * can be used to look up vmlinux BTF type ids. Traversing the
+ * data structure using BTF, the type information and values are
+ * stored in the first *str_size* - 1 bytes of *str*. Safe copy of
+ * the pointer data is carried out to avoid kernel crashes during
+ * operation. Smaller types can use string space on the stack;
+ * larger programs can use map data to store the string
+ * representation.
+ *
+ * The string can be subsequently shared with userspace via
+ * bpf_perf_event_output() or ring buffer interfaces.
+ * bpf_trace_printk() is to be avoided as it places too small
+ * a limit on string size to be useful.
+ *
+ * *flags* is a combination of
+ *
+ * **BTF_F_COMPACT**
+ * no formatting around type information
+ * **BTF_F_NONAME**
+ * no struct/union member names/types
+ * **BTF_F_PTR_RAW**
+ * show raw (unobfuscated) pointer values;
+ * equivalent to printk specifier %px.
+ * **BTF_F_ZERO**
+ * show zero-valued struct/union members; they
+ * are not displayed by default
+ *
+ * Return
+ * The number of bytes that were written (or would have been
+ * written if output had to be truncated due to string size),
+ * or a negative error in cases of failure.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3738,6 +3774,7 @@ struct bpf_stack_build_id {
FN(inode_storage_delete), \
FN(d_path), \
FN(copy_from_user), \
+ FN(snprintf_btf), \
/* */

/* integer value in 'imm' field of BPF_CALL instruction selects which helper
@@ -4846,4 +4883,34 @@ struct bpf_sk_lookup {
__u32 local_port; /* Host byte order */
};

+/*
+ * struct btf_ptr is used for typed pointer representation; the
+ * type id is used to render the pointer data as the appropriate type
+ * via the bpf_snprintf_btf() helper described above. A flags field -
+ * potentially to specify additional details about the BTF pointer
+ * (rather than its mode of display) - is included for future use.
+ * Display flags - BTF_F_* - are passed to bpf_snprintf_btf separately.
+ */
+struct btf_ptr {
+ void *ptr;
+ __u32 type_id;
+ __u32 flags; /* BTF ptr flags; unused at present. */
+};
+
+/*
+ * Flags to control bpf_snprintf_btf() behaviour.
+ * - BTF_F_COMPACT: no formatting around type information
+ * - BTF_F_NONAME: no struct/union member names/types
+ * - BTF_F_PTR_RAW: show raw (unobfuscated) pointer values;
+ * equivalent to %px.
+ * - BTF_F_ZERO: show zero-valued struct/union members; they
+ * are not displayed by default
+ */
+enum {
+ BTF_F_COMPACT = (1ULL << 0),
+ BTF_F_NONAME = (1ULL << 1),
+ BTF_F_PTR_RAW = (1ULL << 2),
+ BTF_F_ZERO = (1ULL << 3),
+};
+
#endif /* _UAPI__LINUX_BPF_H__ */
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index c4811b13..403fb23 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2216,6 +2216,7 @@ void bpf_user_rnd_init_once(void)
const struct bpf_func_proto bpf_get_current_ancestor_cgroup_id_proto __weak;
const struct bpf_func_proto bpf_get_local_storage_proto __weak;
const struct bpf_func_proto bpf_get_ns_current_pid_tgid_proto __weak;
+const struct bpf_func_proto bpf_snprintf_btf_proto __weak;

const struct bpf_func_proto * __weak bpf_get_trace_printk_proto(void)
{
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 5cc7425..e825441 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -683,6 +683,10 @@ static int __bpf_strtoll(const char *buf, size_t buf_len, u64 flags,
if (!perfmon_capable())
return NULL;
return bpf_get_trace_printk_proto();
+ case BPF_FUNC_snprintf_btf:
+ if (!perfmon_capable())
+ return NULL;
+ return &bpf_snprintf_btf_proto;
case BPF_FUNC_jiffies64:
return &bpf_jiffies64_proto;
default:
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 36508f4..983cbd3 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -7,6 +7,7 @@
#include <linux/slab.h>
#include <linux/bpf.h>
#include <linux/bpf_perf_event.h>
+#include <linux/btf.h>
#include <linux/filter.h>
#include <linux/uaccess.h>
#include <linux/ctype.h>
@@ -16,6 +17,9 @@
#include <linux/error-injection.h>
#include <linux/btf_ids.h>

