From: Marc Zyngier <maz@kernel.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Naresh Kamboju <naresh.kamboju@linaro.org>,
open list <linux-kernel@vger.kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
lkft-triage@lists.linaro.org,
Linux Regressions <regressions@lists.linux.dev>,
Arnd Bergmann <arnd@arndb.de>,
Anders Roxell <anders.roxell@linaro.org>,
joey.gouly@arm.com, Oliver Upton <oliver.upton@linux.dev>
Subject: Re: gcc-8: arm64/kvm/pauth.: Error: unknown architectural extension `pauth'
Date: Mon, 22 Apr 2024 23:58:24 +0100 [thread overview]
Message-ID: <87v849t373.wl-maz@kernel.org> (raw)
In-Reply-To: <ZiYqV-5BWmPwgqbU@FVFF77S0Q05N>
On Mon, 22 Apr 2024 10:13:59 +0100,
Mark Rutland <mark.rutland@arm.com> wrote:
>
> On Mon, Apr 22, 2024 at 02:04:43PM +0530, Naresh Kamboju wrote:
> > The arm64 defconfig build failed with gcc-8 and passed with gcc-13.
> >
> > Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
> >
> > Build log:
> > ---
> > /tmp/ccSUNNZy.s: Assembler messages:
> > /tmp/ccSUNNZy.s:3159: Error: unknown architectural extension `pauth'
> > make[5]: *** [scripts/Makefile.build:244: arch/arm64/kvm/pauth.o] Error 1
> >
> > Steps to reproduce:
> > ---
> > # tuxmake --runtime podman --target-arch arm64 --toolchain gcc-8
> > --kconfig defconfig
>
> I think the key thing here is GCC 8; the associated assembler won't necessarily
> have ARMv8.3-A support, since all the relevant bits got added around GCC 9.
>
> Looking at the commits, I think this is broken since its introduction in commit:
>
> 6ccc971ee2c61a1f ("KVM: arm64: nv: Add emulation for ERETAx instructions")
>
> ... where the pauth.c file only depends on ARM64_PTR_AUTH (which doesn't imply
> AS_HAS_ARMV8_3), but in the file we do:
>
> asm volatile(ARM64_ASM_PREAMBLE ".arch_extension pauth\n"
> "pacga %0, %1, %2" : "=r" (pac) : "r" (ptr), "r" (mod));
>
> Given the minimum supported toolchain comes with an assembler that doesn't
> necessarily support ARMv8.3, I reckon we'll either have to make NV pauth
> support depend upon AS_HAS_ARMV8_3, or manually assemble the PACGA instruction.
>
> I suspect the latter is the better option.
This is what I've done [1]. It certainly isn't pretty, but this counts
as an incentive to drop some of the old stuff in the near-ish future.
I've pushed this out to -next, and hopefully the breakage will be
solved tomorrow.
M.
[1] https://lore.kernel.org/r/20240422224849.2238222-1-maz@kernel.org
--
Without deviation from the norm, progress is not possible.
prev parent reply other threads:[~2024-04-22 22:58 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-22 8:34 gcc-8: arm64/kvm/pauth.: Error: unknown architectural extension `pauth' Naresh Kamboju
2024-04-22 9:13 ` Mark Rutland
2024-04-22 9:25 ` Arnd Bergmann
2024-04-22 9:40 ` Mark Rutland
2024-04-22 12:11 ` Arnd Bergmann
2024-04-22 17:20 ` Mark Rutland
2024-04-22 18:44 ` Arnd Bergmann
2024-04-22 22:58 ` Marc Zyngier [this message]
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