linux-kernel - Re: [RFC PATCH 3/4] gcov: compile specific gcov implementation based on gcc version

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Date:	Fri, 23 Aug 2013 17:21:12 +0200
From:	Peter Oberparleiter <oberpar@...ux.vnet.ibm.com>
To:	Frantisek Hrbata <fhrbata@...hat.com>
CC:	linux-kernel@...r.kernel.org, jstancek@...hat.com,
	keescook@...omium.org, rusty@...tcorp.com.au,
	linux-arch@...r.kernel.org, arnd@...db.de, mgahagan@...hat.com,
	agospoda@...hat.com
Subject: Re: [RFC PATCH 3/4] gcov: compile specific gcov implementation based
 on gcc version

On 23.08.2013 17:15, Peter Oberparleiter wrote:
> On 23.08.2013 10:39, Frantisek Hrbata wrote:
>> Compile the correct gcov implementation file for a specific gcc version. In
>> the future, if another file is added, the conditions will need to be somehow
>> adjusted to if-elif-else case, but at this point the simple cc-ifversion should
>> be enough.

As promised, I'm also adding the patch that makes the format-specific part
of gcov-kernel a loadable kernel module:

---
kernel: gcov: make format-specific code loadable

Turn the format-specific part of gcov-kernel into a loadable kernel
module. This enables the use of gcov-kernel with kernel modules
that were compiled with a version of GCC that produces a different
gcov format when compared to the version of GCC that was used to
compile the kernel.

Signed-off-by: Peter Oberparleiter <oberpar@...ux.vnet.ibm.com>
---
 kernel/gcov/Kconfig  |   19 +++++++++++++++++--
 kernel/gcov/Makefile |    7 ++++---
 2 files changed, 21 insertions(+), 5 deletions(-)

--- a/kernel/gcov/Kconfig
+++ b/kernel/gcov/Kconfig
@@ -29,8 +29,23 @@ config GCOV_KERNEL
 	and:
 	        GCOV_PROFILE := n

-	Note that the debugfs filesystem has to be mounted to access
-	profiling data.
+	Note that GCOV_KERNEL_FS has to specified as well and the debugfs
+	filesystem has to be mounted to access profiling data.
+
+config GCOV_KERNEL_FS
+	tristate "Provide gcov data files in debugfs"
+	depends on GCOV_KERNEL
+	default y
+	---help---
+	Make profiling data available in debugfs at /sys/kernel/debug/gcov.
+
+	Say M if you want to enable collecting coverage data for kernel modules
+	which are compiled using a gcc version different from the one that
+	was used to compile the kernel. In that case, re-compile the gcov
+	kernel module with corresponding format support and load that module
+	instead.
+
+	If unsure, say Y.

 config GCOV_PROFILE_ALL
 	bool "Profile entire Kernel"
--- a/kernel/gcov/Makefile
+++ b/kernel/gcov/Makefile
@@ -13,10 +13,11 @@ else
   cc-ver := $(call cc-version)
 endif

-obj-$(CONFIG_GCOV_KERNEL) := base.o fs.o
+obj-$(CONFIG_GCOV_KERNEL) += base.o
+obj-$(CONFIG_GCOV_KERNEL_FS) += gcov.o

 ifeq ($(call if-lt, $(cc-ver), 0407),1)
-  obj-$(CONFIG_GCOV_KERNEL) += gcc_3_4.o
+  gcov-objs += fs.o gcc_3_4.o
 else
-  obj-$(CONFIG_GCOV_KERNEL) += gcc_4_7.o
+  gcov-objs += fs.o gcc_4_7.o
 endif

-- 
Peter Oberparleiter
Linux on System z Development - IBM Germany

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