powerpc32/ftrace: Unify 32-bit and 64-bit ftrace entry code

Browse source

On 32-bit powerpc, gcc generates a three instruction sequence for
function profiling:
	mflr	r0
	stw	r0, 4(r1)
	bl	_mcount

On kernel boot, the call to _mcount() is nop-ed out, to be patched back
in when ftrace is actually enabled. The 'stw' instruction therefore is
not necessary unless ftrace is enabled. Nop it out during ftrace init.

When ftrace is enabled, we want the 'stw' so that stack unwinding works
properly. Perform the same within the ftrace handler, similar to 64-bit
powerpc.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Naveen N Rao <naveen@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://patch.msgid.link/20241030070850.1361304-5-hbathini@linux.ibm.com

...

This commit is contained in:

Naveen N Rao 2024-10-30 12:38:37 +05:30 • committed by Michael Ellerman

parent 161d62c2b0

commit 654b3fa61b

2 changed files with 6 additions and 4 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

6

arch/powerpc/kernel/trace/ftrace.c

View file

4

arch/powerpc/kernel/trace/ftrace_entry.S

View file