From: Marc Zyngier <maz@kernel.org>
To: D Scott Phillips <scott@os.amperecomputing.com>
Cc: linux-arm-kernel@lists.infradead.org,
Will Deacon <will@kernel.org>,
Darren Hart <darren@os.amperecomputing.com>,
patches@amperecomputing.com
Subject: Re: [PATCH v2] arm64: errata: Fix exec handling in erratum 1418040 workaround
Date: Thu, 16 Dec 2021 19:52:44 +0000 [thread overview]
Message-ID: <af861c0865797d5f38005f7b77ea08e4@kernel.org> (raw)
In-Reply-To: <20211216191618.972956-1-scott@os.amperecomputing.com>
On 2021-12-16 19:16, D Scott Phillips wrote:
> The erratum 1418040 workaround changes vct access trapping when
> switching
> between compat and non-compat threads. The workaround logic assumes
> that
> the hardware vct trapping state matches the previous task's
> compat-ness.
> However, when a non-compat task execs a compat binary or vice versa,
> the
> cntkctl state and task compat-ness get out of sync. Keep the hardware
> trapping state in sync with the task personality.
>
> Fixes: d49f7d7376d0 ("arm64: Move handling of erratum 1418040 into C
> code")
> Signed-off-by: D Scott Phillips <scott@os.amperecomputing.com>
> Reviewed-by: Marc Zyngier <maz@kernel.org>
> Cc: <stable@vger.kernel.org> # 5.4.x
> ---
>
> v2: - Use sysreg_clear_set instead of open coding (Marc)
> - guard this_cpu_has_cap() check under IS_ENABLED() to avoid tons
> of
> WARN_ON(preemptible()) when built with
> !CONFIG_ARM64_ERRATUM_1418040
Indeed.
> arch/arm64/include/asm/elf.h | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/arch/arm64/include/asm/elf.h
> b/arch/arm64/include/asm/elf.h
> index 97932fbf973d..24036b914226 100644
> --- a/arch/arm64/include/asm/elf.h
> +++ b/arch/arm64/include/asm/elf.h
> @@ -160,8 +160,16 @@ typedef struct user_fpsimd_state elf_fpregset_t;
>
> #define SET_PERSONALITY(ex) \
> ({ \
> + if (IS_ENABLED(CONFIG_ARM64_ERRATUM_1418040)) \
> + preempt_disable(); \
> clear_thread_flag(TIF_32BIT); \
> current->personality &= ~READ_IMPLIES_EXEC; \
> + if (IS_ENABLED(CONFIG_ARM64_ERRATUM_1418040)) { \
> + if (this_cpu_has_cap(ARM64_WORKAROUND_1418040)) \
Probably better written as:
if (IS_ENABLED(CONFIG_ARM64_ERRATUM_1418040) &&
this_cpu_has_cap(ARM64_WORKAROUND_1418040))
sysreg_clear_set(...);
Thanks,
M.
--
Jazz is not dead. It just smells funny...
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next prev parent reply other threads:[~2021-12-16 19:54 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-16 19:16 [PATCH v2] arm64: errata: Fix exec handling in erratum 1418040 workaround D Scott Phillips
2021-12-16 19:52 ` Marc Zyngier [this message]
2021-12-17 14:41 ` Catalin Marinas
2021-12-17 16:42 ` D Scott Phillips
2021-12-17 18:38 ` Catalin Marinas
2021-12-17 19:29 ` D Scott Phillips
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