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Subject[PATCH 3.2 016/104] gcov: compile specific gcov implementation based on gcc version
3.2.101-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Frantisek Hrbata <fhrbata@redhat.com>

commit 17c568d60af5a810208baf116dc174a2005c6c3e upstream.

Compile the correct gcov implementation file for the specific gcc version.

Signed-off-by: Frantisek Hrbata <fhrbata@redhat.com>
Cc: Jan Stancek <jstancek@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Acked-by: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Andy Gospodarek <agospoda@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
Documentation/gcov.txt | 4 ++++
kernel/gcov/Kconfig | 30 ++++++++++++++++++++++++++++++
kernel/gcov/Makefile | 32 +++++++++++++++++++++++++++++++-
3 files changed, 65 insertions(+), 1 deletion(-)

--- a/Documentation/gcov.txt
+++ b/Documentation/gcov.txt
@@ -50,6 +50,10 @@ Configure the kernel with:
CONFIG_DEBUG_FS=y
CONFIG_GCOV_KERNEL=y

+select the gcc's gcov format, default is autodetect based on gcc version:
+
+ CONFIG_GCOV_FORMAT_AUTODETECT=y
+
and to get coverage data for the entire kernel:

CONFIG_GCOV_PROFILE_ALL=y
--- a/kernel/gcov/Kconfig
+++ b/kernel/gcov/Kconfig
@@ -46,4 +46,34 @@ config GCOV_PROFILE_ALL
larger and run slower. Also be sure to exclude files from profiling
which are not linked to the kernel image to prevent linker errors.

+choice
+ prompt "Specify GCOV format"
+ depends on GCOV_KERNEL
+ default GCOV_FORMAT_AUTODETECT
+ ---help---
+ The gcov format is usually determined by the GCC version, but there are
+ exceptions where format changes are integrated in lower-version GCCs.
+ In such a case use this option to adjust the format used in the kernel
+ accordingly.
+
+ If unsure, choose "Autodetect".
+
+config GCOV_FORMAT_AUTODETECT
+ bool "Autodetect"
+ ---help---
+ Select this option to use the format that corresponds to your GCC
+ version.
+
+config GCOV_FORMAT_3_4
+ bool "GCC 3.4 format"
+ ---help---
+ Select this option to use the format defined by GCC 3.4.
+
+config GCOV_FORMAT_4_7
+ bool "GCC 4.7 format"
+ ---help---
+ Select this option to use the format defined by GCC 4.7.
+
+endchoice
+
endmenu
--- a/kernel/gcov/Makefile
+++ b/kernel/gcov/Makefile
@@ -1,3 +1,33 @@
ccflags-y := -DSRCTREE='"$(srctree)"' -DOBJTREE='"$(objtree)"'

-obj-$(CONFIG_GCOV_KERNEL) := base.o fs.o gcc_3_4.o
+# if-lt
+# Usage VAR := $(call if-lt, $(a), $(b))
+# Returns 1 if (a < b)
+if-lt = $(shell [ $(1) -lt $(2) ] && echo 1)
+
+ifeq ($(CONFIG_GCOV_FORMAT_3_4),y)
+ cc-ver := 0304
+else ifeq ($(CONFIG_GCOV_FORMAT_4_7),y)
+ cc-ver := 0407
+else
+# Use cc-version if available, otherwise set 0
+#
+# scripts/Kbuild.include, which contains cc-version function, is not included
+# during make clean "make -f scripts/Makefile.clean obj=kernel/gcov"
+# Meaning cc-ver is empty causing if-lt test to fail with
+# "/bin/sh: line 0: [: -lt: unary operator expected" error mesage.
+# This has no affect on the clean phase, but the error message could be
+# confusing/annoying. So this dummy workaround sets cc-ver to zero if cc-version
+# is not available. We can probably move if-lt to Kbuild.include, so it's also
+# not defined during clean or to include Kbuild.include in
+# scripts/Makefile.clean. But the following workaround seems least invasive.
+ cc-ver := $(if $(call cc-version),$(call cc-version),0)
+endif
+
+obj-$(CONFIG_GCOV_KERNEL) := base.o fs.o
+
+ifeq ($(call if-lt, $(cc-ver), 0407),1)
+ obj-$(CONFIG_GCOV_KERNEL) += gcc_3_4.o
+else
+ obj-$(CONFIG_GCOV_KERNEL) += gcc_4_7.o
+endif
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