From nobody Thu Feb 12 02:00:43 2026 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 2F4ECC77B6F for ; Wed, 12 Apr 2023 18:32:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229800AbjDLScV (ORCPT ); Wed, 12 Apr 2023 14:32:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45264 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229713AbjDLScS (ORCPT ); Wed, 12 Apr 2023 14:32:18 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0104519F for ; Wed, 12 Apr 2023 11:32:16 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id 65-20020a250244000000b00b8f53d3e51cso557767ybc.20 for ; Wed, 12 Apr 2023 11:32:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1681324336; x=1683916336; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=fu4wMIjRXEHdvIAwW21s7RwYEcTiORI4Tua6uqoa9YY=; b=gHtYL1L3/MvRx5+mmiO9Wf9I61eB9gEc5SLBb5X0RkYhVx2IUwIvZ4eFfKGyhti9qt abv/ESGYY+yJF5e2O69qmnMZQLbaQqpTPNl6fvdRPCn3IXd3hMLTLkCAacP+kp7VUjsL h8JSdDLKIsIkBXiji42s5ULPXJuYFkWXJLT52AfWqtVn3JsapSovcT0pJ57e1bSFl1cs The24q4o/DhN9pJXCZI3/gpnjfVjKPe2K+UFlIsN8KO2md9x1IH/wMpi4Dd6svXJUNjv 7FtH7mz7iW0t+6Uid5pZXa2FZ3IxQpMMNYGm9wFi/QzIe3O46eBA1oRhE5p59uiEZpS2 bxvg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1681324336; x=1683916336; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=fu4wMIjRXEHdvIAwW21s7RwYEcTiORI4Tua6uqoa9YY=; b=BskERb58q2hpohYfyIBLxa2zJn9eLicA5TFxfUq/efx0uAIspMFC4b19HU90db3hul 0osa1q0o0zSN0Aq3/MjAjvFtAvONAE9GClAz1GQw/iCQX0kUkTgi4oG/uhWk/qq4ODQK 4m36hLyYCEdkRIIhqMb2/Z3/vPP4xEezJqJP56qA0uWGkbpStJsO+yqGjGrhi/WLuW7k 3e2l1UEqfU0Z/nPPE4CUdGxvoHCYaytOGNa6twIrSs2+2WTtswZwxbFdcK/aU1pWYyTL fT6sA+jpybqXg/jGxf1wYQ6E9HKfhheMhKvjtj+WJsnTbY0K7DP9FLtEMz07sN2PuSnj FzkA== X-Gm-Message-State: AAQBX9f6FUr2SMkUvQGHr0mQZiM5gOkRK+5pF/TA8t0tgQFXbqMdvzf9 m2pApZKIPemKUx/JWH85REyxrXW1YvWBCGS3LyQ= X-Google-Smtp-Source: AKy350abn/nvm+6v8bngXNPwCS/keNIyrgzi3uj9PPb3yS2giiIBty1sJGwk06JnKuByumvuAeJrKEZwvKrU4mAm2fU= X-Received: from ndesaulniers-desktop.svl.corp.google.com ([2620:15c:2d1:203:4a4a:51a1:19b:61ab]) (user=ndesaulniers job=sendgmr) by 2002:a25:d252:0:b0:b8e:c5fd:975f with SMTP id j79-20020a25d252000000b00b8ec5fd975fmr8449875ybg.3.1681324336255; Wed, 12 Apr 2023 11:32:16 -0700 (PDT) Date: Wed, 12 Apr 2023 11:32:12 -0700 In-Reply-To: <20230412-no_stackp-v1-0-46a69b507a4b@google.com> Mime-Version: 1.0 References: <20230412-no_stackp-v1-0-46a69b507a4b@google.com> X-Developer-Key: i=ndesaulniers@google.com; a=ed25519; pk=UIrHvErwpgNbhCkRZAYSX0CFd/XFEwqX3D0xqtqjNug= X-Developer-Signature: v=1; a=ed25519-sha256; t=1681324332; l=2837; i=ndesaulniers@google.com; s=20220923; h=from:subject:message-id; bh=pax/072S3TetamqDDk+xEdd8LMndD88F0z/jWCgSc+c=; b=feWilMtakyMgYgr44+djznmjdmueETxHFBPKkFfWW1bTH1HVyqY78TgWu5FMpzJWsr6r8lOEfOQg 4lcKCpVTBZeg36Olp5RFv6nHXPeF88zfaB0JkhsSb1cZw/oGAehf X-Mailer: b4 0.12.2 Message-ID: <20230412-no_stackp-v1-1-46a69b507a4b@google.com> Subject: [PATCH 1/2] start_kernel: add no_stack_protector fn attr From: ndesaulniers@google.com To: "Borislav Petkov (AMD)" Cc: Peter Zijlstra , Josh Poimboeuf , x86@kernel.org, Michael Ellerman , Nicholas Piggin , Christophe Leroy , Miguel Ojeda , Nathan Chancellor , Tom Rix , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, Nick Desaulniers Content-Type: text/plain; charset="utf-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Back during the discussion of commit a9a3ed1eff36 ("x86: Fix early boot crash on gcc-10, third try") we discussed the need for a function attribute to control the omission of stack protectors on a per-function basis; at the time Clang had support for no_stack_protector but GCC did not. This was fixed in gcc-11. Now that the function attribute is available, let's start using it. Callers of boot_init_stack_canary need to use this function attribute unless they're compiled with -fno-stack-protector, otherwise the canary stored in the stack slot of the caller will differ upon the call to boot_init_stack_canary. This will lead to a call to __stack_chk_fail then panic. Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D94722 Link: https://lore.kernel.org/all/20200316130414.GC12561@hirez.programming.= kicks-ass.net/ Signed-off-by: Nick Desaulniers Acked-by: Michael Ellerman (powerpc) Acked-by: Miguel Ojeda Tested-by: Nathan Chancellor --- arch/powerpc/kernel/smp.c | 1 + include/linux/compiler_attributes.h | 12 ++++++++++++ init/main.c | 3 ++- 3 files changed, 15 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c index 6b90f10a6c81..7d4c12b1abb7 100644 --- a/arch/powerpc/kernel/smp.c +++ b/arch/powerpc/kernel/smp.c @@ -1603,6 +1603,7 @@ static void add_cpu_to_masks(int cpu) } =20 /* Activate a secondary processor. */ +__no_stack_protector void start_secondary(void *unused) { unsigned int cpu =3D raw_smp_processor_id(); diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_a= ttributes.h index e659cb6fded3..84864767a56a 100644 --- a/include/linux/compiler_attributes.h +++ b/include/linux/compiler_attributes.h @@ -255,6 +255,18 @@ */ #define __noreturn __attribute__((__noreturn__)) =20 +/* + * Optional: only supported since GCC >=3D 11.1, clang >=3D 7.0. + * + * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.ht= ml#index-no_005fstack_005fprotector-function-attribute + * clang: https://clang.llvm.org/docs/AttributeReference.html#no-stack-p= rotector-safebuffers + */ +#if __has_attribute(__no_stack_protector__) +# define __no_stack_protector __attribute__((__no_stack_protector__)) +#else +# define __no_stack_protector +#endif + /* * Optional: not supported by gcc. * diff --git a/init/main.c b/init/main.c index bb87b789c543..213baf7b8cb1 100644 --- a/init/main.c +++ b/init/main.c @@ -941,7 +941,8 @@ static void __init print_unknown_bootoptions(void) memblock_free(unknown_options, len); } =20 -asmlinkage __visible void __init __no_sanitize_address start_kernel(void) +asmlinkage __visible __init __no_sanitize_address __no_stack_protector +void start_kernel(void) { char *command_line; char *after_dashes; --=20 2.40.0.577.gac1e443424-goog