This patch set adds BTF generation for kernel modules using a compact split
BTF approach. Respective patches have all the details.
Kernel module BTFs rely on pahole's split BTF support, which is added in [0]
and will be available starting from v1.19. Support for it is detected
automatically during kernel build time.
This patch set implements in-kernel support for split BTF loading and
validation. It also extends GET_OBJ_INFO API for BTFs to return BTF's module
name and a flag whether BTF itself is in-kernel or user-provided. vmlinux BTF
is also exposed to user-space through the same BTF object iteration APIs.
Follow up patch set will utilize the fact that vmlinux and module BTFs now
have associated ID to provide ability to attach BPF fentry/fexit/etc programs
to functions defined in kernel modules.
bpftool is also extended to show module/vmlinux BTF's name.
[0] https://patchwork.kernel.org/project/netdevbpf/list/?series=378699&state=*
v2->v3:
- get rid of unnecessary gotos (Song);
v2->v1:
- drop WARNs, add fewer pr_warn()'s instead (Greg);
- properly initialize sysfs binary attribute structure (Greg);
- add __maybe_unused to any_section_objs, used conditionally by module BTF;
rfc->v1:
- CONFIG_DEBUG_INFO_BTF_MODULES is derived automatically (Alexei);
- vmlinux BTF now has explicit "vmlinux" name (Alexei);
- added sysfs ABI documentation for /sys/kernel/btf/<module> (Greg).
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Andrii Nakryiko (5):
bpf: add in-kernel split BTF support
bpf: assign ID to vmlinux BTF and return extra info for BTF in
GET_OBJ_INFO
kbuild: build kernel module BTFs if BTF is enabled and pahole supports
it
bpf: load and verify kernel module BTFs
tools/bpftool: add support for in-kernel and named BTF in `btf show`
Documentation/ABI/testing/sysfs-kernel-btf | 8 +
include/linux/bpf.h | 2 +
include/linux/module.h | 4 +
include/uapi/linux/bpf.h | 3 +
kernel/bpf/btf.c | 402 ++++++++++++++++++---
kernel/bpf/sysfs_btf.c | 2 +-
kernel/module.c | 32 ++
lib/Kconfig.debug | 9 +
scripts/Makefile.modfinal | 20 +-
tools/bpf/bpftool/btf.c | 28 +-
tools/include/uapi/linux/bpf.h | 3 +
11 files changed, 456 insertions(+), 57 deletions(-)
--
2.24.1
Adjust in-kernel BTF implementation to support a split BTF mode of operation.
Changes are mostly mirroring libbpf split BTF changes, with the exception of
start_id being 0 for in-kernel implementation due to simpler read-only mode.
Otherwise, for split BTF logic, most of the logic of jumping to base BTF,
where necessary, is encapsulated in few helper functions. Type numbering and
string offset in a split BTF are logically continuing where base BTF ends, so
most of the high-level logic is kept without changes.
Type verification and size resolution is only doing an added resolution of new
split BTF types and relies on already cached size and type resolution results
in the base BTF.
Signed-off-by: Andrii Nakryiko <[email protected]>
---
kernel/bpf/btf.c | 171 +++++++++++++++++++++++++++++++++--------------
1 file changed, 119 insertions(+), 52 deletions(-)
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index ed7d02e8bc93..894ee33f4c84 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -204,12 +204,17 @@ struct btf {
const char *strings;
void *nohdr_data;
struct btf_header hdr;
- u32 nr_types;
+ u32 nr_types; /* includes VOID for base BTF */
u32 types_size;
u32 data_size;
refcount_t refcnt;
u32 id;
struct rcu_head rcu;
+
+ /* split BTF support */
+ struct btf *base_btf;
+ u32 start_id; /* first type ID in this BTF (0 for base BTF) */
+ u32 start_str_off; /* first string offset (0 for base BTF) */
};
enum verifier_phase {
@@ -450,14 +455,27 @@ static bool btf_type_is_datasec(const struct btf_type *t)
return BTF_INFO_KIND(t->info) == BTF_KIND_DATASEC;
}
+static u32 btf_nr_types_total(const struct btf *btf)
+{
+ u32 total = 0;
+
+ while (btf) {
+ total += btf->nr_types;
+ btf = btf->base_btf;
+ }
+
+ return total;
+}
+
s32 btf_find_by_name_kind(const struct btf *btf, const char *name, u8 kind)
{
const struct btf_type *t;
const char *tname;
- u32 i;
+ u32 i, total;
- for (i = 1; i <= btf->nr_types; i++) {
- t = btf->types[i];
+ total = btf_nr_types_total(btf);
+ for (i = 1; i < total; i++) {
+ t = btf_type_by_id(btf, i);
if (BTF_INFO_KIND(t->info) != kind)
continue;
@@ -600,8 +618,14 @@ static const struct btf_kind_operations *btf_type_ops(const struct btf_type *t)
static bool btf_name_offset_valid(const struct btf *btf, u32 offset)
{
- return BTF_STR_OFFSET_VALID(offset) &&
- offset < btf->hdr.str_len;
+ if (!BTF_STR_OFFSET_VALID(offset))
+ return false;
+
+ while (offset < btf->start_str_off)
+ btf = btf->base_btf;
+
+ offset -= btf->start_str_off;
+ return offset < btf->hdr.str_len;
}
static bool __btf_name_char_ok(char c, bool first, bool dot_ok)
@@ -615,10 +639,22 @@ static bool __btf_name_char_ok(char c, bool first, bool dot_ok)
return true;
