From: Naveen N Rao <naveen@kernel.org>
To: <linuxppc-dev@lists.ozlabs.org>
Cc: llvm@lists.linux.dev, Nathan Chancellor <nathan@kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
Christophe Leroy <christophe.leroy@csgroup.eu>
Subject: [PATCH] powerpc/ftrace: Disable ftrace on ppc32 if using clang
Date: Fri, 9 Jun 2023 09:15:01 +0530 [thread overview]
Message-ID: <20230609034501.407971-1-naveen@kernel.org> (raw)
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: Naveen N Rao <naveen@kernel.org>
---
arch/powerpc/Kconfig | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index bff5820b7cda14..d85e3cf4016d90 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -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
base-commit: bd517a8442b6c6646a136421cd4c1b95bf4ce32b
--
2.40.1
next reply other threads:[~2023-06-09 3:47 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-09 3:45 Naveen N Rao [this message]
2023-06-09 19:45 ` [PATCH] powerpc/ftrace: Disable ftrace on ppc32 if using clang Nick Desaulniers
2023-07-03 5:26 ` Michael Ellerman
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