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=-10.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, T_DKIMWL_WL_MED,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 50DE2C43142 for ; Mon, 25 Jun 2018 22:42:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F2D2126227 for ; Mon, 25 Jun 2018 22:42:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="lQf+Ys1d" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F2D2126227 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755725AbeFYWmb (ORCPT ); Mon, 25 Jun 2018 18:42:31 -0400 Received: from mail-yb0-f201.google.com ([209.85.213.201]:51226 "EHLO mail-yb0-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964802AbeFYWmZ (ORCPT ); Mon, 25 Jun 2018 18:42:25 -0400 Received: by mail-yb0-f201.google.com with SMTP id h6-v6so11068145ybm.18 for ; Mon, 25 Jun 2018 15:42:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:date:in-reply-to:message-id:references:subject:from:to :cc; bh=lRn9EQ4qGSeHmfN0semOwuZ4D4PmrhNt/DbyFqDShzo=; b=lQf+Ys1d4Spz8xS5uEWO1N0hT/Xp8c0aHLGnjlxPgwQhEDbi3Vrnuycm9LmIFJAzk1 dpwAT7YaRZG6s7GE25m3EZWvhy5P084W88AP5c3g0duifH2Sk7SHjytjJ/nF7zuhZBkp nWkXPYVCSBO02wG9itNus8eAh3PcInot3f0EImi/o/KgmYNTiyTr+/6uh06/nsuSjNSd ly5TgyqowwmGDavayTVVBg98HwORAvrpMbNh8qjfD1PR3rXUzVE6+Tgg6lvozU86xCwT q2NOorLOgA+aOgN/MEEOH1I8e0ZKIYMh5HBy5EJQb5DlNzp/p2z9JcxRm4+Ek1f5SQK+ ksew== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:date:in-reply-to:message-id :references:subject:from:to:cc; bh=lRn9EQ4qGSeHmfN0semOwuZ4D4PmrhNt/DbyFqDShzo=; b=T5GC2zPMWRs8LpzJx37YTxnW50J3cZ/doWhDoaQJuUwarSzB83TPZrx7+j11ziy/d7 FbN8KjT7hNni/Qc/qCN6IXmwOE8i1wFVpKBryIMtNUg119VTrrQ66GTBOaBOP8SsVc7O RZGoJPl5pGL+2yV9vhOZuf+u0vhd78sIyQ6kfsaJJlncbcSSH9H7BcOaOthH6+A2Nsyf hqwq1WecsfrzOgIhypKczSmf/gKSn52OATp03rEERgAlV0AldR73FMdIoEW4gUXOlKEb hUjXgefBAe3XIfpM9QLsBQhwUXorGiAjz1QdMm7bBYkuj7u3vhl8pnn1llsR0w9CJUni WTGQ== X-Gm-Message-State: APt69E1YfEtha3Eoy9OtUMmZH/I6A5WKISCWep9ihbFwpjVexbPlam90 lqt+3HmCM7ta41AILkMPyoAmj2oLIszVGQ== X-Google-Smtp-Source: AAOMgpde1GMuNdCsp5JDju0B7L5l3dmx3UBTd7M6+GaFh6vLQ35xVGIoLEyZo9YT1V6v9G+Va0QBtbezd0j7sg== MIME-Version: 1.0 X-Received: by 2002:a0d:e2c3:: with SMTP id l186-v6mr3689571ywe.91.1529966544863; Mon, 25 Jun 2018 15:42:24 -0700 (PDT) Date: Mon, 25 Jun 2018 15:39:09 -0700 In-Reply-To: <20180625224014.134829-1-thgarnie@google.com> Message-Id: <20180625224014.134829-22-thgarnie@google.com> References: <20180625224014.134829-1-thgarnie@google.com> X-Mailer: git-send-email 2.18.0.rc2.346.g013aa6912e-goog Subject: [PATCH v5 21/27] x86/ftrace: Adapt function tracing for PIE support From: Thomas Garnier To: kernel-hardening@lists.openwall.com Cc: Thomas Garnier , Steven Rostedt , Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , x86@kernel.org, James Hogan , "Peter Zijlstra (Intel)" , nixiaoming , Guenter Roeck , linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When using PIE with function tracing, the compiler generates a call through the GOT (call *__fentry__@GOTPCREL). This instruction takes 6-bytes instead of 5-bytes with a relative call. If PIE is enabled, replace the 6th byte of the GOT call by a 1-byte nop so ftrace can handle the previous 5-bytes as before. Position Independent Executable (PIE) support will allow to extend the KASLR randomization range 0xffffffff80000000. Signed-off-by: Thomas Garnier --- arch/x86/kernel/ftrace.c | 51 +++++++++++++++++++++++++- scripts/recordmcount.c | 79 +++++++++++++++++++++++++++------------- 2 files changed, 102 insertions(+), 28 deletions(-) diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 01ebcb6f263e..2194a5d3e095 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -102,7 +102,7 @@ static const unsigned char *ftrace_nop_replace(void) static int ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code, - unsigned const char *new_code) + unsigned const char *new_code) { unsigned char replaced[MCOUNT_INSN_SIZE]; @@ -135,6 +135,53 @@ ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code, return 0; } +/* Bytes before call GOT offset */ +static const unsigned char got_call_preinsn[] = { 0xff, 0x15 }; + +static int +ftrace_modify_initial_code(unsigned long ip, unsigned const char *old_code, + unsigned const char *new_code) +{ + unsigned char replaced[MCOUNT_INSN_SIZE + 1]; + + /* + * If PIE is not enabled default to the original approach to code + * modification. + */ + if (!IS_ENABLED(CONFIG_X86_PIE)) + return ftrace_modify_code_direct(ip, old_code, new_code); + + ftrace_expected = old_code; + + /* Ensure the instructions point to a call to the GOT */ + if (probe_kernel_read(replaced, (void *)ip, sizeof(replaced))) { + WARN_ONCE(1, "invalid function"); + return -EFAULT; + } + + if (memcmp(replaced, got_call_preinsn, sizeof(got_call_preinsn))) { + WARN_ONCE(1, "invalid function call"); + return -EINVAL; + } + + /* + * Build a nop slide with a 5-byte nop and 1-byte nop to keep the ftrace + * hooking algorithm working with the expected 5 bytes instruction. + */ + memset(replaced, ideal_nops[1][0], sizeof(replaced)); + memcpy(replaced, new_code, MCOUNT_INSN_SIZE); + + ip = text_ip_addr(ip); + + if (probe_kernel_write((void *)ip, replaced, sizeof(replaced))) + return -EPERM; + + sync_core(); + + return 0; + +} + int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { @@ -153,7 +200,7 @@ int ftrace_make_nop(struct module *mod, * just modify the code directly. */ if (addr == MCOUNT_ADDR) - return ftrace_modify_code_direct(rec->ip, old, new); + return ftrace_modify_initial_code(rec->ip, old, new); ftrace_expected = NULL; diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c index 895c40e8679f..aa71b912958d 100644 --- a/scripts/recordmcount.c +++ b/scripts/recordmcount.c @@ -171,33 +171,9 @@ umalloc(size_t size) return addr; } -static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 }; -static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 }; -static unsigned char *ideal_nop; - static char rel_type_nop; - static int (*make_nop)(void *map, size_t const offset); - -static int make_nop_x86(void *map, size_t const offset) -{ - uint32_t *ptr; - unsigned char *op; - - /* Confirm we have 0xe8 0x0 0x0 0x0 0x0 */ - ptr = map + offset; - if (*ptr != 0) - return -1; - - op = map + offset - 1; - if (*op != 0xe8) - return -1; - - /* convert to nop */ - ulseek(fd_map, offset - 1, SEEK_SET); - uwrite(fd_map, ideal_nop, 5); - return 0; -} +static unsigned char *ideal_nop; static unsigned char ideal_nop4_arm_le[4] = { 0x00, 0x00, 0xa0, 0xe1 }; /* mov r0, r0 */ static unsigned char ideal_nop4_arm_be[4] = { 0xe1, 0xa0, 0x00, 0x00 }; /* mov r0, r0 */ @@ -447,6 +423,50 @@ static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type) }).r_info; } +static unsigned char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 }; +static unsigned char ideal_nop6_x86_64[6] = { 0x66, 0x0f, 0x1f, 0x44, 0x00, 0x00 }; +static unsigned char ideal_nop5_x86_32[5] = { 0x3e, 0x8d, 0x74, 0x26, 0x00 }; +static size_t ideal_nop_x86_size; + +static unsigned char stub_default_x86[2] = { 0xe8, 0x00 }; /* call relative */ +static unsigned char stub_got_x86[3] = { 0xff, 0x15, 0x00 }; /* call .got */ +static unsigned char *stub_x86; +static size_t stub_x86_size; + +static int make_nop_x86(void *map, size_t const offset) +{ + uint32_t *ptr; + size_t stub_offset = offset - stub_x86_size; + + /* confirm we have the expected stub */ + ptr = map + stub_offset; + if (memcmp(ptr, stub_x86, stub_x86_size)) { + return -1; + } + + /* convert to nop */ + ulseek(fd_map, stub_offset, SEEK_SET); + uwrite(fd_map, ideal_nop, ideal_nop_x86_size); + return 0; +} + +/* Swap the stub and nop for a got call if the binary is built with PIE */ +static int is_fake_mcount_x86_x64(Elf64_Rel const *rp) +{ + if (ELF64_R_TYPE(rp->r_info) == R_X86_64_GOTPCREL) { + ideal_nop = ideal_nop6_x86_64; + ideal_nop_x86_size = sizeof(ideal_nop6_x86_64); + stub_x86 = stub_got_x86; + stub_x86_size = sizeof(stub_got_x86); + mcount_adjust_64 = 1 - stub_x86_size; + } + + /* Once the relocation was checked, rollback to default */ + is_fake_mcount64 = fn_is_fake_mcount64; + return is_fake_mcount64(rp); +} + + static void do_file(char const *const fname) { @@ -509,6 +529,9 @@ do_file(char const *const fname) rel_type_nop = R_386_NONE; make_nop = make_nop_x86; ideal_nop = ideal_nop5_x86_32; + ideal_nop_x86_size = sizeof(ideal_nop5_x86_32); + stub_x86 = stub_default_x86; + stub_x86_size = sizeof(stub_default_x86); mcount_adjust_32 = -1; break; case EM_ARM: reltype = R_ARM_ABS32; @@ -533,9 +556,13 @@ do_file(char const *const fname) case EM_X86_64: make_nop = make_nop_x86; ideal_nop = ideal_nop5_x86_64; + ideal_nop_x86_size = sizeof(ideal_nop5_x86_64); + stub_x86 = stub_default_x86; + stub_x86_size = sizeof(stub_default_x86); reltype = R_X86_64_64; rel_type_nop = R_X86_64_NONE; - mcount_adjust_64 = -1; + is_fake_mcount64 = is_fake_mcount_x86_x64; + mcount_adjust_64 = 1 - stub_x86_size; break; } /* end switch */ -- 2.18.0.rc2.346.g013aa6912e-goog