Add a BTF dumper for typed data, so that the user can dump a typed
version of the data provided.
The API is
int btf_dump__dump_type_data(struct btf_dump *d, __u32 id,
void *data, size_t data_sz,
const struct btf_dump_type_data_opts *opts);
...where the id is the BTF id of the data pointed to by the "void *"
argument; for example the BTF id of "struct sk_buff" for a
"struct skb *" data pointer. Options supported are
- a starting indent level (indent_lvl)
- a user-specified indent string which will be printed once per
indent level; if NULL, tab is chosen but any string <= 32 chars
can be provided.
- a set of boolean options to control dump display, similar to those
used for BPF helper bpf_snprintf_btf(). Options are
- compact : omit newlines and other indentation
- skip_names: omit member names
- emit_zeroes: show zero-value members
Default output format is identical to that dumped by bpf_snprintf_btf(),
for example a "struct sk_buff" representation would look like this:
struct sk_buff){
(union){
(struct){
.next = (struct sk_buff *)0xffffffffffffffff,
.prev = (struct sk_buff *)0xffffffffffffffff,
(union){
.dev = (struct net_device *)0xffffffffffffffff,
.dev_scratch = (long unsigned int)18446744073709551615,
},
},
...
If the data structure is larger than the *data_sz*
number of bytes that are available in *data*, as much
of the data as possible will be dumped and -E2BIG will
be returned. This is useful as tracers will sometimes
not be able to capture all of the data associated with
a type; for example a "struct task_struct" is ~16k.
Being able to specify that only a subset is available is
important for such cases. On success, the amount of data
dumped is returned.
Signed-off-by: Alan Maguire <[email protected]>
---
tools/lib/bpf/btf.h | 19 ++
tools/lib/bpf/btf_dump.c | 819 ++++++++++++++++++++++++++++++++++++++++++++++-
tools/lib/bpf/libbpf.map | 1 +
3 files changed, 834 insertions(+), 5 deletions(-)
diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index b54f1c3..374e9f1 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -184,6 +184,25 @@ struct btf_dump_emit_type_decl_opts {
btf_dump__emit_type_decl(struct btf_dump *d, __u32 id,
const struct btf_dump_emit_type_decl_opts *opts);
+
+struct btf_dump_type_data_opts {
+ /* size of this struct, for forward/backward compatibility */
+ size_t sz;
+ const char *indent_str;
+ int indent_level;
+ /* below match "show" flags for bpf_show_snprintf() */
+ bool compact; /* no newlines/indentation */
+ bool skip_names; /* skip member/type names */
+ bool emit_zeroes; /* show 0-valued fields */
+ size_t :0;
+};
+#define btf_dump_type_data_opts__last_field emit_zeroes
+
+LIBBPF_API int
+btf_dump__dump_type_data(struct btf_dump *d, __u32 id,
+ const void *data, size_t data_sz,
+ const struct btf_dump_type_data_opts *opts);
+
/*
* A set of helpers for easier BTF types handling
*/
diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
index 5dc6b517..929cf93 100644
--- a/tools/lib/bpf/btf_dump.c
+++ b/tools/lib/bpf/btf_dump.c
@@ -10,6 +10,8 @@
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
+#include <ctype.h>
+#include <endian.h>
#include <errno.h>
#include <linux/err.h>
#include <linux/btf.h>
@@ -53,6 +55,26 @@ struct btf_dump_type_aux_state {
__u8 referenced: 1;
};
+/* indent string length; one indent string is added for each indent level */
+#define BTF_DATA_INDENT_STR_LEN 32
+
+/*
+ * Common internal data for BTF type data dump operations.
+ */
+struct btf_dump_data {
+ const void *data_end; /* end of valid data to show */
+ bool compact;
+ bool skip_names;
+ bool emit_zeroes;
+ __u8 indent_lvl; /* base indent level */
+ char indent_str[BTF_DATA_INDENT_STR_LEN];
+ /* below are used during iteration */
+ int depth;
+ bool is_array_member;
+ bool is_array_terminated;
+ bool is_array_char;
+};
+
struct btf_dump {
const struct btf *btf;
const struct btf_ext *btf_ext;
@@ -60,6 +82,7 @@ struct btf_dump {
struct btf_dump_opts opts;
int ptr_sz;
bool strip_mods;
+ bool skip_anon_defs;
int last_id;
/* per-type auxiliary state */
@@ -89,6 +112,10 @@ struct btf_dump {
* name occurrences
*/
struct hashmap *ident_names;
+ /*
+ * data for typed display; allocated if needed.
+ */
+ struct btf_dump_data *typed_dump;
};
static size_t str_hash_fn(const void *key, void *ctx)
@@ -765,11 +792,11 @@ static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id)
break;
case BTF_KIND_FUNC_PROTO: {
const struct btf_param *p = btf_params(t);
- __u16 vlen = btf_vlen(t);
+ __u16 n = btf_vlen(t);
int i;
btf_dump_emit_type(d, t->type, cont_id);
- for (i = 0; i < vlen; i++, p++)
+ for (i = 0; i < n; i++, p++)
btf_dump_emit_type(d, p->type, cont_id);
break;
@@ -852,8 +879,9 @@ static void btf_dump_emit_bit_padding(const struct btf_dump *d,
static void btf_dump_emit_struct_fwd(struct btf_dump *d, __u32 id,
const struct btf_type *t)
{
- btf_dump_printf(d, "%s %s",
+ btf_dump_printf(d, "%s%s%s",
btf_is_struct(t) ? "struct" : "union",
+ t->name_off ? " " : "",
btf_dump_type_name(d, id));
}
@@ -1259,7 +1287,7 @@ static void btf_dump_emit_type_chain(struct btf_dump *d,
case BTF_KIND_UNION:
btf_dump_emit_mods(d, decls);
/* inline anonymous struct/union */
- if (t->name_off == 0)
+ if (t->name_off == 0 && !d->skip_anon_defs)
btf_dump_emit_struct_def(d, id, t, lvl);
else
btf_dump_emit_struct_fwd(d, id, t);
@@ -1267,7 +1295,7 @@ static void btf_dump_emit_type_chain(struct btf_dump *d,
case BTF_KIND_ENUM:
btf_dump_emit_mods(d, decls);
/* inline anonymous enum */
- if (t->name_off == 0)
+ if (t->name_off == 0 && !d->skip_anon_defs)
btf_dump_emit_enum_def(d, id, t, lvl);
else
btf_dump_emit_enum_fwd(d, id, t);
@@ -1392,6 +1420,39 @@ static void btf_dump_emit_type_chain(struct btf_dump *d,
btf_dump_emit_name(d, fname, last_was_ptr);
}
+/* show type name as (type_name) */
+static void btf_dump_emit_type_cast(struct btf_dump *d, __u32 id,
+ bool top_level)
+{
+ const struct btf_type *t;
+
+ /* for array members, we don't bother emitting type name for each
+ * member to avoid the redundancy of
+ * .name = (char[4])[(char)'f',(char)'o',(char)'o',]
+ */
+ if (d->typed_dump->is_array_member)
+ return;
+
+ /* avoid type name specification for variable/section; it will be done
+ * for the associated variable value(s).
+ */
+ t = btf__type_by_id(d->btf, id);
+ if (btf_is_var(t) || btf_is_datasec(t))
+ return;
+
+ if (top_level)
+ btf_dump_printf(d, "(");
+
+ d->skip_anon_defs = true;
+ d->strip_mods = true;
+ btf_dump_emit_type_decl(d, id, "", 0);
+ d->strip_mods = false;
+ d->skip_anon_defs = false;
+
+ if (top_level)
+ btf_dump_printf(d, ")");
+}
+
/* return number of duplicates (occurrences) of a given name */
static size_t btf_dump_name_dups(struct btf_dump *d, struct hashmap *name_map,
const char *orig_name)
@@ -1442,3 +1503,751 @@ static const char *btf_dump_ident_name(struct btf_dump *d, __u32 id)
{
return btf_dump_resolve_name(d, id, d->ident_names);
}
+
+static int btf_dump_dump_type_data(struct btf_dump *d,
+ const char *fname,
+ const struct btf_type *t,
+ __u32 id,
+ const void *data,
+ __u8 bits_offset,
+ __u8 bit_sz);
+
+static const char *btf_dump_data_newline(struct btf_dump *d)
+{
+ return d->typed_dump->compact || d->typed_dump->depth == 0 ? "" : "\n";
+}
+
+static const char *btf_dump_data_delim(struct btf_dump *d)
+{
+ return d->typed_dump->depth == 0 ? "" : ",";
+}
+
+static void btf_dump_data_pfx(struct btf_dump *d)
+{
+ int i, lvl = d->typed_dump->indent_lvl + d->typed_dump->depth;
+
+ if (d->typed_dump->compact)
+ return;
+
+ for (i = 0; i < lvl; i++)
+ btf_dump_printf(d, "%s", d->typed_dump->indent_str);
+}
+
+/* A macro is used here as btf_type_value[s]() appends format specifiers
+ * to the format specifier passed in; these do the work of appending
+ * delimiters etc while the caller simply has to specify the type values
+ * in the format specifier + value(s).
