From: Mark Rutland <mark.rutland@arm.com>
To: Sumit Garg <sumit.garg@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org, rostedt@goodmis.org,
mingo@redhat.com, catalin.marinas@arm.com, will@kernel.org,
samitolvanen@google.com, ben.dai@unisoc.com, nathan@kernel.org,
keescook@chromium.org, daniel.thompson@linaro.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm64: ftrace: use function_nocfi for _mcount as well
Date: Tue, 5 Oct 2021 11:41:31 +0100 [thread overview]
Message-ID: <20211005104131.GB1664@C02TD0UTHF1T.local> (raw)
In-Reply-To: <20211005103208.2763305-1-sumit.garg@linaro.org>
On Tue, Oct 05, 2021 at 04:02:08PM +0530, Sumit Garg wrote:
> Commit 800618f955a9 ("arm64: ftrace: use function_nocfi for ftrace_call")
> only fixed address of ftrace_call but address of _mcount needs to be
> fixed as well. Use function_nocfi() to get the actual address of _mcount
> function as with CONFIG_CFI_CLANG, the compiler replaces function pointers
> with jump table addresses which breaks dynamic ftrace as the address of
> _mcount is replaced with the address of _mcount.cfi_jt.
It might be worth noting that where the toolchain implements
patchable-function-entry, we'll use that in preference to regular -pg,
and this problem won't apply. i.e. this won't show with recent versions
of clang.
> Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
This probably wants:
Fixes: 9186ad8e66bab6a1 ("arm64: allow CONFIG_CFI_CLANG to be selected")
With that:
Acked-by: Mark Rutland <mark.rutland@arm.com>
Mark.
> ---
> arch/arm64/include/asm/ftrace.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
> index 91fa4baa1a93..347b0cc68f07 100644
> --- a/arch/arm64/include/asm/ftrace.h
> +++ b/arch/arm64/include/asm/ftrace.h
> @@ -15,7 +15,7 @@
> #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
> #define ARCH_SUPPORTS_FTRACE_OPS 1
> #else
> -#define MCOUNT_ADDR ((unsigned long)_mcount)
> +#define MCOUNT_ADDR ((unsigned long)function_nocfi(_mcount))
> #endif
>
> /* The BL at the callsite's adjusted rec->ip */
> --
> 2.17.1
>
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next prev parent reply other threads:[~2021-10-05 10:43 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-05 10:32 [PATCH] arm64: ftrace: use function_nocfi for _mcount as well Sumit Garg
2021-10-05 10:41 ` Mark Rutland [this message]
2021-10-05 12:22 ` Sumit Garg
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