On Wed, Apr 10, 2019 at 6:14 PM Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > 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)) Right, got it. Martin, do you want me to send a replacement patch, or can you commit the patch with #ifdef CONFIG_CC_IS_CLANG /* https://bugs.llvm.org/show_bug.cgi?id=41424 */ #define ftrace_return_address(n) 0UL #else #define ftrace_return_address(n) __builtin_return_address(n) #endif instead? Arnd