+ */
+#define btf_dump_type_values(d, fmt, ...) \
+ btf_dump_printf(d, fmt "%s%s", \
+ ##__VA_ARGS__, \
+ btf_dump_data_delim(d), \
+ btf_dump_data_newline(d))
+
+static int btf_dump_unsupported_data(struct btf_dump *d,
+ const struct btf_type *t,
+ __u32 id)
+{
+ btf_dump_printf(d, "<unsupported kind:%u>", btf_kind(t));
+ return -ENOTSUP;
+}
+
+static void btf_dump_int128(struct btf_dump *d,
+ const struct btf_type *t,
+ const void *data)
+{
+ __int128 num = *(__int128 *)data;
+
+ if ((num >> 64) == 0)
+ btf_dump_type_values(d, "0x%llx", (long long)num);
+ else
+ btf_dump_type_values(d, "0x%llx%016llx", (long long)num >> 32,
+ (long long)num);
+}
+
+static unsigned __int128 btf_dump_bitfield_get_data(struct btf_dump *d,
+ const struct btf_type *t,
+ const void *data,
+ __u8 bits_offset,
+ __u8 bit_sz)
+{
+ __u16 left_shift_bits, right_shift_bits;
+ __u8 nr_copy_bits, nr_copy_bytes;
+ unsigned __int128 num = 0, ret;
+ const __u8 *bytes = data;
+ int i;
+
+ /* Bitfield value retrieval is done in two steps; first relevant bytes are
+ * stored in num, then we left/right shift num to eliminate irrelevant bits.
+ */
+ nr_copy_bits = bit_sz + bits_offset;
+ nr_copy_bytes = t->size;
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+ for (i = nr_copy_bytes - 1; i >= 0; i--)
+ num = num * 256 + bytes[i];
+#elif __BYTE_ORDER == __BIG_ENDIAN
+ for (i = 0; i < nr_copy_bytes; i++)
+ num = num * 256 + bytes[i];
+#else
+# error "Unrecognized __BYTE_ORDER__"
+#endif
+ left_shift_bits = 128 - nr_copy_bits;
+ right_shift_bits = 128 - bit_sz;
+
+ ret = (num << left_shift_bits) >> right_shift_bits;
+
+ return ret;
+}
+
+static int btf_dump_bitfield_check_zero(struct btf_dump *d,
+ const struct btf_type *t,
+ const void *data,
+ __u8 bits_offset,
+ __u8 bit_sz)
+{
+ __int128 check_num;
+
+ check_num = btf_dump_bitfield_get_data(d, t, data, bits_offset, bit_sz);
+ if (check_num == 0)
+ return -ENODATA;
+ return 0;
+}
+
+static int btf_dump_bitfield_data(struct btf_dump *d,
+ const struct btf_type *t,
+ const void *data,
+ __u8 bits_offset,
+ __u8 bit_sz)
+{
+ unsigned __int128 print_num;
+
+ print_num = btf_dump_bitfield_get_data(d, t, data, bits_offset, bit_sz);
+ btf_dump_int128(d, t, &print_num);
+
+ return 0;
+}
+
+/* ints, floats and ptrs */
+static int btf_dump_base_type_check_zero(struct btf_dump *d,
+ const struct btf_type *t,
+ __u32 id,
+ const void *data)
+{
+ static __u8 bytecmp[16] = {};
+ int nr_bytes;
+
+ /* For pointer types, pointer size is not defined on a per-type basis.
+ * On dump creation however, we store the pointer size.
+ */
+ if (btf_kind(t) == BTF_KIND_PTR)
+ nr_bytes = d->ptr_sz;
+ else
+ nr_bytes = t->size;
+
+ if (nr_bytes < 1 || nr_bytes > 16) {
+ pr_warn("unexpected size %d for id [%u]\n", nr_bytes, id);
+ return -EINVAL;
+ }
+
+ if (memcmp(data, bytecmp, nr_bytes) == 0)
+ return -ENODATA;
+ return 0;
+}
+
+static int btf_dump_int_data(struct btf_dump *d,
+ const struct btf_type *t,
+ __u32 type_id,
+ const void *data,
+ __u8 bits_offset)
+{
+ __u8 encoding = btf_int_encoding(t);
+ bool sign = encoding & BTF_INT_SIGNED;
+ int sz = t->size;
+
+ if (sz == 0) {
+ pr_warn("unexpected size %d for id [%u]\n", sz, type_id);
+ return -EINVAL;
+ }
+
+ /* handle packed int data - accesses of integers not aligned on
+ * int boundaries can cause problems on some platforms.
+ */
+ if (((uintptr_t)data) % sz)
+ return btf_dump_bitfield_data(d, t, data, 0, 0);
+
+ switch (sz) {
+ case 16:
+ btf_dump_int128(d, t, data);
+ break;
+ case 8:
+ if (sign)
+ btf_dump_type_values(d, "%lld", *(long long *)data);
+ else
+ btf_dump_type_values(d, "%llu", *(unsigned long long *)data);
+ break;
+ case 4:
+ if (sign)
+ btf_dump_type_values(d, "%d", *(__s32 *)data);
+ else
+ btf_dump_type_values(d, "%u", *(__u32 *)data);
+ break;
+ case 2:
+ if (sign)
+ btf_dump_type_values(d, "%d", *(__s16 *)data);
+ else
+ btf_dump_type_values(d, "%u", *(__u16 *)data);
+ break;
+ case 1:
+ if (d->typed_dump->is_array_char) {
+ /* check for null terminator */
+ if (d->typed_dump->is_array_terminated)
+ break;
+ if (*(char *)data == '\0') {
+ d->typed_dump->is_array_terminated = true;
+ break;
+ }
+ if (isprint(*(char *)data)) {
+ btf_dump_type_values(d, "'%c'", *(char *)data);
+ break;
+ }
+ }
+ if (sign)
+ btf_dump_type_values(d, "%d", *(__s8 *)data);
+ else
+ btf_dump_type_values(d, "%u", *(__u8 *)data);
+ break;
+ default:
+ pr_warn("unexpected sz %d for id [%u]\n", sz, type_id);
+ return -EINVAL;
+ }
+ return 0;
+}
+
+union float_data {
+ long double ld;
+ double d;
+ float f;
+};
+
+static int btf_dump_float_data(struct btf_dump *d,
+ const struct btf_type *t,
+ __u32 type_id,
+ const void *data)
+{
+ const union float_data *flp = data;
+ union float_data fl;
+ int sz = t->size;
+
+ /* handle unaligned data; copy to local union */
+ if (((uintptr_t)data) % sz) {
+ memcpy(&fl, data, sz);
+ flp = &fl;
+ }
+
+ switch (sz) {
+ case 16:
+ btf_dump_type_values(d, "%Lf", flp->ld);
+ break;
+ case 8:
+ btf_dump_type_values(d, "%lf", flp->d);
+ break;
+ case 4:
+ btf_dump_type_values(d, "%f", flp->f);
+ break;
+ default:
+ pr_warn("unexpected size %d for id [%u]\n", sz, type_id);
+ return -EINVAL;
+ }
+ return 0;
+}
+
+static int btf_dump_var_data(struct btf_dump *d,
+ const struct btf_type *v,
+ __u32 id,
+ const void *data)
+{
+ enum btf_func_linkage linkage = btf_var(v)->linkage;
+ const struct btf_type *t;
+ const char *l;
+ __u32 type_id;
+
+ switch (linkage) {
+ case BTF_FUNC_STATIC:
+ l = "static ";
+ break;
+ case BTF_FUNC_EXTERN:
+ l = "extern ";
+ break;
+ case BTF_FUNC_GLOBAL:
+ default:
+ l = "";
+ break;
+ }
+
+ /* format of output here is [linkage] [type] [varname] = (type)value,
+ * for example "static int cpu_profile_flip = (int)1"
+ */
+ btf_dump_printf(d, "%s", l);
+ type_id = v->type;
+ t = btf__type_by_id(d->btf, type_id);
+ btf_dump_emit_type_cast(d, type_id, false);
+ btf_dump_printf(d, " %s = ", btf_name_of(d, v->name_off));
+ return btf_dump_dump_type_data(d, NULL, t, type_id, data, 0, 0);
+}
+
+static int btf_dump_array_data(struct btf_dump *d,
+ const struct btf_type *t,
+ __u32 id,
+ const void *data)
+{
+ const struct btf_array *array = btf_array(t);
+ const struct btf_type *elem_type;
+ __u32 i, elem_size = 0, elem_type_id;
+ bool is_array_member;
+
+ elem_type_id = array->type;
+ elem_type = skip_mods_and_typedefs(d->btf, elem_type_id, NULL);
+ elem_size = btf__resolve_size(d->btf, elem_type_id);
+ if (elem_size <= 0) {
+ pr_warn("unexpected elem size %d for array type [%u]\n", elem_size, id);
+ return -EINVAL;
+ }
+
+ if (btf_is_int(elem_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)
+ d->typed_dump->is_array_char = true;
+ }
+
+ /* note that we increment depth before calling btf_dump_print() below;
+ * this is intentional. btf_dump_data_newline() will not print a
+ * newline for depth 0 (since this leaves us with trailing newlines
+ * at the end of typed display), so depth is incremented first.
+ * For similar reasons, we decrement depth before showing the closing
+ * parenthesis.
