[PATCH v3 2/4] asm-generic: Provide a fncpy() implementation

Yury Norov
2017-06-19T01:11:05Z

> > +/*
> > + * Minimum alignment requirement for the source and destination addresses
> > + * for function copying.
> > + */
> > +#define FNCPY_ALIGN 8
>
> >From now this is not arm-only, and it's possible that some architectures
> might want to redefine it in their arch/xxx/include/asm/fncpy.h files.
> So it will be easier for them if you'll wrap FNCPY_ALIGN here with #ifdef
> guards.
>
> By the way, compiler already has an information on the proper alignment.
> Maybe it's better to use it as the default value here instead of the
> hardcoded value?
>
> #ifndef FNCPY_ALIGN
> #define FNCPY_ALIGN ({void foo(); __alignof__(&foo);})
> #endif

Ah sorry, at first it should be like this:
#define FNCPY_ALIGN ({void foo(); __alignof__(foo);})

And at second, the correct version returns 1 always.

Even if I pass falign-functions=4096 to gcc, and I see that functions
are aligned accordingly in elf file, the macro returns 1 anyway. So if
it doesn't work, the hardcoded '8' is the only option.

Yury