13 files changed, 1726 insertions, 5 deletions

diff --git a/Documentation/gcov.txt b/Documentation/gcov.txt
new file mode 100644
index 00000000000..e716aadb3a3
--- /dev/null
+++ b/Documentation/gcov.txt
@@ -0,0 +1,246 @@
+Using gcov with the Linux kernel
+================================
+
+1. Introduction
+2. Preparation
+3. Customization
+4. Files
+5. Modules
+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
+===============
+
+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):
+
+# cd /tmp/linux-out
+# gcov -o /sys/kernel/debug/gcov/tmp/linux-out/kernel spinlock.c
+
+This will create source code files annotated with execution counts
+in the current directory. In addition, graphical gcov front-ends such
+as lcov [2] can be used to automate the process of collecting data
+for the entire kernel and provide coverage overviews in HTML format.
+
+Possible uses:
+
+* debugging (has this line been reached at all?)
+* test improvement (how do I change my test to cover these lines?)
+* minimizing kernel configurations (do I need this option if the
+  associated code is never run?)
+
+--
+
+[1] http://gcc.gnu.org/onlinedocs/gcc/Gcov.html
+[2] http://ltp.sourceforge.net/coverage/lcov.php
+
+
+2. Preparation
+==============
+
+Configure the kernel with:
+
+        CONFIG_DEBUGFS=y
+        CONFIG_GCOV_KERNEL=y
+
+and to get coverage data for the entire kernel:
+
+        CONFIG_GCOV_PROFILE_ALL=y
+
+Note that kernels compiled with profiling flags will be significantly
+larger and run slower. Also CONFIG_GCOV_PROFILE_ALL may not be supported
+on all architectures.
+
+Profiling data will only become accessible once debugfs has been
+mounted:
+
+        mount -t debugfs none /sys/kernel/debug
+
+
+3. Customization
+================
+
+To enable profiling for specific files or directories, add a line
+similar to the following to the respective kernel Makefile:
+
+        For a single file (e.g. main.o):
+                GCOV_PROFILE_main.o := y
+
+        For all files in one directory:
+                GCOV_PROFILE := y
+
+To exclude files from being profiled even when CONFIG_GCOV_PROFILE_ALL
+is specified, use:
+
+                GCOV_PROFILE_main.o := n
+        and:
+                GCOV_PROFILE := n
+
+Only files which are linked to the main kernel image or are compiled as
+kernel modules are supported by this mechanism.
+
+
+4. Files
+========
+
+The gcov kernel support creates the following files in debugfs:
+
+        /sys/kernel/debug/gcov
+                Parent directory for all gcov-related files.
+
+        /sys/kernel/debug/gcov/reset
+                Global reset file: resets all coverage data to zero when
+                written to.
+
+        /sys/kernel/debug/gcov/path/to/compile/dir/file.gcda
+                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
+==========
+
+Kernel modules may contain cleanup code which is only run during
+module unload time. The gcov mechanism provides a means to collect
+coverage data for such code by keeping a copy of the data associated
+with the unloaded module. This data remains available through debugfs.
+Once the module is loaded again, the associated coverage counters are
+initialized with the data from its previous instantiation.
+
+This behavior can be deactivated by specifying the gcov_persist kernel
+parameter:
+
+        gcov_persist=0
+
+At run-time, a user can also choose to discard data for an unloaded
+module by writing to its data file or the global reset file.
+
+
+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.
+Cause:    Profiling flags are specified for source files which are not
+          linked to the main kernel or which are linked by a custom
+          linker procedure.
+Solution: Exclude affected source files from profiling by specifying
+          GCOV_PROFILE := n or GCOV_PROFILE_basename.o := n in the
+          corresponding Makefile.
+
+
+Appendix A: gather_on_build.sh
+==============================
+
+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 --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 5578248c18a..08def8deb5f 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -48,6 +48,7 @@ parameter is applicable:
         EFI     EFI Partitioning (GPT) is enabled
         EIDE    EIDE/ATAPI support is enabled.
         FB      The frame buffer device is enabled.
+        GCOV    GCOV profiling is enabled.
         HW      Appropriate hardware is enabled.
         IA-64   IA-64 architecture is enabled.
         IMA     Integrity measurement architecture is enabled.
@@ -796,6 +797,12 @@ and is between 256 and 4096 characters. It is defined in the file
                         Format: off | on
                         default: on
 
+        gcov_persist=   [GCOV] When non-zero (default), profiling data for
+                        kernel modules is saved and remains accessible via
+                        debugfs, even when the module is unloaded/reloaded.
+                        When zero, profiling data is discarded and associated
+                        debugfs files are removed at module unload time.
+
         gdth=           [HW,SCSI]
                         See header of drivers/scsi/gdth.c.
 
diff --git a/Makefile b/Makefile
index ea63667617f..46e1c9d03d5 100644
--- a/Makefile
+++ b/Makefile
@@ -330,6 +330,7 @@ AFLAGS_MODULE   = $(MODFLAGS)
 LDFLAGS_MODULE  =
 CFLAGS_KERNEL   =
 AFLAGS_KERNEL   =
+CFLAGS_GCOV     = -fprofile-arcs -ftest-coverage
 
 
 # Use LINUXINCLUDE when you must reference the include/ directory.
@@ -356,7 +357,7 @@ export CPP AR NM STRIP OBJCOPY OBJDUMP MAKE AWK GENKSYMS PERL UTS_MACHINE
 export HOSTCXX HOSTCXXFLAGS LDFLAGS_MODULE CHECK CHECKFLAGS
 
 export KBUILD_CPPFLAGS NOSTDINC_FLAGS LINUXINCLUDE OBJCOPYFLAGS LDFLAGS
-export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE
+export KBUILD_CFLAGS CFLAGS_KERNEL CFLAGS_MODULE CFLAGS_GCOV
 export KBUILD_AFLAGS AFLAGS_KERNEL AFLAGS_MODULE
 
 # When compiling out-of-tree modules, put MODVERDIR in the module
@@ -1216,8 +1217,8 @@ clean: archclean $(clean-dirs)
                 \( -name '*.[oas]' -o -name '*.ko' -o -name '.*.cmd' \
                 -o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' \
                 -o -name '*.symtypes' -o -name 'modules.order' \
-                -o -name 'Module.markers' -o -name '.tmp_*.o.*' \) \
-                -type f -print | xargs rm -f
+                -o -name 'Module.markers' -o -name '.tmp_*.o.*' \
+                -o -name '*.gcno' \) -type f -print | xargs rm -f
 
 # mrproper - Delete all generated files, including .config
 #
@@ -1421,8 +1422,8 @@ clean: $(clean-dirs)
         $(call cmd,rmfiles)
         @find $(KBUILD_EXTMOD) $(RCS_FIND_IGNORE) \
                 \( -name '*.[oas]' -o -name '*.ko' -o -name '.*.cmd' \
-                -o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' \) \
-                -type f -print | xargs rm -f
+                -o -name '.*.d' -o -name '.*.tmp' -o -name '*.mod.c' \
+                -o -name '*.gcno' \) -type f -print | xargs rm -f
 
 help:
         @echo  '  Building external modules.'
