Re: [STABLE BACKPORT 4.4.y, 4.9.y and 4.14.y] compiler.h: Raise minimum version of GCC to 5.1 for arm64

[Nathan Chancellor <natechancellor@gmail.com>]

On Tue, Jan 19, 2021 at 02:15:43PM -0800, Nick Desaulniers wrote:
> On Mon, Jan 18, 2021 at 5:54 AM Will Deacon <will@kernel.org> wrote:
> >
> > commit dca5244d2f5b94f1809f0c02a549edf41ccd5493 upstream.
> >
> > GCC versions >= 4.9 and < 5.1 have been shown to emit memory references
> > beyond the stack pointer, resulting in memory corruption if an interrupt
> > is taken after the stack pointer has been adjusted but before the
> > reference has been executed. This leads to subtle, infrequent data
> > corruption such as the EXT4 problems reported by Russell King at the
> > link below.
> >
> > Life is too short for buggy compilers, so raise the minimum GCC version
> > required by arm64 to 5.1.
> >
> > Reported-by: Russell King <linux@armlinux.org.uk>
> > Suggested-by: Arnd Bergmann <arnd@kernel.org>
> > Signed-off-by: Will Deacon <will@kernel.org>
> > Tested-by: Nathan Chancellor <natechancellor@gmail.com>
> > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> > Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
> > Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
> > Cc: <stable@vger.kernel.org> # 4.4.y, 4.9.y and 4.14.y only
> > Cc: Theodore Ts'o <tytso@mit.edu>
> > Cc: Florian Weimer <fweimer@redhat.com>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > Cc: Nick Desaulniers <ndesaulniers@google.com>
> > Link: https://lore.kernel.org/r/20210105154726.GD1551@shell.armlinux.org.uk
> > Link: https://lore.kernel.org/r/20210112224832.10980-1-will@kernel.org
> > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
> > [will: backport to 4.4.y/4.9.y/4.14.y]
> 
> Merging this from stable into "Android Common Kernel" trees that were
> built with AOSP GCC 4.9, I expect this to break some builds.  Arnd,
> IIRC did you mention that AOSP GCC had picked up a fix?  If so, did
> you verify that via disassembly, or gerrit patch file?
> 
> (AOSP GCC 4.9: https://android.googlesource.com/platform/prebuilts/gcc/linux-x86/aarch64/aarch64-linux-android-4.9/
> master branch, roll back a few commits).
> It looks like AOSP GCC `#defines __android__ 1`.

It seems like this is the source for that toolchain?

https://android.googlesource.com/toolchain/gcc

If so, it looks like that patch was picked up in this commit.

https://android.googlesource.com/toolchain/gcc/+/5ae0308a147ec3f6502fd321860524e634a647a6

Cheers,
Nathan