+#include <uapi/linux/bpf.h>
+#include <uapi/linux/btf.h>
+
#include <asm/tlb.h>

#include "trace_probe.h"
@@ -1147,6 +1151,65 @@ static bool bpf_d_path_allowed(const struct bpf_prog *prog)
.allowed = bpf_d_path_allowed,
};

+#define BTF_F_ALL (BTF_F_COMPACT | BTF_F_NONAME | \
+ BTF_F_PTR_RAW | BTF_F_ZERO)
+
+static int bpf_btf_printf_prepare(struct btf_ptr *ptr, u32 btf_ptr_size,
+ u64 flags, const struct btf **btf,
+ s32 *btf_id)
+{
+ const struct btf_type *t;
+
+ if (unlikely(flags & ~(BTF_F_ALL)))
+ return -EINVAL;
+
+ if (btf_ptr_size != sizeof(struct btf_ptr))
+ return -EINVAL;
+
+ *btf = bpf_get_btf_vmlinux();
+
+ if (IS_ERR_OR_NULL(*btf))
+ return PTR_ERR(*btf);
+
+ if (ptr->type_id > 0)
+ *btf_id = ptr->type_id;
+ else
+ return -EINVAL;
+
+ if (*btf_id > 0)
+ t = btf_type_by_id(*btf, *btf_id);
+ if (*btf_id <= 0 || !t)
+ return -ENOENT;
+
+ return 0;
+}
+
+BPF_CALL_5(bpf_snprintf_btf, char *, str, u32, str_size, struct btf_ptr *, ptr,
+ u32, btf_ptr_size, u64, flags)
+{
+ const struct btf *btf;
+ s32 btf_id;
+ int ret;
+
+ ret = bpf_btf_printf_prepare(ptr, btf_ptr_size, flags, &btf, &btf_id);
+ if (ret)
+ return ret;
+
+ return btf_type_snprintf_show(btf, btf_id, ptr->ptr, str, str_size,
+ flags);
+}
+
+const struct bpf_func_proto bpf_snprintf_btf_proto = {
+ .func = bpf_snprintf_btf,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_MEM,
+ .arg2_type = ARG_CONST_SIZE,
+ .arg3_type = ARG_PTR_TO_MEM,
+ .arg4_type = ARG_CONST_SIZE,
+ .arg5_type = ARG_ANYTHING,
+};
+
const struct bpf_func_proto *
bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
{
@@ -1233,6 +1296,8 @@ static bool bpf_d_path_allowed(const struct bpf_prog *prog)
return &bpf_get_task_stack_proto;
case BPF_FUNC_copy_from_user:
return prog->aux->sleepable ? &bpf_copy_from_user_proto : NULL;
+ case BPF_FUNC_snprintf_btf:
+ return &bpf_snprintf_btf_proto;
default:
return NULL;
}
diff --git a/scripts/bpf_helpers_doc.py b/scripts/bpf_helpers_doc.py
index 0838817..7d86fdd 100755
--- a/scripts/bpf_helpers_doc.py
+++ b/scripts/bpf_helpers_doc.py
@@ -433,6 +433,7 @@ class PrinterHelpers(Printer):
'struct sk_msg_md',
'struct xdp_md',
'struct path',
+ 'struct btf_ptr',
]
known_types = {
'...',
@@ -474,6 +475,7 @@ class PrinterHelpers(Printer):
'struct udp6_sock',
'struct task_struct',
'struct path',
+ 'struct btf_ptr',
}
mapped_types = {
'u8': '__u8',
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 2d6519a..fcafe80 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3587,6 +3587,42 @@ struct bpf_stack_build_id {
* the data in *dst*. This is a wrapper of **copy_from_user**\ ().
* Return
* 0 on success, or a negative error in case of failure.
+ *
+ * long bpf_snprintf_btf(char *str, u32 str_size, struct btf_ptr *ptr, u32 btf_ptr_size, u64 flags)
+ * Description
+ * Use BTF to store a string representation of *ptr*->ptr in *str*,
+ * using *ptr*->type_id. This value should specify the type
+ * that *ptr*->ptr points to. LLVM __builtin_btf_type_id(type, 1)
+ * can be used to look up vmlinux BTF type ids. Traversing the
+ * data structure using BTF, the type information and values are
+ * stored in the first *str_size* - 1 bytes of *str*. Safe copy of
+ * the pointer data is carried out to avoid kernel crashes during
+ * operation. Smaller types can use string space on the stack;
+ * larger programs can use map data to store the string
+ * representation.
+ *
+ * The string can be subsequently shared with userspace via
+ * bpf_perf_event_output() or ring buffer interfaces.
+ * bpf_trace_printk() is to be avoided as it places too small
+ * a limit on string size to be useful.
+ *
+ * *flags* is a combination of
+ *
+ * **BTF_F_COMPACT**
+ * no formatting around type information
+ * **BTF_F_NONAME**
+ * no struct/union member names/types
+ * **BTF_F_PTR_RAW**
+ * show raw (unobfuscated) pointer values;
+ * equivalent to printk specifier %px.
+ * **BTF_F_ZERO**
+ * show zero-valued struct/union members; they
+ * are not displayed by default
+ *
+ * Return
+ * The number of bytes that were written (or would have been
+ * written if output had to be truncated due to string size),
+ * or a negative error in cases of failure.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3738,6 +3774,7 @@ struct bpf_stack_build_id {
FN(inode_storage_delete), \
FN(d_path), \
FN(copy_from_user), \
+ FN(snprintf_btf), \
/* */