}
+static const char *btf_str_by_offset(const struct btf *btf, u32 offset)
+{
+ while (offset < btf->start_str_off)
+ btf = btf->base_btf;
+
+ offset -= btf->start_str_off;
+ if (offset < btf->hdr.str_len)
+ return &btf->strings[offset];
+
+ return NULL;
+}
+
static bool __btf_name_valid(const struct btf *btf, u32 offset, bool dot_ok)
{
/* offset must be valid */
- const char *src = &btf->strings[offset];
+ const char *src = btf_str_by_offset(btf, offset);
const char *src_limit;
if (!__btf_name_char_ok(*src, true, dot_ok))
@@ -651,27 +687,28 @@ static bool btf_name_valid_section(const struct btf *btf, u32 offset)
static const char *__btf_name_by_offset(const struct btf *btf, u32 offset)
{
+ const char *name;
+
if (!offset)
return "(anon)";
- else if (offset < btf->hdr.str_len)
- return &btf->strings[offset];
- else
- return "(invalid-name-offset)";
+
+ name = btf_str_by_offset(btf, offset);
+ return name ?: "(invalid-name-offset)";
}
const char *btf_name_by_offset(const struct btf *btf, u32 offset)
{
- if (offset < btf->hdr.str_len)
- return &btf->strings[offset];
-
- return NULL;
+ return btf_str_by_offset(btf, offset);
}
const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id)
{
- if (type_id > btf->nr_types)
- return NULL;
+ while (type_id < btf->start_id)
+ btf = btf->base_btf;
+ type_id -= btf->start_id;
+ if (type_id >= btf->nr_types)
+ return NULL;
return btf->types[type_id];
}
@@ -1391,17 +1428,13 @@ static int btf_add_type(struct btf_verifier_env *env, struct btf_type *t)
{
struct btf *btf = env->btf;
- /* < 2 because +1 for btf_void which is always in btf->types[0].
- * btf_void is not accounted in btf->nr_types because btf_void
- * does not come from the BTF file.
- */
- if (btf->types_size - btf->nr_types < 2) {
+ if (btf->types_size == btf->nr_types) {
/* Expand 'types' array */
struct btf_type **new_types;
u32 expand_by, new_size;
- if (btf->types_size == BTF_MAX_TYPE) {
+ if (btf->start_id + btf->types_size == BTF_MAX_TYPE) {
btf_verifier_log(env, "Exceeded max num of types");
return -E2BIG;
}
@@ -1415,18 +1448,23 @@ static int btf_add_type(struct btf_verifier_env *env, struct btf_type *t)
if (!new_types)
return -ENOMEM;
- if (btf->nr_types == 0)
- new_types[0] = &btf_void;
- else
+ if (btf->nr_types == 0) {
+ if (!btf->base_btf) {
+ /* lazily init VOID type */
+ new_types[0] = &btf_void;
+ btf->nr_types++;
+ }
+ } else {
memcpy(new_types, btf->types,
- sizeof(*btf->types) * (btf->nr_types + 1));
+ sizeof(*btf->types) * btf->nr_types);
+ }
kvfree(btf->types);
btf->types = new_types;
btf->types_size = new_size;
}
- btf->types[++(btf->nr_types)] = t;
+ btf->types[btf->nr_types++] = t;
return 0;
}
@@ -1499,18 +1537,17 @@ static int env_resolve_init(struct btf_verifier_env *env)
u32 *resolved_ids = NULL;
u8 *visit_states = NULL;
- /* +1 for btf_void */
- resolved_sizes = kvcalloc(nr_types + 1, sizeof(*resolved_sizes),
+ resolved_sizes = kvcalloc(nr_types, sizeof(*resolved_sizes),
GFP_KERNEL | __GFP_NOWARN);
if (!resolved_sizes)
goto nomem;
- resolved_ids = kvcalloc(nr_types + 1, sizeof(*resolved_ids),
+ resolved_ids = kvcalloc(nr_types, sizeof(*resolved_ids),
GFP_KERNEL | __GFP_NOWARN);
if (!resolved_ids)
goto nomem;
- visit_states = kvcalloc(nr_types + 1, sizeof(*visit_states),
+ visit_states = kvcalloc(nr_types, sizeof(*visit_states),
GFP_KERNEL | __GFP_NOWARN);
if (!visit_states)
goto nomem;
@@ -1562,21 +1599,27 @@ static bool env_type_is_resolve_sink(const struct btf_verifier_env *env,
static bool env_type_is_resolved(const struct btf_verifier_env *env,
u32 type_id)
{
- return env->visit_states[type_id] == RESOLVED;
+ /* base BTF types should be resolved by now */
+ if (type_id < env->btf->start_id)
+ return true;
+
+ return env->visit_states[type_id - env->btf->start_id] == RESOLVED;
}
static int env_stack_push(struct btf_verifier_env *env,
const struct btf_type *t, u32 type_id)
{
+ const struct btf *btf = env->btf;
struct resolve_vertex *v;
if (env->top_stack == MAX_RESOLVE_DEPTH)
return -E2BIG;
- if (env->visit_states[type_id] != NOT_VISITED)
+ if (type_id < btf->start_id
+ || env->visit_states[type_id - btf->start_id] != NOT_VISITED)
return -EEXIST;
- env->visit_states[type_id] = VISITED;
+ env->visit_states[type_id - btf->start_id] = VISITED;
v = &env->stack[env->top_stack++];
v->t = t;
@@ -1606,6 +1649,7 @@ static void env_stack_pop_resolved(struct btf_verifier_env *env,
u32 type_id = env->stack[--(env->top_stack)].type_id;
struct btf *btf = env->btf;
+ type_id -= btf->start_id; /* adjust to local type id */
btf->resolved_sizes[type_id] = resolved_size;
btf->resolved_ids[type_id] = resolved_type_id;
env->visit_states[type_id] = RESOLVED;
@@ -1710,14 +1754,30 @@ btf_resolve_size(const struct btf *btf, const struct btf_type *type,
return __btf_resolve_size(btf, type, type_size, NULL, NULL, NULL, NULL);
}
+static u32 btf_resolved_type_id(const struct btf *btf, u32 type_id)
