On 2015/11/30 0:14, Namhyung Kim wrote:
Hi Wang, On Fri, Nov 27, 2015 at 08:47:36AM +0000, Wang Nan wrote:This patch collects name of maps in BPF object files and saves them into 'maps' field in 'struct bpf_object'. 'bpf_object__get_map_by_name' is introduced to retrive fd and definitions of a map through its name. Signed-off-by: Wang Nan <wangn...@huawei.com> Signed-off-by: He Kuang <heku...@huawei.com> Cc: Alexei Starovoitov <a...@kernel.org> Cc: Arnaldo Carvalho de Melo <a...@redhat.com> Cc: Masami Hiramatsu <masami.hiramatsu...@hitachi.com> Cc: Namhyung Kim <namhy...@kernel.org> Cc: Zefan Li <lize...@huawei.com> Cc: pi3or...@163.com --- tools/lib/bpf/libbpf.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++--- tools/lib/bpf/libbpf.h | 3 +++ 2 files changed, 65 insertions(+), 3 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index f509825..a298614 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -165,6 +165,7 @@ struct bpf_program {struct bpf_map {int fd; + char *name; struct bpf_map_def def; void *priv; bpf_map_clear_priv_t clear_priv; @@ -526,12 +527,46 @@ bpf_object__init_maps(struct bpf_object *obj, void *data, return 0; }+static void+bpf_object__init_maps_name(struct bpf_object *obj, int maps_shndx) +{ + int i; + Elf_Data *symbols = obj->efile.symbols; + + if (!symbols || maps_shndx < 0) + return; + + for (i = 0; i < symbols->d_size / sizeof(GElf_Sym); i++) { + GElf_Sym sym; + size_t map_idx; + const char *map_name; + + if (!gelf_getsym(symbols, i, &sym)) + continue; + if (sym.st_shndx != maps_shndx) + continue; + + map_name = elf_strptr(obj->efile.elf, + obj->efile.ehdr.e_shstrndx, + sym.st_name);It means that each map name is saved in section header string table?
According to elf format specification: For an symbol table entry, the st_name field "holds an index into the object file’s symbol string table, which holds the character representations of the symbol names. If the value is non-zero, it represents a string table index that gives the symbol name. Otherwise, the symbol table entry has no name." And so called "object file’s symbol string table" is a section in the object file which index is stored into ehdr and be loaded during gelf_getehdr(), and its index would be set to ehdr->e_shstrndx. So I think for each map its name should be saved in that string table.
+ map_idx = sym.st_value / sizeof(struct bpf_map_def); + if (map_idx >= obj->nr_maps) { + pr_warning("index of map \"%s\" is buggy: %zu > %zu\n", + map_name, map_idx, obj->nr_maps); + continue; + } + obj->maps[map_idx].name = strdup(map_name);You need to check the return value.
Will send a patch for it. Thank you. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
