The patch titled
gcov: revert link changes
has been added to the -mm tree. Its filename is
gcov-add-gcov-profiling-infrastructure-revert-link-changes.patch
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------------------------------------------------------
Subject: gcov: revert link changes
From: Peter Oberparleiter <peter.oberparleiter@xxxxxxxxxx>
Change the gcov mechanism back to using symbolic links in sysfs. This
is necessary to fix problems when profiling with CONFIG_MODVERSIONS=y.
The correct usage of the gcov tool now looks like this:
# cd $OBJTREE
# gcov -o /sys/kernel/debug/gcov/$OBJTREE/init main.c
Also update documentation to include a description on how to use gcov
profiling in a separated build/test machine environment.
Signed-off-by: Peter Oberparleiter <peter.oberparleiter@xxxxxxxxxx>
Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/gcov.txt | 138 +++++++++++++++++++++++++++++++++++----
kernel/gcov/Makefile | 2
kernel/gcov/fs.c | 123 ++++++++++++++++++++++++++++++++++
kernel/gcov/gcc_3_4.c | 6 +
kernel/gcov/gcov.h | 9 ++
5 files changed, 262 insertions(+), 16 deletions(-)
diff -puN Documentation/gcov.txt~gcov-add-gcov-profiling-infrastructure-revert-link-changes Documentation/gcov.txt
--- a/Documentation/gcov.txt~gcov-add-gcov-profiling-infrastructure-revert-link-changes
+++ a/Documentation/gcov.txt
@@ -6,7 +6,10 @@ Using gcov with the Linux kernel
3. Customization
4. Files
5. Modules
-6. Troubleshooting
+6. Separated build and test machines
+7. Troubleshooting
+Appendix A: sample script: gather_on_build.sh
+Appendix B: sample script: gather_on_test.sh
1. Introduction
@@ -15,16 +18,11 @@ Using gcov with the Linux kernel
gcov profiling kernel support enables the use of GCC's coverage testing
tool gcov [1] with the Linux kernel. Coverage data of a running kernel
is exported in gcov-compatible format via the "gcov "debugfs directory.
+To get coverage data for a specific file, change to the kernel build
+directory and use gcov with the -o option as follows (requires root):
-Example:
-
-To get coverage data for file base.c in directory drivers/base, simply
-change to the kernel build directory and run gcov with the -o option
-(assumptions: kernel was built in /tmp/linux and debugfs is mounted at
-/sys/kernel/debug):
-
-# cd /tmp/linux
-# gcov -o drivers/base/ bus.c
+# cd /tmp/linux-out
+# gcov -o /sys/kernel/debug/gcov/tmp/linux/kernel spinlock.c
This will create source code files annotated with execution counts
in the current directory. In addition, graphical gcov front-ends such
@@ -38,6 +36,11 @@ Possible uses:
* minimizing kernel configurations (do I need this option if the
associated code is never executed?)
+--
+
+[1] http://gcc.gnu.org/onlinedocs/gcc/Gcov.html
+[2] http://ltp.sourceforge.net/coverage/lcov.php
+
2. Preparation
==============
@@ -99,6 +102,11 @@ The gcov kernel support creates the foll
The actual gcov data file as understood by the gcov
tool. Resets file coverage data to zero when written to.
+ /sys/kernel/debug/gcov/path/to/compile/dir/file.gcno
+ Symbolic link to a static data file required by the gcov
+ tool. This file is generated by gcc when compiling with
+ option -ftest-coverage.
+
5. Modules
==========
@@ -119,7 +127,56 @@ At run-time, a user can also choose to d
module by writing to its data file or the global reset file.
-6. Troubleshooting
+6. Separated build and test machines
+====================================
+
+The gcov kernel profiling infrastructure is designed to work out-of-the
+box for setups where kernels are built and run on the same machine. In
+cases where the kernel runs on a separate machine, special preparations
+must be made, depending on where the gcov tool is used:
+
+a) gcov is run on the TEST machine
+
+The gcov tool version on the test machine must be compatible with the
+gcc version used for kernel build. Also the following files need to be
+copied from build to test machine:
+
+from the source tree:
+ - all C source files + headers
+
+from the build tree:
+ - all C source files + headers
+ - all .gcda and .gcno files
+ - all links to directories
+
+It is important to note that these files need to be placed into the
+exact same file system location on the test machine as on the build
+machine. If any of the path components is symbolic link, the actual
+directory needs to be used instead (due to make's CURDIR handling).
