Re: [tip: x86/asm] x86/asm: Make ASM_CALL_CONSTRAINT conditional on frame pointers

[Josh Poimboeuf]

On Mon, Mar 03, 2025 at 02:45:50PM -0800, Josh Poimboeuf wrote:
> On Mon, Mar 03, 2025 at 02:31:50PM -0800, H. Peter Anvin wrote:
> > >+#ifdef CONFIG_UNWINDER_FRAME_POINTER
> > > #define ASM_CALL_CONSTRAINT "r" (__builtin_frame_address(0))
> > >+#else
> > >+#define ASM_CALL_CONSTRAINT
> > >+#endif
> > > 
> > > #endif /* __ASSEMBLY__ */
> > > 
> > 
> > Wait, why was this changed? I actually tested this form at least once
> > and found that it didn't work under all circumstances...
> 
> Do you have any more details about where this didn't work?  I tested
> with several configs and it seems to work fine.  Objtool will complain
> if it doesn't work.
> 
> See here for the justification (the previous version was producing crap
> code in Clang):

Gah, that link doesn't work because I forgot to cc lkml.

Here's the tip bot link:

  https://lore.kernel.org/all/174099976253.10177.12542657892256193630.tip-bot2@tip-bot2/

-- 
Josh