+ */
+ d->typed_dump->depth++;
+ btf_dump_printf(d, "[%s", btf_dump_data_newline(d));
+
+ /* may be a multidimensional array, so store current "is array member"
+ * status so we can restore it correctly later.
+ */
+ is_array_member = d->typed_dump->is_array_member;
+ d->typed_dump->is_array_member = true;
+ for (i = 0; i < array->nelems; i++, data += elem_size) {
+ if (d->typed_dump->is_array_terminated)
+ break;
+ btf_dump_dump_type_data(d, NULL, elem_type, elem_type_id, data, 0, 0);
+ }
+ d->typed_dump->is_array_member = is_array_member;
+ d->typed_dump->depth--;
+ btf_dump_data_pfx(d);
+ btf_dump_type_values(d, "]");
+
+ return 0;
+}
+
+static int btf_dump_struct_data(struct btf_dump *d,
+ const struct btf_type *t,
+ __u32 id,
+ const void *data)
+{
+ const struct btf_member *m = btf_members(t);
+ __u16 n = btf_vlen(t);
+ int i, err;
+
+ /* note that we increment depth before calling btf_dump_print() below;
+ * this is intentional. btf_dump_data_newline() will not print a
+ * newline for depth 0 (since this leaves us with trailing newlines
+ * at the end of typed display), so depth is incremented first.
+ * For similar reasons, we decrement depth before showing the closing
+ * parenthesis.
+ */
+ d->typed_dump->depth++;
+ btf_dump_printf(d, "{%s", btf_dump_data_newline(d));
+
+ for (i = 0; i < n; i++, m++) {
+ const struct btf_type *mtype;
+ const char *mname;
+ __u32 moffset;
+ __u8 bit_sz;
+
+ mtype = btf__type_by_id(d->btf, m->type);
+ mname = btf_name_of(d, m->name_off);
+ moffset = btf_member_bit_offset(t, i);
+
+ bit_sz = btf_member_bitfield_size(t, i);
+ err = btf_dump_dump_type_data(d, mname, mtype, m->type, data + moffset / 8,
+ moffset % 8, bit_sz);
+ if (err < 0)
+ return err;
+ }
+ d->typed_dump->depth--;
+ btf_dump_data_pfx(d);
+ btf_dump_type_values(d, "}");
+ return err;
+}
+
+static int btf_dump_ptr_data(struct btf_dump *d,
+ const struct btf_type *t,
+ __u32 id,
+ const void *data)
+{
+ btf_dump_type_values(d, "%p", *(void **)data);
+ return 0;
+}
+
+static int btf_dump_get_enum_value(struct btf_dump *d,
+ const struct btf_type *t,
+ const void *data,
+ __u32 id,
+ __s64 *value)
+{
+ int sz = t->size;
+
+ /* handle unaligned enum value */
+ if (((uintptr_t)data) % sz) {
+ *value = (__s64)btf_dump_bitfield_get_data(d, t, data, 0, 0);
+ return 0;
+ }
+ switch (t->size) {
+ case 8:
+ *value = *(__s64 *)data;
+ return 0;
+ case 4:
+ *value = *(__s32 *)data;
+ return 0;
+ case 2:
+ *value = *(__s16 *)data;
+ return 0;
+ case 1:
+ *value = *(__s8 *)data;
+ return 0;
+ default:
+ pr_warn("unexpected size %d for enum, id:[%u]\n", t->size, id);
+ return -EINVAL;
+ }
+}
+
+static int btf_dump_enum_data(struct btf_dump *d,
+ const struct btf_type *t,
+ __u32 id,
+ const void *data)
+{
+ const struct btf_enum *e;
+ __s64 value;
+ int i, err;
+
+ err = btf_dump_get_enum_value(d, t, data, id, &value);
+ if (err)
+ return err;
+
+ for (i = 0, e = btf_enum(t); i < btf_vlen(t); i++, e++) {
+ if (value != e->val)
+ continue;
+ btf_dump_type_values(d, "%s", btf_name_of(d, e->name_off));
+ return 0;
+ }
+
+ btf_dump_type_values(d, "%d", value);
+ return 0;
+}
+
+static int btf_dump_datasec_data(struct btf_dump *d,
+ const struct btf_type *t,
+ __u32 id,
+ const void *data)
+{
+ const struct btf_var_secinfo *vsi;
+ const struct btf_type *var;
+ __u32 i;
+ int err;
+
+ btf_dump_type_values(d, "SEC(\"%s\") ", btf_name_of(d, t->name_off));
+
+ for (i = 0, vsi = btf_var_secinfos(t); i < btf_vlen(t); i++, vsi++) {
+ var = btf__type_by_id(d->btf, vsi->type);
+ err = btf_dump_dump_type_data(d, NULL, var, vsi->type, data + vsi->offset, 0, 0);
+ if (err < 0)
+ return err;
+ btf_dump_printf(d, ";");
+ }
+ return 0;
+}
+
+/* return size of type, or if base type overflows, return -E2BIG. */
+static int btf_dump_type_data_check_overflow(struct btf_dump *d,
+ const struct btf_type *t,
+ __u32 id,
+ const void *data,
+ __u8 bits_offset)
+{
+ __s64 size = btf__resolve_size(d->btf, id);
+
+ if (size < 0 || size >= INT_MAX) {
+ pr_warn("unexpected size [%lld] for id [%u]\n",
+ size, id);
+ return -EINVAL;
+ }
+
+ /* Only do overflow checking for base types; we do not want to
+ * avoid showing part of a struct, union or array, even if we
+ * do not have enough data to show the full object. By
+ * restricting overflow checking to base types we can ensure
+ * that partial display succeeds, while avoiding overflowing
+ * and using bogus data for display.
+ */
+ t = skip_mods_and_typedefs(d->btf, id, NULL);
+ if (!t) {
+ pr_warn("unexpected error skipping mods/typedefs for id [%u]\n",
+ id);
+ return -EINVAL;
+ }
+
+ switch (btf_kind(t)) {
+ case BTF_KIND_INT:
+ case BTF_KIND_FLOAT:
+ case BTF_KIND_PTR:
+ case BTF_KIND_ENUM:
+ if (data + bits_offset / 8 + size > d->typed_dump->data_end)
+ return -E2BIG;
+ break;
+ default:
+ break;
+ }
+ return (int)size;
+}
+
+static int btf_dump_type_data_check_zero(struct btf_dump *d,
+ const struct btf_type *t,
+ __u32 id,
+ const void *data,
+ __u8 bits_offset,
+ __u8 bit_sz)
+{
+ __s64 value;
+ int i, err;
+
+ /* toplevel exceptions; we show zero values if
+ * - we ask for them (emit_zeros)
+ * - if we are at top-level so we see "struct empty { }"
+ * - or if we are an array member and the array is non-empty and
+ * not a char array; we don't want to be in a situation where we
+ * have an integer array 0, 1, 0, 1 and only show non-zero values.
+ * If the array contains zeroes only, or is a char array starting
+ * with a '\0', the array-level check_zero() will prevent showing it;
+ * we are concerned with determining zero value at the array member
+ * level here.
+ */
+ if (d->typed_dump->emit_zeroes || d->typed_dump->depth == 0 ||
+ (d->typed_dump->is_array_member &&
+ !d->typed_dump->is_array_char))
+ return 0;
+
+ t = skip_mods_and_typedefs(d->btf, id, NULL);
+
+ switch (btf_kind(t)) {
+ case BTF_KIND_INT:
+ if (bit_sz)
+ return btf_dump_bitfield_check_zero(d, t, data, bits_offset, bit_sz);
+ return btf_dump_base_type_check_zero(d, t, id, data);
+ case BTF_KIND_FLOAT:
+ case BTF_KIND_PTR:
+ return btf_dump_base_type_check_zero(d, t, id, data);
+ case BTF_KIND_ARRAY: {
+ const struct btf_array *array = btf_array(t);
+ const struct btf_type *elem_type;
+ __u32 elem_type_id, elem_size;
+ bool ischar;
+
+ elem_type_id = array->type;
+ elem_size = btf__resolve_size(d->btf, elem_type_id);
+ elem_type = skip_mods_and_typedefs(d->btf, elem_type_id, NULL);
+
+ ischar = btf_is_int(elem_type) && elem_size == 1;
+
+ /* check all elements; if _any_ element is nonzero, all
+ * of array is displayed. We make an exception however
+ * for char arrays where the first element is 0; these
+ * are considered zeroed also, even if later elements are
+ * non-zero because the string is terminated.
+ */
+ for (i = 0; i < array->nelems; i++) {
+ if (i == 0 && ischar && *(char *)data == 0)
+ return -ENODATA;
+ err = btf_dump_type_data_check_zero(d, elem_type,
+ elem_type_id,
+ data +
+ (i * elem_size),
+ bits_offset, 0);
+ if (err != -ENODATA)
+ return err;
+ }
+ return -ENODATA;
+ }
+ case BTF_KIND_STRUCT:
+ case BTF_KIND_UNION: {
+ const struct btf_member *m = btf_members(t);
+ __u16 n = btf_vlen(t);
+
+ /* if any struct/union member is non-zero, the struct/union
+ * is considered non-zero and dumped.
