Enhance bpftool to generate skeletons that properly handle global percpu
variables. The generated skeleton now includes a dedicated structure for
percpu data, allowing users to initialize and access percpu variables more
efficiently.
For global percpu variables, the skeleton now includes a nested
structure, e.g.:
struct test_global_percpu_data {
struct bpf_object_skeleton *skeleton;
struct bpf_object *obj;
struct {
struct bpf_map *percpu;
} maps;
// ...
struct test_global_percpu_data__percpu {
int data;
char run;
struct {
char set;
int i;
int nums[7];
} struct_data;
int nums[7];
} *percpu;
// ...
};
* The "struct test_global_percpu_data__percpu *percpu" points to
initialized data, which is actually "maps.percpu->mmaped".
* Before loading the skeleton, updating the
"struct test_global_percpu_data__percpu *percpu" modifies the initial
value of the corresponding global percpu variables.
* After loading the skeleton, "maps.percpu->mmaped" has been marked as
read-only in libbpf. If users want to update the global percpu
variables, they have to update the "maps.percpu" map instead.
* For lightweight skeleton, "lskel->percpu" will be protected by
"mprotect(p, sz, PROT_READ)".
* For subskeleton, those variables of global percpu data will be
skipped.
Acked-by: Quentin Monnet <[email protected]>
Assisted-by: Codex:gpt-5.5-xhigh
Signed-off-by: Leon Hwang <[email protected]>
---
tools/bpf/bpftool/gen.c | 76 +++++++++++++++++++++++++++--------
tools/lib/bpf/skel_internal.h | 24 ++++++++++-
2 files changed, 81 insertions(+), 19 deletions(-)
diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index a01d06d22d1a..b60db1108149 100644
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -101,6 +101,12 @@ static bool get_map_ident(const struct bpf_map *map, char
*buf, size_t buf_sz)
return true;
}
+ if (bpf_map__type(map) == BPF_MAP_TYPE_PERCPU_ARRAY) {
+ snprintf(buf, buf_sz, "%s", name + 1);
+ sanitize_identifier(buf);
+ return true;
+ }
+
for (i = 0, n = ARRAY_SIZE(sfxs); i < n; i++) {
const char *sfx = sfxs[i], *p;
@@ -117,7 +123,7 @@ static bool get_map_ident(const struct bpf_map *map, char
*buf, size_t buf_sz)
static bool get_datasec_ident(const char *sec_name, char *buf, size_t buf_sz)
{
- static const char *pfxs[] = { ".data", ".rodata", ".bss", ".kconfig" };
+ static const char *pfxs[] = { ".data", ".rodata", ".bss", ".percpu",
".kconfig" };
int i, n;
/* recognize hard coded LLVM section name */
@@ -254,7 +260,7 @@ static const struct btf_type *find_type_for_map(struct btf
*btf, const char *map
return NULL;
}
-static bool is_mmapable_map(const struct bpf_map *map, char *buf, size_t sz)
+static bool is_skel_data(const struct bpf_map *map, char *buf, size_t sz)
{
size_t tmp_sz;
@@ -263,13 +269,19 @@ static bool is_mmapable_map(const struct bpf_map *map,
char *buf, size_t sz)
return true;
}
- if (!bpf_map__is_internal(map) || !(bpf_map__map_flags(map) &
BPF_F_MMAPABLE))
+ if (!bpf_map__is_internal(map))
return false;
if (!get_map_ident(map, buf, sz))
return false;
- return true;
+ if (bpf_map__map_flags(map) & BPF_F_MMAPABLE)
+ return true;
+
+ if (bpf_map__type(map) == BPF_MAP_TYPE_PERCPU_ARRAY)
+ return true;
+
+ return false;
}
static int codegen_datasecs(struct bpf_object *obj, const char *obj_name)
@@ -286,8 +298,11 @@ static int codegen_datasecs(struct bpf_object *obj, const
char *obj_name)
return -errno;
bpf_object__for_each_map(map, obj) {
- /* only generate definitions for memory-mapped internal maps */
- if (!is_mmapable_map(map, map_ident, sizeof(map_ident)))
+ /*
+ * Only generate definitions for internal maps that have
+ * mmapped data.
+ */
+ if (!is_skel_data(map, map_ident, sizeof(map_ident)))
continue;
sec = find_type_for_map(btf, map_ident);
@@ -339,8 +354,14 @@ static int codegen_subskel_datasecs(struct bpf_object
*obj, const char *obj_name
return -errno;
bpf_object__for_each_map(map, obj) {
- /* only generate definitions for memory-mapped internal maps */
- if (!is_mmapable_map(map, map_ident, sizeof(map_ident)))
+ /*
+ * Only generate definitions for internal maps that have
+ * mmapped data.
+ */
+ if (!is_skel_data(map, map_ident, sizeof(map_ident)))
+ continue;
+
+ if (bpf_map__type(map) == BPF_MAP_TYPE_PERCPU_ARRAY)
continue;
sec = find_type_for_map(btf, map_ident);
@@ -493,7 +514,10 @@ static size_t bpf_map_mmap_sz(const struct bpf_map *map)
return map_sz;
}
-/* Emit type size asserts for all top-level fields in memory-mapped internal
maps. */
+/*
+ * Emit type size asserts for all top-level fields in internal maps that
+ * have mmaped data.
