From patchwork Thu Jul 20 11:35:33 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jiri Olsa X-Patchwork-Id: 13320366 X-Patchwork-Delegate: bpf@iogearbox.net Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 35960174E9 for ; Thu, 20 Jul 2023 11:37:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F0631C433C9; Thu, 20 Jul 2023 11:37:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1689853068; bh=JRRJz8/nLZw6vAx2LW1/td9rYqJfps4sUneIFNzu93M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dswsoghEiynehqsscLz8wLGXb7CY93EObBVgns4kPyFgJidObbdP18htpvWz2SPK8 nHjmJcX5++xO6KMs9/wLtDAJDfNEsn4gB8gxuU+EZapd3Tz5FaHnNaN5ZNgXPx2Lc6 GyrWiERgLM1QYEhkVH4FzkugH55bTDfaonDJgoEJnZAlJ39TT+bjL0HhEQJxpSSGIS ct8hMuAjKzzGKuUOxgrx/HvOp8fy/JQ7NC1z4vckOwCPB63aau5sOSdgUPsqMHf9fq xxPvLRyTzNjhV++vfzBgBBTT1EllLfNZk9doVZfwNGcWtGS/HGyeJRU/XWTrJFXtee m51c+Gvmn2jow== From: Jiri Olsa To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko Cc: bpf@vger.kernel.org, Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo Subject: [PATCHv4 bpf-next 11/28] libbpf: Add elf_resolve_syms_offsets function Date: Thu, 20 Jul 2023 13:35:33 +0200 Message-ID: <20230720113550.369257-12-jolsa@kernel.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230720113550.369257-1-jolsa@kernel.org> References: <20230720113550.369257-1-jolsa@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net Adding elf_resolve_syms_offsets function that looks up offsets for symbols specified in syms array argument. Offsets are returned in allocated array with the 'cnt' size, that needs to be released by the caller. Signed-off-by: Jiri Olsa --- tools/lib/bpf/elf.c | 110 ++++++++++++++++++++++++++++++++ tools/lib/bpf/libbpf_internal.h | 2 + 2 files changed, 112 insertions(+) diff --git a/tools/lib/bpf/elf.c b/tools/lib/bpf/elf.c index 8a3f8a725981..8c512641c1d7 100644 --- a/tools/lib/bpf/elf.c +++ b/tools/lib/bpf/elf.c @@ -267,3 +267,113 @@ long elf_find_func_offset_from_file(const char *binary_path, const char *name) elf_close(&elf_fd); return ret; } + +struct symbol { + const char *name; + int bind; + int idx; +}; + +static int symbol_cmp(const void *a, const void *b) +{ + const struct symbol *sym_a = a; + const struct symbol *sym_b = b; + + return strcmp(sym_a->name, sym_b->name); +} + +/* + * Return offsets in @poffsets for symbols specified in @syms array argument. + * On success returns 0 and offsets are returned in allocated array with @cnt + * size, that needs to be released by the caller. + */ +int elf_resolve_syms_offsets(const char *binary_path, int cnt, + const char **syms, unsigned long **poffsets) +{ + int sh_types[2] = { SHT_DYNSYM, SHT_SYMTAB }; + int err = 0, i, cnt_done = 0; + unsigned long *offsets; + struct symbol *symbols; + struct elf_fd elf_fd; + + err = elf_open(binary_path, &elf_fd); + if (err) + return err; + + offsets = calloc(cnt, sizeof(*offsets)); + symbols = calloc(cnt, sizeof(*symbols)); + + if (!offsets || !symbols) { + err = -ENOMEM; + goto out; + } + + for (i = 0; i < cnt; i++) { + symbols[i].name = syms[i]; + symbols[i].idx = i; + } + + qsort(symbols, cnt, sizeof(*symbols), symbol_cmp); + + for (i = 0; i < ARRAY_SIZE(sh_types); i++) { + struct elf_sym_iter iter; + struct elf_sym *sym; + + err = elf_sym_iter_new(&iter, elf_fd.elf, binary_path, sh_types[i], STT_FUNC); + if (err == -ENOENT) + continue; + if (err) + goto out; + + while ((sym = elf_sym_iter_next(&iter))) { + unsigned long sym_offset = elf_sym_offset(sym); + int bind = GELF_ST_BIND(sym->sym.st_info); + struct symbol *found, tmp = { + .name = sym->name, + }; + unsigned long *offset; + + found = bsearch(&tmp, symbols, cnt, sizeof(*symbols), symbol_cmp); + if (!found) + continue; + + offset = &offsets[found->idx]; + if (*offset > 0) { + /* same offset, no problem */ + if (*offset == sym_offset) + continue; + /* handle multiple matches */ + if (found->bind != STB_WEAK && bind != STB_WEAK) { + /* Only accept one non-weak bind. */ + pr_warn("elf: ambiguous match found '%s@%lu' in '%s' previous offset %lu\n", + sym->name, sym_offset, binary_path, *offset); + err = -ESRCH; + goto out; + } else if (bind == STB_WEAK) { + /* already have a non-weak bind, and + * this is a weak bind, so ignore. + */ + continue; + } + } else { + cnt_done++; + } + *offset = sym_offset; + found->bind = bind; + } + } + + if (cnt != cnt_done) { + err = -ENOENT; + goto out; + } + + *poffsets = offsets; + +out: + free(symbols); + if (err) + free(offsets); + elf_close(&elf_fd); + return err; +} diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h index 0bbcd8e6fdc5..92851c5f912d 100644 --- a/tools/lib/bpf/libbpf_internal.h +++ b/tools/lib/bpf/libbpf_internal.h @@ -589,4 +589,6 @@ struct elf_fd { int elf_open(const char *binary_path, struct elf_fd *elf_fd); void elf_close(struct elf_fd *elf_fd); +int elf_resolve_syms_offsets(const char *binary_path, int cnt, + const char **syms, unsigned long **poffsets); #endif /* __LIBBPF_LIBBPF_INTERNAL_H */