+
+b) gcov is run on the BUILD machine
+
+The following files need to be copied after each test case from test
+to build machine:
+
+from the gcov directory in sysfs:
+ - all .gcda files
+ - all links to .gcno files
+
+These files can be copied to any location on the build machine. gcov
+must then be called with the -o option pointing to that directory.
+
+Example directory setup on the build machine:
+
+ /tmp/linux: kernel source tree
+ /tmp/out: kernel build directory as specified by make O=
+ /tmp/coverage: location of the files copied from the test machine
+
+ [user@build] cd /tmp/out
+ [user@build] gcov -o /tmp/coverage/tmp/out/init main.c
+
+
+7. Troubleshooting
==================
Problem: Compilation aborts during linker step.
@@ -127,10 +184,62 @@ Cause: Profiling flags are specified
linked to the main kernel or which are linked by a custom
linker procedure.
Solution: Exclude affected source files from profiling by specifying
- GCOV := n in the corresponding Makefile.
+ GCOV := n or GCOV_basename.o := n in the corresponding
+ Makefile.
---
+Appendix A: gather_on_build.sh
+==============================
-[1] http://gcc.gnu.org/onlinedocs/gcc/Gcov.html
-[2] http://ltp.sourceforge.net/coverage/lcov.php
+Sample script to gather coverage meta files on the build machine
+(see 6a):
+
+#!/bin/bash
+
+KSRC=$1
+KOBJ=$2
+DEST=$3
+
+if [ -z "$KSRC" ] || [ -z "$KOBJ" ] || [ -z "$DEST" ]; then
+ echo "Usage: $0 <ksrc directory> <kobj directory> <output.tar.gz>" >&2
+ exit 1
+fi
+
+KSRC=$(cd $KSRC; printf "all:\n\t@echo \${CURDIR}\n" | make -f -)
+KOBJ=$(cd $KOBJ; printf "all:\n\t@echo \${CURDIR}\n" | make -f -)
+
+find $KSRC $KOBJ \( -name '*.gcno' -o -name '*.[ch]' -o -type l \) -a \
+ -perm /u+r,g+r | tar cfz $DEST -P -T -
+
+if [ $? -eq 0 ] ; then
+ echo "$DEST successfully created, copy to test system and unpack with:"
+ echo " tar xfz $DEST -P"
+else
+ echo "Could not create file $DEST"
+fi
+
+
+Appendix B: gather_on_test.sh
+=============================
+
+Sample script to gather coverage data files on the test machine
+(see 6b):
+
+#!/bin/bash
+
+DEST=$1
+GCDA=/sys/kernel/debug/gcov
+
+if [ -z "$DEST" ] ; then
+ echo "Usage: $0 <output.tar.gz>" >&2
+ exit 1
+fi
+
+find $GCDA -name '*.gcno' -o -name '*.gcda' | tar cfz $DEST -T -
+
+if [ $? -eq 0 ] ; then
+ echo "$DEST successfully created, copy to build system and unpack with:"
+ echo " tar xfz $DEST"
+else
+ echo "Could not create file $DEST"
+fi
diff -puN kernel/gcov/Makefile~gcov-add-gcov-profiling-infrastructure-revert-link-changes kernel/gcov/Makefile
--- a/kernel/gcov/Makefile~gcov-add-gcov-profiling-infrastructure-revert-link-changes
+++ a/kernel/gcov/Makefile
@@ -1 +1,3 @@
+EXTRA_CFLAGS := -DSRCTREE='"$(srctree)"' -DOBJTREE='"$(objtree)"'
+
obj-$(CONFIG_GCOV_PROFILE) := base.o fs.o gcc_3_4.o
diff -puN kernel/gcov/fs.c~gcov-add-gcov-profiling-infrastructure-revert-link-changes kernel/gcov/fs.c
--- a/kernel/gcov/fs.c~gcov-add-gcov-profiling-infrastructure-revert-link-changes
+++ a/kernel/gcov/fs.c
@@ -36,11 +36,13 @@
* copy of the profiling data here to allow collecting coverage data
* for cleanup code. Such a node is called a "ghost".