+{
+ while (type_id < btf->start_id)
+ btf = btf->base_btf;
+
+ return btf->resolved_ids[type_id - btf->start_id];
+}
+
/* The input param "type_id" must point to a needs_resolve type */
static const struct btf_type *btf_type_id_resolve(const struct btf *btf,
u32 *type_id)
{
- *type_id = btf->resolved_ids[*type_id];
+ *type_id = btf_resolved_type_id(btf, *type_id);
return btf_type_by_id(btf, *type_id);
}
+static u32 btf_resolved_type_size(const struct btf *btf, u32 type_id)
+{
+ while (type_id < btf->start_id)
+ btf = btf->base_btf;
+
+ return btf->resolved_sizes[type_id - btf->start_id];
+}
+
const struct btf_type *btf_type_id_size(const struct btf *btf,
u32 *type_id, u32 *ret_size)
{
@@ -1732,7 +1792,7 @@ const struct btf_type *btf_type_id_size(const struct btf *btf,
if (btf_type_has_size(size_type)) {
size = size_type->size;
} else if (btf_type_is_array(size_type)) {
- size = btf->resolved_sizes[size_type_id];
+ size = btf_resolved_type_size(btf, size_type_id);
} else if (btf_type_is_ptr(size_type)) {
size = sizeof(void *);
} else {
@@ -1740,14 +1800,14 @@ const struct btf_type *btf_type_id_size(const struct btf *btf,
!btf_type_is_var(size_type)))
return NULL;
- size_type_id = btf->resolved_ids[size_type_id];
+ size_type_id = btf_resolved_type_id(btf, size_type_id);
size_type = btf_type_by_id(btf, size_type_id);
if (btf_type_nosize_or_null(size_type))
return NULL;
else if (btf_type_has_size(size_type))
size = size_type->size;
else if (btf_type_is_array(size_type))
- size = btf->resolved_sizes[size_type_id];
+ size = btf_resolved_type_size(btf, size_type_id);
else if (btf_type_is_ptr(size_type))
size = sizeof(void *);
else
@@ -3799,7 +3859,7 @@ static int btf_check_all_metas(struct btf_verifier_env *env)
cur = btf->nohdr_data + hdr->type_off;
end = cur + hdr->type_len;
- env->log_type_id = 1;
+ env->log_type_id = btf->base_btf ? btf->start_id : 1;
while (cur < end) {
struct btf_type *t = cur;
s32 meta_size;
@@ -3826,8 +3886,8 @@ static bool btf_resolve_valid(struct btf_verifier_env *env,
return false;
if (btf_type_is_struct(t) || btf_type_is_datasec(t))
- return !btf->resolved_ids[type_id] &&
- !btf->resolved_sizes[type_id];
+ return !btf_resolved_type_id(btf, type_id) &&
+ !btf_resolved_type_size(btf, type_id);
if (btf_type_is_modifier(t) || btf_type_is_ptr(t) ||
btf_type_is_var(t)) {
@@ -3847,7 +3907,7 @@ static bool btf_resolve_valid(struct btf_verifier_env *env,
elem_type = btf_type_id_size(btf, &elem_type_id, &elem_size);
return elem_type && !btf_type_is_modifier(elem_type) &&
(array->nelems * elem_size ==
- btf->resolved_sizes[type_id]);
+ btf_resolved_type_size(btf, type_id));
}
return false;
@@ -3889,7 +3949,8 @@ static int btf_resolve(struct btf_verifier_env *env,
static int btf_check_all_types(struct btf_verifier_env *env)
{
struct btf *btf = env->btf;
- u32 type_id;
+ const struct btf_type *t;
+ u32 type_id, i;
int err;
err = env_resolve_init(env);
@@ -3897,8 +3958,9 @@ static int btf_check_all_types(struct btf_verifier_env *env)
return err;
env->phase++;
- for (type_id = 1; type_id <= btf->nr_types; type_id++) {
- const struct btf_type *t = btf_type_by_id(btf, type_id);
+ for (i = btf->base_btf ? 0 : 1; i < btf->nr_types; i++) {
+ type_id = btf->start_id + i;
+ t = btf_type_by_id(btf, type_id);
env->log_type_id = type_id;
if (btf_type_needs_resolve(t) &&
@@ -3935,7 +3997,7 @@ static int btf_parse_type_sec(struct btf_verifier_env *env)
return -EINVAL;
}
- if (!hdr->type_len) {
+ if (!env->btf->base_btf && !hdr->type_len) {
btf_verifier_log(env, "No type found");
return -EINVAL;
}
@@ -3962,13 +4024,18 @@ static int btf_parse_str_sec(struct btf_verifier_env *env)
return -EINVAL;
}
- if (!hdr->str_len || hdr->str_len - 1 > BTF_MAX_NAME_OFFSET ||
- start[0] || end[-1]) {
+ btf->strings = start;
+
+ if (btf->base_btf && !hdr->str_len)
+ return 0;
+ if (!hdr->str_len || hdr->str_len - 1 > BTF_MAX_NAME_OFFSET || end[-1]) {
+ btf_verifier_log(env, "Invalid string section");
+ return -EINVAL;
+ }
+ if (!btf->base_btf && start[0]) {
btf_verifier_log(env, "Invalid string section");
return -EINVAL;
}
-
- btf->strings = start;
return 0;
}
@@ -4909,7 +4976,7 @@ static int __get_type_size(struct btf *btf, u32 btf_id,
while (t && btf_type_is_modifier(t))
t = btf_type_by_id(btf, t->type);
if (!t) {
- *bad_type = btf->types[0];
+ *bad_type = btf_type_by_id(btf, 0);
return -EINVAL;
}
if (btf_type_is_ptr(t))
--
2.24.1
Allocate ID for vmlinux BTF. This makes it visible when iterating over all BTF
objects in the system. To allow distinguishing vmlinux BTF (and later kernel
module BTF) from user-provided BTFs, expose extra kernel_btf flag, as well as
BTF name ("vmlinux" for vmlinux BTF, will equal to module's name for module
BTF). We might want to later allow specifying BTF name for user-provided BTFs
as well, if that makes sense. But currently this is reserved only for
in-kernel BTFs.
