From patchwork Thu Mar 18 23:54:15 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nicolas Boichat X-Patchwork-Id: 12149451 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=-19.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, 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,USER_AGENT_GIT 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 8CA0EC433DB for ; Thu, 18 Mar 2021 23:55:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4F8F164E81 for ; Thu, 18 Mar 2021 23:55:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233257AbhCRXzS (ORCPT ); Thu, 18 Mar 2021 19:55:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36594 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231327AbhCRXyq (ORCPT ); Thu, 18 Mar 2021 19:54:46 -0400 Received: from mail-pg1-x535.google.com (mail-pg1-x535.google.com [IPv6:2607:f8b0:4864:20::535]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 95344C061761 for ; Thu, 18 Mar 2021 16:54:46 -0700 (PDT) Received: by mail-pg1-x535.google.com with SMTP id h25so2480211pgm.3 for ; Thu, 18 Mar 2021 16:54:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=OCWO8N3ciaDG5tRci/9OOSktf6u6kKfWPDbEI5DCf7o=; b=WRe8C6UgMjCfEYGM8A9qqEXszowP4m9MBxRvDIUSLFv4+7D/vPSuAfvwQ8D+CcuV9I iIAqGPSHiAwejcRDHGoRA9F7iKAt8FFYglqwP8SxZK5dd9pp2Lw4uH5004n/w7f8jcmN YJwsypl5g2M32rFTG1OjPRNTmApUN4NoEfI7E= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=OCWO8N3ciaDG5tRci/9OOSktf6u6kKfWPDbEI5DCf7o=; b=c8rX7HfcZ2blRuArETjuo1CozvaZGulAlybpU3nJbMODq11lQWnGhSUJ6HEqIQNs7C 1M8hmU44GMbX5tX+INheNsA2Mfwfiy85G/lmj7tC75svB7jtTuEiTRbAviXOITDXIQ2R ZBGQg/5sI1ATwM7mZkI4ZrVyeOb+YXRmtxm2CEkO82HETFF4nEdtByBvtwYa+0+FxSXp Ym7LW+86J2fZFE8JjU7+w+jVbZinM1BJwEVxdKh1/PcJzwfjYN18lqpZszmxqet5J+Qa 506PdrEDfh/dYQ4XV/k+uuJ4tj1TJHxawQIs6aMyUPU3woU/nYXpd3m+/Lh3tq1goiZJ JmQg== X-Gm-Message-State: AOAM530VV8sywEFdeGIaokaZt+tJ0Do12m5AVmeSIsZtZ4KkO+KxKGqG bGTLWaSnqXBxp0Mm+jVLvpQMVw== X-Google-Smtp-Source: ABdhPJwcmwgERjcGCtyxeXhaLRfeMUh3vGXJXsd4rwk0cO3KLmx0J2DGiKfq15S3JcQU6GkrQ5NBdQ== X-Received: by 2002:a62:7ecc:0:b029:1ee:f61b:a63f with SMTP id z195-20020a627ecc0000b02901eef61ba63fmr6276804pfc.57.1616111686051; Thu, 18 Mar 2021 16:54:46 -0700 (PDT) Received: from drinkcat2.tpe.corp.google.com ([2401:fa00:1:b:dc70:2def:a801:e21b]) by smtp.gmail.com with ESMTPSA id t7sm3295816pfg.69.2021.03.18.16.54.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Mar 2021 16:54:45 -0700 (PDT) From: Nicolas Boichat To: stable@vger.kernel.org Cc: Thomas Gleixner , Alexandre Chartre , Peter Zijlstra , Nicolas Boichat , Arnd Bergmann , Benjamin Herrenschmidt , Christopher Li , Daniel Axtens , Greg Kroah-Hartman , Masahiro Yamada , Michael Ellerman , Michal Marek , "Naveen N. Rao" , Nicholas Piggin , Paul Mackerras , Sasha Levin , linux-arch@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-sparse@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: [for-stable-4.19 PATCH 1/2] vmlinux.lds.h: Create section for protection against instrumentation Date: Fri, 19 Mar 2021 07:54:15 +0800 Message-Id: <20210319075410.for-stable-4.19.1.I222f801866f71be9f7d85e5b10665cd4506d78ec@changeid> X-Mailer: git-send-email 2.31.0.rc2.261.g7f71774620-goog In-Reply-To: <20210318235416.794798-1-drinkcat@chromium.org> References: <20210318235416.794798-1-drinkcat@chromium.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-sparse@vger.kernel.org From: Thomas Gleixner commit 6553896666433e7efec589838b400a2a652b3ffa upstream. Some code pathes, especially the low level entry code, must be protected against instrumentation for various reasons: - Low level entry code can be a fragile beast, especially on x86. - With NO_HZ_FULL RCU state needs to be established before using it. Having a dedicated section for such code allows to validate with tooling that no unsafe functions are invoked. Add the .noinstr.text section and the noinstr attribute to mark functions. noinstr implies notrace. Kprobes will gain a section check later. Provide also a set of markers: instrumentation_begin()/end() These are used to mark code inside a noinstr function which calls into regular instrumentable text section as safe. The instrumentation markers are only active when CONFIG_DEBUG_ENTRY is enabled as the end marker emits a NOP to prevent the compiler from merging the annotation points. This means the objtool verification requires a kernel compiled with this option. Signed-off-by: Thomas Gleixner Reviewed-by: Alexandre Chartre Acked-by: Peter Zijlstra Link: https://lkml.kernel.org/r/20200505134100.075416272@linutronix.de [Nicolas: context conflicts in: arch/powerpc/kernel/vmlinux.lds.S include/asm-generic/vmlinux.lds.h include/linux/compiler.h include/linux/compiler_types.h] Signed-off-by: Nicolas Boichat --- arch/powerpc/kernel/vmlinux.lds.S | 1 + include/asm-generic/sections.h | 3 ++ include/asm-generic/vmlinux.lds.h | 10 ++++++ include/linux/compiler.h | 54 +++++++++++++++++++++++++++++++ include/linux/compiler_types.h | 4 +++ scripts/mod/modpost.c | 2 +- 6 files changed, 73 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S index 695432965f20..9b346f3d2814 100644 --- a/arch/powerpc/kernel/vmlinux.lds.S +++ b/arch/powerpc/kernel/vmlinux.lds.S @@ -99,6 +99,7 @@ SECTIONS #endif /* careful! __ftr_alt_* sections need to be close to .text */ *(.text.hot TEXT_MAIN .text.fixup .text.unlikely .fixup __ftr_alt_* .ref.text); + NOINSTR_TEXT SCHED_TEXT CPUIDLE_TEXT LOCK_TEXT diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h index 849cd8eb5ca0..ea5987bb0b84 100644 --- a/include/asm-generic/sections.h +++ b/include/asm-generic/sections.h @@ -53,6 +53,9 @@ extern char __ctors_start[], __ctors_end[]; /* Start and end of .opd section - used for function descriptors. */ extern char __start_opd[], __end_opd[]; +/* Start and end of instrumentation protected text section */ +extern char __noinstr_text_start[], __noinstr_text_end[]; + extern __visible const void __nosave_begin, __nosave_end; /* Function descriptor handling (if any). Override in asm/sections.h */ diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 2d632a74cc5e..88484ee023ca 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -482,6 +482,15 @@ __security_initcall_end = .; \ } +/* + * Non-instrumentable text section + */ +#define NOINSTR_TEXT \ + ALIGN_FUNCTION(); \ + __noinstr_text_start = .; \ + *(.noinstr.text) \ + __noinstr_text_end = .; + /* * .text section. Map to function alignment to avoid address changes * during second ld run in second ld pass when generating System.map @@ -496,6 +505,7 @@ *(TEXT_MAIN .text.fixup) \ *(.text.unlikely .text.unlikely.*) \ *(.text.unknown .text.unknown.*) \ + NOINSTR_TEXT \ *(.text..refcount) \ *(.ref.text) \ MEM_KEEP(init.text*) \ diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 6b6505e3b2c7..6a53300cbd1e 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -129,11 +129,65 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, ".pushsection .discard.unreachable\n\t" \ ".long 999b - .\n\t" \ ".popsection\n\t" + +#ifdef CONFIG_DEBUG_ENTRY +/* Begin/end of an instrumentation safe region */ +#define instrumentation_begin() ({ \ + asm volatile("%c0:\n\t" \ + ".pushsection .discard.instr_begin\n\t" \ + ".long %c0b - .\n\t" \ + ".popsection\n\t" : : "i" (__COUNTER__)); \ +}) + +/* + * Because instrumentation_{begin,end}() can nest, objtool validation considers + * _begin() a +1 and _end() a -1 and computes a sum over the instructions. + * When the value is greater than 0, we consider instrumentation allowed. + * + * There is a problem with code like: + * + * noinstr void foo() + * { + * instrumentation_begin(); + * ... + * if (cond) { + * instrumentation_begin(); + * ... + * instrumentation_end(); + * } + * bar(); + * instrumentation_end(); + * } + * + * If instrumentation_end() would be an empty label, like all the other + * annotations, the inner _end(), which is at the end of a conditional block, + * would land on the instruction after the block. + * + * If we then consider the sum of the !cond path, we'll see that the call to + * bar() is with a 0-value, even though, we meant it to happen with a positive + * value. + * + * To avoid this, have _end() be a NOP instruction, this ensures it will be + * part of the condition block and does not escape. + */ +#define instrumentation_end() ({ \ + asm volatile("%c0: nop\n\t" \ + ".pushsection .discard.instr_end\n\t" \ + ".long %c0b - .\n\t" \ + ".popsection\n\t" : : "i" (__COUNTER__)); \ +}) +#endif /* CONFIG_DEBUG_ENTRY */ + #else #define annotate_reachable() #define annotate_unreachable() #endif +#ifndef instrumentation_begin +#define instrumentation_begin() do { } while(0) +#define instrumentation_end() do { } while(0) +#endif + #ifndef ASM_UNREACHABLE # define ASM_UNREACHABLE #endif diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index 2b8ed70c4c77..a9b0495051a3 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -234,6 +234,10 @@ struct ftrace_likely_data { #define notrace __attribute__((no_instrument_function)) #endif +/* Section for code which can't be instrumented at all */ +#define noinstr \ + noinline notrace __attribute((__section__(".noinstr.text"))) + /* * it doesn't make sense on ARM (currently the only user of __naked) * to trace naked functions because then mcount is called without diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index 91a80036c05d..7c693bd775c1 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -895,7 +895,7 @@ static void check_section(const char *modname, struct elf_info *elf, #define DATA_SECTIONS ".data", ".data.rel" #define TEXT_SECTIONS ".text", ".text.unlikely", ".sched.text", \ - ".kprobes.text", ".cpuidle.text" + ".kprobes.text", ".cpuidle.text", ".noinstr.text" #define OTHER_TEXT_SECTIONS ".ref.text", ".head.text", ".spinlock.text", \ ".fixup", ".entry.text", ".exception.text", ".text.*", \ ".coldtext"