+ */
+ for (i = 0; i < n; i++, m++) {
+ const struct btf_type *mtype;
+ __u32 moffset;
+
+ mtype = btf__type_by_id(d->btf, m->type);
+ moffset = btf_member_bit_offset(t, i);
+
+ /* btf_int_bits() does not store member bitfield size;
+ * bitfield size needs to be stored here so int display
+ * of member can retrieve it.
+ */
+ bit_sz = btf_member_bitfield_size(t, i);
+ err = btf_dump_type_data_check_zero(d, mtype, m->type, data + moffset / 8,
+ moffset % 8, bit_sz);
+ if (err != ENODATA)
+ return err;
+ }
+ return -ENODATA;
+ }
+ case BTF_KIND_ENUM:
+ if (btf_dump_get_enum_value(d, t, data, id, &value))
+ return 0;
+ if (value == 0)
+ return -ENODATA;
+ return 0;
+ default:
+ return 0;
+ }
+}
+
+/* returns size of data dumped, or error. */
+static int btf_dump_dump_type_data(struct btf_dump *d,
+ const char *fname,
+ const struct btf_type *t,
+ __u32 id,
+ const void *data,
+ __u8 bits_offset,
+ __u8 bit_sz)
+{
+ int size, err;
+
+ size = btf_dump_type_data_check_overflow(d, t, id, data, bits_offset);
+ if (size < 0)
+ return size;
+ err = btf_dump_type_data_check_zero(d, t, id, data, bits_offset, bit_sz);
+ if (err) {
+ /* zeroed data is expected and not an error, so simply skip
+ * dumping such data. Record other errors however.
+ */
+ if (err == -ENODATA)
+ return size;
+ return err;
+ }
+ btf_dump_data_pfx(d);
+
+ if (!d->typed_dump->skip_names) {
+ if (fname && strlen(fname) > 0)
+ btf_dump_printf(d, ".%s = ", fname);
+ btf_dump_emit_type_cast(d, id, true);
+ }
+
+ t = skip_mods_and_typedefs(d->btf, id, NULL);
+
+ switch (btf_kind(t)) {
+ case BTF_KIND_UNKN:
+ case BTF_KIND_FWD:
+ case BTF_KIND_FUNC:
+ case BTF_KIND_FUNC_PROTO:
+ err = btf_dump_unsupported_data(d, t, id);
+ break;
+ case BTF_KIND_INT:
+ if (bit_sz)
+ err = btf_dump_bitfield_data(d, t, data, bits_offset, bit_sz);
+ else
+ err = btf_dump_int_data(d, t, id, data, bits_offset);
+ break;
+ case BTF_KIND_FLOAT:
+ err = btf_dump_float_data(d, t, id, data);
+ break;
+ case BTF_KIND_PTR:
+ err = btf_dump_ptr_data(d, t, id, data);
+ break;
+ case BTF_KIND_ARRAY:
+ err = btf_dump_array_data(d, t, id, data);
+ break;
+ case BTF_KIND_STRUCT:
+ case BTF_KIND_UNION:
+ err = btf_dump_struct_data(d, t, id, data);
+ break;
+ case BTF_KIND_ENUM:
+ /* handle bitfield and int enum values */
+ if (bit_sz) {
+ unsigned __int128 print_num;
+ __s64 enum_val;
+
+ print_num = btf_dump_bitfield_get_data(d, t, data, bits_offset, bit_sz);
+ enum_val = (__s64)print_num;
+ err = btf_dump_enum_data(d, t, id, &enum_val);
+ } else
+ err = btf_dump_enum_data(d, t, id, data);
+ break;
+ case BTF_KIND_VAR:
+ err = btf_dump_var_data(d, t, id, data);
+ break;
+ case BTF_KIND_DATASEC:
+ err = btf_dump_datasec_data(d, t, id, data);
+ break;
+ default:
+ pr_warn("unexpected kind [%u] for id [%u]\n",
+ BTF_INFO_KIND(t->info), id);
+ return -EINVAL;
+ }
+ if (err < 0)
+ return err;
+ return size;
+}
+
+int btf_dump__dump_type_data(struct btf_dump *d, __u32 id,
+ const void *data, size_t data_sz,
+ const struct btf_dump_type_data_opts *opts)
+{
+ const struct btf_type *t;
+ int ret;
+
+ if (!OPTS_VALID(opts, btf_dump_type_data_opts))
+ return libbpf_err(-EINVAL);
+
+ t = btf__type_by_id(d->btf, id);
+ if (!t)
+ return libbpf_err(-ENOENT);
+
+ d->typed_dump = calloc(1, sizeof(struct btf_dump_data));
+ if (!d->typed_dump)
+ return libbpf_err(-ENOMEM);
+
+ d->typed_dump->data_end = data + data_sz;
+ d->typed_dump->indent_lvl = OPTS_GET(opts, indent_level, 0);
+ /* default indent string is a tab */
+ if (!opts->indent_str)
+ d->typed_dump->indent_str[0] = '\t';
+ else
+ strncat(d->typed_dump->indent_str, opts->indent_str,
+ sizeof(d->typed_dump->indent_str) - 1);
+
+ d->typed_dump->compact = OPTS_GET(opts, compact, false);
+ d->typed_dump->skip_names = OPTS_GET(opts, skip_names, false);
+ d->typed_dump->emit_zeroes = OPTS_GET(opts, emit_zeroes, false);
+
+ ret = btf_dump_dump_type_data(d, NULL, t, id, data, 0, 0);
+
+ free(d->typed_dump);
+
+ return libbpf_err(ret);
+}
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 944c99d..5bfc107 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -373,5 +373,6 @@ LIBBPF_0.5.0 {
bpf_map__initial_value;
bpf_map_lookup_and_delete_elem_flags;
bpf_object__gen_loader;
+ btf_dump__dump_type_data;
libbpf_set_strict_mode;
} LIBBPF_0.4.0;
--
1.8.3.1
On Thu, Jul 15, 2021 at 8:15 AM Alan Maguire <[email protected]> wrote:
>
> Add a BTF dumper for typed data, so that the user can dump a typed
> version of the data provided.
>
> The API is
>
> int btf_dump__dump_type_data(struct btf_dump *d, __u32 id,
> void *data, size_t data_sz,
> const struct btf_dump_type_data_opts *opts);
>
> ...where the id is the BTF id of the data pointed to by the "void *"
> argument; for example the BTF id of "struct sk_buff" for a
> "struct skb *" data pointer. Options supported are
>
> - a starting indent level (indent_lvl)
> - a user-specified indent string which will be printed once per
> indent level; if NULL, tab is chosen but any string <= 32 chars
> can be provided.
> - a set of boolean options to control dump display, similar to those
> used for BPF helper bpf_snprintf_btf(). Options are
> - compact : omit newlines and other indentation
> - skip_names: omit member names
> - emit_zeroes: show zero-value members
>
> Default output format is identical to that dumped by bpf_snprintf_btf(),
> for example a "struct sk_buff" representation would look like this:
>
> struct sk_buff){
> (union){
> (struct){
> .next = (struct sk_buff *)0xffffffffffffffff,
> .prev = (struct sk_buff *)0xffffffffffffffff,
> (union){
> .dev = (struct net_device *)0xffffffffffffffff,
> .dev_scratch = (long unsigned int)18446744073709551615,
> },
> },
> ...
>
> If the data structure is larger than the *data_sz*
> number of bytes that are available in *data*, as much
> of the data as possible will be dumped and -E2BIG will
> be returned. This is useful as tracers will sometimes
> not be able to capture all of the data associated with
> a type; for example a "struct task_struct" is ~16k.
> Being able to specify that only a subset is available is
> important for such cases. On success, the amount of data
> dumped is returned.
>
> Signed-off-by: Alan Maguire <[email protected]>
> ---
Ok, this looks great. I think I found a few residual problems, so
please see comments below and address them. But I'm inclined to land
this patch set as is because it's in a good shape already, and it is
pretty, so it's hard and time-consuming to weed through minor (at this
point) changes between versions. So please send follow-up patch(es)
with fixes. Hopefully soon enough before the libbpf release. Thanks a
lot for working on this and persevering, this is a great API!
I'll apply a patch set to bpf-next when it will open up for new patches. Thanks.
> tools/lib/bpf/btf.h | 19 ++
> tools/lib/bpf/btf_dump.c | 819 ++++++++++++++++++++++++++++++++++++++++++++++-
> tools/lib/bpf/libbpf.map | 1 +
> 3 files changed, 834 insertions(+), 5 deletions(-)
I also wanted to call out this ^^ versus:
a) initial kernel-sharing version:
> 18 files changed, 3236 insertions(+), 1319 deletions(-)
b) initial libbpf-only version:
> 6 files changed, 1251 insertions(+), 3 deletions(-)
And the API actually gained in supported features and correctness.
>
[...]
> +
> +union float_data {
> + long double ld;
> + double d;
> + float f;
> +};
clever
> +
> +static int btf_dump_float_data(struct btf_dump *d,
> + const struct btf_type *t,
> + __u32 type_id,
> + const void *data)
> +{
> + const union float_data *flp = data;
> + union float_data fl;
> + int sz = t->size;
> +
> + /* handle unaligned data; copy to local union */
> + if (((uintptr_t)data) % sz) {
> + memcpy(&fl, data, sz);
> + flp = &fl;
> + }
> +
> + switch (sz) {
> + case 16:
> + btf_dump_type_values(d, "%Lf", flp->ld);
> + break;
> + case 8:
> + btf_dump_type_values(d, "%lf", flp->d);
> + break;
> + case 4:
> + btf_dump_type_values(d, "%f", flp->f);
> + break;
> + default:
> + pr_warn("unexpected size %d for id [%u]\n", sz, type_id);
> + return -EINVAL;
> + }
> + return 0;
> +}
> +
[...]
