Messages in this thread | | | Date | Fri, 14 Mar 2014 13:55:07 +0900 | From | AKASHI Takahiro <> | Subject | Re: [PATCH v6 6/7] arm64: ftrace: Add CALLER_ADDRx macros |
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On 03/14/2014 03:07 AM, Steven Rostedt wrote: > On Thu, 2014-03-13 at 15:54 +0000, 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? > > Perhaps -pg does the same thing? > >>> +#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? > > We could add a new macro: > > /* All archs should have this, but we define it for consistency */ > #ifndef ftrace_return_address0 > # define ftrace_return_address0 __builtin_return_address(0) > #endif > /* Archs may use other ways for ADDR1 and beyond */ > #ifndef ftrace_return_address > # define ftrace_return_address(n) __builtin_return_address(n) > #endif > > And then have: > > #define CALLER_ADDR0 ((unsigned long)ftrace_return_address0) > #define CALLER_ADDR1 ((unsigned long)ftrace_return_address(1)) > [...] > > And then you would only need to redefine ftrace_return_address.
I'm going to create a separate RFC, including fixes for other archs.
-Takahiro AKASHI
> -- Steve > >
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