From patchwork Sun Oct 16 21:18:33 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Leblond X-Patchwork-Id: 682744 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3sxvRL3mcGz9s9c for ; Mon, 17 Oct 2016 08:21:50 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757465AbcJPVVp (ORCPT ); Sun, 16 Oct 2016 17:21:45 -0400 Received: from home.regit.org ([37.187.126.138]:45270 "EHLO home.regit.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757058AbcJPVVT (ORCPT ); Sun, 16 Oct 2016 17:21:19 -0400 Received: from [2a01:e35:2fb6:1160:c685:8ff:feb3:c9c8] (helo=localhost.localdomain) by home.regit.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.84_2) (envelope-from ) id 1bvsrs-0005Ad-Pc; Sun, 16 Oct 2016 23:21:17 +0200 From: Eric Leblond To: netdev@vger.kernel.org, wangnan0@huawei.com Cc: linux-kernel@vger.kernel.org, ast@fb.com, Eric Leblond Subject: [PATCH 7/8] tools lib bpf: fix maps resolution Date: Sun, 16 Oct 2016 23:18:33 +0200 Message-Id: <20161016211834.11732-8-eric@regit.org> X-Mailer: git-send-email 2.9.3 In-Reply-To: <20161016211834.11732-1-eric@regit.org> References: <20161016211834.11732-1-eric@regit.org> X-Spam-Score: -1.0 (-) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org It is not correct to assimilate the elf data of the maps section to an array of map definition. In fact the sizes differ. The offset provided in the symbol section has to be used instead. This patch fixes a bug causing a elf with two maps not to load correctly. Signed-off-by: Eric Leblond --- tools/lib/bpf/libbpf.c | 50 +++++++++++++++++++++++++++++++++++--------------- 1 file changed, 35 insertions(+), 15 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 1fe4532..f72628b 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -186,6 +186,7 @@ struct bpf_program { struct bpf_map { int fd; char *name; + size_t offset; struct bpf_map_def def; void *priv; bpf_map_clear_priv_t clear_priv; @@ -529,13 +530,6 @@ bpf_object__init_maps(struct bpf_object *obj, void *data, pr_debug("maps in %s: %zd bytes\n", obj->path, size); - obj->maps = calloc(nr_maps, sizeof(obj->maps[0])); - if (!obj->maps) { - pr_warning("alloc maps for object failed\n"); - return -ENOMEM; - } - obj->nr_maps = nr_maps; - for (i = 0; i < nr_maps; i++) { struct bpf_map_def *def = &obj->maps[i].def; @@ -547,23 +541,42 @@ bpf_object__init_maps(struct bpf_object *obj, void *data, obj->maps[i].fd = -1; /* Save map definition into obj->maps */ - *def = ((struct bpf_map_def *)data)[i]; + *def = *(struct bpf_map_def *)(data + obj->maps[i].offset); } return 0; } static int -bpf_object__init_maps_name(struct bpf_object *obj) +bpf_object__init_maps_symbol(struct bpf_object *obj) { int i; + int nr_maps = 0; Elf_Data *symbols = obj->efile.symbols; + size_t map_idx = 0; if (!symbols || obj->efile.maps_shndx < 0) return -EINVAL; + /* get the number of maps */ + for (i = 0; i < symbols->d_size / sizeof(GElf_Sym); i++) { + GElf_Sym sym; + + if (!gelf_getsym(symbols, i, &sym)) + continue; + if (sym.st_shndx != obj->efile.maps_shndx) + continue; + nr_maps++; + } + + obj->maps = calloc(nr_maps, sizeof(obj->maps[0])); + if (!obj->maps) { + pr_warning("alloc maps for object failed\n"); + return -ENOMEM; + } + obj->nr_maps = nr_maps; + 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)) @@ -574,12 +587,12 @@ bpf_object__init_maps_name(struct bpf_object *obj) map_name = elf_strptr(obj->efile.elf, obj->efile.strtabidx, sym.st_name); - 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].offset = sym.st_value; obj->maps[map_idx].name = strdup(map_name); if (!obj->maps[map_idx].name) { pr_warning("failed to alloc map name\n"); @@ -587,6 +600,7 @@ bpf_object__init_maps_name(struct bpf_object *obj) } pr_debug("map %zu is \"%s\"\n", map_idx, obj->maps[map_idx].name); + map_idx++; } return 0; } @@ -647,8 +661,6 @@ static int bpf_object__elf_collect(struct bpf_object *obj) data->d_buf, data->d_size); else if (strcmp(name, "maps") == 0) { - err = bpf_object__init_maps(obj, data->d_buf, - data->d_size); obj->efile.maps_shndx = idx; } else if (sh.sh_type == SHT_SYMTAB) { if (obj->efile.symbols) { @@ -698,8 +710,16 @@ static int bpf_object__elf_collect(struct bpf_object *obj) pr_warning("Corrupted ELF file: index of strtab invalid\n"); return LIBBPF_ERRNO__FORMAT; } - if (obj->efile.maps_shndx >= 0) - err = bpf_object__init_maps_name(obj); + if (obj->efile.maps_shndx >= 0) { + Elf_Data *data; + err = bpf_object__init_maps_symbol(obj); + if (err) + goto out; + + scn = elf_getscn(elf, obj->efile.maps_shndx); + data = elf_getdata(scn, 0); + err = bpf_object__init_maps(obj, data->d_buf, data->d_size); + } out: return err; }