> +
> +static int btf_dump_array_data(struct btf_dump *d,
> + const struct btf_type *t,
> + __u32 id,
> + const void *data)
> +{
> + const struct btf_array *array = btf_array(t);
> + const struct btf_type *elem_type;
> + __u32 i, elem_size = 0, elem_type_id;
> + bool is_array_member;
> +
> + elem_type_id = array->type;
> + elem_type = skip_mods_and_typedefs(d->btf, elem_type_id, NULL);
> + elem_size = btf__resolve_size(d->btf, elem_type_id);
> + if (elem_size <= 0) {
> + pr_warn("unexpected elem size %d for array type [%u]\n", elem_size, id);
> + return -EINVAL;
> + }
> +
> + if (btf_is_int(elem_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)
> + d->typed_dump->is_array_char = true;
> + }
> +
> + /* note that we increment depth before calling btf_dump_print() below;
> + * this is intentional. btf_dump_data_newline() will not print a
> + * newline for depth 0 (since this leaves us with trailing newlines
> + * at the end of typed display), so depth is incremented first.
> + * For similar reasons, we decrement depth before showing the closing
> + * parenthesis.
> + */
> + d->typed_dump->depth++;
> + btf_dump_printf(d, "[%s", btf_dump_data_newline(d));
> +
> + /* may be a multidimensional array, so store current "is array member"
> + * status so we can restore it correctly later.
> + */
> + is_array_member = d->typed_dump->is_array_member;
> + d->typed_dump->is_array_member = true;
> + for (i = 0; i < array->nelems; i++, data += elem_size) {
> + if (d->typed_dump->is_array_terminated)
> + break;
I suspect this logic breaks for multi-dimensional char arrays. Please
check and add follow-up tests and fixes, no need to address that in
this patch set, you've suffered enough.
> + btf_dump_dump_type_data(d, NULL, elem_type, elem_type_id, data, 0, 0);
> + }
> + d->typed_dump->is_array_member = is_array_member;
> + d->typed_dump->depth--;
> + btf_dump_data_pfx(d);
> + btf_dump_type_values(d, "]");
> +
> + return 0;
> +}
> +
> +static int btf_dump_struct_data(struct btf_dump *d,
> + const struct btf_type *t,
> + __u32 id,
> + const void *data)
> +{
> + const struct btf_member *m = btf_members(t);
> + __u16 n = btf_vlen(t);
> + int i, err;
> +
> + /* note that we increment depth before calling btf_dump_print() below;
> + * this is intentional. btf_dump_data_newline() will not print a
> + * newline for depth 0 (since this leaves us with trailing newlines
> + * at the end of typed display), so depth is incremented first.
> + * For similar reasons, we decrement depth before showing the closing
> + * parenthesis.
> + */
ah, ok, I see. I sort of randomly stumbled on this from a purely
aesthetic reasons, but I'm happy we clarified this because it's
completely non-obvious
> + d->typed_dump->depth++;
> + btf_dump_printf(d, "{%s", btf_dump_data_newline(d));
> +
> + for (i = 0; i < n; i++, m++) {
> + const struct btf_type *mtype;
> + const char *mname;
> + __u32 moffset;
> + __u8 bit_sz;
> +
> + mtype = btf__type_by_id(d->btf, m->type);
> + mname = btf_name_of(d, m->name_off);
> + moffset = btf_member_bit_offset(t, i);
> +
> + bit_sz = btf_member_bitfield_size(t, i);
> + err = btf_dump_dump_type_data(d, mname, mtype, m->type, data + moffset / 8,
> + moffset % 8, bit_sz);
> + if (err < 0)
> + return err;
> + }
> + d->typed_dump->depth--;
> + btf_dump_data_pfx(d);
> + btf_dump_type_values(d, "}");
> + return err;
> +}
> +
> +static int btf_dump_ptr_data(struct btf_dump *d,
> + const struct btf_type *t,
> + __u32 id,
> + const void *data)
> +{
> + btf_dump_type_values(d, "%p", *(void **)data);
Wait, you fixed pointer zero checking logic and misaligned reads for
ints/floats, but none of that for actually printing pointers?...
Please send a follow-up fix.
> + return 0;
> +}
> +
> +static int btf_dump_get_enum_value(struct btf_dump *d,
> + const struct btf_type *t,
> + const void *data,
> + __u32 id,
> + __s64 *value)
> +{
> + int sz = t->size;
> +
> + /* handle unaligned enum value */
> + if (((uintptr_t)data) % sz) {
nit: probably worth a small helper with obvious name to avoid extra
comments and all those ((()))
> + *value = (__s64)btf_dump_bitfield_get_data(d, t, data, 0, 0);
> + return 0;
> + }
[...]
> + elem_type_id = array->type;
> + elem_size = btf__resolve_size(d->btf, elem_type_id);
> + elem_type = skip_mods_and_typedefs(d->btf, elem_type_id, NULL);
> +
> + ischar = btf_is_int(elem_type) && elem_size == 1;
> +
> + /* check all elements; if _any_ element is nonzero, all
> + * of array is displayed. We make an exception however
> + * for char arrays where the first element is 0; these
> + * are considered zeroed also, even if later elements are
> + * non-zero because the string is terminated.
> + */
> + for (i = 0; i < array->nelems; i++) {
> + if (i == 0 && ischar && *(char *)data == 0)
> + return -ENODATA;
same here, this might be too aggressive for something like char a[2][10] ?
> + err = btf_dump_type_data_check_zero(d, elem_type,
> + elem_type_id,
> + data +
> + (i * elem_size),
> + bits_offset, 0);
> + if (err != -ENODATA)
> + return err;
> + }
> + return -ENODATA;
> + }
> + case BTF_KIND_STRUCT:
> + case BTF_KIND_UNION: {
> + const struct btf_member *m = btf_members(t);
> + __u16 n = btf_vlen(t);
> +
> + /* if any struct/union member is non-zero, the struct/union
> + * is considered non-zero and dumped.
> + */
> + for (i = 0; i < n; i++, m++) {
> + const struct btf_type *mtype;
> + __u32 moffset;
> +
> + mtype = btf__type_by_id(d->btf, m->type);
> + moffset = btf_member_bit_offset(t, i);
> +
> + /* btf_int_bits() does not store member bitfield size;
> + * bitfield size needs to be stored here so int display
> + * of member can retrieve it.
> + */
> + bit_sz = btf_member_bitfield_size(t, i);
> + err = btf_dump_type_data_check_zero(d, mtype, m->type, data + moffset / 8,
> + moffset % 8, bit_sz);
> + if (err != ENODATA)
> + return err;
> + }
> + return -ENODATA;
> + }
> + case BTF_KIND_ENUM:
> + if (btf_dump_get_enum_value(d, t, data, id, &value))
> + return 0;
why not propagating error here?
> + if (value == 0)
> + return -ENODATA;
> + return 0;
> + default:
> + return 0;
> + }
> +}
> +
[...]
> + case BTF_KIND_ARRAY:
> + err = btf_dump_array_data(d, t, id, data);
> + break;
> + case BTF_KIND_STRUCT:
> + case BTF_KIND_UNION:
> + err = btf_dump_struct_data(d, t, id, data);
> + break;
> + case BTF_KIND_ENUM:
> + /* handle bitfield and int enum values */
> + if (bit_sz) {
> + unsigned __int128 print_num;
> + __s64 enum_val;
> +
> + print_num = btf_dump_bitfield_get_data(d, t, data, bits_offset, bit_sz);
> + enum_val = (__s64)print_num;
> + err = btf_dump_enum_data(d, t, id, &enum_val);
this is broken on big-endian, no? Basically almost always it will be
printing either 0, -1 or 0xffffffff?..
> + } else
> + err = btf_dump_enum_data(d, t, id, data);
> + break;
> + case BTF_KIND_VAR:
> + err = btf_dump_var_data(d, t, id, data);
> + break;
> + case BTF_KIND_DATASEC:
> + err = btf_dump_datasec_data(d, t, id, data);
> + break;
> + default:
> + pr_warn("unexpected kind [%u] for id [%u]\n",
> + BTF_INFO_KIND(t->info), id);
> + return -EINVAL;
> + }
> + if (err < 0)
> + return err;
> + return size;
> +}
> +
> +int btf_dump__dump_type_data(struct btf_dump *d, __u32 id,
> + const void *data, size_t data_sz,
> + const struct btf_dump_type_data_opts *opts)
> +{
> + const struct btf_type *t;
> + int ret;
> +
> + if (!OPTS_VALID(opts, btf_dump_type_data_opts))
> + return libbpf_err(-EINVAL);
> +
> + t = btf__type_by_id(d->btf, id);
> + if (!t)
> + return libbpf_err(-ENOENT);
> +
> + d->typed_dump = calloc(1, sizeof(struct btf_dump_data));
just realized this doesn't have to be calloc()'ed, it can be on the
stack zero-initialized variable; feel free to switch in the follow up
as well
> + if (!d->typed_dump)
> + return libbpf_err(-ENOMEM);
then we won't need to handle this at all
> +
> + d->typed_dump->data_end = data + data_sz;
> + d->typed_dump->indent_lvl = OPTS_GET(opts, indent_level, 0);
> + /* default indent string is a tab */
> + if (!opts->indent_str)
> + d->typed_dump->indent_str[0] = '\t';
[...]