/* integer value in 'imm' field of BPF_CALL instruction selects which helper
@@ -4846,4 +4883,34 @@ struct bpf_sk_lookup {
__u32 local_port; /* Host byte order */
};

+/*
+ * struct btf_ptr is used for typed pointer representation; the
+ * type id is used to render the pointer data as the appropriate type
+ * via the bpf_snprintf_btf() helper described above. A flags field -
+ * potentially to specify additional details about the BTF pointer
+ * (rather than its mode of display) - is included for future use.
+ * Display flags - BTF_F_* - are passed to bpf_snprintf_btf separately.
+ */
+struct btf_ptr {
+ void *ptr;
+ __u32 type_id;
+ __u32 flags; /* BTF ptr flags; unused at present. */
+};
+
+/*
+ * Flags to control bpf_snprintf_btf() behaviour.
+ * - BTF_F_COMPACT: no formatting around type information
+ * - BTF_F_NONAME: no struct/union member names/types
+ * - BTF_F_PTR_RAW: show raw (unobfuscated) pointer values;
+ * equivalent to %px.
+ * - BTF_F_ZERO: show zero-valued struct/union members; they
+ * are not displayed by default
+ */
+enum {
+ BTF_F_COMPACT = (1ULL << 0),
+ BTF_F_NONAME = (1ULL << 1),
+ BTF_F_PTR_RAW = (1ULL << 2),
+ BTF_F_ZERO = (1ULL << 3),
+};
+
#endif /* _UAPI__LINUX_BPF_H__ */
--
1.8.3.1

2020-09-28 11:38:14

by Alan Maguire

Subject: [PATCH v7 bpf-next 6/8] selftests/bpf: fix overflow tests to reflect iter size increase

bpf iter size increase to PAGE_SIZE << 3 means overflow tests assuming
page size need to be bumped also.

Signed-off-by: Alan Maguire <[email protected]>
---
tools/testing/selftests/bpf/prog_tests/bpf_iter.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
index fe1a83b9..ad9de13 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
@@ -352,7 +352,7 @@ static void test_overflow(bool test_e2big_overflow, bool ret1)
struct bpf_map_info map_info = {};
struct bpf_iter_test_kern4 *skel;
struct bpf_link *link;
- __u32 page_size;
+ __u32 iter_size;
char *buf;

skel = bpf_iter_test_kern4__open();
@@ -374,19 +374,19 @@ static void test_overflow(bool test_e2big_overflow, bool ret1)
"map_creation failed: %s\n", strerror(errno)))
goto free_map1;

