On Wed, Jan 10, 2024 at 06:31:11PM +0000, Russell King (Oracle) wrote:

On Wed, Jan 10, 2024 at 08:05:25PM +0200, Vladimir Oltean wrote:

quoted

On Wed, Jan 10, 2024 at 08:15:20PM +0300, Arınç ÜNAL wrote:

quoted

__builtin_return_address(1) doesn't seem to work. I'm running this on arm64.

I can't tell you why either, I'm sorry. I can just point to the
documentation, which does specify that "On some machines it may be
impossible to determine the return address of any function other than
the current one". If somebody knows what this depends on, feel free to
interject.
https://gcc.gnu.org/onlinedocs/gcc/Return-Address.html

On my NXP LS1028A (also arm64) plus clang-16 compiler, __builtin_return_address()
does work with multiple nesting levels.

gcc will probably need to be using frame pointers so it can walk the
stack, if gcc even implements non-zero values to
__builtin_return_address(). Without frame pointers, it would need an
unwinder.

Yeah, I guess it's a gcc limitation. I recompiled the kernel for the same
platform with gcc 11.2 from Arm, and I get the same result as Arınç now.