From 2ad97d473db57ab866f0756806bb94515f7f2551 Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Fri, 13 Dec 2019 17:47:09 -0800 Subject: [PATCH] bpftool: Generate externs datasec in BPF skeleton 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 Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20191214014710.3449601-4-andriin@fb.com --- tools/bpf/bpftool/gen.c | 4 ++++ tools/lib/bpf/libbpf.c | 10 +++++----- 2 files changed, 9 insertions(+), 5 deletions(-) diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c index 7379dae35dca..a07c80429c7a 100644 --- a/tools/bpf/bpftool/gen.c +++ b/tools/bpf/bpftool/gen.c @@ -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; diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 26144706ba0b..c9f90bfd2f0d 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -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",