Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932096AbbFAJ45 (ORCPT ); Mon, 1 Jun 2015 05:56:57 -0400 Received: from lhrrgout.huawei.com ([194.213.3.17]:13177 "EHLO lhrrgout.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752839AbbFAJ4g (ORCPT ); Mon, 1 Jun 2015 05:56:36 -0400 From: Wang Nan To: , , , , , , , , , , CC: , , , , Subject: [RFC PATCH v5 14/30] bpf tools: Record map accessing instructions for each program Date: Mon, 1 Jun 2015 07:38:00 +0000 Message-ID: <1433144296-74992-15-git-send-email-wangnan0@huawei.com> X-Mailer: git-send-email 1.8.3.4 In-Reply-To: <1433144296-74992-1-git-send-email-wangnan0@huawei.com> References: <1433144296-74992-1-git-send-email-wangnan0@huawei.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.107.197.200] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5684 Lines: 213 This patch records the indics of instructions which are needed to be relocated. Those information are saved in 'reloc_desc' field in 'struct bpf_program'. In loading phase (this patch takes effect in opening phase), the collected instructions will be replaced by map loading instructions. Since we are going to close the ELF file and clear all data at the end of 'opening' phase, ELF information will no longer be valid in 'loading' phase. We have to locate the instructions before maps are loaded, instead of directly modifying the instruction. 'struct bpf_map_def' is introduce in this patch to let us know how many maps defined in the object. Signed-off-by: Wang Nan --- tools/lib/bpf/libbpf.c | 124 +++++++++++++++++++++++++++++++++++++++++++++++++ tools/lib/bpf/libbpf.h | 13 ++++++ 2 files changed, 137 insertions(+) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index a761b34..7d871ca 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -9,6 +9,7 @@ #include #include #include +#include #include #include #include @@ -88,6 +89,12 @@ struct bpf_program { char *section_name; struct bpf_insn *insns; size_t insns_cnt; + + struct { + int insn_idx; + int map_idx; + } *reloc_desc; + int nr_reloc; }; struct bpf_object { @@ -125,6 +132,9 @@ static void bpf_program__clear(struct bpf_program *prog) zfree(&prog->section_name); zfree(&prog->insns); + zfree(&prog->reloc_desc); + + prog->nr_reloc = 0; prog->insns_cnt = 0; prog->idx = -1; } @@ -447,6 +457,118 @@ out: return err; } +static struct bpf_program * +bpf_object__find_prog_by_idx(struct bpf_object *obj, int idx) +{ + struct bpf_program *prog; + size_t i; + + for (i = 0; i < obj->nr_programs; i++) { + prog = &obj->programs[i]; + if (prog->idx == idx) + return prog; + } + return NULL; +} + +static int +bpf_program__collect_reloc(struct bpf_program *prog, + size_t nr_maps, GElf_Shdr *shdr, + Elf_Data *data, Elf_Data *symbols) +{ + int i, nrels; + + pr_debug("collecting relocating info for: '%s'\n", + prog->section_name); + nrels = shdr->sh_size / shdr->sh_entsize; + + prog->reloc_desc = malloc(sizeof(*prog->reloc_desc) * nrels); + if (!prog->reloc_desc) { + pr_warning("failed to alloc memory in relocation\n"); + return -ENOMEM; + } + prog->nr_reloc = nrels; + + for (i = 0; i < nrels; i++) { + GElf_Sym sym; + GElf_Rel rel; + unsigned int insn_idx; + struct bpf_insn *insns = prog->insns; + size_t map_idx; + + if (!gelf_getrel(data, i, &rel)) { + pr_warning("relocation: failed to get %d reloc\n", i); + return -EINVAL; + } + + insn_idx = rel.r_offset / sizeof(struct bpf_insn); + pr_debug("relocation: insn_idx=%u\n", insn_idx); + + if (!gelf_getsym(symbols, + GELF_R_SYM(rel.r_info), + &sym)) { + pr_warning("relocation: symbol %"PRIx64" not found\n", + GELF_R_SYM(rel.r_info)); + return -EINVAL; + } + + if (insns[insn_idx].code != (BPF_LD | BPF_IMM | BPF_DW)) { + pr_warning("bpf: relocation: invalid relo for insns[%d].code 0x%x\n", + insn_idx, insns[insn_idx].code); + return -EINVAL; + } + + map_idx = sym.st_value / sizeof(struct bpf_map_def); + if (map_idx >= nr_maps) { + pr_warning("bpf relocation: map_idx %d large than %d\n", + (int)map_idx, (int)nr_maps - 1); + return -EINVAL; + } + + prog->reloc_desc[i].insn_idx = insn_idx; + prog->reloc_desc[i].map_idx = map_idx; + } + return 0; +} + +static int bpf_object__collect_reloc(struct bpf_object *obj) +{ + int i, err; + + if (!obj_elf_valid(obj)) { + pr_warning("Internal error: elf object is closed\n"); + return -EINVAL; + } + + for (i = 0; i < obj->efile.nr_reloc; i++) { + GElf_Shdr *shdr = &obj->efile.reloc[i].shdr; + Elf_Data *data = obj->efile.reloc[i].data; + int idx = shdr->sh_info; + struct bpf_program *prog; + size_t nr_maps = obj->maps_buf_sz / + sizeof(struct bpf_map_def); + + if (shdr->sh_type != SHT_REL) { + pr_warning("internal error at %d\n", __LINE__); + return -EINVAL; + } + + prog = bpf_object__find_prog_by_idx(obj, idx); + if (!prog) { + pr_warning("relocation failed: no %d section\n", + idx); + return -ENOENT; + } + + err = bpf_program__collect_reloc(prog, nr_maps, + shdr, data, + obj->efile.symbols); + if (err) + return -EINVAL; + } + return 0; +} + static int bpf_object__validate(struct bpf_object *obj) { if (obj->kern_version == 0) { @@ -482,6 +604,8 @@ struct bpf_object *bpf_object__open(const char *path) goto out; if (bpf_object__elf_collect(obj)) goto out; + if (bpf_object__collect_reloc(obj)) + goto out; if (bpf_object__validate(obj)) goto out; diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index ec3301c..84faa12 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -28,4 +28,17 @@ struct bpf_object; struct bpf_object *bpf_object__open(const char *path); void bpf_object__close(struct bpf_object *object); +/* + * We don't need __attribute__((packed)) now since it is + * unnecessary for 'bpf_map_def' because they are all aligned. + * In addition, using it will trigger -Wpacked warning message, + * and will be treated as an error due to -Werror. + */ +struct bpf_map_def { + unsigned int type; + unsigned int key_size; + unsigned int value_size; + unsigned int max_entries; +}; + #endif -- 1.8.3.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/