On Thu, Jul 15, 2021 at 11:24 PM Andrii Nakryiko
<[email protected]> wrote:
>
> On Thu, Jul 15, 2021 at 8:15 AM Alan Maguire <[email protected]> wrote:
> >
> > Add a BTF dumper for typed data, so that the user can dump a typed
> > version of the data provided.
> >
> > The API is
> >
> > int btf_dump__dump_type_data(struct btf_dump *d, __u32 id,
> > void *data, size_t data_sz,
> > const struct btf_dump_type_data_opts *opts);
> >
> > ...where the id is the BTF id of the data pointed to by the "void *"
> > argument; for example the BTF id of "struct sk_buff" for a
> > "struct skb *" data pointer. Options supported are
> >
> > - a starting indent level (indent_lvl)
> > - a user-specified indent string which will be printed once per
> > indent level; if NULL, tab is chosen but any string <= 32 chars
> > can be provided.
> > - a set of boolean options to control dump display, similar to those
> > used for BPF helper bpf_snprintf_btf(). Options are
> > - compact : omit newlines and other indentation
> > - skip_names: omit member names
> > - emit_zeroes: show zero-value members
> >
> > Default output format is identical to that dumped by bpf_snprintf_btf(),
> > for example a "struct sk_buff" representation would look like this:
> >
> > struct sk_buff){
> > (union){
> > (struct){
> > .next = (struct sk_buff *)0xffffffffffffffff,
> > .prev = (struct sk_buff *)0xffffffffffffffff,
> > (union){
> > .dev = (struct net_device *)0xffffffffffffffff,
> > .dev_scratch = (long unsigned int)18446744073709551615,
> > },
> > },
> > ...
> >
> > If the data structure is larger than the *data_sz*
> > number of bytes that are available in *data*, as much
> > of the data as possible will be dumped and -E2BIG will
> > be returned. This is useful as tracers will sometimes
> > not be able to capture all of the data associated with
> > a type; for example a "struct task_struct" is ~16k.
> > Being able to specify that only a subset is available is
> > important for such cases. On success, the amount of data
> > dumped is returned.
> >
> > Signed-off-by: Alan Maguire <[email protected]>
> > ---
>
> Ok, this looks great. I think I found a few residual problems, so
> please see comments below and address them. But I'm inclined to land
> this patch set as is because it's in a good shape already, and it is
> pretty, so it's hard and time-consuming to weed through minor (at this
> point) changes between versions. So please send follow-up patch(es)
> with fixes. Hopefully soon enough before the libbpf release. Thanks a
> lot for working on this and persevering, this is a great API!
>
> I'll apply a patch set to bpf-next when it will open up for new patches. Thanks.
Applied to bpf-next.
>
> > tools/lib/bpf/btf.h | 19 ++
> > tools/lib/bpf/btf_dump.c | 819 ++++++++++++++++++++++++++++++++++++++++++++++-
> > tools/lib/bpf/libbpf.map | 1 +
> > 3 files changed, 834 insertions(+), 5 deletions(-)
>
> I also wanted to call out this ^^ versus:
>
> a) initial kernel-sharing version:
>
> > 18 files changed, 3236 insertions(+), 1319 deletions(-)
>
> b) initial libbpf-only version:
>
> > 6 files changed, 1251 insertions(+), 3 deletions(-)
>
> And the API actually gained in supported features and correctness.
>
> >
>
> [...]
>
> > +
> > +union float_data {
> > + long double ld;
> > + double d;
> > + float f;
> > +};
>
> clever
>
> > +
> > +static int btf_dump_float_data(struct btf_dump *d,
> > + const struct btf_type *t,
> > + __u32 type_id,
> > + const void *data)
> > +{
> > + const union float_data *flp = data;
> > + union float_data fl;
> > + int sz = t->size;
> > +
> > + /* handle unaligned data; copy to local union */
> > + if (((uintptr_t)data) % sz) {
> > + memcpy(&fl, data, sz);
> > + flp = &fl;
> > + }
> > +
> > + switch (sz) {
> > + case 16:
> > + btf_dump_type_values(d, "%Lf", flp->ld);
> > + break;
> > + case 8:
> > + btf_dump_type_values(d, "%lf", flp->d);
> > + break;
> > + case 4:
> > + btf_dump_type_values(d, "%f", flp->f);
> > + break;
> > + default:
> > + pr_warn("unexpected size %d for id [%u]\n", sz, type_id);
> > + return -EINVAL;
> > + }
> > + return 0;
> > +}
> > +
>
> [...]
>
> > +
> > +static int btf_dump_array_data(struct btf_dump *d,
> > + const struct btf_type *t,
> > + __u32 id,
> > + const void *data)
> > +{
> > + const struct btf_array *array = btf_array(t);
> > + const struct btf_type *elem_type;
> > + __u32 i, elem_size = 0, elem_type_id;
> > + bool is_array_member;
> > +
> > + elem_type_id = array->type;
> > + elem_type = skip_mods_and_typedefs(d->btf, elem_type_id, NULL);
> > + elem_size = btf__resolve_size(d->btf, elem_type_id);
> > + if (elem_size <= 0) {
> > + pr_warn("unexpected elem size %d for array type [%u]\n", elem_size, id);
> > + return -EINVAL;
> > + }
> > +
> > + if (btf_is_int(elem_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)
> > + d->typed_dump->is_array_char = true;
> > + }
> > +
> > + /* note that we increment depth before calling btf_dump_print() below;
> > + * this is intentional. btf_dump_data_newline() will not print a
> > + * newline for depth 0 (since this leaves us with trailing newlines
> > + * at the end of typed display), so depth is incremented first.
> > + * For similar reasons, we decrement depth before showing the closing
> > + * parenthesis.
> > + */
> > + d->typed_dump->depth++;
> > + btf_dump_printf(d, "[%s", btf_dump_data_newline(d));
> > +
> > + /* may be a multidimensional array, so store current "is array member"
> > + * status so we can restore it correctly later.
> > + */
> > + is_array_member = d->typed_dump->is_array_member;
> > + d->typed_dump->is_array_member = true;
> > + for (i = 0; i < array->nelems; i++, data += elem_size) {
> > + if (d->typed_dump->is_array_terminated)
> > + break;
>
> I suspect this logic breaks for multi-dimensional char arrays. Please
> check and add follow-up tests and fixes, no need to address that in
> this patch set, you've suffered enough.
>
>
> > + btf_dump_dump_type_data(d, NULL, elem_type, elem_type_id, data, 0, 0);
> > + }
> > + d->typed_dump->is_array_member = is_array_member;
> > + d->typed_dump->depth--;
> > + btf_dump_data_pfx(d);
> > + btf_dump_type_values(d, "]");
> > +
> > + return 0;
> > +}
> > +
> > +static int btf_dump_struct_data(struct btf_dump *d,
> > + const struct btf_type *t,
> > + __u32 id,
> > + const void *data)
> > +{
> > + const struct btf_member *m = btf_members(t);
> > + __u16 n = btf_vlen(t);
> > + int i, err;
> > +
> > + /* note that we increment depth before calling btf_dump_print() below;
> > + * this is intentional. btf_dump_data_newline() will not print a
> > + * newline for depth 0 (since this leaves us with trailing newlines
> > + * at the end of typed display), so depth is incremented first.
> > + * For similar reasons, we decrement depth before showing the closing
> > + * parenthesis.
> > + */
>
> ah, ok, I see. I sort of randomly stumbled on this from a purely
> aesthetic reasons, but I'm happy we clarified this because it's
> completely non-obvious
>
> > + d->typed_dump->depth++;
> > + btf_dump_printf(d, "{%s", btf_dump_data_newline(d));
> > +
> > + for (i = 0; i < n; i++, m++) {
> > + const struct btf_type *mtype;
> > + const char *mname;
> > + __u32 moffset;
> > + __u8 bit_sz;
> > +
> > + mtype = btf__type_by_id(d->btf, m->type);
> > + mname = btf_name_of(d, m->name_off);
> > + moffset = btf_member_bit_offset(t, i);
> > +
> > + bit_sz = btf_member_bitfield_size(t, i);
> > + err = btf_dump_dump_type_data(d, mname, mtype, m->type, data + moffset / 8,
> > + moffset % 8, bit_sz);
> > + if (err < 0)
> > + return err;
> > + }
> > + d->typed_dump->depth--;
> > + btf_dump_data_pfx(d);
> > + btf_dump_type_values(d, "}");
> > + return err;
> > +}
> > +
> > +static int btf_dump_ptr_data(struct btf_dump *d,
> > + const struct btf_type *t,
> > + __u32 id,
> > + const void *data)
> > +{
> > + btf_dump_type_values(d, "%p", *(void **)data);
>
> Wait, you fixed pointer zero checking logic and misaligned reads for
> ints/floats, but none of that for actually printing pointers?...