diff --git a/arch/Kconfig b/arch/Kconfig
index 78a35e9dc10..99193b16023 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -112,3 +112,5 @@ config HAVE_DMA_API_DEBUG
 
 config HAVE_DEFAULT_NO_SPIN_MUTEXES
         bool
+
+source "kernel/gcov/Kconfig"
diff --git a/include/linux/compiler-gcc3.h b/include/linux/compiler-gcc3.h
index 8005effc04f..b721129e046 100644
--- a/include/linux/compiler-gcc3.h
+++ b/include/linux/compiler-gcc3.h
@@ -16,6 +16,12 @@
 #define __must_check            __attribute__((warn_unused_result))
 #endif
 
+#ifdef CONFIG_GCOV_KERNEL
+# if __GNUC_MINOR__ < 4
+#   error "GCOV profiling support for gcc versions below 3.4 not included"
+# endif /* __GNUC_MINOR__ */
+#endif /* CONFIG_GCOV_KERNEL */
+
 /*
  * A trick to suppress uninitialized variable warning without generating any
  * code
diff --git a/kernel/Makefile b/kernel/Makefile
index 9df4501cb92..0a32cb21ec9 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -71,6 +71,7 @@ obj-$(CONFIG_STOP_MACHINE) += stop_machine.o
 obj-$(CONFIG_KPROBES_SANITY_TEST) += test_kprobes.o
 obj-$(CONFIG_AUDIT) += audit.o auditfilter.o
 obj-$(CONFIG_AUDITSYSCALL) += auditsc.o
+obj-$(CONFIG_GCOV_KERNEL) += gcov/
 obj-$(CONFIG_AUDIT_TREE) += audit_tree.o
 obj-$(CONFIG_KPROBES) += kprobes.o
 obj-$(CONFIG_KGDB) += kgdb.o
diff --git a/kernel/gcov/Kconfig b/kernel/gcov/Kconfig
new file mode 100644
index 00000000000..aab593abfba
--- /dev/null
+++ b/kernel/gcov/Kconfig
@@ -0,0 +1,48 @@
+menu "GCOV-based kernel profiling"
+
+config GCOV_KERNEL
+        bool "Enable gcov-based kernel profiling"
+        depends on DEBUG_FS && CONSTRUCTORS
+        default n
+        ---help---
+        This option enables gcov-based code profiling (e.g. for code coverage
+        measurements).
+
+        If unsure, say N.
+
+        Additionally specify CONFIG_GCOV_PROFILE_ALL=y to get profiling data
+        for the entire kernel. To enable profiling for specific files or
+        directories, add a line similar to the following to the respective
+        Makefile:
+
+        For a single file (e.g. main.o):
+                GCOV_PROFILE_main.o := y
+
+        For all files in one directory:
+                GCOV_PROFILE := y
+
+        To exclude files from being profiled even when CONFIG_GCOV_PROFILE_ALL
+        is specified, use:
+
+                GCOV_PROFILE_main.o := n
+        and:
+                GCOV_PROFILE := n
+
+        Note that the debugfs filesystem has to be mounted to access
+        profiling data.
+
+config GCOV_PROFILE_ALL
+        bool "Profile entire Kernel"
+        depends on GCOV_KERNEL
+        depends on S390 || X86_32
+        default n
+        ---help---
+        This options activates profiling for the entire kernel.
+
+        If unsure, say N.
+
+        Note that a kernel compiled with profiling flags will be significantly
+        larger and run slower. Also be sure to exclude files from profiling
+        which are not linked to the kernel image to prevent linker errors.
+
+endmenu
diff --git a/kernel/gcov/Makefile b/kernel/gcov/Makefile
new file mode 100644
index 00000000000..3f761001d51
--- /dev/null
+++ b/kernel/gcov/Makefile
@@ -0,0 +1,3 @@
+EXTRA_CFLAGS := -DSRCTREE='"$(srctree)"' -DOBJTREE='"$(objtree)"'
+
+obj-$(CONFIG_GCOV_KERNEL) := base.o fs.o gcc_3_4.o
diff --git a/kernel/gcov/base.c b/kernel/gcov/base.c
new file mode 100644
index 00000000000..9b22d03cc58
--- /dev/null
+++ b/kernel/gcov/base.c
@@ -0,0 +1,148 @@
+/*
+ *  This code maintains a list of active profiling data structures.
+ *
+ *    Copyright IBM Corp. 2009
+ *    Author(s): Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
+ *
+ *    Uses gcc-internal data definitions.
+ *    Based on the gcov-kernel patch by:
+ *               Hubertus Franke <frankeh@us.ibm.com>
+ *               Nigel Hinds <nhinds@us.ibm.com>
+ *               Rajan Ravindran <rajancr@us.ibm.com>
+ *               Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
+ *               Paul Larson
+ */
+
+#define pr_fmt(fmt)     "gcov: " fmt
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include "gcov.h"
+
+static struct gcov_info *gcov_info_head;
+static int gcov_events_enabled;
+static DEFINE_MUTEX(gcov_lock);
+
+/*
+ * __gcov_init is called by gcc-generated constructor code for each object
+ * file compiled with -fprofile-arcs.
+ */
+void __gcov_init(struct gcov_info *info)
+{
+        static unsigned int gcov_version;
+
+        mutex_lock(&gcov_lock);
+        if (gcov_version == 0) {
+                gcov_version = info->version;
+                /*
+                 * Printing gcc's version magic may prove useful for debugging
+                 * incompatibility reports.
