On Wed, 10 Apr 2019 18:03:57 +0200 Martin Schwidefsky <schwidefsky@xxxxxxxxxx> wrote: > > --- a/arch/s390/include/asm/ftrace.h > > +++ b/arch/s390/include/asm/ftrace.h > > @@ -13,7 +13,12 @@ > > > > #ifndef __ASSEMBLY__ > > > > +#ifdef CONFIG_CC_IS_CLANG > > +/* https://bugs.llvm.org/show_bug.cgi?id=41424 */ > > +#define ftrace_return_address(n) __builtin_return_address(0) > > +#else > > #define ftrace_return_address(n) __builtin_return_address(n) > > +#endif > > > > void _mcount(void); > > void ftrace_caller(void); > > I can say I like this one. If the compiler can not do __builtin_return_address(n) > it feels wrong to just use __builtin_return_address(0). I agree. The proper return value is 0UL, see include/linux/ftrace.h /* Archs may use other ways for ADDR1 and beyond */ #ifndef ftrace_return_address # ifdef CONFIG_FRAME_POINTER # define ftrace_return_address(n) __builtin_return_address(n) # else # define ftrace_return_address(n) 0UL # endif #endif This is why we treat zero differently: #define CALLER_ADDR0 ((unsigned long)ftrace_return_address0) #define CALLER_ADDR1 ((unsigned long)ftrace_return_address(1)) #define CALLER_ADDR2 ((unsigned long)ftrace_return_address(2)) #define CALLER_ADDR3 ((unsigned long)ftrace_return_address(3)) #define CALLER_ADDR4 ((unsigned long)ftrace_return_address(4)) #define CALLER_ADDR5 ((unsigned long)ftrace_return_address(5)) #define CALLER_ADDR6 ((unsigned long)ftrace_return_address(6)) -- Steve