Having in-kernel BTFs exposed IDs will allow to extend BPF APIs that require
in-kernel BTF type with ability to specify BTF types from kernel modules, not
just vmlinux BTF. This will be implemented in a follow up patch set for
fentry/fexit/fmod_ret/lsm/etc.
Signed-off-by: Andrii Nakryiko <[email protected]>
---
include/uapi/linux/bpf.h | 3 +++
kernel/bpf/btf.c | 39 ++++++++++++++++++++++++++++++++--
tools/include/uapi/linux/bpf.h | 3 +++
3 files changed, 43 insertions(+), 2 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 9879d6793e90..162999b12790 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -4466,6 +4466,9 @@ struct bpf_btf_info {
__aligned_u64 btf;
__u32 btf_size;
__u32 id;
+ __aligned_u64 name;
+ __u32 name_len;
+ __u32 kernel_btf;
} __attribute__((aligned(8)));
struct bpf_link_info {
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 894ee33f4c84..663c3fb4e614 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -215,6 +215,8 @@ struct btf {
struct btf *base_btf;
u32 start_id; /* first type ID in this BTF (0 for base BTF) */
u32 start_str_off; /* first string offset (0 for base BTF) */
+ char name[MODULE_NAME_LEN];
+ bool kernel_btf;
};
enum verifier_phase {
@@ -4430,6 +4432,8 @@ struct btf *btf_parse_vmlinux(void)
btf->data = __start_BTF;
btf->data_size = __stop_BTF - __start_BTF;
+ btf->kernel_btf = true;
+ snprintf(btf->name, sizeof(btf->name), "vmlinux");
err = btf_parse_hdr(env);
if (err)
@@ -4455,8 +4459,13 @@ struct btf *btf_parse_vmlinux(void)
bpf_struct_ops_init(btf, log);
- btf_verifier_env_free(env);
refcount_set(&btf->refcnt, 1);
+
+ err = btf_alloc_id(btf);
+ if (err)
+ goto errout;
+
+ btf_verifier_env_free(env);
return btf;
errout:
@@ -5554,7 +5563,8 @@ int btf_get_info_by_fd(const struct btf *btf,
struct bpf_btf_info info;
u32 info_copy, btf_copy;
void __user *ubtf;
- u32 uinfo_len;
+ char __user *uname;
+ u32 uinfo_len, uname_len, name_len;
uinfo = u64_to_user_ptr(attr->info.info);
uinfo_len = attr->info.info_len;
@@ -5571,6 +5581,31 @@ int btf_get_info_by_fd(const struct btf *btf,
return -EFAULT;
info.btf_size = btf->data_size;
+ info.kernel_btf = btf->kernel_btf;
+
+ uname = u64_to_user_ptr(info.name);
+ uname_len = info.name_len;
+ if (!uname ^ !uname_len)
+ return -EINVAL;
+
+ name_len = strlen(btf->name);
+ info.name_len = name_len;
+
+ if (uname) {
+ if (uname_len >= name_len + 1) {
+ if (copy_to_user(uname, btf->name, name_len + 1))
+ return -EFAULT;
+ } else {
+ char zero = '\0';
+
+ if (copy_to_user(uname, btf->name, uname_len - 1))
+ return -EFAULT;
+ if (put_user(zero, uname + uname_len - 1))
+ return -EFAULT;
+ return -ENOSPC;
+ }
+ }
+
if (copy_to_user(uinfo, &info, info_copy) ||
put_user(info_copy, &uattr->info.info_len))
return -EFAULT;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 9879d6793e90..162999b12790 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -4466,6 +4466,9 @@ struct bpf_btf_info {
__aligned_u64 btf;
__u32 btf_size;
__u32 id;
+ __aligned_u64 name;
+ __u32 name_len;
+ __u32 kernel_btf;
} __attribute__((aligned(8)));
struct bpf_link_info {
--
2.24.1
Add kernel module listener that will load/validate and unload module BTF.
Module BTFs gets ID generated for them, which makes it possible to iterate
them with existing BTF iteration API. They are given their respective module's
names, which will get reported through GET_OBJ_INFO API. They are also marked
as in-kernel BTFs for tooling to distinguish them from user-provided BTFs.
