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.
Assisted-by: Codex:gpt-5.5-xhigh
Signed-off-by: Leon Hwang <[email protected]>
---
tools/bpf/bpftool/gen.c | 43 +++++++++++++++++++++++++++--------
tools/lib/bpf/skel_internal.h | 24 +++++++++++++++++--
2 files changed, 56 insertions(+), 11 deletions(-)
diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index 6ae7262ebe0c..2200ab004d2b 100644
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -92,7 +92,7 @@ static void get_header_guard(char *guard, const char
*obj_name, const char *suff
static bool get_map_ident(const struct bpf_map *map, char *buf, size_t buf_sz)
{
- static const char *sfxs[] = { ".data", ".rodata", ".bss", ".kconfig" };
+ static const char *sfxs[] = { ".data", ".rodata", ".bss", ".percpu",
".kconfig" };
const char *name = bpf_map__name(map);
int i, n;
@@ -117,7 +117,7 @@ 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 */
@@ -254,6 +254,11 @@ static const struct btf_type *find_type_for_map(struct btf
*btf, const char *map
return NULL;
}
+static bool bpf_map_is_percpu_data(const struct bpf_map *map)
+{
+ return bpf_map__is_internal(map) && bpf_map__type(map) ==
BPF_MAP_TYPE_PERCPU_ARRAY;
+}
+
static bool is_mmapable_map(const struct bpf_map *map, char *buf, size_t sz)
{
size_t tmp_sz;
@@ -263,13 +268,12 @@ 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))
- return false;
-
- if (!get_map_ident(map, buf, sz))
- return false;
+ if (bpf_map__is_internal(map) &&
+ ((bpf_map__map_flags(map) & BPF_F_MMAPABLE) ||
bpf_map_is_percpu_data(map)) &&
+ get_map_ident(map, buf, sz))
+ return true;
- return true;
+ return false;
}
static int codegen_datasecs(struct bpf_object *obj, const char *obj_name)
@@ -343,6 +347,9 @@ static int codegen_subskel_datasecs(struct bpf_object *obj,
const char *obj_name
if (!is_mmapable_map(map, map_ident, sizeof(map_ident)))
continue;
+ if (bpf_map_is_percpu_data(map))
+ continue;
+
sec = find_type_for_map(btf, map_ident);
if (!sec)
continue;
@@ -669,7 +676,7 @@ 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_is_percpu_data(map)))
printf("\tskel_free_map_data(skel->%1$s,
skel->maps.%1$s.initial_value, %2$zu);\n",
ident, bpf_map_mmap_sz(map));
codegen("\
@@ -850,6 +857,20 @@ static int gen_trace(struct bpf_object *obj, const char
*obj_name, const char *h
if (!is_mmapable_map(map, ident, sizeof(ident)))
continue;
+ if (bpf_map_is_percpu_data(map)) {
+ codegen("\
+ \n\
+ err = skel_protect_map_data(skel->%1$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";
else
@@ -1740,6 +1761,8 @@ static int do_subskeleton(int argc, char **argv)
if (!is_mmapable_map(map, ident, sizeof(ident)))
continue;
+ if (bpf_map_is_percpu_data(map))
+ continue;
map_type_id = bpf_map__btf_value_type_id(map);
if (map_type_id <= 0) {
@@ -1863,6 +1886,8 @@ static int do_subskeleton(int argc, char **argv)
bpf_object__for_each_map(map, obj) {
if (!is_mmapable_map(map, ident, sizeof(ident)))
continue;
+ if (bpf_map_is_percpu_data(map))
+ continue;
map_type_id = bpf_map__btf_value_type_id(map);
if (map_type_id <= 0)
diff --git a/tools/lib/bpf/skel_internal.h b/tools/lib/bpf/skel_internal.h
index 74503d358bc8..485b0cd17017 100644
--- a/tools/lib/bpf/skel_internal.h
+++ b/tools/lib/bpf/skel_internal.h
@@ -135,8 +135,10 @@ 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.
*/
}
@@ -174,6 +176,15 @@ 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)
@@ -212,6 +223,15 @@ 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)
--
2.54.0