+                 */
+                pr_info("version magic: 0x%x\n", gcov_version);
+        }
+        /*
+         * Add new profiling data structure to list and inform event
+         * listener.
+         */
+        info->next = gcov_info_head;
+        gcov_info_head = info;
+        if (gcov_events_enabled)
+                gcov_event(GCOV_ADD, info);
+        mutex_unlock(&gcov_lock);
+}
+EXPORT_SYMBOL(__gcov_init);
+
+/*
+ * These functions may be referenced by gcc-generated profiling code but serve
+ * no function for kernel profiling.
+ */
+void __gcov_flush(void)
+{
+        /* Unused. */
+}
+EXPORT_SYMBOL(__gcov_flush);
+
+void __gcov_merge_add(gcov_type *counters, unsigned int n_counters)
+{
+        /* Unused. */
+}
+EXPORT_SYMBOL(__gcov_merge_add);
+
+void __gcov_merge_single(gcov_type *counters, unsigned int n_counters)
+{
+        /* Unused. */
+}
+EXPORT_SYMBOL(__gcov_merge_single);
+
+void __gcov_merge_delta(gcov_type *counters, unsigned int n_counters)
+{
+        /* Unused. */
+}
+EXPORT_SYMBOL(__gcov_merge_delta);
+
+/**
+ * gcov_enable_events - enable event reporting through gcov_event()
+ *
+ * Turn on reporting of profiling data load/unload-events through the
+ * gcov_event() callback. Also replay all previous events once. This function
+ * is needed because some events are potentially generated too early for the
+ * callback implementation to handle them initially.
+ */
+void gcov_enable_events(void)
+{
+        struct gcov_info *info;
+
+        mutex_lock(&gcov_lock);
+        gcov_events_enabled = 1;
+        /* Perform event callback for previously registered entries. */
+        for (info = gcov_info_head; info; info = info->next)
+                gcov_event(GCOV_ADD, info);
+        mutex_unlock(&gcov_lock);
+}
+
+#ifdef CONFIG_MODULES
+static inline int within(void *addr, void *start, unsigned long size)
+{
+        return ((addr >= start) && (addr < start + size));
+}
+
+/* Update list and generate events when modules are unloaded. */
+static int gcov_module_notifier(struct notifier_block *nb, unsigned long event,
+                                void *data)
+{
+        struct module *mod = data;
+        struct gcov_info *info;
+        struct gcov_info *prev;
+
+        if (event != MODULE_STATE_GOING)
+                return NOTIFY_OK;
+        mutex_lock(&gcov_lock);
+        prev = NULL;
+        /* Remove entries located in module from linked list. */
+        for (info = gcov_info_head; info; info = info->next) {
+                if (within(info, mod->module_core, mod->core_size)) {
+                        if (prev)
+                                prev->next = info->next;
+                        else
+                                gcov_info_head = info->next;
+                        if (gcov_events_enabled)
+                                gcov_event(GCOV_REMOVE, info);
+                } else
+                        prev = info;
+        }
+        mutex_unlock(&gcov_lock);
+
+        return NOTIFY_OK;
+}
+
+static struct notifier_block gcov_nb = {
+        .notifier_call  = gcov_module_notifier,
+};
+
+static int __init gcov_init(void)
+{
+        return register_module_notifier(&gcov_nb);
+}
+device_initcall(gcov_init);
+#endif /* CONFIG_MODULES */
diff --git a/kernel/gcov/fs.c b/kernel/gcov/fs.c
new file mode 100644
index 00000000000..ef3c3f88a7a
--- /dev/null
+++ b/kernel/gcov/fs.c
@@ -0,0 +1,673 @@
+/*
+ *  This code exports profiling data as debugfs files to userspace.
+ *
+ *    Copyright IBM Corp. 2009
+ *    Author(s): Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
+ *
+ *    Uses gcc-internal data definitions.
+ *    Based on the gcov-kernel patch by:
+ *               Hubertus Franke <frankeh@us.ibm.com>
+ *               Nigel Hinds <nhinds@us.ibm.com>
+ *               Rajan Ravindran <rajancr@us.ibm.com>
+ *               Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
+ *               Paul Larson
+ *               Yi CDL Yang
+ */
+
+#define pr_fmt(fmt)     "gcov: " fmt
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/debugfs.h>
+#include <linux/fs.h>
+#include <linux/list.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/mutex.h>
+#include <linux/seq_file.h>
+#include "gcov.h"
+
+/**
+ * struct gcov_node - represents a debugfs entry
+ * @list: list head for child node list
+ * @children: child nodes
+ * @all: list head for list of all nodes
+ * @parent: parent node
+ * @info: associated profiling data structure if not a directory
+ * @ghost: when an object file containing profiling data is unloaded we keep a
+ *         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 plus any associated symbolic links which
+ * are needed by the gcov tool to work correctly.
+ */
+struct gcov_node {
+        struct list_head list;
+        struct list_head children;
+        struct list_head all;
+        struct gcov_node *parent;
+        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);
+static DEFINE_MUTEX(node_lock);
+
+/* If non-zero, keep copies of profiling data for unloaded modules. */
+static int gcov_persist = 1;
+
+static int __init gcov_persist_setup(char *str)
+{
+        unsigned long val;
+
+        if (strict_strtoul(str, 0, &val)) {
+                pr_warning("invalid gcov_persist parameter '%s'\n", str);
+                return 0;
+        }
+        gcov_persist = val;
+        pr_info("setting gcov_persist to %d\n", gcov_persist);
+
+        return 1;
+}
+__setup("gcov_persist=", gcov_persist_setup);
+
+/*
+ * seq_file.start() implementation for gcov data files. Note that the
+ * gcov_iterator interface is designed to be more restrictive than seq_file
+ * (no start from arbitrary position, etc.), to simplify the iterator
+ * implementation.