Also, similarly to vmlinux BTF, kernel module BTFs are exposed through
sysfs as /sys/kernel/btf/<module-name>. This is convenient for user-space
tools to inspect module BTF contents and dump their types with existing tools:
[vmuser@archvm bpf]$ ls -la /sys/kernel/btf
total 0
drwxr-xr-x 2 root root 0 Nov 4 19:46 .
drwxr-xr-x 13 root root 0 Nov 4 19:46 ..
...
-r--r--r-- 1 root root 888 Nov 4 19:46 irqbypass
-r--r--r-- 1 root root 100225 Nov 4 19:46 kvm
-r--r--r-- 1 root root 35401 Nov 4 19:46 kvm_intel
-r--r--r-- 1 root root 120 Nov 4 19:46 pcspkr
-r--r--r-- 1 root root 399 Nov 4 19:46 serio_raw
-r--r--r-- 1 root root 4094095 Nov 4 19:46 vmlinux
Reviewed-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
---
Documentation/ABI/testing/sysfs-kernel-btf | 8 +
include/linux/bpf.h | 2 +
include/linux/module.h | 4 +
kernel/bpf/btf.c | 194 +++++++++++++++++++++
kernel/bpf/sysfs_btf.c | 2 +-
kernel/module.c | 32 ++++
6 files changed, 241 insertions(+), 1 deletion(-)
diff --git a/Documentation/ABI/testing/sysfs-kernel-btf b/Documentation/ABI/testing/sysfs-kernel-btf
index 2c9744b2cd59..fe96efdc9b6c 100644
--- a/Documentation/ABI/testing/sysfs-kernel-btf
+++ b/Documentation/ABI/testing/sysfs-kernel-btf
@@ -15,3 +15,11 @@ Description:
information with description of all internal kernel types. See
Documentation/bpf/btf.rst for detailed description of format
itself.
+
+What: /sys/kernel/btf/<module-name>
+Date: Nov 2020
+KernelVersion: 5.11
+Contact: [email protected]
+Description:
+ Read-only binary attribute exposing kernel module's BTF type
+ information as an add-on to the kernel's BTF (/sys/kernel/btf/vmlinux).
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 73d5381a5d5c..581b2a2e78eb 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -36,9 +36,11 @@ struct seq_operations;
struct bpf_iter_aux_info;
struct bpf_local_storage;
struct bpf_local_storage_map;
+struct kobject;
extern struct idr btf_idr;
extern spinlock_t btf_idr_lock;
+extern struct kobject *btf_kobj;
typedef int (*bpf_iter_init_seq_priv_t)(void *private_data,
struct bpf_iter_aux_info *aux);
diff --git a/include/linux/module.h b/include/linux/module.h
index a29187f7c360..20fce258ffba 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -475,6 +475,10 @@ struct module {
unsigned int num_bpf_raw_events;
struct bpf_raw_event_map *bpf_raw_events;
#endif
+#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+ unsigned int btf_data_size;
+ void *btf_data;
+#endif
#ifdef CONFIG_JUMP_LABEL
struct jump_entry *jump_entries;
unsigned int num_jump_entries;
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 663c3fb4e614..ad2348e95ac7 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -23,6 +23,8 @@
#include <linux/perf_event.h>
#include <linux/bsearch.h>
#include <linux/btf_ids.h>
+#include <linux/kobject.h>
+#include <linux/sysfs.h>
#include <net/sock.h>
/* BTF (BPF Type Format) is the meta data format which describes
@@ -4477,6 +4479,75 @@ struct btf *btf_parse_vmlinux(void)
return ERR_PTR(err);
}
+static struct btf *btf_parse_module(const char *module_name, const void *data, unsigned int data_size)
+{
+ struct btf_verifier_env *env = NULL;
+ struct bpf_verifier_log *log;
+ struct btf *btf = NULL, *base_btf;
+ int err;
+
+ base_btf = bpf_get_btf_vmlinux();
+ if (IS_ERR(base_btf))
+ return base_btf;
+ if (!base_btf)
+ return ERR_PTR(-EINVAL);
+
+ env = kzalloc(sizeof(*env), GFP_KERNEL | __GFP_NOWARN);
+ if (!env)
+ return ERR_PTR(-ENOMEM);
+
+ log = &env->log;
+ log->level = BPF_LOG_KERNEL;
+
+ btf = kzalloc(sizeof(*btf), GFP_KERNEL | __GFP_NOWARN);
+ if (!btf) {
+ err = -ENOMEM;
+ goto errout;
+ }
+ env->btf = btf;
+
+ btf->base_btf = base_btf;
+ btf->start_id = base_btf->nr_types;
+ btf->start_str_off = base_btf->hdr.str_len;
+ btf->kernel_btf = true;
+ snprintf(btf->name, sizeof(btf->name), "%s", module_name);
+
+ btf->data = kvmalloc(data_size, GFP_KERNEL | __GFP_NOWARN);
+ if (!btf->data) {
+ err = -ENOMEM;
+ goto errout;
+ }
+ memcpy(btf->data, data, data_size);
+ btf->data_size = data_size;
+
+ err = btf_parse_hdr(env);
+ if (err)
+ goto errout;
+
+ btf->nohdr_data = btf->data + btf->hdr.hdr_len;
+
+ err = btf_parse_str_sec(env);
+ if (err)
+ goto errout;
+
+ err = btf_check_all_metas(env);
+ if (err)
+ goto errout;
+
+ btf_verifier_env_free(env);