+ */
static void codegen_asserts(struct bpf_object *obj, const char *obj_name)
{
struct btf *btf = bpf_object__btf(obj);
@@ -517,7 +541,7 @@ static void codegen_asserts(struct bpf_object *obj, const
char *obj_name)
", obj_name);
bpf_object__for_each_map(map, obj) {
- if (!is_mmapable_map(map, map_ident, sizeof(map_ident)))
+ if (!is_skel_data(map, map_ident, sizeof(map_ident)))
continue;
sec = find_type_for_map(btf, map_ident);
@@ -669,7 +693,8 @@ static void codegen_destroy(struct bpf_object *obj, const
char *obj_name)
if (!get_map_ident(map, ident, sizeof(ident)))
continue;
if (bpf_map__is_internal(map) &&
- (bpf_map__map_flags(map) & BPF_F_MMAPABLE))
+ ((bpf_map__map_flags(map) & BPF_F_MMAPABLE) ||
+ bpf_map__type(map) == BPF_MAP_TYPE_PERCPU_ARRAY))
printf("\tskel_free_map_data(skel->%1$s,
skel->maps.%1$s.initial_value, %2$zu);\n",
ident, bpf_map_mmap_sz(map));
codegen("\
@@ -741,7 +766,7 @@ static int gen_trace(struct bpf_object *obj, const char
*obj_name, const char *h
const void *mmap_data = NULL;
size_t mmap_size = 0;
- if (!is_mmapable_map(map, ident, sizeof(ident)))
+ if (!is_skel_data(map, ident, sizeof(ident)))
continue;
codegen("\
@@ -849,8 +874,22 @@ static int gen_trace(struct bpf_object *obj, const char
*obj_name, const char *h
bpf_object__for_each_map(map, obj) {
const char *mmap_flags;
- if (!is_mmapable_map(map, ident, sizeof(ident)))
+ if (!is_skel_data(map, ident, sizeof(ident)))
+ continue;
+
+ if (bpf_map__type(map) == BPF_MAP_TYPE_PERCPU_ARRAY) {
+ codegen("\
+ \n\
+ err = skel_protect_map_data(skel->%1$s,
&skel->maps.%1$s.initial_value, %2$zd);\n\
+ if (err) \n\
+ return err; \n\
+ #ifdef __KERNEL__ \n\
+ skel->%1$s = NULL; \n\
+ #endif \n\
+ ",
+ ident, bpf_map_mmap_sz(map));
continue;
+ }
if (bpf_map__map_flags(map) & BPF_F_RDONLY_PROG)
mmap_flags = "PROT_READ";
@@ -955,8 +994,7 @@ codegen_maps_skeleton(struct bpf_object *obj, size_t
map_cnt, bool mmaped, bool
map->map = &obj->maps.%s; \n\
",
i, bpf_map__name(map), ident);
- /* memory-mapped internal maps */
- if (mmaped && is_mmapable_map(map, ident, sizeof(ident))) {
+ if (mmaped && is_skel_data(map, ident, sizeof(ident))) {
printf("\tmap->mmaped = (void **)&obj->%s;\n", ident);
}
@@ -1740,7 +1778,9 @@ static int do_subskeleton(int argc, char **argv)
/* Also count all maps that have a name */
map_cnt++;
- if (!is_mmapable_map(map, ident, sizeof(ident)))
+ if (!is_skel_data(map, ident, sizeof(ident)))
+ continue;
+ if (bpf_map__type(map) == BPF_MAP_TYPE_PERCPU_ARRAY)
continue;
map_type_id = bpf_map__btf_value_type_id(map);
@@ -1863,7 +1903,9 @@ static int do_subskeleton(int argc, char **argv)
/* walk through each symbol and emit the runtime representation */
bpf_object__for_each_map(map, obj) {
- if (!is_mmapable_map(map, ident, sizeof(ident)))
+ if (!is_skel_data(map, ident, sizeof(ident)))
+ continue;
+ if (bpf_map__type(map) == BPF_MAP_TYPE_PERCPU_ARRAY)
continue;
map_type_id = bpf_map__btf_value_type_id(map);
diff --git a/tools/lib/bpf/skel_internal.h b/tools/lib/bpf/skel_internal.h
index 53fee53d36d5..1f3f332dffbe 100644
--- a/tools/lib/bpf/skel_internal.h
+++ b/tools/lib/bpf/skel_internal.h
@@ -131,8 +131,10 @@ static inline void skel_free_map_data(void *p, __u64 addr,
size_t sz)
{
if (addr != ~0ULL)
kvfree(p);
- /* When addr == ~0ULL the 'p' points to
- * ((struct bpf_array *)map)->value. See skel_finalize_map_data.
+ /*
+ * When addr == ~0ULL the init buffer has already been released.
+ * For skel_finalize_map_data(), 'p' points to
+ * ((struct bpf_array *)map)->value.
*/
}
@@ -170,6 +172,15 @@ static inline void *skel_finalize_map_data(__u64
*init_val, size_t mmap_sz, int
return addr;
}
+static inline int skel_protect_map_data(void *p, __u64 *init_val, size_t sz)
+{
+ (void)sz;
+
+ kvfree(p);
+ *init_val = ~0ULL;
+ return 0;
+}
+
#else
static inline void *skel_alloc(size_t size)
@@ -208,6 +219,15 @@ static inline void *skel_finalize_map_data(__u64
*init_val, size_t mmap_sz, int
return NULL;
return addr;
}
+
+static inline int skel_protect_map_data(void *p, __u64 *init_val, size_t sz)
+{
+ (void)init_val;
+
+ if (mprotect(p, sz, PROT_READ))
+ return -errno;
+ return 0;
+}
#endif
static inline int skel_closenz(int fd)
--
2.55.0
