From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yonghong Song Subject: [PATCH iproute2] bpf: check map symbol type properly with newer llvm compiler Date: Mon, 29 Oct 2018 15:32:03 -0700 Message-ID: <20181029223203.3135200-1-yhs@fb.com> Mime-Version: 1.0 Content-Type: text/plain Cc: To: , , Return-path: Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:39016 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726568AbeJ3HWs (ORCPT ); Tue, 30 Oct 2018 03:22:48 -0400 Received: from pps.filterd (m0001303.ppops.net [127.0.0.1]) by m0001303.ppops.net (8.16.0.22/8.16.0.22) with SMTP id w9TMMeha008047 for ; Mon, 29 Oct 2018 15:32:05 -0700 Received: from maileast.thefacebook.com ([199.201.65.23]) by m0001303.ppops.net with ESMTP id 2neakbr408-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-SHA384 bits=256 verify=NOT) for ; Mon, 29 Oct 2018 15:32:05 -0700 Sender: netdev-owner@vger.kernel.org List-ID: With llvm 7.0 or earlier, the map symbol type is STT_NOTYPE. -bash-4.4$ cat t.c __attribute__((section("maps"))) int g; -bash-4.4$ clang -target bpf -O2 -c t.c -bash-4.4$ readelf -s t.o Symbol table '.symtab' contains 2 entries: Num: Value Size Type Bind Vis Ndx Name 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND 1: 0000000000000000 0 NOTYPE GLOBAL DEFAULT 3 g -bash-4.4$ The following llvm commit enables BPF target to generate proper symbol type and size. commit bf6ec206615b9718869d48b4e5400d0c6e3638dd Author: Yonghong Song Date: Wed Sep 19 16:04:13 2018 +0000 [bpf] Symbol sizes and types in object file Clang-compiled object files currently don't include the symbol sizes and types. Some tools however need that information. For example, ctfconvert uses that information to generate FreeBSD's CTF representation from ELF files. With this patch, symbol sizes and types are included in object files. Signed-off-by: Paul Chaignon Reported-by: Yutaro Hayakawa Hence, for llvm 8.0.0 (currently trunk), symbol type will be not NOTYPE, but OBJECT. -bash-4.4$ clang -target bpf -O2 -c t.c -bash-4.4$ readelf -s t.o Symbol table '.symtab' contains 3 entries: Num: Value Size Type Bind Vis Ndx Name 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND 1: 0000000000000000 0 FILE LOCAL DEFAULT ABS t.c 2: 0000000000000000 4 OBJECT GLOBAL DEFAULT 3 g -bash-4.4$ This patch makes sure bpf library accepts both NOTYPE and OBJECT types of global map symbols. Signed-off-by: Yonghong Song --- lib/bpf.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/lib/bpf.c b/lib/bpf.c index d093d0bd..45f279fa 100644 --- a/lib/bpf.c +++ b/lib/bpf.c @@ -1758,11 +1758,13 @@ static const char *bpf_map_fetch_name(struct bpf_elf_ctx *ctx, int which) int i; for (i = 0; i < ctx->sym_num; i++) { + int type = GELF_ST_TYPE(sym.st_info); + if (gelf_getsym(ctx->sym_tab, i, &sym) != &sym) continue; if (GELF_ST_BIND(sym.st_info) != STB_GLOBAL || - GELF_ST_TYPE(sym.st_info) != STT_NOTYPE || + (type != STT_NOTYPE && type != STT_OBJECT) || sym.st_shndx != ctx->sec_maps || sym.st_value / ctx->map_len != which) continue; @@ -1849,11 +1851,13 @@ static int bpf_map_num_sym(struct bpf_elf_ctx *ctx) GElf_Sym sym; for (i = 0; i < ctx->sym_num; i++) { + int type = GELF_ST_TYPE(sym.st_info); + if (gelf_getsym(ctx->sym_tab, i, &sym) != &sym) continue; if (GELF_ST_BIND(sym.st_info) != STB_GLOBAL || - GELF_ST_TYPE(sym.st_info) != STT_NOTYPE || + (type != STT_NOTYPE && type != STT_OBJECT) || sym.st_shndx != ctx->sec_maps) continue; num++; @@ -1927,10 +1931,12 @@ static int bpf_map_verify_all_offs(struct bpf_elf_ctx *ctx, int end) * the table again. */ for (i = 0; i < ctx->sym_num; i++) { + int type = GELF_ST_TYPE(sym.st_info); + if (gelf_getsym(ctx->sym_tab, i, &sym) != &sym) continue; if (GELF_ST_BIND(sym.st_info) != STB_GLOBAL || - GELF_ST_TYPE(sym.st_info) != STT_NOTYPE || + (type != STT_NOTYPE && type != STT_OBJECT) || sym.st_shndx != ctx->sec_maps) continue; if (sym.st_value == off) -- 2.17.1