+ refcount_set(&btf->refcnt, 1);
+ return btf;
+
+errout:
+ btf_verifier_env_free(env);
+ if (btf) {
+ kvfree(btf->data);
+ kvfree(btf->types);
+ kfree(btf);
+ }
+ return ERR_PTR(err);
+}
+
struct btf *bpf_prog_get_target_btf(const struct bpf_prog *prog)
{
struct bpf_prog *tgt_prog = prog->aux->dst_prog;
@@ -5650,3 +5721,126 @@ bool btf_id_set_contains(const struct btf_id_set *set, u32 id)
{
return bsearch(&id, set->ids, set->cnt, sizeof(u32), btf_id_cmp_func) != NULL;
}
+
+#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+struct btf_module {
+ struct list_head list;
+ struct module *module;
+ struct btf *btf;
+ struct bin_attribute *sysfs_attr;
+};
+
+static LIST_HEAD(btf_modules);
+static DEFINE_MUTEX(btf_module_mutex);
+
+static ssize_t
+btf_module_read(struct file *file, struct kobject *kobj,
+ struct bin_attribute *bin_attr,
+ char *buf, loff_t off, size_t len)
+{
+ const struct btf *btf = bin_attr->private;
+
+ memcpy(buf, btf->data + off, len);
+ return len;
+}
+
+static int btf_module_notify(struct notifier_block *nb, unsigned long op,
+ void *module)
+{
+ struct btf_module *btf_mod, *tmp;
+ struct module *mod = module;
+ struct btf *btf;
+ int err = 0;
+
+ if (mod->btf_data_size == 0 ||
+ (op != MODULE_STATE_COMING && op != MODULE_STATE_GOING))
+ goto out;
+
+ switch (op) {
+ case MODULE_STATE_COMING:
+ btf_mod = kzalloc(sizeof(*btf_mod), GFP_KERNEL);
+ if (!btf_mod) {
+ err = -ENOMEM;
+ goto out;
+ }
+ btf = btf_parse_module(mod->name, mod->btf_data, mod->btf_data_size);
+ if (IS_ERR(btf)) {
+ pr_warn("failed to validate module [%s] BTF: %ld\n",
+ mod->name, PTR_ERR(btf));
+ kfree(btf_mod);
+ err = PTR_ERR(btf);
+ goto out;
+ }
+ err = btf_alloc_id(btf);
+ if (err) {
+ btf_free(btf);
+ kfree(btf_mod);
+ goto out;
+ }
+
+ mutex_lock(&btf_module_mutex);
+ btf_mod->module = module;
+ btf_mod->btf = btf;
+ list_add(&btf_mod->list, &btf_modules);
+ mutex_unlock(&btf_module_mutex);
+
+ if (IS_ENABLED(CONFIG_SYSFS)) {
+ struct bin_attribute *attr;
+
+ attr = kzalloc(sizeof(*attr), GFP_KERNEL);
+ if (!attr)
+ goto out;
+
+ sysfs_bin_attr_init(attr);
+ attr->attr.name = btf->name;
+ attr->attr.mode = 0444;
+ attr->size = btf->data_size;
+ attr->private = btf;
+ attr->read = btf_module_read;
+
+ err = sysfs_create_bin_file(btf_kobj, attr);
+ if (err) {
+ pr_warn("failed to register module [%s] BTF in sysfs: %d\n",
+ mod->name, err);
+ kfree(attr);
+ err = 0;
+ goto out;
+ }
+
+ btf_mod->sysfs_attr = attr;
+ }
+
+ break;
+ case MODULE_STATE_GOING:
+ mutex_lock(&btf_module_mutex);
+ list_for_each_entry_safe(btf_mod, tmp, &btf_modules, list) {
+ if (btf_mod->module != module)
+ continue;
+
+ list_del(&btf_mod->list);
+ if (btf_mod->sysfs_attr)
+ sysfs_remove_bin_file(btf_kobj, btf_mod->sysfs_attr);
+ btf_put(btf_mod->btf);
+ kfree(btf_mod->sysfs_attr);
+ kfree(btf_mod);
+ break;
+ }
+ mutex_unlock(&btf_module_mutex);
+ break;
+ }
+out:
+ return notifier_from_errno(err);
+}
+
+static struct notifier_block btf_module_nb = {
+ .notifier_call = btf_module_notify,
+};
+
+static int __init btf_module_init(void)
+{
+ register_module_notifier(&btf_module_nb);
+ return 0;
+}
+
+fs_initcall(btf_module_init);
+#endif /* CONFIG_DEBUG_INFO_BTF_MODULES */
diff --git a/kernel/bpf/sysfs_btf.c b/kernel/bpf/sysfs_btf.c
index 11b3380887fa..ef6911aee3bb 100644
--- a/kernel/bpf/sysfs_btf.c
+++ b/kernel/bpf/sysfs_btf.c
@@ -26,7 +26,7 @@ static struct bin_attribute bin_attr_btf_vmlinux __ro_after_init = {
.read = btf_vmlinux_read,
};
-static struct kobject *btf_kobj;
+struct kobject *btf_kobj;
static int __init btf_vmlinux_init(void)
{
diff --git a/kernel/module.c b/kernel/module.c
index a4fa44a652a7..f2996b02ab2e 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -380,6 +380,35 @@ static void *section_objs(const struct load_info *info,
return (void *)info->sechdrs[sec].sh_addr;
}
+/* Find a module section: 0 means not found. Ignores SHF_ALLOC flag. */
+static unsigned int find_any_sec(const struct load_info *info, const char *name)
+{
+ unsigned int i;
+
+ for (i = 1; i < info->hdr->e_shnum; i++) {
+ Elf_Shdr *shdr = &info->sechdrs[i];
+ if (strcmp(info->secstrings + shdr->sh_name, name) == 0)
+ return i;
+ }
+ return 0;
+}
+
+/*
+ * Find a module section, or NULL. Fill in number of "objects" in section.
