[RFC PATCH 2/2] powerpc/kbuild: move -mprofile-kernel check to Kconfig

Nicholas Piggin
2018-04-30T01:24:08Z

This eliminates the workaround that requires disabling
-mprofile-kernel by default in Kconfig.
---
arch/powerpc/Kconfig | 16 +---------------
arch/powerpc/Makefile | 14 ++------------
arch/powerpc/tools/gcc-check-mprofile-kernel.sh | 4 ++--
3 files changed, 5 insertions(+), 29 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 512fcc177c87..af527f894f9b 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -460,23 +460,9 @@ config LD_HEAD_STUB_CATCH

If unsure, say "N".

-config DISABLE_MPROFILE_KERNEL
- bool "Disable use of mprofile-kernel for kernel tracing"
- depends on PPC64 && CPU_LITTLE_ENDIAN
- default y
- help
- Selecting this options disables use of the mprofile-kernel ABI for
- kernel tracing. That will cause options such as live patching
- (CONFIG_LIVEPATCH) which depend on CONFIG_DYNAMIC_FTRACE_WITH_REGS to
- be disabled also.
-
- If you have a toolchain which supports mprofile-kernel, then you can
- disable this. Otherwise leave it enabled. If you're not sure, say
- "Y".
-
config MPROFILE_KERNEL
depends on PPC64 && CPU_LITTLE_ENDIAN
- def_bool !DISABLE_MPROFILE_KERNEL
+ def_bool $(success $(srctree)/arch/powerpc/tools/gcc-check-mprofile-kernel.sh $(CC) -I$(srctree)/include -D__KERNEL__)

config IOMMU_HELPER
def_bool PPC64
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 046b5dde9ff5..efab4d66043b 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -158,18 +158,8 @@ CFLAGS-$(CONFIG_GENERIC_CPU) += -mcpu=powerpc64
endif

ifdef CONFIG_MPROFILE_KERNEL
- ifeq ($(shell $(srctree)/arch/powerpc/tools/gcc-check-mprofile-kernel.sh $(CC) -I$(srctree)/include -D__KERNEL__),OK)
- CC_FLAGS_FTRACE := -pg -mprofile-kernel
- KBUILD_CPPFLAGS += -DCC_USING_MPROFILE_KERNEL
- else
- # If the user asked for mprofile-kernel but the toolchain doesn't
- # support it, emit a warning and deliberately break the build later
- # with mprofile-kernel-not-supported. We would prefer to make this an
- # error right here, but then the user would never be able to run
- # oldconfig to change their configuration.
- $(warning Compiler does not support mprofile-kernel, set CONFIG_DISABLE_MPROFILE_KERNEL)
- CC_FLAGS_FTRACE := -mprofile-kernel-not-supported
- endif
+ CC_FLAGS_FTRACE := -pg -mprofile-kernel
+ KBUILD_CPPFLAGS += -DCC_USING_MPROFILE_KERNEL
endif

CFLAGS-$(CONFIG_CELL_CPU) += $(call cc-option,-mcpu=cell)
diff --git a/arch/powerpc/tools/gcc-check-mprofile-kernel.sh b/arch/powerpc/tools/gcc-check-mprofile-kernel.sh
index 061f8035bdbe..ec4486a9c4a3 100755
--- a/arch/powerpc/tools/gcc-check-mprofile-kernel.sh
+++ b/arch/powerpc/tools/gcc-check-mprofile-kernel.sh
@@ -10,13 +10,13 @@ set -o pipefail
# Test whether the compile option -mprofile-kernel exists and generates
# profiling code (ie. a call to _mcount()).
echo "int func() { return 0; }" | \
- $* -S -x c -O2 -p -mprofile-kernel - -o - 2> /dev/null | \
+ $* -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; }" | \
- $* -S -x c -O2 -p -mprofile-kernel - -o - 2> /dev/null | \
+ $* -m64 -S -x c -O2 -p -mprofile-kernel - -o - 2> /dev/null | \
grep -q "_mcount" && \
exit 1

--
2.17.0