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From: Michael Ellerman <patch-notifications@ellerman.id.au>
To: Michael Ellerman <mpe@ellerman.id.au>, linuxppc-dev@lists.ozlabs.org
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Subject: Re: [PATCH] powerpc/vdso: Don't use r30 to avoid breaking Go lang
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Date: Sun, 01 Aug 2021 23:14:00 +1000
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On Thu, 29 Jul 2021 23:12:44 +1000, Michael Ellerman wrote:
> The Go runtime uses r30 for some special value called 'g'. It assumes
> that value will remain unchanged even when calling VDSO functions.
> Although r30 is non-volatile across function calls, the callee is free
> to use it, as long as the callee saves the value and restores it before
> returning.
> 
> It used to be true by accident that the VDSO didn't use r30, because the
> VDSO was hand-written asm. When we switched to building the VDSO from C
> the compiler started using r30, at least in some builds, leading to
> crashes in Go. eg:
> 
> [...]

Applied to powerpc/fixes.

[1/1] powerpc/vdso: Don't use r30 to avoid breaking Go lang
      https://git.kernel.org/powerpc/c/a88603f4b92ecef9e2359e40bcb99ad399d85dd7

cheers