Messages in this thread | | | Date | Fri, 8 Oct 2021 09:05:46 +0100 | From | Will Deacon <> | Subject | Re: [PATCH v2] arm64: ftrace: use function_nocfi for _mcount as well |
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Hi Sumit,
On Wed, Oct 06, 2021 at 11:05:52AM +0530, Sumit Garg wrote: > On Tue, 5 Oct 2021 at 21:05, Mark Rutland <mark.rutland@arm.com> wrote: > > On Tue, Oct 05, 2021 at 08:20:02AM -0700, Sami Tolvanen wrote: > > > On Tue, Oct 5, 2021 at 5:37 AM Sumit Garg <sumit.garg@linaro.org> wrote: > > > > 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 > > > > > > > > > > Clang >= 10 supports -fpatchable-function-entry and CFI requires Clang > > > 12, so I assume this is only an issue if > > > CONFIG_DYNAMIC_FTRACE_WITH_REGS is explicitly disabled? > > > > I don't believe it's possible to disable explicitly, since > > DYNAMIC_FTRACE_WITH_REGS isn't user selectable, and is def bool y, > > depending on HAVE_DYNAMIC_FTRACE_WITH_REGS. > > > > Ah, I see. > > > Sumit, have you actually seen a problem, or was this found by > > inspection? > > > > Actually I have seen this ftrace problem with the android11-5.4-lts > kernel and AOSP master user-space on db845c. The reason being kernel > v5.4 LTS doesn't support ftrace with -fpatchable-function-entry on > arm64. > > With the mainline, I haven't tried to reproduce this issue but it was > rather by inspection that this needs to be fixed as well. > > > If this isn't an issue in practice, we could add the funciton_nocfi() > > for consistency, but we should make that clear in the commit message, > > and drop the fixes tag. > > Sure, let me drop the fixes tag and update the commit description in > v3 as mainline only enabled CFI_CLANG for arm64 when > "-fpatchable-function-entry" is supported.
Did you post a v3? Just want to make sure I didn't miss it.
Will
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