From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id ACD88C433E9 for ; Fri, 26 Mar 2021 15:14:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9B19161A2A for ; Fri, 26 Mar 2021 15:14:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231359AbhCZPOa (ORCPT ); Fri, 26 Mar 2021 11:14:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32996 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231165AbhCZPNo (ORCPT ); Fri, 26 Mar 2021 11:13:44 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2539CC0613B1 for ; Fri, 26 Mar 2021 08:13:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Content-Type:MIME-Version:References: Subject:Cc:To:From:Date:Message-ID:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:In-Reply-To; bh=9UZwhEdTZIWzuKJCBvisbhXRBLCBRVkqI9z6qW4xhqM=; b=mgdOPPKJ6Bp0gRSwdmfYCJELdY NtZULLvcdV7fZBcHu4X5JARNmT97MgAmUtvyrCHuEcHMI+rH0VQL90Ay8x3a2O0Ja+6pnW/nWnGcY JV3Y1kBlxUtB+Xw4oA8gJ+jdqwxZK/No8VfO6GrZFEfoUlxuuLs4kWk+GxJuCKOOQ592lTaX+S6xg 1c+MrcJCM00SM022kQJjJvgWOkdhvOtmkZPn1H2omfFOS6bOMA3MKA6f33zUbL/oFSUeHzCGWPBGT 0ukgI5GrkcOR5/AdVcWYV+azfx+5k7JfbrNb8N/sTmwJeJeqyeJdH+FC/qZsAj0iP69VmSo3oOAfI JRsr8BTQ==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94 #2 (Red Hat Linux)) id 1lPo9Y-003s0Q-FD; Fri, 26 Mar 2021 15:13:36 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id AE4403079A1; Fri, 26 Mar 2021 16:13:34 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 69B172BD7339C; Fri, 26 Mar 2021 16:13:34 +0100 (CET) Message-ID: <20210326151300.064743095@infradead.org> User-Agent: quilt/0.66 Date: Fri, 26 Mar 2021 16:12:11 +0100 From: Peter Zijlstra To: x86@kernel.org, jpoimboe@redhat.com, jgross@suse.com, mbenes@suse.com Cc: linux-kernel@vger.kernel.org, peterz@infradead.org Subject: [PATCH v3 12/16] objtool: Add elf_create_undef_symbol() References: <20210326151159.128534163@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Allow objtool to create undefined symbols; this allows creating relocations to symbols not currently in the symbol table. Signed-off-by: Peter Zijlstra (Intel) --- tools/objtool/elf.c | 60 ++++++++++++++++++++++++++++++++++++ tools/objtool/include/objtool/elf.h | 1 2 files changed, 61 insertions(+) --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -715,6 +715,66 @@ static int elf_add_string(struct elf *el return len; } +struct symbol *elf_create_undef_symbol(struct elf *elf, const char *name) +{ + struct section *symtab; + struct symbol *sym; + Elf_Data *data; + Elf_Scn *s; + + sym = malloc(sizeof(*sym)); + if (!sym) { + perror("malloc"); + return NULL; + } + memset(sym, 0, sizeof(*sym)); + + sym->name = strdup(name); + + sym->sym.st_name = elf_add_string(elf, NULL, sym->name); + if (sym->sym.st_name == -1) + return NULL; + + sym->sym.st_info = GELF_ST_INFO(STB_GLOBAL, STT_NOTYPE); + // st_other 0 + // st_shndx 0 + // st_value 0 + // st_size 0 + + symtab = find_section_by_name(elf, ".symtab"); + if (!symtab) { + WARN("can't find .symtab"); + return NULL; + } + + s = elf_getscn(elf->elf, symtab->idx); + if (!s) { + WARN_ELF("elf_getscn"); + return NULL; + } + + data = elf_newdata(s); + if (!data) { + WARN_ELF("elf_newdata"); + return NULL; + } + + data->d_buf = &sym->sym; + data->d_size = sizeof(sym->sym); + data->d_align = 1; + + sym->idx = symtab->len / sizeof(sym->sym); + + symtab->len += data->d_size; + symtab->changed = true; + + sym->sec = find_section_by_index(elf, 0); + + elf_add_symbol(elf, sym); + + return sym; +} + struct section *elf_create_section(struct elf *elf, const char *name, unsigned int sh_flags, size_t entsize, int nr) { --- a/tools/objtool/include/objtool/elf.h +++ b/tools/objtool/include/objtool/elf.h @@ -133,6 +133,7 @@ int elf_write_insn(struct elf *elf, stru unsigned long offset, unsigned int len, const char *insn); int elf_write_reloc(struct elf *elf, struct reloc *reloc); +struct symbol *elf_create_undef_symbol(struct elf *elf, const char *name); int elf_write(struct elf *elf); void elf_close(struct elf *elf);