+ */
+static void *gcov_seq_start(struct seq_file *seq, loff_t *pos)
+{
+        loff_t i;
+
+        gcov_iter_start(seq->private);
+        for (i = 0; i < *pos; i++) {
+                if (gcov_iter_next(seq->private))
+                        return NULL;
+        }
+        return seq->private;
+}
+
+/* seq_file.next() implementation for gcov data files. */
+static void *gcov_seq_next(struct seq_file *seq, void *data, loff_t *pos)
+{
+        struct gcov_iterator *iter = data;
+
+        if (gcov_iter_next(iter))
+                return NULL;
+        (*pos)++;
+
+        return iter;
+}
+
+/* seq_file.show() implementation for gcov data files. */
+static int gcov_seq_show(struct seq_file *seq, void *data)
+{
+        struct gcov_iterator *iter = data;
+
+        if (gcov_iter_write(iter, seq))
+                return -EINVAL;
+        return 0;
+}
+
+static void gcov_seq_stop(struct seq_file *seq, void *data)
+{
+        /* Unused. */
+}
+
+static const struct seq_operations gcov_seq_ops = {
+        .start  = gcov_seq_start,
+        .next   = gcov_seq_next,
+        .show   = gcov_seq_show,
+        .stop   = gcov_seq_stop,
+};
+
+/*
+ * Return the profiling data set for a given node. This can either be the
+ * original profiling data structure or a duplicate (also called "ghost")
+ * in case the associated object file has been unloaded.
+ */
+static struct gcov_info *get_node_info(struct gcov_node *node)
+{
+        if (node->info)
+                return node->info;
+
+        return node->ghost;
+}
+
+/*
+ * open() implementation for gcov data files. Create a copy of the profiling
+ * data set and initialize the iterator and seq_file interface.
+ */
+static int gcov_seq_open(struct inode *inode, struct file *file)
+{
+        struct gcov_node *node = inode->i_private;
+        struct gcov_iterator *iter;
+        struct seq_file *seq;
+        struct gcov_info *info;
+        int rc = -ENOMEM;
+
+        mutex_lock(&node_lock);
+        /*
+         * Read from a profiling data copy to minimize reference tracking
+         * complexity and concurrent access.
+         */
+        info = gcov_info_dup(get_node_info(node));
+        if (!info)
+                goto out_unlock;
+        iter = gcov_iter_new(info);
+        if (!iter)
+                goto err_free_info;
+        rc = seq_open(file, &gcov_seq_ops);
+        if (rc)
+                goto err_free_iter_info;
+        seq = file->private_data;
+        seq->private = iter;
+out_unlock:
+        mutex_unlock(&node_lock);
+        return rc;
+
+err_free_iter_info:
+        gcov_iter_free(iter);
+err_free_info:
+        gcov_info_free(info);
+        goto out_unlock;
+}
+
+/*
+ * release() implementation for gcov data files. Release resources allocated
+ * by open().
+ */
+static int gcov_seq_release(struct inode *inode, struct file *file)
+{
+        struct gcov_iterator *iter;
+        struct gcov_info *info;
+        struct seq_file *seq;
+
+        seq = file->private_data;
+        iter = seq->private;
+        info = gcov_iter_get_info(iter);
+        gcov_iter_free(iter);
+        gcov_info_free(info);
+        seq_release(inode, file);
+
+        return 0;
+}
+
+/*
+ * Find a node by the associated data file name. Needs to be called with
+ * node_lock held.
+ */
+static struct gcov_node *get_node_by_name(const char *name)
+{
+        struct gcov_node *node;
+        struct gcov_info *info;
+
+        list_for_each_entry(node, &all_head, all) {
+                info = get_node_info(node);
+                if (info && (strcmp(info->filename, name) == 0))
+                        return node;
+        }
+
+        return NULL;
+}
+
+static void remove_node(struct gcov_node *node);
+
+/*
+ * write() implementation for gcov data files. Reset profiling data for the
+ * associated file. If the object file has been unloaded (i.e. this is
+ * a "ghost" node), remove the debug fs node as well.
+ */
+static ssize_t gcov_seq_write(struct file *file, const char __user *addr,
+                              size_t len, loff_t *pos)
+{
+        struct seq_file *seq;
+        struct gcov_info *info;
+        struct gcov_node *node;
+
+        seq = file->private_data;
+        info = gcov_iter_get_info(seq->private);
+        mutex_lock(&node_lock);
+        node = get_node_by_name(info->filename);
+        if (node) {
+                /* Reset counts or remove node for unloaded modules. */
+                if (node->ghost)
+                        remove_node(node);
+                else
+                        gcov_info_reset(node->info);
+        }
+        /* Reset counts for open file. */
+        gcov_info_reset(info);
+        mutex_unlock(&node_lock);
+
+        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 const struct file_operations gcov_data_fops = {
+        .open           = gcov_seq_open,
+        .release        = gcov_seq_release,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .write          = gcov_seq_write,
+};
+
+/* Basic initialization of a new node. */
+static void init_node(struct gcov_node *node, struct gcov_info *info,
+                      const char *name, struct gcov_node *parent)
+{
+        INIT_LIST_HEAD(&node->list);
+        INIT_LIST_HEAD(&node->children);
+        INIT_LIST_HEAD(&node->all);
+        node->info = info;
+        node->parent = parent;
+        if (name)
+                strcpy(node->name, name);
+}
+
+/*
+ * Create a new node and associated debugfs entry. Needs to be called with
+ * node_lock held.
+ */
+static struct gcov_node *new_node(struct gcov_node *parent,
+                                  struct gcov_info *info, const char *name)
+{
+        struct gcov_node *node;
+
+        node = kzalloc(sizeof(struct gcov_node) + strlen(name) + 1, GFP_KERNEL);
+        if (!node) {
+                pr_warning("out of memory\n");
+                return NULL;
+        }
+        init_node(node, info, name, parent);
+        /* Differentiate between gcov data file nodes and directory nodes. */
+        if (info) {
+                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);
+        if (!node->dentry) {
+                pr_warning("could not create file\n");
+                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)
+{
+        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);
+}
+
+/* Release node and empty parents. Needs to be called with node_lock held. */
+static void remove_node(struct gcov_node *node)
+{
+        struct gcov_node *parent;
+
+        while ((node != &root_node) && list_empty(&node->children)) {
+                parent = node->parent;
+                release_node(node);
+                node = parent;
+        }
+}
+
+/*
+ * Find child node with given basename. Needs to be called with node_lock
+ * held.
+ */
+static struct gcov_node *get_child_by_name(struct gcov_node *parent,
+                                           const char *name)
+{
+        struct gcov_node *node;
+
+        list_for_each_entry(node, &parent->children, list) {
+                if (strcmp(node->name, name) == 0)
+                        return node;
+        }
+
+        return NULL;
+}
+
+/*
+ * write() implementation for reset file. Reset all profiling data to zero
+ * and remove ghost nodes.
