From patchwork Tue Sep 14 19:10:30 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sami Tolvanen X-Patchwork-Id: 12537691 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=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL 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 1C6D7C433FE for ; Tue, 14 Sep 2021 19:10:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 04F3D60E52 for ; Tue, 14 Sep 2021 19:10:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232582AbhINTMI (ORCPT ); Tue, 14 Sep 2021 15:12:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49002 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232535AbhINTMI (ORCPT ); Tue, 14 Sep 2021 15:12:08 -0400 Received: from mail-qt1-x84a.google.com (mail-qt1-x84a.google.com [IPv6:2607:f8b0:4864:20::84a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7E876C061762 for ; Tue, 14 Sep 2021 12:10:50 -0700 (PDT) Received: by mail-qt1-x84a.google.com with SMTP id c11-20020ac81e8b000000b002a0d78f8f9fso20005qtm.2 for ; Tue, 14 Sep 2021 12:10:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=6wsaeVs2pKdYr3cjE54GmOMKWkqFIYtd4ul6D2XgoZU=; b=SltRY0PhqLK7FYtJkRMpj0cip7N3mIDzycHhJwSJI/vXbbxiBlS/DkOmt1Bam+2NaS KNqcNsjuZHP2NrWLhUY05IfpzjDC9bG/2nBjT4fJAVqlS6mjc61BQWEl0JpHpFJ8CJGs tS7wC9+QSXSSkJ/Lg7n1c03rmwmHz9phqCM1Zr4mVysI+SRsNQ2mRuQ+0jQpxyIKmDxO 5X3WotGkHldgI8P4dkwN8eSZs0YdF55zFQx6v5t5a9P9mI1dbku9QqjpOBr7lZY0fQzZ 9t3RkXjkzFiOIqtPKmwq0CcGZP+d35k6Am/sYlrNKXs3bhDVve8A5bzd+NV2w3Y/1qfX 2pJw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=6wsaeVs2pKdYr3cjE54GmOMKWkqFIYtd4ul6D2XgoZU=; b=5MaC3E2zuB/7sX+8i71jIXv/Sz98bqJT2+gLIwKDfeqGeZhykrm/FjlAvUDJd1FpPe ecf+TbBxZpIgm9B2snL1ByNr6ZArVLoPCzhMEcizheKL05nxTQE22LmsUybuNrr7jJ5L fddigKuWF082tEpJoTqMKrBCXAUSyvvj6tCtxH+eWrkN8mN3Z8QT9sqo9EBlzBMltybS j78v4pSQnSf1jGJeGnjx7Tu/dyNvMZFN7hvS2LIFylr0DxHnsHvXTSq2muZZ4M/9JRWk W9MJB/MgVo/b2yIThg1Y2Tdar74n/IAlBf5PWSBp44M4T4T63PKyFWu1gaoh+b/QDIEb L3Nw== X-Gm-Message-State: AOAM531+MEbAoUQgT7BrMrUNjadQ2Gu3hEVX1LQi6J1IqgvoOcT4HLfJ HW1w6HEVs2FRE1O+McrtCrFKup519ppJfM811qc= X-Google-Smtp-Source: ABdhPJyDx0Z0D7ip/W8X0y/WUO54NQO7F+xb7o3bHjGEkSDgPZVhwNYUYk8ghI2IPK1QbCY4mIINfa4EP8DImMu+pLA= X-Received: from samitolvanen1.mtv.corp.google.com ([2620:15c:201:2:d19c:5902:49bb:c41]) (user=samitolvanen job=sendgmr) by 2002:a0c:aa01:: with SMTP id d1mr7115315qvb.47.1631646649694; Tue, 14 Sep 2021 12:10:49 -0700 (PDT) Date: Tue, 14 Sep 2021 12:10:30 -0700 In-Reply-To: <20210914191045.2234020-1-samitolvanen@google.com> Message-Id: <20210914191045.2234020-2-samitolvanen@google.com> Mime-Version: 1.0 References: <20210914191045.2234020-1-samitolvanen@google.com> X-Mailer: git-send-email 2.33.0.309.g3052b89438-goog Subject: [PATCH v3 01/16] objtool: Add CONFIG_CFI_CLANG support From: Sami Tolvanen To: x86@kernel.org Cc: Kees Cook , Josh Poimboeuf , Peter Zijlstra , Nathan Chancellor , Nick Desaulniers , Sedat Dilek , linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Sami Tolvanen Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org With CONFIG_CFI_CLANG, the compiler replaces function references with references to the CFI jump table, which confuses objtool. This change, based on Josh's initial patch [1], goes through the list of relocations and replaces jump table symbols with the actual function symbols. [1] https://lore.kernel.org/r/d743f4b36e120c06506567a9f87a062ae03da47f.1611263462.git.jpoimboe@redhat.com/ Reported-by: Sedat Dilek Suggested-by: Josh Poimboeuf Signed-off-by: Sami Tolvanen --- tools/objtool/arch/x86/decode.c | 16 +++++++++ tools/objtool/elf.c | 51 ++++++++++++++++++++++++++++ tools/objtool/include/objtool/arch.h | 3 ++ tools/objtool/include/objtool/elf.h | 2 +- 4 files changed, 71 insertions(+), 1 deletion(-) diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c index bc821056aba9..318189c8065e 100644 --- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -62,6 +62,22 @@ bool arch_callee_saved_reg(unsigned char reg) } } +unsigned long arch_cfi_section_reloc_offset(struct reloc *reloc) +{ + if (!reloc->addend) + return 0; + + if (reloc->type == R_X86_64_PC32 || reloc->type == R_X86_64_PLT32) + return reloc->addend + 4; + + return reloc->addend; +} + +unsigned long arch_cfi_jump_reloc_offset(unsigned long offset) +{ + return offset + 1; +} + unsigned long arch_dest_reloc_offset(int addend) { return addend + 4; diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index 8676c7598728..05a5f51aad2c 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -18,6 +18,7 @@ #include #include +#include #include #include @@ -291,6 +292,10 @@ static int read_sections(struct elf *elf) if (sec->sh.sh_flags & SHF_EXECINSTR) elf->text_size += sec->len; + /* Detect -fsanitize=cfi jump table sections */ + if (!strncmp(sec->name, ".text..L.cfi.jumptable", 22)) + sec->cfi_jt = true; + list_add_tail(&sec->list, &elf->sections); elf_hash_add(section, &sec->hash, sec->idx); elf_hash_add(section_name, &sec->name_hash, str_hash(sec->name)); @@ -576,6 +581,49 @@ static int read_rela_reloc(struct section *sec, int i, struct reloc *reloc, unsi return 0; } +/* + * CONFIG_CFI_CLANG replaces function relocations to refer to an intermediate + * jump table. Undo the conversion so objtool can make sense of things. + */ +static int fix_cfi_relocs(const struct elf *elf) +{ + struct section *sec; + struct reloc *reloc; + + list_for_each_entry(sec, &elf->sections, list) { + list_for_each_entry(reloc, &sec->reloc_list, list) { + struct reloc *cfi_reloc; + unsigned long offset; + + if (!reloc->sym->sec->cfi_jt) + continue; + + if (reloc->sym->type == STT_SECTION) + offset = arch_cfi_section_reloc_offset(reloc); + else + offset = reloc->sym->offset; + + /* + * The jump table immediately jumps to the actual function, + * so look up the relocation there. + */ + offset = arch_cfi_jump_reloc_offset(offset); + cfi_reloc = find_reloc_by_dest(elf, reloc->sym->sec, offset); + + if (!cfi_reloc || !cfi_reloc->sym) { + WARN("can't find a CFI jump table relocation at %s+0x%lx", + reloc->sym->sec->name, offset); + return -1; + } + + reloc->sym = cfi_reloc->sym; + reloc->addend = 0; + } + } + + return 0; +} + static int read_relocs(struct elf *elf) { struct section *sec; @@ -639,6 +687,9 @@ static int read_relocs(struct elf *elf) tot_reloc += nr_reloc; } + if (fix_cfi_relocs(elf)) + return -1; + if (stats) { printf("max_reloc: %lu\n", max_reloc); printf("tot_reloc: %lu\n", tot_reloc); diff --git a/tools/objtool/include/objtool/arch.h b/tools/objtool/include/objtool/arch.h index 062bb6e9b865..2205b2b08268 100644 --- a/tools/objtool/include/objtool/arch.h +++ b/tools/objtool/include/objtool/arch.h @@ -81,6 +81,9 @@ unsigned long arch_jump_destination(struct instruction *insn); unsigned long arch_dest_reloc_offset(int addend); +unsigned long arch_cfi_section_reloc_offset(struct reloc *reloc); +unsigned long arch_cfi_jump_reloc_offset(unsigned long offset); + const char *arch_nop_insn(int len); int arch_decode_hint_reg(struct instruction *insn, u8 sp_reg); diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h index e34395047530..d9c1dacc6572 100644 --- a/tools/objtool/include/objtool/elf.h +++ b/tools/objtool/include/objtool/elf.h @@ -39,7 +39,7 @@ struct section { char *name; int idx; unsigned int len; - bool changed, text, rodata, noinstr; + bool changed, text, rodata, noinstr, cfi_jt; }; struct symbol {