* @dentry: main debugfs entry, either a directory or data file
+ * @links: associated symbolic links
* @name: data file basename
*
* struct gcov_node represents an entity within the gcov/ subdirectory
* of debugfs. There are directory and data file nodes. The latter represent
- * the actual synthesized data file.
+ * the actual synthesized data file plus any associated symbolic links which
+ * are needed by the gcov tool to work correctly.
*/
struct gcov_node {
struct list_head list;
@@ -50,9 +52,12 @@ struct gcov_node {
struct gcov_info *info;
struct gcov_info *ghost;
struct dentry *dentry;
+ struct dentry **links;
char name[0];
};
+static const char objtree[] = OBJTREE;
+static const char srctree[] = SRCTREE;
static struct gcov_node root_node;
static struct dentry *reset_dentry;
static LIST_HEAD(all_head);
@@ -238,6 +243,104 @@ static ssize_t gcov_seq_write(struct fil
return len;
}
+/* Given a string <path> representing a file path of format:
+ * path/to/file.gcda
+ * construct and return a new string:
+ * <dir/>path/to/file.<ext> */
+static char *link_target(const char *dir, const char *path, const char *ext)
+{
+ char *target;
+ char *old_ext;
+ char *copy;
+
+ copy = kstrdup(path, GFP_KERNEL);
+ if (!copy)
+ return NULL;
+ old_ext = strrchr(copy, '.');
+ if (old_ext)
+ *old_ext = '\0';
+ if (dir)
+ target = kasprintf(GFP_KERNEL, "%s/%s.%s", dir, copy, ext);
+ else
+ target = kasprintf(GFP_KERNEL, "%s.%s", copy, ext);
+ kfree(copy);
+
+ return target;
+}
+
+/* Construct a string representing the symbolic link target for the given
+ * gcov data file name and link type. Depending on the link type and the
+ * location of the data file, the link target can either point to a
+ * subdirectory of srctree, objtree or in an external location. */
+static char *get_link_target(const char *filename, const struct gcov_link *ext)
+{
+ const char *rel;
+ char *result;
+
+ if (strncmp(filename, objtree, strlen(objtree)) == 0) {
+ rel = filename + strlen(objtree) + 1;
+ if (ext->dir == src_tree)
+ result = link_target(srctree, rel, ext->ext);
+ else
+ result = link_target(objtree, rel, ext->ext);
+ } else {
+ /* External compilation. */
+ result = link_target(NULL, filename, ext->ext);
+ }
+
+ return result;
+}
+
+#define SKEW_PREFIX ".tmp_"
+
+/* For a filename .tmp_filename.ext return filename.ext. Needed to compensate
+ * for filename skewing caused by the mod-versioning mechanism. */
+static const char *deskew(const char *basename)
+{
+ if (strncmp(basename, SKEW_PREFIX, sizeof(SKEW_PREFIX) - 1) == 0)
+ return basename + sizeof(SKEW_PREFIX) - 1;
+ return basename;
+}
+
+/* Create links to additional files (usually .c and .gcno files) which the
+ * gcov tool expects to find in the same directory as the gcov data file. */
+static void add_links(struct gcov_node *node, struct dentry *parent)
+{
+ char *basename;
+ char *target;
+ int num;
+ int i;
+
+ for (num = 0; gcov_link[num].ext; num++)
+ /* Nothing. */;
+ node->links = kcalloc(num, sizeof(struct dentry *), GFP_KERNEL);
+ if (!node->links)
+ return;
+ for (i = 0; i < num; i++) {
+ target = get_link_target(get_node_info(node)->filename,
+ &gcov_link[i]);
+ if (!target)
+ goto out_err;
+ basename = strrchr(target, '/');
+ if (!basename)
+ goto out_err;
+ basename++;
+ node->links[i] = debugfs_create_symlink(deskew(basename),
+ parent, target);
+ if (!node->links[i])
+ goto out_err;
+ kfree(target);
+ }
+
+ return;
+out_err:
+ kfree(target);
+ while (i-- > 0)
+ debugfs_remove(node->links[i]);
+ kfree(node->links);
+ node->links = NULL;
+}
+
static struct file_operations gcov_data_fops = {
.open = gcov_seq_open,
.release = gcov_seq_release,
@@ -273,7 +376,7 @@ static struct gcov_node *new_node(struct
init_node(node, info, name);
/* Differentiate between gcov data file nodes and directory nodes. */
if (info) {
- node->dentry = debugfs_create_file(node->name, 0600,
+ node->dentry = debugfs_create_file(deskew(node->name), 0600,
parent->dentry, node, &gcov_data_fops);
} else
node->dentry = debugfs_create_dir(node->name, parent->dentry);
@@ -282,12 +385,27 @@ static struct gcov_node *new_node(struct
kfree(node);
return NULL;
}
+ if (info)
+ add_links(node, parent->dentry);
list_add(&node->list, &parent->children);
list_add(&node->all, &all_head);
return node;
}
+/* Remove symbolic links associated with node. */
+static void remove_links(struct gcov_node *node)
+{
+ int i;
+
+ if (!node->links)
+ return;
+ for (i = 0; gcov_link[i].ext; i++)
+ debugfs_remove(node->links[i]);
+ kfree(node->links);
+ node->links = NULL;
+}
+
/* Remove node from all lists and debugfs and release associated resources.
* Needs to be called with node_lock held. */
static void release_node(struct gcov_node *node)
@@ -295,6 +413,7 @@ static void release_node(struct gcov_nod
list_del(&node->list);
list_del(&node->all);
debugfs_remove(node->dentry);
+ remove_links(node);
if (node->ghost)
gcov_info_free(node->ghost);
kfree(node);
diff -puN kernel/gcov/gcc_3_4.c~gcov-add-gcov-profiling-infrastructure-revert-link-changes kernel/gcov/gcc_3_4.c
--- a/kernel/gcov/gcc_3_4.c~gcov-add-gcov-profiling-infrastructure-revert-link-changes
+++ a/kernel/gcov/gcc_3_4.c
@@ -20,6 +20,12 @@
#include <linux/seq_file.h>
#include "gcov.h"
+/* Symbolic links to be created for each profiling data file. */
+const struct gcov_link gcov_link[] = {
+ { obj_tree, "gcno" }, /* Link to .gcno file in $(objtree). */
+ { 0, NULL},
+};
+
/* Determine whether a counter is active. Based on gcc magic. Doesn't change
* at run-time. */
static int counter_active(struct gcov_info *info, unsigned int type)
diff -puN kernel/gcov/gcov.h~gcov-add-gcov-profiling-infrastructure-revert-link-changes kernel/gcov/gcov.h
--- a/kernel/gcov/gcov.h~gcov-add-gcov-profiling-infrastructure-revert-link-changes
+++ a/kernel/gcov/gcov.h
@@ -116,4 +116,13 @@ void gcov_info_add(struct gcov_info *des
struct gcov_info *gcov_info_dup(struct gcov_info *info);
void gcov_info_free(struct gcov_info *info);
+struct gcov_link {
+ enum {
+ obj_tree,
+ src_tree,
+ } dir;
+ const char *ext;
+};
+extern const struct gcov_link gcov_link[];
+
#endif /* GCOV_H */
_
Patches currently in -mm which might be from peter.oberparleiter@xxxxxxxxxx are
s390-cio-use-memory_read_from_buffer.patch
kernel-call-constructors.patch
kernel-call-constructors-uml-fix-1.patch
kernel-call-constructors-uml-fix-2.patch
kernel-introduce-gcc_version_lower-macro.patch
seq_file-add-function-to-write-binary-data.patch
gcov-add-gcov-profiling-infrastructure.patch
gcov-add-gcov-profiling-infrastructure-revert-link-changes.patch
gcov-create-links-to-gcda-files-in-build-directory.patch
gcov-architecture-specific-compile-flag-adjustments.patch
gcov-architecture-specific-compile-flag-adjustments-powerpc-moved-stuff.patch
gcov-architecture-specific-compile-flag-adjustments-powerpc-fix.patch
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