> Please send a follow-up fix.
>
> > + return 0;
> > +}
> > +
> > +static int btf_dump_get_enum_value(struct btf_dump *d,
> > + const struct btf_type *t,
> > + const void *data,
> > + __u32 id,
> > + __s64 *value)
> > +{
> > + int sz = t->size;
> > +
> > + /* handle unaligned enum value */
> > + if (((uintptr_t)data) % sz) {
>
> nit: probably worth a small helper with obvious name to avoid extra
> comments and all those ((()))
>
> > + *value = (__s64)btf_dump_bitfield_get_data(d, t, data, 0, 0);
> > + return 0;
> > + }
>
> [...]
>
> > + elem_type_id = array->type;
> > + elem_size = btf__resolve_size(d->btf, elem_type_id);
> > + elem_type = skip_mods_and_typedefs(d->btf, elem_type_id, NULL);
> > +
> > + ischar = btf_is_int(elem_type) && elem_size == 1;
> > +
> > + /* check all elements; if _any_ element is nonzero, all
> > + * of array is displayed. We make an exception however
> > + * for char arrays where the first element is 0; these
> > + * are considered zeroed also, even if later elements are
> > + * non-zero because the string is terminated.
> > + */
> > + for (i = 0; i < array->nelems; i++) {
> > + if (i == 0 && ischar && *(char *)data == 0)
> > + return -ENODATA;
>
> same here, this might be too aggressive for something like char a[2][10] ?
>
> > + err = btf_dump_type_data_check_zero(d, elem_type,
> > + elem_type_id,
> > + data +
> > + (i * elem_size),
> > + bits_offset, 0);
> > + if (err != -ENODATA)
> > + return err;
> > + }
> > + return -ENODATA;
> > + }
> > + case BTF_KIND_STRUCT:
> > + case BTF_KIND_UNION: {
> > + const struct btf_member *m = btf_members(t);
> > + __u16 n = btf_vlen(t);
> > +
> > + /* if any struct/union member is non-zero, the struct/union
> > + * is considered non-zero and dumped.
> > + */
> > + for (i = 0; i < n; i++, m++) {
> > + const struct btf_type *mtype;
> > + __u32 moffset;
> > +
> > + mtype = btf__type_by_id(d->btf, m->type);
> > + moffset = btf_member_bit_offset(t, i);
> > +
> > + /* btf_int_bits() does not store member bitfield size;
> > + * bitfield size needs to be stored here so int display
> > + * of member can retrieve it.
> > + */
> > + bit_sz = btf_member_bitfield_size(t, i);
> > + err = btf_dump_type_data_check_zero(d, mtype, m->type, data + moffset / 8,
> > + moffset % 8, bit_sz);
> > + if (err != ENODATA)
> > + return err;
> > + }
> > + return -ENODATA;
> > + }
> > + case BTF_KIND_ENUM:
> > + if (btf_dump_get_enum_value(d, t, data, id, &value))
> > + return 0;
>
> why not propagating error here?
>
> > + if (value == 0)
> > + return -ENODATA;
> > + return 0;
> > + default:
> > + return 0;
> > + }
> > +}
> > +
>
> [...]
>
> > + case BTF_KIND_ARRAY:
> > + err = btf_dump_array_data(d, t, id, data);
> > + break;
> > + case BTF_KIND_STRUCT:
> > + case BTF_KIND_UNION:
> > + err = btf_dump_struct_data(d, t, id, data);
> > + break;
> > + case BTF_KIND_ENUM:
> > + /* handle bitfield and int enum values */
> > + if (bit_sz) {
> > + unsigned __int128 print_num;
> > + __s64 enum_val;
> > +
> > + print_num = btf_dump_bitfield_get_data(d, t, data, bits_offset, bit_sz);
> > + enum_val = (__s64)print_num;
> > + err = btf_dump_enum_data(d, t, id, &enum_val);
>
> this is broken on big-endian, no? Basically almost always it will be
> printing either 0, -1 or 0xffffffff?..
>
> > + } else
> > + err = btf_dump_enum_data(d, t, id, data);
> > + break;
> > + case BTF_KIND_VAR:
> > + err = btf_dump_var_data(d, t, id, data);
> > + break;
> > + case BTF_KIND_DATASEC:
> > + err = btf_dump_datasec_data(d, t, id, data);
> > + break;
> > + default:
> > + pr_warn("unexpected kind [%u] for id [%u]\n",
> > + BTF_INFO_KIND(t->info), id);
> > + return -EINVAL;
> > + }
> > + if (err < 0)
> > + return err;
> > + return size;
> > +}
> > +
> > +int btf_dump__dump_type_data(struct btf_dump *d, __u32 id,
> > + const void *data, size_t data_sz,
> > + const struct btf_dump_type_data_opts *opts)
> > +{
> > + const struct btf_type *t;
> > + int ret;
> > +
> > + if (!OPTS_VALID(opts, btf_dump_type_data_opts))
> > + return libbpf_err(-EINVAL);
> > +
> > + t = btf__type_by_id(d->btf, id);
> > + if (!t)
> > + return libbpf_err(-ENOENT);
> > +
> > + d->typed_dump = calloc(1, sizeof(struct btf_dump_data));
>
> just realized this doesn't have to be calloc()'ed, it can be on the
> stack zero-initialized variable; feel free to switch in the follow up
> as well
>
> > + if (!d->typed_dump)
> > + return libbpf_err(-ENOMEM);
>
> then we won't need to handle this at all
>
> > +
> > + d->typed_dump->data_end = data + data_sz;
> > + d->typed_dump->indent_lvl = OPTS_GET(opts, indent_level, 0);
> > + /* default indent string is a tab */
> > + if (!opts->indent_str)
> > + d->typed_dump->indent_str[0] = '\t';
>
> [...]
On Thu, Jul 15, 2021 at 8:15 AM Alan Maguire <[email protected]> wrote:
>
> Add a BTF dumper for typed data, so that the user can dump a typed
> version of the data provided.
>
> The API is
>
> int btf_dump__dump_type_data(struct btf_dump *d, __u32 id,
> void *data, size_t data_sz,
> const struct btf_dump_type_data_opts *opts);
>
> ...where the id is the BTF id of the data pointed to by the "void *"
> argument; for example the BTF id of "struct sk_buff" for a
> "struct skb *" data pointer. Options supported are
>
> - a starting indent level (indent_lvl)
> - a user-specified indent string which will be printed once per
> indent level; if NULL, tab is chosen but any string <= 32 chars
> can be provided.
> - a set of boolean options to control dump display, similar to those
> used for BPF helper bpf_snprintf_btf(). Options are
> - compact : omit newlines and other indentation
> - skip_names: omit member names
> - emit_zeroes: show zero-value members
>
> Default output format is identical to that dumped by bpf_snprintf_btf(),
> for example a "struct sk_buff" representation would look like this:
>
> struct sk_buff){
> (union){
> (struct){
> .next = (struct sk_buff *)0xffffffffffffffff,
> .prev = (struct sk_buff *)0xffffffffffffffff,
> (union){
> .dev = (struct net_device *)0xffffffffffffffff,
> .dev_scratch = (long unsigned int)18446744073709551615,
> },
> },
> ...
>
> If the data structure is larger than the *data_sz*
> number of bytes that are available in *data*, as much
> of the data as possible will be dumped and -E2BIG will
> be returned. This is useful as tracers will sometimes
> not be able to capture all of the data associated with
> a type; for example a "struct task_struct" is ~16k.
> Being able to specify that only a subset is available is
> important for such cases. On success, the amount of data
> dumped is returned.
>
> Signed-off-by: Alan Maguire <[email protected]>
> ---
> tools/lib/bpf/btf.h | 19 ++
> tools/lib/bpf/btf_dump.c | 819 ++++++++++++++++++++++++++++++++++++++++++++++-
> tools/lib/bpf/libbpf.map | 1 +
> 3 files changed, 834 insertions(+), 5 deletions(-)
>
[...]
> +/* return size of type, or if base type overflows, return -E2BIG. */
> +static int btf_dump_type_data_check_overflow(struct btf_dump *d,
> + const struct btf_type *t,
> + __u32 id,
> + const void *data,
> + __u8 bits_offset)
> +{
> + __s64 size = btf__resolve_size(d->btf, id);
> +
> + if (size < 0 || size >= INT_MAX) {
> + pr_warn("unexpected size [%lld] for id [%u]\n",
> + size, id);
ppc64le arch doesn't like the %lld:
In file included from btf_dump.c:22:
btf_dump.c: In function 'btf_dump_type_data_check_overflow':
libbpf_internal.h:111:22: error: format '%lld' expects argument of
type 'long long int', but argument 3 has type '__s64' {aka 'long int'}
[-Werror=format=]
111 | libbpf_print(level, "libbpf: " fmt, ##__VA_ARGS__); \
| ^~~~~~~~~~
libbpf_internal.h:114:27: note: in expansion of macro '__pr'
114 | #define pr_warn(fmt, ...) __pr(LIBBPF_WARN, fmt, ##__VA_ARGS__)
| ^~~~
btf_dump.c:1992:3: note: in expansion of macro 'pr_warn'
1992 | pr_warn("unexpected size [%lld] for id [%u]\n",
| ^~~~~~~
btf_dump.c:1992:32: note: format string is defined here
1992 | pr_warn("unexpected size [%lld] for id [%u]\n",
| ~~~^
| |
| long long int
| %ld
Cast to size_t and use %zu.
