| Message ID | 20211005103208.2763305-1-sumit.garg@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: ftrace: use function_nocfi for _mcount as well | expand |
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 >
On Tue, 5 Oct 2021 at 16:11, Mark Rutland <mark.rutland@arm.com> wrote: > > 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. Okay, I will add it to the commit description. > > > Signed-off-by: Sumit Garg <sumit.garg@linaro.org> > > This probably wants: > > Fixes: 9186ad8e66bab6a1 ("arm64: allow CONFIG_CFI_CLANG to be selected") > Okay, I will add it in v2. > With that: > > Acked-by: Mark Rutland <mark.rutland@arm.com> > Thanks, Sumit > 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 > >
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 */
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. Signed-off-by: Sumit Garg <sumit.garg@linaro.org> --- arch/arm64/include/asm/ftrace.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)