- /* bpf_seq_printf kernel buffer is one page, so one map
+ /* bpf_seq_printf kernel buffer is 8 pages, so one map
* bpf_seq_write will mostly fill it, and the other map
* will partially fill and then trigger overflow and need
* bpf_seq_read restart.
*/
- page_size = sysconf(_SC_PAGE_SIZE);
+ iter_size = sysconf(_SC_PAGE_SIZE) << 3;

if (test_e2big_overflow) {
- skel->rodata->print_len = (page_size + 8) / 8;
- expected_read_len = 2 * (page_size + 8);
+ skel->rodata->print_len = (iter_size + 8) / 8;
+ expected_read_len = 2 * (iter_size + 8);
} else if (!ret1) {
- skel->rodata->print_len = (page_size - 8) / 8;
- expected_read_len = 2 * (page_size - 8);
+ skel->rodata->print_len = (iter_size - 8) / 8;
+ expected_read_len = 2 * (iter_size - 8);
} else {
skel->rodata->print_len = 1;
expected_read_len = 2 * 8;
--
1.8.3.1

2020-09-28 11:38:56

by Alan Maguire

Subject: [PATCH v7 bpf-next 8/8] selftests/bpf: add test for bpf_seq_printf_btf helper

Add a test verifying iterating over tasks and displaying BTF
representation of task_struct succeeds.

Suggested-by: Alexei Starovoitov <[email protected]>
Signed-off-by: Alan Maguire <[email protected]>
---
tools/testing/selftests/bpf/prog_tests/bpf_iter.c | 74 ++++++++++++++++++++++
.../selftests/bpf/progs/bpf_iter_task_btf.c | 50 +++++++++++++++
2 files changed, 124 insertions(+)
create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_task_btf.c

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
index ad9de13..af15630 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
@@ -7,6 +7,7 @@
#include "bpf_iter_task.skel.h"
#include "bpf_iter_task_stack.skel.h"
#include "bpf_iter_task_file.skel.h"
+#include "bpf_iter_task_btf.skel.h"
#include "bpf_iter_tcp4.skel.h"
#include "bpf_iter_tcp6.skel.h"
#include "bpf_iter_udp4.skel.h"
@@ -167,6 +168,77 @@ static void test_task_file(void)
bpf_iter_task_file__destroy(skel);
}

