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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 745F7C433EF for ; Tue, 12 Jul 2022 19:01:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235092AbiGLTBm (ORCPT ); Tue, 12 Jul 2022 15:01:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41050 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235071AbiGLTAJ (ORCPT ); Tue, 12 Jul 2022 15:00:09 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 15039F54E6; Tue, 12 Jul 2022 11:48:31 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id A1E9C61257; Tue, 12 Jul 2022 18:48:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 95479C3411C; Tue, 12 Jul 2022 18:48:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1657651706; bh=v7l30+D0LWtvMBq1kanEuucWSQ3qhjI9Upn4PCw1Ods=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=FhQ9h/wpMmE1zoUS+N6xJGgCutfNgZdxXc5g4/PfmN7JkDI1dA7Mp5V4xN7hOLWAu Yi9mAcqtrd1OcQKsO2dl2ZteEjgh9iM1QoKzgAwKeA71SsLP728PuhwylBfc4eQ1Ql 71Pm2IL5JtC2T1UMYKDg1j4CUrJ7pca4haC/Zgz0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Peter Zijlstra (Intel)" , Borislav Petkov , Josh Poimboeuf , Thadeu Lima de Souza Cascardo Subject: [PATCH 5.15 30/78] x86,objtool: Create .return_sites Date: Tue, 12 Jul 2022 20:39:00 +0200 Message-Id: <20220712183240.004475446@linuxfoundation.org> X-Mailer: git-send-email 2.37.0 In-Reply-To: <20220712183238.844813653@linuxfoundation.org> References: <20220712183238.844813653@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra commit d9e9d2300681d68a775c28de6aa6e5290ae17796 upstream. Find all the return-thunk sites and record them in a .return_sites section such that the kernel can undo this. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Reviewed-by: Josh Poimboeuf Signed-off-by: Borislav Petkov [cascardo: conflict fixup because of functions added to support IBT] Signed-off-by: Thadeu Lima de Souza Cascardo Signed-off-by: Greg Kroah-Hartman --- tools/objtool/arch/x86/decode.c | 5 ++ tools/objtool/check.c | 75 ++++++++++++++++++++++++++++++++ tools/objtool/include/objtool/arch.h | 1 tools/objtool/include/objtool/elf.h | 1 tools/objtool/include/objtool/objtool.h | 1 tools/objtool/objtool.c | 1 6 files changed, 84 insertions(+) --- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -722,3 +722,8 @@ bool arch_is_retpoline(struct symbol *sy { return !strncmp(sym->name, "__x86_indirect_", 15); } + +bool arch_is_rethunk(struct symbol *sym) +{ + return !strcmp(sym->name, "__x86_return_thunk"); +} --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -654,6 +654,52 @@ static int create_retpoline_sites_sectio return 0; } +static int create_return_sites_sections(struct objtool_file *file) +{ + struct instruction *insn; + struct section *sec; + int idx; + + sec = find_section_by_name(file->elf, ".return_sites"); + if (sec) { + WARN("file already has .return_sites, skipping"); + return 0; + } + + idx = 0; + list_for_each_entry(insn, &file->return_thunk_list, call_node) + idx++; + + if (!idx) + return 0; + + sec = elf_create_section(file->elf, ".return_sites", 0, + sizeof(int), idx); + if (!sec) { + WARN("elf_create_section: .return_sites"); + return -1; + } + + idx = 0; + list_for_each_entry(insn, &file->return_thunk_list, call_node) { + + int *site = (int *)sec->data->d_buf + idx; + *site = 0; + + if (elf_add_reloc_to_insn(file->elf, sec, + idx * sizeof(int), + R_X86_64_PC32, + insn->sec, insn->offset)) { + WARN("elf_add_reloc_to_insn: .return_sites"); + return -1; + } + + idx++; + } + + return 0; +} + static int create_mcount_loc_sections(struct objtool_file *file) { struct section *sec; @@ -932,6 +978,11 @@ __weak bool arch_is_retpoline(struct sym return false; } +__weak bool arch_is_rethunk(struct symbol *sym) +{ + return false; +} + #define NEGATIVE_RELOC ((void *)-1L) static struct reloc *insn_reloc(struct objtool_file *file, struct instruction *insn) @@ -1092,6 +1143,19 @@ static void add_retpoline_call(struct ob annotate_call_site(file, insn, false); } + +static void add_return_call(struct objtool_file *file, struct instruction *insn) +{ + /* + * Return thunk tail calls are really just returns in disguise, + * so convert them accordingly. + */ + insn->type = INSN_RETURN; + insn->retpoline_safe = true; + + list_add_tail(&insn->call_node, &file->return_thunk_list); +} + /* * Find the destination instructions for all jumps. */ @@ -1116,6 +1180,9 @@ static int add_jump_destinations(struct } else if (reloc->sym->retpoline_thunk) { add_retpoline_call(file, insn); continue; + } else if (reloc->sym->return_thunk) { + add_return_call(file, insn); + continue; } else if (insn->func) { /* internal or external sibling call (with reloc) */ add_call_dest(file, insn, reloc->sym, true); @@ -1937,6 +2004,9 @@ static int classify_symbols(struct objto if (arch_is_retpoline(func)) func->retpoline_thunk = true; + if (arch_is_rethunk(func)) + func->return_thunk = true; + if (!strcmp(func->name, "__fentry__")) func->fentry = true; @@ -3413,6 +3483,11 @@ int check(struct objtool_file *file) if (ret < 0) goto out; warnings += ret; + + ret = create_return_sites_sections(file); + if (ret < 0) + goto out; + warnings += ret; } if (mcount) { --- a/tools/objtool/include/objtool/arch.h +++ b/tools/objtool/include/objtool/arch.h @@ -88,6 +88,7 @@ const char *arch_ret_insn(int len); int arch_decode_hint_reg(u8 sp_reg, int *base); bool arch_is_retpoline(struct symbol *sym); +bool arch_is_rethunk(struct symbol *sym); int arch_rewrite_retpolines(struct objtool_file *file); --- a/tools/objtool/include/objtool/elf.h +++ b/tools/objtool/include/objtool/elf.h @@ -57,6 +57,7 @@ struct symbol { u8 uaccess_safe : 1; u8 static_call_tramp : 1; u8 retpoline_thunk : 1; + u8 return_thunk : 1; u8 fentry : 1; u8 kcov : 1; }; --- a/tools/objtool/include/objtool/objtool.h +++ b/tools/objtool/include/objtool/objtool.h @@ -19,6 +19,7 @@ struct objtool_file { struct list_head insn_list; DECLARE_HASHTABLE(insn_hash, 20); struct list_head retpoline_call_list; + struct list_head return_thunk_list; struct list_head static_call_list; struct list_head mcount_loc_list; bool ignore_unreachables, c_file, hints, rodata; --- a/tools/objtool/objtool.c +++ b/tools/objtool/objtool.c @@ -126,6 +126,7 @@ struct objtool_file *objtool_open_read(c INIT_LIST_HEAD(&file.insn_list); hash_init(file.insn_hash); INIT_LIST_HEAD(&file.retpoline_call_list); + INIT_LIST_HEAD(&file.return_thunk_list); INIT_LIST_HEAD(&file.static_call_list); INIT_LIST_HEAD(&file.mcount_loc_list); file.c_file = !vmlinux && find_section_by_name(file.elf, ".comment");