Messages in this thread | | | Date | Tue, 5 Oct 2021 11:41:31 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH] arm64: ftrace: use function_nocfi for _mcount as well |
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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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