+#define TASKBUFSZ 32768
+
+static char taskbuf[TASKBUFSZ];
+
+static void do_btf_read(struct bpf_iter_task_btf *skel)
+{
+ struct bpf_program *prog = skel->progs.dump_task_struct;
+ struct bpf_iter_task_btf__bss *bss = skel->bss;
+ int iter_fd = -1, len = 0, bufleft = TASKBUFSZ;
+ struct bpf_link *link;
+ char *buf = taskbuf;
+
+ link = bpf_program__attach_iter(prog, NULL);
+ if (CHECK(IS_ERR(link), "attach_iter", "attach_iter failed\n"))
+ return;
+
+ iter_fd = bpf_iter_create(bpf_link__fd(link));
+ if (CHECK(iter_fd < 0, "create_iter", "create_iter failed\n"))
+ goto free_link;
+
+ do {
+ len = read(iter_fd, buf, bufleft);
+ if (len > 0) {
+ buf += len;
+ bufleft -= len;
+ }
+ } while (len > 0);
+
+ if (bss->skip) {
+ printf("%s:SKIP:no __builtin_btf_type_id\n", __func__);
+ test__skip();
+ goto free_link;
+ }
+
+ if (CHECK(len < 0, "read", "read failed: %s\n", strerror(errno)))
+ goto free_link;
+
+ CHECK(strstr(taskbuf, "(struct task_struct)") == NULL,
+ "check for btf representation of task_struct in iter data",
+ "struct task_struct not found");
+free_link:
+ if (iter_fd > 0)
+ close(iter_fd);
+ bpf_link__destroy(link);
+}
+
+static void test_task_btf(void)
+{
+ struct bpf_iter_task_btf__bss *bss;
+ struct bpf_iter_task_btf *skel;
+
+ skel = bpf_iter_task_btf__open_and_load();
+ if (CHECK(!skel, "bpf_iter_task_btf__open_and_load",
+ "skeleton open_and_load failed\n"))
+ return;
+
+ bss = skel->bss;
+
+ do_btf_read(skel);
+
+ if (CHECK(bss->tasks == 0, "check if iterated over tasks",
+ "no task iteration, did BPF program run?\n"))
+ goto cleanup;
+
+ CHECK(bss->seq_err != 0, "check for unexpected err",
+ "bpf_seq_printf_btf returned %ld", bss->seq_err);
+
+cleanup:
+ bpf_iter_task_btf__destroy(skel);
+}
+
static void test_tcp4(void)
{
struct bpf_iter_tcp4 *skel;
@@ -957,6 +1029,8 @@ void test_bpf_iter(void)
test_task_stack();
if (test__start_subtest("task_file"))
test_task_file();
+ if (test__start_subtest("task_btf"))
+ test_task_btf();
if (test__start_subtest("tcp4"))
test_tcp4();
if (test__start_subtest("tcp6"))
diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_task_btf.c b/tools/testing/selftests/bpf/progs/bpf_iter_task_btf.c
new file mode 100644
index 0000000..a1ddc36
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_iter_task_btf.c
@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020, Oracle and/or its affiliates. */
+#include "bpf_iter.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_core_read.h>
+
+#include <errno.h>
+
+char _license[] SEC("license") = "GPL";
+
+long tasks = 0;
+long seq_err = 0;
+bool skip = false;
+
+SEC("iter/task")
+int dump_task_struct(struct bpf_iter__task *ctx)
+{
+ struct seq_file *seq = ctx->meta->seq;
+ struct task_struct *task = ctx->task;
+ static struct btf_ptr ptr = { };
+ long ret;
+
+#if __has_builtin(__builtin_btf_type_id)
+ ptr.type_id = bpf_core_type_id_kernel(struct task_struct);
+ ptr.ptr = task;
+
+ if (ctx->meta->seq_num == 0)
+ BPF_SEQ_PRINTF(seq, "Raw BTF task\n");
+
+ ret = bpf_seq_printf_btf(seq, &ptr, sizeof(ptr), 0);
+ switch (ret) {
+ case 0:
+ tasks++;
+ break;
+ case -ERANGE:
+ /* NULL task or task->fs, don't count it as an error. */
+ break;
+ case -E2BIG:
+ return 1;
+ default:
+ seq_err = ret;
+ break;
+ }
+#else
+ skip = true;
+#endif
+
+ return 0;
+}
--
1.8.3.1

2020-09-29 01:43:07

by Alexei Starovoitov

Subject: Re: [PATCH v7 bpf-next 0/8] bpf: add helpers to support BTF-based kernel data display

On Mon, Sep 28, 2020 at 4:33 AM Alan Maguire <[email protected]> wrote:
>
> Default output for an sk_buff looks like this (zeroed fields
> are omitted):
>
> (struct sk_buff){
> .transport_header = (__u16)65535,
> .mac_header = (__u16)65535,
> .end = (sk_buff_data_t)192,
> .head = (unsigned char *)0x000000007524fd8b,
> .data = (unsigned char *)0x000000007524fd8b,
> .truesize = (unsigned int)768,
> .users = (refcount_t){
> .refs = (atomic_t){
> .counter = (int)1,
> },
> },
> }
>
> Flags can modify aspects of output format; see patch 3
> for more details.

Applied. Thanks a lot.

2020-09-29 04:44:29

by Andrii Nakryiko

Subject: Re: [PATCH v7 bpf-next 8/8] selftests/bpf: add test for bpf_seq_printf_btf helper

On Mon, Sep 28, 2020 at 4:36 AM Alan Maguire <[email protected]> wrote:
>
> Add a test verifying iterating over tasks and displaying BTF
> representation of task_struct succeeds.
>
> Suggested-by: Alexei Starovoitov <[email protected]>
> Signed-off-by: Alan Maguire <[email protected]>
> ---