+ * Ignores SHF_ALLOC flag.
+ */
+static __maybe_unused void *any_section_objs(const struct load_info *info,
+ const char *name,
+ size_t object_size,
+ unsigned int *num)
+{
+ unsigned int sec = find_any_sec(info, name);
+
+ /* Section 0 has sh_addr 0 and sh_size 0. */
+ *num = info->sechdrs[sec].sh_size / object_size;
+ return (void *)info->sechdrs[sec].sh_addr;
+}
+
/* Provided by the linker */
extern const struct kernel_symbol __start___ksymtab[];
extern const struct kernel_symbol __stop___ksymtab[];
@@ -3250,6 +3279,9 @@ static int find_module_sections(struct module *mod, struct load_info *info)
sizeof(*mod->bpf_raw_events),
&mod->num_bpf_raw_events);
#endif
+#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+ mod->btf_data = any_section_objs(info, ".BTF", 1, &mod->btf_data_size);
+#endif
#ifdef CONFIG_JUMP_LABEL
mod->jump_entries = section_objs(info, "__jump_table",
sizeof(*mod->jump_entries),
--
2.24.1
On Mon, Nov 09, 2020 at 01:00:21PM -0800, Andrii Nakryiko wrote:
> Allocate ID for vmlinux BTF. This makes it visible when iterating over all BTF
> objects in the system. To allow distinguishing vmlinux BTF (and later kernel
> module BTF) from user-provided BTFs, expose extra kernel_btf flag, as well as
> BTF name ("vmlinux" for vmlinux BTF, will equal to module's name for module
> BTF). We might want to later allow specifying BTF name for user-provided BTFs
> as well, if that makes sense. But currently this is reserved only for
> in-kernel BTFs.
>
> Having in-kernel BTFs exposed IDs will allow to extend BPF APIs that require
> in-kernel BTF type with ability to specify BTF types from kernel modules, not
> just vmlinux BTF. This will be implemented in a follow up patch set for
> fentry/fexit/fmod_ret/lsm/etc.
>
> Signed-off-by: Andrii Nakryiko <[email protected]>
> ---
> include/uapi/linux/bpf.h | 3 +++
> kernel/bpf/btf.c | 39 ++++++++++++++++++++++++++++++++--
> tools/include/uapi/linux/bpf.h | 3 +++
> 3 files changed, 43 insertions(+), 2 deletions(-)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 9879d6793e90..162999b12790 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -4466,6 +4466,9 @@ struct bpf_btf_info {
> __aligned_u64 btf;
> __u32 btf_size;
> __u32 id;
> + __aligned_u64 name;
> + __u32 name_len;
> + __u32 kernel_btf;
> } __attribute__((aligned(8)));
>
> struct bpf_link_info {
> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> index 894ee33f4c84..663c3fb4e614 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c
> @@ -215,6 +215,8 @@ struct btf {
> struct btf *base_btf;
> u32 start_id; /* first type ID in this BTF (0 for base BTF) */
> u32 start_str_off; /* first string offset (0 for base BTF) */
> + char name[MODULE_NAME_LEN];
> + bool kernel_btf;
> };
>
> enum verifier_phase {
> @@ -4430,6 +4432,8 @@ struct btf *btf_parse_vmlinux(void)
>
> btf->data = __start_BTF;
> btf->data_size = __stop_BTF - __start_BTF;
> + btf->kernel_btf = true;
> + snprintf(btf->name, sizeof(btf->name), "vmlinux");
>
> err = btf_parse_hdr(env);
> if (err)
> @@ -4455,8 +4459,13 @@ struct btf *btf_parse_vmlinux(void)
>
> bpf_struct_ops_init(btf, log);
>
> - btf_verifier_env_free(env);
> refcount_set(&btf->refcnt, 1);
> +
> + err = btf_alloc_id(btf);
> + if (err)
> + goto errout;
> +
> + btf_verifier_env_free(env);
> return btf;
>
> errout:
> @@ -5554,7 +5563,8 @@ int btf_get_info_by_fd(const struct btf *btf,
> struct bpf_btf_info info;
> u32 info_copy, btf_copy;
> void __user *ubtf;
> - u32 uinfo_len;
> + char __user *uname;
> + u32 uinfo_len, uname_len, name_len;
>
> uinfo = u64_to_user_ptr(attr->info.info);
> uinfo_len = attr->info.info_len;
> @@ -5571,6 +5581,31 @@ int btf_get_info_by_fd(const struct btf *btf,
> return -EFAULT;
> info.btf_size = btf->data_size;
>
> + info.kernel_btf = btf->kernel_btf;
> +
> + uname = u64_to_user_ptr(info.name);
> + uname_len = info.name_len;
> + if (!uname ^ !uname_len)
> + return -EINVAL;
> +
> + name_len = strlen(btf->name);
> + info.name_len = name_len;
> +
> + if (uname) {
> + if (uname_len >= name_len + 1) {
> + if (copy_to_user(uname, btf->name, name_len + 1))
> + return -EFAULT;
> + } else {
> + char zero = '\0';
> +
> + if (copy_to_user(uname, btf->name, uname_len - 1))
> + return -EFAULT;
> + if (put_user(zero, uname + uname_len - 1))
> + return -EFAULT;
> + return -ENOSPC;
It should still do copy_to_user() even it will return -ENOSPC.