+ */
+static ssize_t reset_write(struct file *file, const char __user *addr,
+                           size_t len, loff_t *pos)
+{
+        struct gcov_node *node;
+
+        mutex_lock(&node_lock);
+restart:
+        list_for_each_entry(node, &all_head, all) {
+                if (node->info)
+                        gcov_info_reset(node->info);
+                else if (list_empty(&node->children)) {
+                        remove_node(node);
+                        /* Several nodes may have gone - restart loop. */
+                        goto restart;
+                }
+        }
+        mutex_unlock(&node_lock);
+
+        return len;
+}
+
+/* read() implementation for reset file. Unused. */
+static ssize_t reset_read(struct file *file, char __user *addr, size_t len,
+                          loff_t *pos)
+{
+        /* Allow read operation so that a recursive copy won't fail. */
+        return 0;
+}
+
+static const struct file_operations gcov_reset_fops = {
+        .write  = reset_write,
+        .read   = reset_read,
+};
+
+/*
+ * Create a node for a given profiling data set and add it to all lists and
+ * debugfs. Needs to be called with node_lock held.
+ */
+static void add_node(struct gcov_info *info)
+{
+        char *filename;
+        char *curr;
+        char *next;
+        struct gcov_node *parent;
+        struct gcov_node *node;
+
+        filename = kstrdup(info->filename, GFP_KERNEL);
+        if (!filename)
+                return;
+        parent = &root_node;
+        /* Create directory nodes along the path. */
+        for (curr = filename; (next = strchr(curr, '/')); curr = next + 1) {
+                if (curr == next)
+                        continue;
+                *next = 0;
+                if (strcmp(curr, ".") == 0)
+                        continue;
+                if (strcmp(curr, "..") == 0) {
+                        if (!parent->parent)
+                                goto err_remove;
+                        parent = parent->parent;
+                        continue;
+                }
+                node = get_child_by_name(parent, curr);
+                if (!node) {
+                        node = new_node(parent, NULL, curr);
+                        if (!node)
+                                goto err_remove;
+                }
+                parent = node;
+        }
+        /* Create file node. */
+        node = new_node(parent, info, curr);
+        if (!node)
+                goto err_remove;
+out:
+        kfree(filename);
+        return;
+
+err_remove:
+        remove_node(parent);
+        goto out;
+}
+
+/*
+ * The profiling data set associated with this node is being unloaded. Store a
+ * copy of the profiling data and turn this node into a "ghost".
+ */
+static int ghost_node(struct gcov_node *node)
+{
+        node->ghost = gcov_info_dup(node->info);
+        if (!node->ghost) {
+                pr_warning("could not save data for '%s' (out of memory)\n",
+                           node->info->filename);
+                return -ENOMEM;
+        }
+        node->info = NULL;
+
+        return 0;
+}
+
+/*
+ * Profiling data for this node has been loaded again. Add profiling data
+ * from previous instantiation and turn this node into a regular node.
+ */
+static void revive_node(struct gcov_node *node, struct gcov_info *info)
+{
+        if (gcov_info_is_compatible(node->ghost, info))
+                gcov_info_add(info, node->ghost);
+        else {
+                pr_warning("discarding saved data for '%s' (version changed)\n",
+                           info->filename);
+        }
+        gcov_info_free(node->ghost);
+        node->ghost = NULL;
+        node->info = info;
+}
+
+/*
+ * Callback to create/remove profiling files when code compiled with
+ * -fprofile-arcs is loaded/unloaded.
+ */
+void gcov_event(enum gcov_action action, struct gcov_info *info)
+{
+        struct gcov_node *node;
+
+        mutex_lock(&node_lock);
+        node = get_node_by_name(info->filename);
+        switch (action) {
+        case GCOV_ADD:
+                /* Add new node or revive ghost. */
+                if (!node) {
+                        add_node(info);
+                        break;
+                }
+                if (gcov_persist)
+                        revive_node(node, info);
+                else {
+                        pr_warning("could not add '%s' (already exists)\n",
+                                   info->filename);
+                }
+                break;
+        case GCOV_REMOVE:
+                /* Remove node or turn into ghost. */
+                if (!node) {
+                        pr_warning("could not remove '%s' (not found)\n",
+                                   info->filename);
+                        break;
+                }
+                if (gcov_persist) {
+                        if (!ghost_node(node))
+                                break;
+                }
+                remove_node(node);
+                break;
+        }
+        mutex_unlock(&node_lock);
+}
+
+/* Create debugfs entries. */
+static __init int gcov_fs_init(void)
+{
+        int rc = -EIO;
+
+        init_node(&root_node, NULL, NULL, NULL);
+        /*
+         * /sys/kernel/debug/gcov will be parent for the reset control file
+         * and all profiling files.
+         */
+        root_node.dentry = debugfs_create_dir("gcov", NULL);
+        if (!root_node.dentry)
+                goto err_remove;
+        /*
+         * Create reset file which resets all profiling counts when written
+         * to.
+         */
+        reset_dentry = debugfs_create_file("reset", 0600, root_node.dentry,
+                                           NULL, &gcov_reset_fops);
+        if (!reset_dentry)
+                goto err_remove;
+        /* Replay previous events to get our fs hierarchy up-to-date. */
+        gcov_enable_events();
+        return 0;
+
+err_remove:
+        pr_err("init failed\n");
+        if (root_node.dentry)
+                debugfs_remove(root_node.dentry);
+
+        return rc;
+}
+device_initcall(gcov_fs_init);
diff --git a/kernel/gcov/gcc_3_4.c b/kernel/gcov/gcc_3_4.c
new file mode 100644
index 00000000000..ae5bb426003
--- /dev/null
+++ b/kernel/gcov/gcc_3_4.c
@@ -0,0 +1,447 @@
+/*
+ *  This code provides functions to handle gcc's profiling data format
+ *  introduced with gcc 3.4. Future versions of gcc may change the gcov
+ *  format (as happened before), so all format-specific information needs
+ *  to be kept modular and easily exchangeable.
+ *
+ *  This file is based on gcc-internal definitions. Functions and data
+ *  structures are defined to be compatible with gcc counterparts.
+ *  For a better understanding, refer to gcc source: gcc/gcov-io.h.
