From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.mindbit.ro (xs1.mindbit.ro [80.86.107.70]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B9E4D3B7742; Wed, 8 Jul 2026 20:59:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=80.86.107.70 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783544389; cv=none; b=j1baHBe8tdCYtysoHH8iMKizT3ruXSmRBcJT1s3oWT59BXpSOYtsSmyunQxcjZmwwn64uGYkFN+ayAgN/IN8bHDwU9vxlvlQaV18zlI1t02Imjup5oMddgwIRQ9UKYiWYdUd1k2kTzWvG/jb6ak/2Qn5s9e+RJM52nB4wTFCrh8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783544389; c=relaxed/simple; bh=G/nBh18gOxJI1Qg481B6FfoZLdcPt51fF1KIckW/8fM=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=OZbwDdw48mDhrqEAXbZNInWu5k8AH2+6w0vPWVm4hFDEa71T+h1WTXBiV0PvLCjqq6oeCBRtnpPfyk+8aWS9JlEOkZ4TZIjHpcgOa8wnSj6DJzDYn+bskFo8pE494l2Opk/dbIVGOPb3LXcoiFi9J31PTRd9rzaLADH4XSLicW4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=rendec.net; spf=pass smtp.mailfrom=rendec.net; dkim=pass (2048-bit key) header.d=rendec.net header.i=@rendec.net header.b=QFBhNiYB; arc=none smtp.client-ip=80.86.107.70 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=rendec.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=rendec.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=rendec.net header.i=@rendec.net header.b="QFBhNiYB" Received: from bat.kanata.rendec.net (unknown [24.114.111.125]) by mail.mindbit.ro (Postfix) with ESMTPSA id EEAC6C3450; Wed, 8 Jul 2026 23:59:23 +0300 (EEST) DKIM-Filter: OpenDKIM Filter v2.11.0 mail.mindbit.ro EEAC6C3450 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=rendec.net; s=default; t=1783544386; bh=apD89r/ATd0i91X5PLxPXmWRbZb01NLEEn83tYTPdj8=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=QFBhNiYBGqyqIPaE0Z//h9Otg8dr2LXIHvr8YLUlcTh/kNU/NIbu5jC1lBV3pHdLh Ytm1aPdmx5IPwKpmRwSjzNZATFEnv+SX4IQqX325g318JKX/ahM7OZftwyNPWkKh+8 Vevi8c0s6FZB90ZqbVizrkH3lX3FU2ik1T1I5Ls6uZhVB+87d+ps/uU5qQR8vbqmGm WzIaaobCMK1Q68zS0EMjVKisaOGjotqeY2kfDArzrlfOxIAdRTtnnfA8P+I6Lpe81U e7IwFFdqW2LVSX+vRtsYW7C8+F7/fgH4EcUIK6C4eJGLJR5jk9VqhbYq1bnaYAPt14 W5V6aNnbwuOcA== Message-ID: Subject: Re: [patch 08/18] x86/syscall: Use [syscall_]enter_from_user_mode_randomize_stack() From: Radu Rendec To: Thomas Gleixner , LKML Cc: Peter Zijlstra , x86@kernel.org, Michael Ellerman , Shrikanth Hegde , linuxppc-dev@lists.ozlabs.org, Kees Cook , Huacai Chen , loongarch@lists.linux.dev, Paul Walmsley , Palmer Dabbelt , linux-riscv@lists.infradead.org, Sven Schnelle , linux-s390@vger.kernel.org, Mark Rutland , Jinjie Ruan , Andy Lutomirski , Oleg Nesterov , Richard Henderson , Russell King , Catalin Marinas , Guo Ren , Geert Uytterhoeven , Thomas Bogendoerfer , Helge Deller , Yoshinori Sato , Richard Weinberger , Chris Zankel , linux-arm-kernel@lists.infradead.org, linux-alpha@vger.kernel.org, linux-csky@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-sh@vger.kernel.org, linux-um@lists.infradead.org, Arnd Bergmann , Vineet Gupta , Will Deacon , Brian Cain , Michal Simek , Dinh Nguyen , "David S. Miller" , Andreas Larsson , linux-snps-arc@lists.infradead.org, linux-hexagon@vger.kernel.org, linux-openrisc@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, Michal =?ISO-8859-1?Q?Such=E1nek?= , Jonathan Corbet , linux-doc@vger.kernel.org Date: Wed, 08 Jul 2026 16:59:18 -0400 In-Reply-To: <20260707190254.079478122@kernel.org> References: <20260707181957.433213175@kernel.org> <20260707190254.079478122@kernel.