On Wed, 21 Jun 2023 10:43:49 +0530, Naveen N Rao wrote:

With ppc64 -mprofile-kernel and ppc32 -pg, profiling instructions to
call into ftrace are emitted right at function entry. The instruction
sequence used is minimal to reduce overhead. Crucially, a stackframe is
not created for the function being traced. This breaks stack unwinding
since the function being traced does not have a stackframe for itself.
As such, it never shows up in the backtrace:

[...]

Applied to powerpc/fixes.

[1/1] powerpc/ftrace: Create a dummy stackframe to fix stack unwind
      https://git.kernel.org/powerpc/c/41a506ef71eb38d94fe133f565c87c3e06ccc072

cheers