Messages in this thread Patch in this message | | | Date | Fri, 14 Mar 2014 10:09:14 +0000 | From | Will Deacon <> | Subject | Re: [PATCH v6 6/7] arm64: ftrace: Add CALLER_ADDRx macros |
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On Fri, Mar 14, 2014 at 03:00:14AM +0000, AKASHI Takahiro wrote: > On 03/14/2014 12:54 AM, Will Deacon wrote: > > On Thu, Mar 13, 2014 at 10:13:49AM +0000, AKASHI Takahiro wrote: > >> CALLER_ADDRx returns caller's address at specified level in call stacks. > >> They are used for several tracers like irqsoff and preemptoff. > >> Strange to say, however, they are refered even without FTRACE. > >> > >> Please note that this implementation assumes that we have frame pointers. > >> (which means kernel should be compiled with -fno-omit-frame-pointer.) > > > > How do you ensure that -fno-omit-frame-pointer is passed? > > arm64 selects ARCH_WANT_FRAME_POINTERS, then FRAME_POINTER is on (lib/Kconfig.debug) > and so -fno-omit-frame-pointer is appended (${TOP}/Makefile). > (stacktrace.c also assumes FRAME_POINTER.) > > Do you think I should remove the comment above?
Yes please, it sounds like everything is taken care of automatically, so there's no need to scare people in the commit message!
> >> diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h > >> index ed5c448..c44c4b1 100644 > >> --- a/arch/arm64/include/asm/ftrace.h > >> +++ b/arch/arm64/include/asm/ftrace.h > >> @@ -18,6 +18,7 @@ > >> > >> #ifndef __ASSEMBLY__ > >> extern void _mcount(unsigned long); > >> +extern void *return_address(unsigned int); > >> > >> struct dyn_arch_ftrace { > >> /* No extra data needed for arm64 */ > >> @@ -33,6 +34,16 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr) > >> */ > >> return addr; > >> } > >> -#endif /* __ASSEMBLY__ */ > >> + > >> +#define HAVE_ARCH_CALLER_ADDR > >> + > >> +#define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0)) > >> +#define CALLER_ADDR1 ((unsigned long)return_address(1)) > >> +#define CALLER_ADDR2 ((unsigned long)return_address(2)) > >> +#define CALLER_ADDR3 ((unsigned long)return_address(3)) > >> +#define CALLER_ADDR4 ((unsigned long)return_address(4)) > >> +#define CALLER_ADDR5 ((unsigned long)return_address(5)) > >> +#define CALLER_ADDR6 ((unsigned long)return_address(6)) > > > > Could we change the core definitions of these macros (in linux/ftrace.h) to > > use return_address, then provide an overridable version of return_address > > that defaults to __builtin_return_address, instead of copy-pasting this > > sequence? > > I think I understand what you mean, and will try to post a separate RFC, > but I also want to hold off this change on this patch since such a change > may raise a small controversy from other archs' maintainers.
I don't see anything controversial here, but ok. Steve already posted something you can get started with.
Will
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