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