> + return -EINVAL;
> + }
> +
[...]
On Thu, 15 Jul 2021 at 20:46, Alan Maguire <[email protected]> wrote:
>
> Add a BTF dumper for typed data, so that the user can dump a typed
> version of the data provided.
>
> The API is
>
> int btf_dump__dump_type_data(struct btf_dump *d, __u32 id,
> void *data, size_t data_sz,
> const struct btf_dump_type_data_opts *opts);
>
> ...where the id is the BTF id of the data pointed to by the "void *"
> argument; for example the BTF id of "struct sk_buff" for a
> "struct skb *" data pointer. Options supported are
>
> - a starting indent level (indent_lvl)
> - a user-specified indent string which will be printed once per
> indent level; if NULL, tab is chosen but any string <= 32 chars
> can be provided.
> - a set of boolean options to control dump display, similar to those
> used for BPF helper bpf_snprintf_btf(). Options are
> - compact : omit newlines and other indentation
> - skip_names: omit member names
> - emit_zeroes: show zero-value members
>
> Default output format is identical to that dumped by bpf_snprintf_btf(),
> for example a "struct sk_buff" representation would look like this:
>
> struct sk_buff){
> (union){
> (struct){
> .next = (struct sk_buff *)0xffffffffffffffff,
> .prev = (struct sk_buff *)0xffffffffffffffff,
> (union){
> .dev = (struct net_device *)0xffffffffffffffff,
> .dev_scratch = (long unsigned int)18446744073709551615,
> },
> },
> ...
>
> If the data structure is larger than the *data_sz*
> number of bytes that are available in *data*, as much
> of the data as possible will be dumped and -E2BIG will
> be returned. This is useful as tracers will sometimes
> not be able to capture all of the data associated with
> a type; for example a "struct task_struct" is ~16k.
> Being able to specify that only a subset is available is
> important for such cases. On success, the amount of data
> dumped is returned.
>
> Signed-off-by: Alan Maguire <[email protected]>
> ---
> tools/lib/bpf/btf.h | 19 ++
> tools/lib/bpf/btf_dump.c | 819 ++++++++++++++++++++++++++++++++++++++++++++++-
> tools/lib/bpf/libbpf.map | 1 +
> 3 files changed, 834 insertions(+), 5 deletions(-)
<trim>
> diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
> index 5dc6b517..929cf93 100644
> --- a/tools/lib/bpf/btf_dump.c
> +++ b/tools/lib/bpf/btf_dump.c
Following perf build errors noticed on i386 and arm 32-bit architectures on
linux next 20210719 tag with gcc-11.
metadata:
--------------
git_repo: https://gitlab.com/Linaro/lkft/mirrors/next/linux-next
git_short_log: 08076eab6fef ( Add linux-next specific files for 20210719 )
toolchain: gcc-11
target_arch: arm and i386
> +static void btf_dump_int128(struct btf_dump *d,
> + const struct btf_type *t,
> + const void *data)
> +{
> + __int128 num = *(__int128 *)data;
btf_dump.c: In function 'btf_dump_int128':
btf_dump.c:1559:9: error: expected expression before '__int128'
1559 | __int128 num = *(__int128 *)data;
| ^~~~~~~~
btf_dump.c:1561:14: error: 'num' undeclared (first use in this function)
1561 | if ((num >> 64) == 0)
| ^~~
btf_dump.c:1561:14: note: each undeclared identifier is reported only
once for each function it appears in
btf_dump.c: At top level:
btf_dump.c:1568:17: error: '__int128' is not supported on this target
1568 | static unsigned __int128 btf_dump_bitfield_get_data(struct btf_dump *d,
| ^~~~~~~~
btf_dump.c: In function 'btf_dump_bitfield_get_data':
btf_dump.c:1576:18: error: '__int128' is not supported on this target
1576 | unsigned __int128 num = 0, ret;
| ^~~~~~~~
btf_dump.c: In function 'btf_dump_bitfield_check_zero':
btf_dump.c:1608:9: error: expected expression before '__int128'
1608 | __int128 check_num;
| ^~~~~~~~
btf_dump.c:1610:9: error: 'check_num' undeclared (first use in this function)
1610 | check_num = btf_dump_bitfield_get_data(d, t, data,
bits_offset, bit_sz);
| ^~~~~~~~~
btf_dump.c: In function 'btf_dump_bitfield_data':
btf_dump.c:1622:18: error: '__int128' is not supported on this target
1622 | unsigned __int128 print_num;
| ^~~~~~~~
btf_dump.c: In function 'btf_dump_dump_type_data':
btf_dump.c:2212:34: error: '__int128' is not supported on this target
2212 | unsigned __int128 print_num;
| ^~~~~~~~
Reported-by: Linux Kernel Functional Testing <[email protected]>
reference build link,
build: https://builds.tuxbuild.com/1vWeCpIox9EoV35c80bwOvU9nbb/
config: https://builds.tuxbuild.com/1vWeCpIox9EoV35c80bwOvU9nbb/config
steps to reproduce:
---------------------
# TuxMake is a command line tool and Python library that provides
# portable and repeatable Linux kernel builds across a variety of
# architectures, toolchains, kernel configurations, and make targets.
#
# TuxMake supports the concept of runtimes.
# See https://docs.tuxmake.org/runtimes/, for that to work it requires
# that you install podman or docker on your system.
#
# To install tuxmake on your system globally:
# sudo pip3 install -U tuxmake
#
# See https://docs.tuxmake.org/ for complete documentation.
tuxmake --runtime podman --target-arch arm --toolchain gcc-11
--kconfig defconfig --kconfig-add
https://builds.tuxbuild.com/1vWeCpIox9EoV35c80bwOvU9nbb/config
--
Linaro LKFT
https://lkft.linaro.org
On Mon, 19 Jul 2021, Naresh Kamboju wrote:
> On Thu, 15 Jul 2021 at 20:46, Alan Maguire <[email protected]> wrote:
> >
> > Add a BTF dumper for typed data, so that the user can dump a typed
> > version of the data provided.
>
> <trim>
>
> > diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
> > index 5dc6b517..929cf93 100644
> > --- a/tools/lib/bpf/btf_dump.c
> > +++ b/tools/lib/bpf/btf_dump.c
>
>
> Following perf build errors noticed on i386 and arm 32-bit architectures on
> linux next 20210719 tag with gcc-11.
>
> metadata:
> --------------
> git_repo: https://gitlab.com/Linaro/lkft/mirrors/next/linux-next
> git_short_log: 08076eab6fef ( Add linux-next specific files for 20210719 )
> toolchain: gcc-11
> target_arch: arm and i386
>
>
> > +static void btf_dump_int128(struct btf_dump *d,
> > + const struct btf_type *t,
> > + const void *data)
> > +{
> > + __int128 num = *(__int128 *)data;
>
>
> btf_dump.c: In function 'btf_dump_int128':
> btf_dump.c:1559:9: error: expected expression before '__int128'
> 1559 | __int128 num = *(__int128 *)data;
> | ^~~~~~~~
> btf_dump.c:1561:14: error: 'num' undeclared (first use in this function)
> 1561 | if ((num >> 64) == 0)
> | ^~~
> btf_dump.c:1561:14: note: each undeclared identifier is reported only
> once for each function it appears in
> btf_dump.c: At top level:
> btf_dump.c:1568:17: error: '__int128' is not supported on this target
> 1568 | static unsigned __int128 btf_dump_bitfield_get_data(struct btf_dump *d,
> | ^~~~~~~~
> btf_dump.c: In function 'btf_dump_bitfield_get_data':
> btf_dump.c:1576:18: error: '__int128' is not supported on this target
> 1576 | unsigned __int128 num = 0, ret;
> | ^~~~~~~~
> btf_dump.c: In function 'btf_dump_bitfield_check_zero':
> btf_dump.c:1608:9: error: expected expression before '__int128'
> 1608 | __int128 check_num;
> | ^~~~~~~~
> btf_dump.c:1610:9: error: 'check_num' undeclared (first use in this function)
> 1610 | check_num = btf_dump_bitfield_get_data(d, t, data,
> bits_offset, bit_sz);
> | ^~~~~~~~~
> btf_dump.c: In function 'btf_dump_bitfield_data':
> btf_dump.c:1622:18: error: '__int128' is not supported on this target
> 1622 | unsigned __int128 print_num;
> | ^~~~~~~~
> btf_dump.c: In function 'btf_dump_dump_type_data':
> btf_dump.c:2212:34: error: '__int128' is not supported on this target
> 2212 | unsigned __int128 print_num;
> | ^~~~~~~~
>
>
Thanks for the report Naresh! Andrii, I'm thinking the best
approach might be to remove use of int128 and have the bitfield
computations operate on a __u64 representation instead. With
that change, we would only lose the ability to handle int128
bitfields; what do you think? I hope to have something ready
shortly covering that, the non-propogation of return values
and the endianness issues with enum handling - in fact the
latter goes away if the bitfield computations are done for
64-bit values.
Thanks!
Alan