> + }
> + }
> +
> if (copy_to_user(uinfo, &info, info_copy) ||
> put_user(info_copy, &uattr->info.info_len))
> return -EFAULT;
On Mon, Nov 9, 2020 at 1:55 PM Martin KaFai Lau <[email protected]> wrote:
>
> On Mon, Nov 09, 2020 at 01:00:21PM -0800, Andrii Nakryiko wrote:
> > Allocate ID for vmlinux BTF. This makes it visible when iterating over all BTF
> > objects in the system. To allow distinguishing vmlinux BTF (and later kernel
> > module BTF) from user-provided BTFs, expose extra kernel_btf flag, as well as
> > BTF name ("vmlinux" for vmlinux BTF, will equal to module's name for module
> > BTF). We might want to later allow specifying BTF name for user-provided BTFs
> > as well, if that makes sense. But currently this is reserved only for
> > in-kernel BTFs.
> >
> > Having in-kernel BTFs exposed IDs will allow to extend BPF APIs that require
> > in-kernel BTF type with ability to specify BTF types from kernel modules, not
> > just vmlinux BTF. This will be implemented in a follow up patch set for
> > fentry/fexit/fmod_ret/lsm/etc.
> >
> > Signed-off-by: Andrii Nakryiko <[email protected]>
> > ---
> > include/uapi/linux/bpf.h | 3 +++
> > kernel/bpf/btf.c | 39 ++++++++++++++++++++++++++++++++--
> > tools/include/uapi/linux/bpf.h | 3 +++
> > 3 files changed, 43 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 9879d6793e90..162999b12790 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -4466,6 +4466,9 @@ struct bpf_btf_info {
> > __aligned_u64 btf;
> > __u32 btf_size;
> > __u32 id;
> > + __aligned_u64 name;
> > + __u32 name_len;
> > + __u32 kernel_btf;
> > } __attribute__((aligned(8)));
> >
> > struct bpf_link_info {
> > diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> > index 894ee33f4c84..663c3fb4e614 100644
> > --- a/kernel/bpf/btf.c
> > +++ b/kernel/bpf/btf.c
> > @@ -215,6 +215,8 @@ struct btf {
> > struct btf *base_btf;
> > u32 start_id; /* first type ID in this BTF (0 for base BTF) */
> > u32 start_str_off; /* first string offset (0 for base BTF) */
> > + char name[MODULE_NAME_LEN];
> > + bool kernel_btf;
> > };
> >
> > enum verifier_phase {
> > @@ -4430,6 +4432,8 @@ struct btf *btf_parse_vmlinux(void)
> >
> > btf->data = __start_BTF;
> > btf->data_size = __stop_BTF - __start_BTF;
> > + btf->kernel_btf = true;
> > + snprintf(btf->name, sizeof(btf->name), "vmlinux");
> >
> > err = btf_parse_hdr(env);
> > if (err)
> > @@ -4455,8 +4459,13 @@ struct btf *btf_parse_vmlinux(void)
> >
> > bpf_struct_ops_init(btf, log);
> >
> > - btf_verifier_env_free(env);
> > refcount_set(&btf->refcnt, 1);
> > +
> > + err = btf_alloc_id(btf);
> > + if (err)
> > + goto errout;
> > +
> > + btf_verifier_env_free(env);
> > return btf;
> >
> > errout:
> > @@ -5554,7 +5563,8 @@ int btf_get_info_by_fd(const struct btf *btf,
> > struct bpf_btf_info info;
> > u32 info_copy, btf_copy;
> > void __user *ubtf;
> > - u32 uinfo_len;
> > + char __user *uname;
> > + u32 uinfo_len, uname_len, name_len;
> >
> > uinfo = u64_to_user_ptr(attr->info.info);
> > uinfo_len = attr->info.info_len;
> > @@ -5571,6 +5581,31 @@ int btf_get_info_by_fd(const struct btf *btf,
> > return -EFAULT;
> > info.btf_size = btf->data_size;
> >
> > + info.kernel_btf = btf->kernel_btf;
> > +
> > + uname = u64_to_user_ptr(info.name);
> > + uname_len = info.name_len;
> > + if (!uname ^ !uname_len)
> > + return -EINVAL;
> > +
> > + name_len = strlen(btf->name);
> > + info.name_len = name_len;
> > +
> > + if (uname) {
> > + if (uname_len >= name_len + 1) {
> > + if (copy_to_user(uname, btf->name, name_len + 1))
> > + return -EFAULT;
> > + } else {
> > + char zero = '\0';
> > +
> > + if (copy_to_user(uname, btf->name, uname_len - 1))
> > + return -EFAULT;
> > + if (put_user(zero, uname + uname_len - 1))
> > + return -EFAULT;
> > + return -ENOSPC;
> It should still do copy_to_user() even it will return -ENOSPC.
>
Good catch! I'll use "ret" variable, will set it to -ENOSPC here and
will let the code fall through.
> > + }
> > + }
> > +
> > if (copy_to_user(uinfo, &info, info_copy) ||
> > put_user(info_copy, &uattr->info.info_len))
> > return -EFAULT;