+ *
+ *    Copyright IBM Corp. 2009
+ *    Author(s): Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
+ *
+ *    Uses gcc-internal data definitions.
+ */
+
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/seq_file.h>
+#include <linux/vmalloc.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)
+{
+        return (1 << type) & info->ctr_mask;
+}
+
+/* Determine number of active counters. Based on gcc magic. */
+static unsigned int num_counter_active(struct gcov_info *info)
+{
+        unsigned int i;
+        unsigned int result = 0;
+
+        for (i = 0; i < GCOV_COUNTERS; i++) {
+                if (counter_active(info, i))
+                        result++;
+        }
+        return result;
+}
+
+/**
+ * gcov_info_reset - reset profiling data to zero
+ * @info: profiling data set
+ */
+void gcov_info_reset(struct gcov_info *info)
+{
+        unsigned int active = num_counter_active(info);
+        unsigned int i;
+
+        for (i = 0; i < active; i++) {
+                memset(info->counts[i].values, 0,
+                       info->counts[i].num * sizeof(gcov_type));
+        }
+}
+
+/**
+ * gcov_info_is_compatible - check if profiling data can be added
+ * @info1: first profiling data set
+ * @info2: second profiling data set
+ *
+ * Returns non-zero if profiling data can be added, zero otherwise.
+ */
+int gcov_info_is_compatible(struct gcov_info *info1, struct gcov_info *info2)
+{
+        return (info1->stamp == info2->stamp);
+}
+
+/**
+ * gcov_info_add - add up profiling data
+ * @dest: profiling data set to which data is added
+ * @source: profiling data set which is added
+ *
+ * Adds profiling counts of @source to @dest.
+ */
+void gcov_info_add(struct gcov_info *dest, struct gcov_info *source)
+{
+        unsigned int i;
+        unsigned int j;
+
+        for (i = 0; i < num_counter_active(dest); i++) {
+                for (j = 0; j < dest->counts[i].num; j++) {
+                        dest->counts[i].values[j] +=
+                                source->counts[i].values[j];
+                }
+        }
+}
+
+/* Get size of function info entry. Based on gcc magic. */
+static size_t get_fn_size(struct gcov_info *info)
+{
+        size_t size;
+
+        size = sizeof(struct gcov_fn_info) + num_counter_active(info) *
+               sizeof(unsigned int);
+        if (__alignof__(struct gcov_fn_info) > sizeof(unsigned int))
+                size = ALIGN(size, __alignof__(struct gcov_fn_info));
+        return size;
+}
+
+/* Get address of function info entry. Based on gcc magic. */
+static struct gcov_fn_info *get_fn_info(struct gcov_info *info, unsigned int fn)
+{
+        return (struct gcov_fn_info *)
+                ((char *) info->functions + fn * get_fn_size(info));
+}
+
+/**
+ * gcov_info_dup - duplicate profiling data set
+ * @info: profiling data set to duplicate
+ *
+ * Return newly allocated duplicate on success, %NULL on error.
+ */
+struct gcov_info *gcov_info_dup(struct gcov_info *info)
+{
+        struct gcov_info *dup;
+        unsigned int i;
+        unsigned int active;
+
+        /* Duplicate gcov_info. */
+        active = num_counter_active(info);
+        dup = kzalloc(sizeof(struct gcov_info) +
+                      sizeof(struct gcov_ctr_info) * active, GFP_KERNEL);
+        if (!dup)
+                return NULL;
+        dup->version            = info->version;
+        dup->stamp              = info->stamp;
+        dup->n_functions        = info->n_functions;
+        dup->ctr_mask           = info->ctr_mask;
+        /* Duplicate filename. */
+        dup->filename           = kstrdup(info->filename, GFP_KERNEL);
+        if (!dup->filename)
+                goto err_free;
+        /* Duplicate table of functions. */
+        dup->functions = kmemdup(info->functions, info->n_functions *
+                                 get_fn_size(info), GFP_KERNEL);
+        if (!dup->functions)
+                goto err_free;
+        /* Duplicate counter arrays. */
+        for (i = 0; i < active ; i++) {
+                struct gcov_ctr_info *ctr = &info->counts[i];
+                size_t size = ctr->num * sizeof(gcov_type);
+
+                dup->counts[i].num = ctr->num;
+                dup->counts[i].merge = ctr->merge;
+                dup->counts[i].values = vmalloc(size);
+                if (!dup->counts[i].values)
+                        goto err_free;
+                memcpy(dup->counts[i].values, ctr->values, size);
+        }
+        return dup;
+
+err_free:
+        gcov_info_free(dup);
+        return NULL;
+}
+
+/**
+ * gcov_info_free - release memory for profiling data set duplicate
+ * @info: profiling data set duplicate to free
+ */
+void gcov_info_free(struct gcov_info *info)
+{
+        unsigned int active = num_counter_active(info);
+        unsigned int i;
+
+        for (i = 0; i < active ; i++)
+                vfree(info->counts[i].values);
+        kfree(info->functions);
+        kfree(info->filename);
+        kfree(info);
+}
+
+/**
+ * struct type_info - iterator helper array
+ * @ctr_type: counter type
+ * @offset: index of the first value of the current function for this type
+ *
+ * This array is needed to convert the in-memory data format into the in-file
+ * data format:
+ *
+ * In-memory:
+ *   for each counter type
+ *     for each function
+ *       values
+ *
+ * In-file:
+ *   for each function
+ *     for each counter type
+ *       values
+ *
+ * See gcc source gcc/gcov-io.h for more information on data organization.
+ */
+struct type_info {
+        int ctr_type;
+        unsigned int offset;
+};
+
+/**
+ * struct gcov_iterator - specifies current file position in logical records
+ * @info: associated profiling data
+ * @record: record type
+ * @function: function number
+ * @type: counter type
+ * @count: index into values array
+ * @num_types: number of counter types
+ * @type_info: helper array to get values-array offset for current function
+ */
+struct gcov_iterator {
+        struct gcov_info *info;
+
+        int record;
+        unsigned int function;
+        unsigned int type;
+        unsigned int count;
+
+        int num_types;
+        struct type_info type_info[0];
+};
+
+static struct gcov_fn_info *get_func(struct gcov_iterator *iter)
+{
+        return get_fn_info(iter->info, iter->function);
+}
+
+static struct type_info *get_type(struct gcov_iterator *iter)
+{
+        return &iter->type_info[iter->type];
+}
+
+/**
+ * gcov_iter_new - allocate and initialize profiling data iterator
+ * @info: profiling data set to be iterated
+ *
+ * Return file iterator on success, %NULL otherwise.
