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Subject: Re: [PATCH 02/24] x86/traps: Move arch/x86/kernel/traps.c to
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To:     Nick Desaulniers <ndesaulniers@google.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Miguel Ojeda <ojeda@kernel.org>,
        Lai Jiangshan <laijs@linux.alibaba.com>,
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        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Brijesh Singh <brijesh.singh@amd.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Arvind Sankar <nivedita@alum.mit.edu>,
        Chester Lin <clin@suse.com>, Juergen Gross <jgross@suse.com>,
        andrew.cooper3@citrix.com, linux-toolchains@vger.kernel.org
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From:   =?UTF-8?Q?Martin_Li=c5=a1ka?= <mliska@suse.cz>
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On 9/7/21 23:12, Nick Desaulniers wrote:
> On Fri, Sep 3, 2021 at 12:36 AM Martin Liška <mliska@suse.cz> wrote:
>>
>> On 9/2/21 19:05, Nick Desaulniers wrote:
>>> IIRC GCC only
>>> added the attribute recently in the 10.X release, so it might be too
>>> new to rely on quite yet.
>>
>> The no_stack_protector attribute was actually added in the GCC 11.x release:
>> https://gcc.gnu.org/gcc-11/changes.html
> 
> Ah right, that lays more weight though that this feature is still too
> new to rely on quite yet.

Sure.

> Martin, do you know if what happens with
> regards to inlining when the callee and caller mismatch on this
> function attribute in GCC?  This is very much a problem for the
> kernel.

That's a know issue that was already discusses both in a Kernel mailing and
GCC bugzilla:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94722#c9

Martin

> 
>> Note the compiler is definitely used by Fedora, openSUSE Tumbleweed
>> and other cutting edge distributions.
> 
> Kernel supports GCC 4.9+ currently. This feature can only be emulated
> with the coarse grain -fno-stack-protector (or gnu_inline with out of
> line assembler definition...:( ).
>