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    SubjectRe: [PATCH] make CALLER_ADDRx overwriteable
    Date
    > The current definition of CALLER_ADDRx isn't suitable for all platforms.
    > E.g. for ARM __builtin_return_address(N) doesn't work for N > 0 and
    > AFAIK for powerpc there are no frame pointers needed to have a working
    > __builtin_return_address. This patch allows defining the CALLER_ADDRx
    > macros in <asm/ftrace.h> and let these take precedence.
    >
    > Because now <asm/ftrace.h> is included unconditionally in
    > <linux/ftrace.h> all archs that don't already had this include get an
    > empty one for free.

    AFAIK, ia64 also doesn't work for N > 0.
    thanks, good patch.



    > -#ifdef CONFIG_FRAME_POINTER
    > -/* TODO: need to fix this for ARM */
    > -# define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
    > -# define CALLER_ADDR1 ((unsigned long)__builtin_return_address(1))
    > -# define CALLER_ADDR2 ((unsigned long)__builtin_return_address(2))
    > -# define CALLER_ADDR3 ((unsigned long)__builtin_return_address(3))
    > -# define CALLER_ADDR4 ((unsigned long)__builtin_return_address(4))
    > -# define CALLER_ADDR5 ((unsigned long)__builtin_return_address(5))
    > -# define CALLER_ADDR6 ((unsigned long)__builtin_return_address(6))
    > -#else
    > -# define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
    > -# define CALLER_ADDR1 0UL
    > -# define CALLER_ADDR2 0UL
    > -# define CALLER_ADDR3 0UL
    > -# define CALLER_ADDR4 0UL
    > -# define CALLER_ADDR5 0UL
    > -# define CALLER_ADDR6 0UL
    > -#endif
    > +#ifndef CALLER_ADDR0

    but I think this "#ifndef CALLER_ADDR0" don't explain developer intention at all.
    ARCH_HAS_XXXXX macro is better?

    I would like to hear another developer opinions.


    > +# ifdef CONFIG_FRAME_POINTER
    > +# define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
    > +# define CALLER_ADDR1 ((unsigned long)__builtin_return_address(1))
    > +# define CALLER_ADDR2 ((unsigned long)__builtin_return_address(2))
    > +# define CALLER_ADDR3 ((unsigned long)__builtin_return_address(3))
    > +# define CALLER_ADDR4 ((unsigned long)__builtin_return_address(4))
    > +# define CALLER_ADDR5 ((unsigned long)__builtin_return_address(5))
    > +# define CALLER_ADDR6 ((unsigned long)__builtin_return_address(6))
    > +# else
    > +# define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
    > +# define CALLER_ADDR1 0UL
    > +# define CALLER_ADDR2 0UL
    > +# define CALLER_ADDR3 0UL
    > +# define CALLER_ADDR4 0UL
    > +# define CALLER_ADDR5 0UL
    > +# define CALLER_ADDR6 0UL
    > +# endif
    > +#endif /* ifndef CALLER_ADDR0 */






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