Commit d24da1f8 authored by Naveen N Rao's avatar Naveen N Rao Committed by Michael Ellerman
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powerpc/ftrace: Disable ftrace on ppc32 if using clang 



Ftrace on ppc32 expects a three instruction sequence at the beginning of
each function when specifying -pg:
	mflr	r0
	stw	r0,4(r1)
	bl	_mcount

This is the case with all supported versions of gcc. Clang however emits
a branch to _mcount after the function prologue, similar to the pre
-mprofile-kernel ABI on ppc64. This is not supported.

Disable ftrace on ppc32 if using clang for now. This can be re-enabled
later if clang picks up support for -fpatchable-function-entry on ppc32.

Signed-off-by: default avatarNaveen N Rao <naveen@kernel.org>
Acked-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Link: https://github.com/llvm/llvm-project/issues/63220


Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230609034501.407971-1-naveen@kernel.org
parent f4f913c9

arch/powerpc/Kconfig

+1 −1
Original line number Diff line number Diff line
@@ -236,7 +236,7 @@ config PPC 
	select HAVE_FUNCTION_DESCRIPTORS	if PPC64_ELF_ABI_V1

	select HAVE_FUNCTION_ERROR_INJECTION

	select HAVE_FUNCTION_GRAPH_TRACER

	select HAVE_FUNCTION_TRACER

	select HAVE_FUNCTION_TRACER		if PPC64 || (PPC32 && CC_IS_GCC)

	select HAVE_GCC_PLUGINS			if GCC_VERSION >= 50200   # plugin support on gcc <= 5.1 is buggy on PPC

	select HAVE_GENERIC_VDSO

	select HAVE_HARDLOCKUP_DETECTOR_ARCH	if PPC_BOOK3S_64 && SMP