+ */
+struct gcov_iterator *gcov_iter_new(struct gcov_info *info)
+{
+        struct gcov_iterator *iter;
+
+        iter = kzalloc(sizeof(struct gcov_iterator) +
+                       num_counter_active(info) * sizeof(struct type_info),
+                       GFP_KERNEL);
+        if (iter)
+                iter->info = info;
+
+        return iter;
+}
+
+/**
+ * gcov_iter_free - release memory for iterator
+ * @iter: file iterator to free
+ */
+void gcov_iter_free(struct gcov_iterator *iter)
+{
+        kfree(iter);
+}
+
+/**
+ * gcov_iter_get_info - return profiling data set for given file iterator
+ * @iter: file iterator
+ */
+struct gcov_info *gcov_iter_get_info(struct gcov_iterator *iter)
+{
+        return iter->info;
+}
+
+/**
+ * gcov_iter_start - reset file iterator to starting position
+ * @iter: file iterator
+ */
+void gcov_iter_start(struct gcov_iterator *iter)
+{
+        int i;
+
+        iter->record = 0;
+        iter->function = 0;
+        iter->type = 0;
+        iter->count = 0;
+        iter->num_types = 0;
+        for (i = 0; i < GCOV_COUNTERS; i++) {
+                if (counter_active(iter->info, i)) {
+                        iter->type_info[iter->num_types].ctr_type = i;
+                        iter->type_info[iter->num_types++].offset = 0;
+                }
+        }
+}
+
+/* Mapping of logical record number to actual file content. */
+#define RECORD_FILE_MAGIC       0
+#define RECORD_GCOV_VERSION     1
+#define RECORD_TIME_STAMP       2
+#define RECORD_FUNCTION_TAG     3
+#define RECORD_FUNCTON_TAG_LEN  4
+#define RECORD_FUNCTION_IDENT   5
+#define RECORD_FUNCTION_CHECK   6
+#define RECORD_COUNT_TAG        7
+#define RECORD_COUNT_LEN        8
+#define RECORD_COUNT            9
+
+/**
+ * gcov_iter_next - advance file iterator to next logical record
+ * @iter: file iterator
+ *
+ * Return zero if new position is valid, non-zero if iterator has reached end.
+ */
+int gcov_iter_next(struct gcov_iterator *iter)
+{
+        switch (iter->record) {
+        case RECORD_FILE_MAGIC:
+        case RECORD_GCOV_VERSION:
+        case RECORD_FUNCTION_TAG:
+        case RECORD_FUNCTON_TAG_LEN:
+        case RECORD_FUNCTION_IDENT:
+        case RECORD_COUNT_TAG:
+                /* Advance to next record */
+                iter->record++;
+                break;
+        case RECORD_COUNT:
+                /* Advance to next count */
+                iter->count++;
+                /* fall through */
+        case RECORD_COUNT_LEN:
+                if (iter->count < get_func(iter)->n_ctrs[iter->type]) {
+                        iter->record = 9;
+                        break;
+                }
+                /* Advance to next counter type */
+                get_type(iter)->offset += iter->count;
+                iter->count = 0;
+                iter->type++;
+                /* fall through */
+        case RECORD_FUNCTION_CHECK:
+                if (iter->type < iter->num_types) {
+                        iter->record = 7;
+                        break;
+                }
+                /* Advance to next function */
+                iter->type = 0;
+                iter->function++;
+                /* fall through */
+        case RECORD_TIME_STAMP:
+                if (iter->function < iter->info->n_functions)
+                        iter->record = 3;
+                else
+                        iter->record = -1;
+                break;
+        }
+        /* Check for EOF. */
+        if (iter->record == -1)
+                return -EINVAL;
+        else
+                return 0;
+}
+
+/**
+ * seq_write_gcov_u32 - write 32 bit number in gcov format to seq_file
+ * @seq: seq_file handle
+ * @v: value to be stored
+ *
+ * Number format defined by gcc: numbers are recorded in the 32 bit
+ * unsigned binary form of the endianness of the machine generating the
+ * file.
+ */
+static int seq_write_gcov_u32(struct seq_file *seq, u32 v)
+{
+        return seq_write(seq, &v, sizeof(v));
+}
+
+/**
+ * seq_write_gcov_u64 - write 64 bit number in gcov format to seq_file
+ * @seq: seq_file handle
+ * @v: value to be stored
+ *
+ * Number format defined by gcc: numbers are recorded in the 32 bit
+ * unsigned binary form of the endianness of the machine generating the
+ * file. 64 bit numbers are stored as two 32 bit numbers, the low part
+ * first.
+ */
+static int seq_write_gcov_u64(struct seq_file *seq, u64 v)
+{
+        u32 data[2];
+
+        data[0] = (v & 0xffffffffUL);
+        data[1] = (v >> 32);
+        return seq_write(seq, data, sizeof(data));
+}
+
+/**
+ * gcov_iter_write - write data for current pos to seq_file
+ * @iter: file iterator
+ * @seq: seq_file handle
+ *
+ * Return zero on success, non-zero otherwise.
+ */
+int gcov_iter_write(struct gcov_iterator *iter, struct seq_file *seq)
+{
+        int rc = -EINVAL;
+
+        switch (iter->record) {
+        case RECORD_FILE_MAGIC:
+                rc = seq_write_gcov_u32(seq, GCOV_DATA_MAGIC);
+                break;
+        case RECORD_GCOV_VERSION:
+                rc = seq_write_gcov_u32(seq, iter->info->version);
+                break;
+        case RECORD_TIME_STAMP:
+                rc = seq_write_gcov_u32(seq, iter->info->stamp);
+                break;
+        case RECORD_FUNCTION_TAG:
+                rc = seq_write_gcov_u32(seq, GCOV_TAG_FUNCTION);
+                break;
+        case RECORD_FUNCTON_TAG_LEN:
+                rc = seq_write_gcov_u32(seq, 2);
+                break;
+        case RECORD_FUNCTION_IDENT:
+                rc = seq_write_gcov_u32(seq, get_func(iter)->ident);
+                break;
+        case RECORD_FUNCTION_CHECK:
+                rc = seq_write_gcov_u32(seq, get_func(iter)->checksum);
+                break;
+        case RECORD_COUNT_TAG:
+                rc = seq_write_gcov_u32(seq,
+                        GCOV_TAG_FOR_COUNTER(get_type(iter)->ctr_type));
+                break;
+        case RECORD_COUNT_LEN:
+                rc = seq_write_gcov_u32(seq,
+                                get_func(iter)->n_ctrs[iter->type] * 2);
+                break;
+        case RECORD_COUNT:
+                rc = seq_write_gcov_u64(seq,
+                        iter->info->counts[iter->type].