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.3 (3.58.3-1.fc43) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Tue, 2026-07-07 at 21:06 +0200, Thomas Gleixner wrote: > These functions integrate the stack randomization. >=20 > syscall_enter_from_user_mode_randomize_stack() has the advantage that the > randomization happens early right after enter_from_user_mode(). >=20 > In both cases also the overhead of get/put_cpu_var() in > add_random_kstack_offset() is avoided. >=20 > No functional change. >=20 > Signed-off-by: Thomas Gleixner > Cc: x86@kernel.org > --- > =C2=A0arch/x86/entry/syscall_32.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0 |=C2=A0=C2=A0 19 +++++-------------- > =C2=A0arch/x86/entry/syscall_64.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0 |=C2=A0=C2=A0=C2=A0 3 +-- > =C2=A0arch/x86/include/asm/entry-common.h |=C2=A0=C2=A0=C2=A0 1 - > =C2=A03 files changed, 6 insertions(+), 17 deletions(-) >=20 > --- a/arch/x86/entry/syscall_32.c > +++ b/arch/x86/entry/syscall_32.c > @@ -142,10 +142,9 @@ static __always_inline bool int80_is_ext > =C2=A0 * int80_is_external() below which calls into the APIC driver. > =C2=A0 * Identical for soft and external interrupts. > =C2=A0 */ > - enter_from_user_mode(regs); > + enter_from_user_mode_randomize_stack(regs); > =C2=A0 > =C2=A0 instrumentation_begin(); > - add_random_kstack_offset(); > =C2=A0 > =C2=A0 /* Validate that this is a soft interrupt to the extent possible *= / > =C2=A0 if (unlikely(int80_is_external())) > @@ -210,11 +209,9 @@ DEFINE_FREDENTRY_RAW(int80_emulation) > =C2=A0{ > =C2=A0 int nr; > =C2=A0 > - enter_from_user_mode(regs); > + enter_from_user_mode_randomize_stack(regs); > =C2=A0 > =C2=A0 instrumentation_begin(); > - add_random_kstack_offset(); > - > =C2=A0 /* > =C2=A0 * FRED pushed 0 into regs::orig_ax and regs::ax contains the > =C2=A0 * syscall number. > @@ -252,10 +249,10 @@ DEFINE_FREDENTRY_RAW(int80_emulation) > =C2=A0 * orig_ax, the int return value truncates it. This matches > =C2=A0 * the semantics of syscall_get_nr(). > =C2=A0 */ > - nr =3D syscall_enter_from_user_mode(regs, nr); > + nr =3D syscall_enter_from_user_mode_randomize_stack(regs, nr); > + > =C2=A0 instrumentation_begin(); > =C2=A0 > - add_random_kstack_offset(); > =C2=A0 do_syscall_32_irqs_on(regs, nr); > =C2=A0 > =C2=A0 instrumentation_end(); > @@ -268,15 +265,9 @@ static noinstr bool __do_fast_syscall_32 > =C2=A0 int nr =3D syscall_32_enter(regs); > =C2=A0 int res; > =C2=A0 > - /* > - * This cannot use syscall_enter_from_user_mode() as it has to > - * fetch EBP before invoking any of the syscall entry work > - * functions. > - */ > - enter_from_user_mode(regs); > + enter_from_user_mode_randomize_stack(regs); > =C2=A0 > =C2=A0 instrumentation_begin(); > - add_random_kstack_offset(); > =C2=A0 local_irq_enable(); > =C2=A0 /* Fetch EBP from where the vDSO stashed it. */ > =C2=A0 if (IS_ENABLED(CONFIG_X86_64)) { > --- a/arch/x86/entry/syscall_64.c > +++ b/arch/x86/entry/syscall_64.c > @@ -86,10 +86,9 @@ static __always_inline bool do_syscall_x > =C2=A0/* Returns true to return using SYSRET, or false to use IRET */ > =C2=A0__visible noinstr bool do_syscall_64(struct pt_regs *regs, int nr) > =C2=A0{ > - nr =3D syscall_enter_from_user_mode(regs, nr); > + nr =3D syscall_enter_from_user_mode_randomize_stack(regs, nr); > =C2=A0 > =C2=A0 instrumentation_begin(); > - add_random_kstack_offset(); > =C2=A0 > =C2=A0 if (!do_syscall_x64(regs, nr) && !do_syscall_x32(regs, nr) && nr != =3D -1) { > =C2=A0 /* Invalid system call, but still a system call. */ > --- a/arch/x86/include/asm/entry-common.h > +++ b/arch/x86/include/asm/entry-common.h > @@ -2,7 +2,6 @@ > =C2=A0#ifndef _ASM_X86_ENTRY_COMMON_H > =C2=A0#define _ASM_X86_ENTRY_COMMON_H > =C2=A0 > -#include > =C2=A0#include > =C2=A0 > =C2=A0#include Reviewed-by: Radu Rendec