On Wed, Nov 06, 2024 at 05:05:54PM +0100, Uros Bizjak wrote: > Please see [1]: > > /* > * This output constraint should be used for any inline asm which has a "call" > * instruction. Otherwise the asm may be inserted before the frame pointer > * gets set up by the containing function. If you forget to do this, objtool > * may print a "call without frame pointer save/setup" warning. > */ > register unsigned long current_stack_pointer asm(_ASM_SP); > #define ASM_CALL_CONSTRAINT "+r" (current_stack_pointer) > > Perhaps HPA can say some more?
So workaround about issues in some kernel tool? Not sure if gcc needs to provide workaround for that. Just do the call in a separate .subsection or add some magic labels around it that the tool can check and disable the warning. Perhaps just a label at the start of the call insn with some special prefix followed by %= that the tool can use to find out calls coming from inline asm vs. calls from C code. Jakub