Messages in this thread | | | From | David Laight <> | Subject | RE: [PATCH v2 00/11] x86-64: Stack protector and percpu improvements | Date | Mon, 30 Oct 2023 09:05:48 +0000 |
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From: Uros Bizjak > Sent: 30 October 2023 08:07 > > On Sun, Oct 29, 2023 at 10:42 PM David Laight <David.Laight@aculab.com> wrote: > > > > From: Brian Gerst > > > Sent: 26 October 2023 17:01 > > > > > > Currently, x86-64 uses an unusual percpu layout, where the percpu section > > > is linked at absolute address 0. The reason behind this is that older GCC > > > versions placed the stack protector (if enabled) at a fixed offset from the > > > GS segment base. Since the GS segement is also used for percpu variables, > > > this forced the current layout. > > > > > > GCC since version 8.1 supports a configurable location for the stack > > > protector value, which allows removal of the restriction on how the percpu > > > section is linked. This allows the percpu section to be linked > > > normally, like most other architectures. In turn, this allows removal > > > of code that was needed to support the zero-based percpu section. > > > > I didn't think the minimum gcc version was anything like 8.1. > > I'm using 7.5.0 and I don't think that is the oldest version. > > Please see previous discussion regarding modernizing stack protector > on x86_64 [1] > > [1] https://lore.kernel.org/lkml/20211113124035.9180-1-brgerst@gmail.com/ > > and x86_32 [2] > > [2] https://lore.kernel.org/lkml/cover.1601925251.git.luto@kernel.org/ > > The conclusion in [2] is: > > "I'm all in favour of simply requiring GCC-8.1 to build a more secure > x86_64 kernel. Gives people an incentive to not use ancient compilers. > > And if you do want to use your ancient compiler, we'll still build, you > just don't get to have stackprotector."
I didn't see a patch that limited 'stackprotector' to gcc >= 8.1 Without that anyone who already has it enabled and is using an older compiler will get very broken kernels.
David
> > and in [1]: > > "Ack. We did this for 32-bit and got few complaints. Let’s finish the job." > > Uros.
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