Nicholas Piggin wrote:
-mprofile-kernel is an optimised calling convention for mcount that
Linux has only implemented with the ELFv2 ABI, so it was disabled for
big endian kernels. However it does work with ELFv2 big endian, so let's
allow that if the compiler supports it.
Cc: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
Suggested-by: Christophe Leroy <christophe.le...@csgroup.eu>
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
Christophe had the good idea that we could use -mprofile-kernel for
ELFv2 BE. Unfortunately can't remove -pg due to lack of -mprofile-kernel
in clang, but this gives BE the nicer ftrace code with GCC at least.
Function tracer works for me with a BE kernel.
LGTM. With a few minor nits below:
Acked-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
Thanks,
Nick
arch/powerpc/Kconfig | 6 ++++--
arch/powerpc/tools/gcc-check-mprofile-kernel.sh | 4 ++--
2 files changed, 6 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index a64bfd9b8a1d..bd2ee7af1342 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -547,8 +547,10 @@ config LD_HEAD_STUB_CATCH
If unsure, say "N".
config MPROFILE_KERNEL
- depends on PPC64 && CPU_LITTLE_ENDIAN && FUNCTION_TRACER
- def_bool
$(success,$(srctree)/arch/powerpc/tools/gcc-check-mprofile-kernel.sh $(CC)
-I$(srctree)/include -D__KERNEL__)
+ depends on PPC64 && FUNCTION_TRACER
+ depends on CPU_LITTLE_ENDIAN || PPC64_BIG_ENDIAN_ELF_ABI_V2
Can't we just check for PPC64_ELF_ABI_V2?
+ def_bool
$(success,$(srctree)/arch/powerpc/tools/gcc-check-mprofile-kernel.sh $(CC)
-mlittle-endian) if CPU_LITTLE_ENDIAN
+ def_bool
$(success,$(srctree)/arch/powerpc/tools/gcc-check-mprofile-kernel.sh $(CC)
-mbig-endian) if CPU_BIG_ENDIAN
config HOTPLUG_CPU
bool "Support for enabling/disabling CPUs"
diff --git a/arch/powerpc/tools/gcc-check-mprofile-kernel.sh
b/arch/powerpc/tools/gcc-check-mprofile-kernel.sh
index 137f3376ac2b..e78c599251ff 100755
--- a/arch/powerpc/tools/gcc-check-mprofile-kernel.sh
+++ b/arch/powerpc/tools/gcc-check-mprofile-kernel.sh
@@ -14,13 +14,13 @@ set -o pipefail
We have this comment before the below code, which should also be
updated/removed:
# -mprofile-kernel is only supported on 64le, so this should not be invoked
# for other targets. Therefore we can pass in -m64 and -mlittle-endian
# explicitly, to take care of toolchains defaulting to other targets.
# Test whether the compile option -mprofile-kernel exists and generates
# profiling code (ie. a call to _mcount()).
echo "int func() { return 0; }" | \
- $* -m64 -mlittle-endian -S -x c -O2 -p -mprofile-kernel - -o - \
+ $* -m64 -S -x c -O2 -p -mprofile-kernel - -o - \
2> /dev/null | grep -q "_mcount"
# Test whether the notrace attribute correctly suppresses calls to _mcount().
echo -e "#include <linux/compiler.h>\nnotrace int func() { return 0; }" | \
- $* -m64 -mlittle-endian -S -x c -O2 -p -mprofile-kernel - -o - \
+ $* -m64 -S -x c -O2 -p -mprofile-kernel - -o - \
2> /dev/null | grep -q "_mcount" && \
exit 1
- Naveen