Hey Alan,

These selftests rely on having struct btf_ptr and BTF_F_COMPACT (and
other) flags to be present in vmlinux.h. While there is nothing wrong
with that per se, it does break selftests builds on older kernels,
because there struct btf_ptr isn't yet present in kernel:

progs/netif_receive_skb.c:131:21: error: use of undeclared identifier
'BTF_F_NONAME'
TEST_BTF(str, int, BTF_F_NONAME, "0", 0);
^
progs/netif_receive_skb.c:131:2: error: use of undeclared identifier
'BTF_F_COMPACT'; did you mean 'TT_COMPAT'?
TEST_BTF(str, int, BTF_F_NONAME, "0", 0);
^
progs/netif_receive_skb.c:50:28: note: expanded from macro 'TEST_BTF'
__u64 _hflags = _flags | BTF_F_COMPACT; \
^
/data/users/andriin/linux/tools/testing/selftests/bpf/tools/include/vmlinux.h:330:2:
note: 'TT_COMPAT' declared here
TT_COMPAT = 2,
^
fatal error: too many errors emitted, stopping now [-ferror-limit=]

progs/bpf_iter_task_btf.c:21:24: error: variable has incomplete type
'struct btf_ptr'
static struct btf_ptr ptr = { };
^
/data/users/andriin/linux/tools/testing/selftests/bpf/tools/include/bpf/bpf_helper_defs.h:33:8:
note: forward declaration of 'struct btf_ptr'
struct btf_ptr;


We actually do build the very latest selftests against old kernels
(4.9 and 5.5 at the moment) as part of libbpf CI, so it would be nice
to fix this problem and keep selftests compilable.

Do you mind following up with a change to define struct btf_ptr and
those BTF_F_xxx flags explicitly for selftests only, similarly to how
we do it for bpf_iter context structs? See progs/bpf_iter.h for
examples. Thanks.

> tools/testing/selftests/bpf/prog_tests/bpf_iter.c | 74 ++++++++++++++++++++++
> .../selftests/bpf/progs/bpf_iter_task_btf.c | 50 +++++++++++++++
> 2 files changed, 124 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_task_btf.c
>

[...]

2020-09-29 09:22:11

by Daniel Borkmann

Subject: Re: [PATCH v7 bpf-next 4/8] selftests/bpf: add bpf_snprintf_btf helper tests

On 9/28/20 1:31 PM, Alan Maguire wrote:
> Tests verifying snprintf()ing of various data structures,
> flags combinations using a tp_btf program. Tests are skipped
> if __builtin_btf_type_id is not available to retrieve BTF
> type ids.
>
> Signed-off-by: Alan Maguire <[email protected]>
[...]
> +void test_snprintf_btf(void)
> +{
> + struct netif_receive_skb *skel;
> + struct netif_receive_skb__bss *bss;
> + int err, duration = 0;
> +
> + skel = netif_receive_skb__open();
> + if (CHECK(!skel, "skel_open", "failed to open skeleton\n"))
> + return;
> +
> + err = netif_receive_skb__load(skel);
> + if (CHECK(err, "skel_load", "failed to load skeleton: %d\n", err))
> + goto cleanup;
> +
> + bss = skel->bss;
> +
> + err = netif_receive_skb__attach(skel);
> + if (CHECK(err, "skel_attach", "skeleton attach failed: %d\n", err))
> + goto cleanup;
> +
> + /* generate receive event */
> + system("ping -c 1 127.0.0.1 > /dev/null");

This generates the following new warning when compiling BPF selftests:

[...]
EXT-OBJ [test_progs] cgroup_helpers.o
EXT-OBJ [test_progs] trace_helpers.o
EXT-OBJ [test_progs] network_helpers.o
EXT-OBJ [test_progs] testing_helpers.o
TEST-OBJ [test_progs] snprintf_btf.test.o
/root/bpf-next/tools/testing/selftests/bpf/prog_tests/snprintf_btf.c: In function ‘test_snprintf_btf’:
/root/bpf-next/tools/testing/selftests/bpf/prog_tests/snprintf_btf.c:30:2: warning: ignoring return value of ‘system’, declared with attribute warn_unused_result [-Wunused-result]
system("ping -c 1 127.0.0.1 > /dev/null");
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[...]

Please fix, thx!