+                                values[iter->count + get_type(iter)->offset]);
+                break;
+        }
+        return rc;
+}
diff --git a/kernel/gcov/gcov.h b/kernel/gcov/gcov.h
new file mode 100644
index 00000000000..060073ebf7a
--- /dev/null
+++ b/kernel/gcov/gcov.h
@@ -0,0 +1,128 @@
+/*
+ *  Profiling infrastructure declarations.
+ *
+ *  This file is based on gcc-internal definitions. Data structures are
+ *  defined to be compatible with gcc counterparts. For a better
+ *  understanding, refer to gcc source: gcc/gcov-io.h.
+ *
+ *    Copyright IBM Corp. 2009
+ *    Author(s): Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
+ *
+ *    Uses gcc-internal data definitions.
+ */
+
+#ifndef GCOV_H
+#define GCOV_H GCOV_H
+
+#include <linux/types.h>
+
+/*
+ * Profiling data types used for gcc 3.4 and above - these are defined by
+ * gcc and need to be kept as close to the original definition as possible to
+ * remain compatible.
+ */
+#define GCOV_COUNTERS           5
+#define GCOV_DATA_MAGIC         ((unsigned int) 0x67636461)
+#define GCOV_TAG_FUNCTION       ((unsigned int) 0x01000000)
+#define GCOV_TAG_COUNTER_BASE   ((unsigned int) 0x01a10000)
+#define GCOV_TAG_FOR_COUNTER(count)                                     \
+        (GCOV_TAG_COUNTER_BASE + ((unsigned int) (count) << 17))
+
+#if BITS_PER_LONG >= 64
+typedef long gcov_type;
+#else
+typedef long long gcov_type;
+#endif
+
+/**
+ * struct gcov_fn_info - profiling meta data per function
+ * @ident: object file-unique function identifier
+ * @checksum: function checksum
+ * @n_ctrs: number of values per counter type belonging to this function
+ *
+ * This data is generated by gcc during compilation and doesn't change
+ * at run-time.
+ */
+struct gcov_fn_info {
+        unsigned int ident;
+        unsigned int checksum;
+        unsigned int n_ctrs[0];
+};
+
+/**
+ * struct gcov_ctr_info - profiling data per counter type
+ * @num: number of counter values for this type
+ * @values: array of counter values for this type
+ * @merge: merge function for counter values of this type (unused)
+ *
+ * This data is generated by gcc during compilation and doesn't change
+ * at run-time with the exception of the values array.
+ */
+struct gcov_ctr_info {
+        unsigned int    num;
+        gcov_type       *values;
+        void            (*merge)(gcov_type *, unsigned int);
+};
+
+/**
+ * struct gcov_info - profiling data per object file
+ * @version: gcov version magic indicating the gcc version used for compilation
+ * @next: list head for a singly-linked list
+ * @stamp: time stamp
+ * @filename: name of the associated gcov data file
+ * @n_functions: number of instrumented functions
+ * @functions: function data
+ * @ctr_mask: mask specifying which counter types are active
+ * @counts: counter data per counter type
+ *
+ * This data is generated by gcc during compilation and doesn't change
+ * at run-time with the exception of the next pointer.
+ */
+struct gcov_info {
+        unsigned int                    version;
+        struct gcov_info                *next;
+        unsigned int                    stamp;
+        const char                      *filename;
+        unsigned int                    n_functions;
+        const struct gcov_fn_info       *functions;
+        unsigned int                    ctr_mask;
+        struct gcov_ctr_info            counts[0];
+};
+
+/* Base interface. */
+enum gcov_action {
+        GCOV_ADD,
+        GCOV_REMOVE,
+};
+
+void gcov_event(enum gcov_action action, struct gcov_info *info);
+void gcov_enable_events(void);
+
+/* Iterator control. */
+struct seq_file;
+struct gcov_iterator;
+
+struct gcov_iterator *gcov_iter_new(struct gcov_info *info);
+void gcov_iter_free(struct gcov_iterator *iter);
+void gcov_iter_start(struct gcov_iterator *iter);
+int gcov_iter_next(struct gcov_iterator *iter);
+int gcov_iter_write(struct gcov_iterator *iter, struct seq_file *seq);
+struct gcov_info *gcov_iter_get_info(struct gcov_iterator *iter);
+
+/* gcov_info control. */
+void gcov_info_reset(struct gcov_info *info);
+int gcov_info_is_compatible(struct gcov_info *info1, struct gcov_info *info2);
+void gcov_info_add(struct gcov_info *dest, struct gcov_info *source);
+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 */
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 2b706617c89..7a7778746ea 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -116,6 +116,17 @@ _a_flags       = $(KBUILD_CPPFLAGS) $(KBUILD_AFLAGS) $(KBUILD_SUBDIR_ASFLAGS) \
                  $(asflags-y) $(AFLAGS_$(basetarget).o)
 _cpp_flags     = $(KBUILD_CPPFLAGS) $(cppflags-y) $(CPPFLAGS_$(@F))
 
+#
+# Enable gcov profiling flags for a file, directory or for all files depending
+# on variables GCOV_PROFILE_obj.o, GCOV_PROFILE and CONFIG_GCOV_PROFILE_ALL
+# (in this order)
+#
+ifeq ($(CONFIG_GCOV_KERNEL),y)
+_c_flags += $(if $(patsubst n%,, \
+                $(GCOV_PROFILE_$(basetarget).o)$(GCOV_PROFILE)$(CONFIG_GCOV_PROFILE_ALL)), \
+                $(CFLAGS_GCOV))
+endif
+
 # If building the kernel in a separate objtree expand all occurrences
 # of -Idir to -I$(srctree)/dir except for absolute paths (starting with '/').