From: Borislav Petkov <bp@alien8.de>
To: David Laight <David.Laight@ACULAB.COM>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
Andy Lutomirski <luto@amacapital.net>,
Nick Desaulniers <ndesaulniers@google.com>,
Andy Lutomirski <luto@kernel.org>,
Bill Wendling <morbo@google.com>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
Greg Thelen <gthelen@google.com>,
John Sperbeck <jsperbeck@google.com>,
"# 3.4.x" <stable@vger.kernel.org>,
clang-built-linux <clang-built-linux@googlegroups.com>
Subject: Re: [PATCH] x86/smap: Fix the smap_save() asm
Date: Thu, 17 Sep 2020 16:39:20 +0200 [thread overview]
Message-ID: <20200917143920.GJ31960@zn.tnic> (raw)
In-Reply-To: <823af5fadd464c48ade635498d07ba4e@AcuMS.aculab.com>
On Thu, Sep 17, 2020 at 02:25:50PM +0000, David Laight wrote:
> I actually wonder if there is any code that really benefits from
> the red-zone.
The kernel has been without a red zone since 2002 at least:
commit 47f16da277d10ef9494f3e9da2a9113bb22bcd75
Author: Andi Kleen <ak@muc.de>
Date: Tue Feb 12 20:17:35 2002 -0800
[PATCH] x86_64 merge: arch + asm
This adds the x86_64 arch and asm directories and a Documentation/x86_64.
...
+CFLAGS += $(shell if $(CC) -mno-red-zone -S -o /dev/null -xc /dev/null >/dev/null 2>&1; then echo "-mno-red-zone"; fi )
Also, from the ABI doc:
"A.2.2 Stack Layout
The Linux kernel may align the end of the input argument area to a
8, instead of 16, byte boundary. It does not honor the red zone (see
section 3.2.2) and therefore this area is not allowed to be used by
kernel code. Kernel code should be compiled by GCC with the option
-mno-red-zone."
so forget the red zone.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2020-09-17 19:56 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-15 20:55 Andy Lutomirski
2020-09-15 21:24 ` Nick Desaulniers
2020-09-15 21:31 ` Bill Wendling
2020-09-15 23:11 ` Andy Lutomirski
[not found] ` <7233f4cf-5b1d-0fca-0880-f1cf2e6e765b@citrix.com>
2020-09-15 23:43 ` Bill Wendling
2020-09-16 8:26 ` Borislav Petkov
[not found] ` <be498e49-b467-e04c-d833-372f7d83cb1f@citrix.com>
2020-09-17 6:04 ` Borislav Petkov
[not found] ` <ec617df229514fbaa9897683ac88dfda@AcuMS.aculab.com>
2020-09-17 11:57 ` Borislav Petkov
[not found] ` <823af5fadd464c48ade635498d07ba4e@AcuMS.aculab.com>
2020-09-17 14:39 ` Borislav Petkov [this message]
2020-09-17 16:32 ` Andy Lutomirski
2020-09-16 7:28 ` peterz
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