@@ -82,6 +82,8 @@ static const char *get_map_ident(const struct bpf_map *map)
return "rodata";
else if (str_has_suffix(name, ".bss"))
return "bss";
+ else if (str_has_suffix(name, ".extern"))
+ return "externs"; /* extern is a C keyword */
else
return NULL;
}
@@ -109,6 +111,8 @@ static int codegen_datasec_def(struct bpf_object *obj,
sec_ident = "bss";
else if (strcmp(sec_name, ".rodata") == 0)
sec_ident = "rodata";
+ else if (strcmp(sec_name, ".extern") == 0)
+ sec_ident = "externs"; /* extern is a C keyword */
else
return 0;
@@ -7472,7 +7472,8 @@ int bpf_object__open_skeleton(struct bpf_object_skeleton *s,
return -ESRCH;
}
- if (mmaped)
+ /* externs shouldn't be pre-setup from user code */
+ if (mmaped && (*map)->libbpf_type != LIBBPF_MAP_EXTERN)
*mmaped = (*map)->mmaped;
}
@@ -7505,7 +7506,6 @@ int bpf_object__load_skeleton(struct bpf_object_skeleton *s)
size_t mmap_sz = bpf_map_mmap_sz(map);
int prot, map_fd = bpf_map__fd(map);
void **mmaped = s->maps[i].mmaped;
- void *remapped;
if (!mmaped)
continue;
@@ -7530,9 +7530,9 @@ int bpf_object__load_skeleton(struct bpf_object_skeleton *s)
* as per normal clean up procedure, so we don't need to worry
* about it from skeleton's clean up perspective.
*/
- remapped = mmap(*mmaped, mmap_sz, prot, MAP_SHARED | MAP_FIXED,
- map_fd, 0);
- if (remapped == MAP_FAILED) {
+ *mmaped = mmap(map->mmaped, mmap_sz, prot,
+ MAP_SHARED | MAP_FIXED, map_fd, 0);
+ if (*mmaped == MAP_FAILED) {
err = -errno;
*mmaped = NULL;
pr_warn("failed to re-mmap() map '%s': %d\n",
Add support for generation of mmap()-ed read-only view of libbpf-provided extern variables. As externs are not supposed to be provided by user code (that's what .data, .bss, and .rodata is for), don't mmap() it initially. Only after skeleton load is performed, map .extern contents as read-only memory. Signed-off-by: Andrii Nakryiko <andriin@fb.com> --- tools/bpf/bpftool/gen.c | 4 ++++ tools/lib/bpf/libbpf.c | 10 +++++----- 2 files changed, 9 insertions(+), 5 deletions(-)