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 0D269C433DB for ; Fri, 12 Mar 2021 17:18:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C8F1164FB5 for ; Fri, 12 Mar 2021 17:18:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232659AbhCLRSL (ORCPT ); Fri, 12 Mar 2021 12:18:11 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39252 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232647AbhCLRSA (ORCPT ); Fri, 12 Mar 2021 12:18:00 -0500 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 0EF9CC061761 for ; Fri, 12 Mar 2021 09:18:00 -0800 (PST) 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=Rook4fYxEFvspuo0gkFACiC9RJ6QYhXIbzPllSfjTyQ=; b=lieaZsHonoIdWtM6NTQcI8Ik0G gxk3eug0O5axAgN503/zGQ5N71EG6R53Qk8Or0SjxjPlRw3BCyUbbl08el4zHDIaK6XKF62p0onCg eiTuVKtI04GFyR94r7uwA6l4oaFeXMFmixK4S4yHixS7Qa3kyW8COpeWFlfOQBO4b1ywKTtH4jOt7 feOYFQrJXb1jkyNgbTIRsfytFqMRQgO1KWvwMGF4jmu6UnBH2tCzTyOKd8xfTVdqkDdw+LeQUqCYs RCTQNDQAFGpfu68+UcNwUWrHc134hLcydsoiaBCdI1weVtt9bOkPGht9tCWBiSo4ET5a8o6RKxJHN +LgZYkyw==; 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 1lKlQ9-00C533-VD; Fri, 12 Mar 2021 17:17:54 +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 46C6930768E; Fri, 12 Mar 2021 18:17:53 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 0) id 1483B23CC2296; Fri, 12 Mar 2021 18:17:53 +0100 (CET) Message-ID: <20210312171653.710872453@infradead.org> User-Agent: quilt/0.66 Date: Fri, 12 Mar 2021 18:16:19 +0100 From: Peter Zijlstra To: x86@kernel.org, jpoimboe@redhat.com, jgross@suse.com, mbenes@suze.cz Cc: linux-kernel@vger.kernel.org, peterz@infradead.org Subject: [PATCH 6/9] objtool: Add elf_create_undef_symbol() References: <20210312171613.533405394@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 | 180 +++++++++++++++++++++++++++--------- tools/objtool/include/objtool/elf.h | 1 2 files changed, 139 insertions(+), 42 deletions(-) --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -316,12 +316,60 @@ static int read_sections(struct elf *elf return 0; } +static bool elf_symbol_add(struct elf *elf, struct symbol *sym, Elf32_Word shndx) +{ + struct list_head *entry; + struct rb_node *pnode; + + sym->type = GELF_ST_TYPE(sym->sym.st_info); + sym->bind = GELF_ST_BIND(sym->sym.st_info); + + if ((sym->sym.st_shndx > SHN_UNDEF && + sym->sym.st_shndx < SHN_LORESERVE) || + (shndx != SHN_XINDEX && sym->sym.st_shndx == SHN_XINDEX)) { + if (sym->sym.st_shndx != SHN_XINDEX) + shndx = sym->sym.st_shndx; + + sym->sec = find_section_by_index(elf, shndx); + if (!sym->sec) { + WARN("couldn't find section for symbol %s", + sym->name); + return false; + } + if (sym->type == STT_SECTION) { + sym->name = sym->sec->name; + sym->sec->sym = sym; + } + } else + sym->sec = find_section_by_index(elf, 0); + + sym->offset = sym->sym.st_value; + sym->len = sym->sym.st_size; + + rb_add(&sym->node, &sym->sec->symbol_tree, symbol_to_offset); + pnode = rb_prev(&sym->node); + if (pnode) + entry = &rb_entry(pnode, struct symbol, node)->list; + else + entry = &sym->sec->symbol_list; + list_add(&sym->list, entry); + elf_hash_add(elf->symbol_hash, &sym->hash, sym->idx); + elf_hash_add(elf->symbol_name_hash, &sym->name_hash, str_hash(sym->name)); + + /* + * Don't store empty STT_NOTYPE symbols in the rbtree. They + * can exist within a function, confusing the sorting. + */ + if (!sym->len) + rb_erase(&sym->node, &sym->sec->symbol_tree); + + return true; +} + static int read_symbols(struct elf *elf) { struct section *symtab, *symtab_shndx, *sec; struct symbol *sym, *pfunc; - struct list_head *entry; - struct rb_node *pnode; int symbols_nr, i; char *coldstr; Elf_Data *shndx_data = NULL; @@ -366,47 +414,11 @@ static int read_symbols(struct elf *elf) goto err; } - sym->type = GELF_ST_TYPE(sym->sym.st_info); - sym->bind = GELF_ST_BIND(sym->sym.st_info); + if (!shndx_data) + shndx = SHN_XINDEX; - if ((sym->sym.st_shndx > SHN_UNDEF && - sym->sym.st_shndx < SHN_LORESERVE) || - (shndx_data && sym->sym.st_shndx == SHN_XINDEX)) { - if (sym->sym.st_shndx != SHN_XINDEX) - shndx = sym->sym.st_shndx; - - sym->sec = find_section_by_index(elf, shndx); - if (!sym->sec) { - WARN("couldn't find section for symbol %s", - sym->name); - goto err; - } - if (sym->type == STT_SECTION) { - sym->name = sym->sec->name; - sym->sec->sym = sym; - } - } else - sym->sec = find_section_by_index(elf, 0); - - sym->offset = sym->sym.st_value; - sym->len = sym->sym.st_size; - - rb_add(&sym->node, &sym->sec->symbol_tree, symbol_to_offset); - pnode = rb_prev(&sym->node); - if (pnode) - entry = &rb_entry(pnode, struct symbol, node)->list; - else - entry = &sym->sec->symbol_list; - list_add(&sym->list, entry); - elf_hash_add(elf->symbol_hash, &sym->hash, sym->idx); - elf_hash_add(elf->symbol_name_hash, &sym->name_hash, str_hash(sym->name)); - - /* - * Don't store empty STT_NOTYPE symbols in the rbtree. They - * can exist within a function, confusing the sorting. - */ - if (!sym->len) - rb_erase(&sym->node, &sym->sec->symbol_tree); + if (!elf_symbol_add(elf, sym, shndx)) + goto err; } if (stats) @@ -640,6 +652,90 @@ struct elf *elf_open_read(const char *na return NULL; } +struct symbol *elf_create_undef_symbol(struct elf *elf, const char *name) +{ + struct section *strtab, *symtab; + struct symbol *sym; + Elf_Scn *s; + Elf_Data *data; + + sym = malloc(sizeof(*sym)); + if (!sym) { + perror("malloc"); + return NULL; + } + memset(sym, 0, sizeof(*sym)); + + sym->name = strdup(name); + + strtab = find_section_by_name(elf, ".strtab"); + if (!strtab) { + WARN("can't find .strtab"); + return NULL; + } + + s = elf_getscn(elf->elf, strtab->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->name; + data->d_size = strlen(sym->name) + 1; + data->d_align = 1; + + sym->sym.st_name = strtab->len; + sym->sym.st_info = 0x10; /* STB_GLOBAL, STT_NOTYPE */ + // st_other 0 + // st_shndx 0 + // st_value 0 + // st_size 0 + + strtab->len += data->d_size; + strtab->changed = true; + + + 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; + + if (!elf_symbol_add(elf, sym, SHN_XINDEX)) { + WARN("elf_symbol_add"); + return NULL; + } + + 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 @@ -128,6 +128,7 @@ 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);