From: Peter Zijlstra <peterz@infradead.org>
To: David Laight <David.Laight@ACULAB.COM>
Cc: 'Brian Gerst' <brgerst@gmail.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"x86@kernel.org" <x86@kernel.org>,
Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@alien8.de>,
Thomas Gleixner <tglx@linutronix.de>,
"H . Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH v2 2/6] x86-64: Convert stack protector to normal percpu variable
Date: Thu, 2 Dec 2021 23:51:07 +0100 [thread overview]
Message-ID: <20211202225107.GF16608@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <2c23335e98bc4a66b1fd779a78ddd821@AcuMS.aculab.com>
On Wed, Dec 01, 2021 at 09:50:57AM +0000, David Laight wrote:
> From: Brian Gerst
> > Sent: 30 November 2021 20:56
> >
> > Older versions of GCC fixed the location of the stack protector canary
> > at %gs:40. This constraint forced the percpu section to be linked at
> > virtual address 0 so that the canary could be the first data object in
> > the percpu section. Supporting the zero-based percpu section requires
> > additional code to handle relocations for RIP-relative references to
> > percpu data, extra complexity to kallsyms, and workarounds for linker
> > bugs due to the use of absolute symbols.
> >
> > Since version 8.1, GCC has options to configure the location of the
> > canary value. This allows the canary to be turned into a normal
> > percpu variable and removes the constraint that the percpu section
> > be zero-based.
>
> I didn't think the minimum gcc version has been raised as far as 8.1?
Older GCC can still build a kernel, just not with stack protector on.
And 8.1 is already 3 years old. If you run ancient distros, you can run
ancient kernels too.
next prev parent reply other threads:[~2021-12-02 22:51 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-30 20:55 [PATCH v2 0/6] x86-64: Stack protector and percpu improvements Brian Gerst
2021-11-30 20:55 ` [PATCH v2 1/6] x86: Remove stack protector test scripts Brian Gerst
2021-11-30 20:55 ` [PATCH v2 2/6] x86-64: Convert stack protector to normal percpu variable Brian Gerst
2021-12-01 9:50 ` David Laight
2021-12-01 14:21 ` Brian Gerst
2021-12-02 22:51 ` Peter Zijlstra [this message]
2021-11-30 20:55 ` [PATCH v2 3/6] x86-64: Use relative per-cpu offsets Brian Gerst
2021-11-30 20:55 ` [PATCH v2 4/6] x86-64: Remove inverse relocations Brian Gerst
2021-11-30 20:55 ` [PATCH v2 5/6] kallsyms: Remove KALLSYMS_ABSOLUTE_PERCPU Brian Gerst
2021-11-30 20:55 ` [PATCH v2 6/6] percpu: Remove PER_CPU_FIRST_SECTION Brian Gerst
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