Re: [RFC PATCH 4/4] x86/asm: Use ASM_CALL() macro for inline asm statements with call instructions

[Peter Zijlstra]

On Thu, Aug 31, 2017 at 09:11:20AM -0500, Josh Poimboeuf wrote:
> Inline asm statements which have call instructions can be problematic.
> GCC doesn't know about the call instructions, so in some cases it can
> insert the asm before setting up the frame pointer.  This can result in
> bad stack traces when unwinding from the called function.
> 
> Previously we worked around this issue by listing the stack pointer as
> an input/output constraint for the inline asm.  That works for GCC, but
> unfortunately it doesn't work for Clang.  In fact, it causes Clang to
> corrupt the stack pointer.

Sounds like it ought to get fixed regardless and then it might as well
do the right thing ;-)