6 files changed, 105 insertions, 9 deletions

diff --git a/samples/Kconfig b/samples/Kconfig
index b92bde3c6a89..8924f72f0629 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -1,5 +1,3 @@
-# samples/Kconfig
-
 menuconfig SAMPLES
         bool "Sample kernel code"
         help
@@ -40,5 +38,10 @@ config SAMPLE_KRETPROBES
         default m
         depends on SAMPLE_KPROBES && KRETPROBES
 
-endif # SAMPLES
+config SAMPLE_HW_BREAKPOINT
+        tristate "Build kernel hardware breakpoint examples -- loadable module only"
+        depends on HAVE_HW_BREAKPOINT && m
+        help
+          This builds kernel hardware breakpoint example modules.
 
+endif # SAMPLES
diff --git a/samples/Makefile b/samples/Makefile
index 43343a03b1f4..0f15e6d77fd6 100644
--- a/samples/Makefile
+++ b/samples/Makefile
@@ -1,3 +1,4 @@
 # Makefile for Linux samples code
 
-obj-$(CONFIG_SAMPLES)   += kobject/ kprobes/ tracepoints/ trace_events/
+obj-$(CONFIG_SAMPLES)   += kobject/ kprobes/ tracepoints/ trace_events/ \
+                           hw_breakpoint/
diff --git a/samples/hw_breakpoint/Makefile b/samples/hw_breakpoint/Makefile
new file mode 100644
index 000000000000..0f5c31c2fc47
--- /dev/null
+++ b/samples/hw_breakpoint/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_SAMPLE_HW_BREAKPOINT) += data_breakpoint.o
diff --git a/samples/hw_breakpoint/data_breakpoint.c b/samples/hw_breakpoint/data_breakpoint.c
new file mode 100644
index 000000000000..bd0f337afcab
--- /dev/null
+++ b/samples/hw_breakpoint/data_breakpoint.c
@@ -0,0 +1,90 @@
+/*
+ * data_breakpoint.c - Sample HW Breakpoint file to watch kernel data address
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * usage: insmod data_breakpoint.ko ksym=<ksym_name>
+ *
+ * This file is a kernel module that places a breakpoint over ksym_name kernel
+ * variable using Hardware Breakpoint register. The corresponding handler which
+ * prints a backtrace is invoked everytime a write operation is performed on
+ * that variable.
+ *
+ * Copyright (C) IBM Corporation, 2009
+ *
+ * Author: K.Prasad <prasad@linux.vnet.ibm.com>
+ */
+#include <linux/module.h>       /* Needed by all modules */
+#include <linux/kernel.h>       /* Needed for KERN_INFO */
+#include <linux/init.h>         /* Needed for the macros */
+#include <linux/kallsyms.h>
+
+#include <linux/perf_event.h>
+#include <linux/hw_breakpoint.h>
+
+struct perf_event * __percpu *sample_hbp;
+
+static char ksym_name[KSYM_NAME_LEN] = "pid_max";
+module_param_string(ksym, ksym_name, KSYM_NAME_LEN, S_IRUGO);
+MODULE_PARM_DESC(ksym, "Kernel symbol to monitor; this module will report any"
+                        " write operations on the kernel symbol");
+
+static void sample_hbp_handler(struct perf_event *bp, int nmi,
+                               struct perf_sample_data *data,
+                               struct pt_regs *regs)
+{
+        printk(KERN_INFO "%s value is changed\n", ksym_name);
+        dump_stack();
+        printk(KERN_INFO "Dump stack from sample_hbp_handler\n");
+}
+
+static int __init hw_break_module_init(void)
+{
+        int ret;
+        struct perf_event_attr attr;
+
+        hw_breakpoint_init(&attr);
+        attr.bp_addr = kallsyms_lookup_name(ksym_name);
+        attr.bp_len = HW_BREAKPOINT_LEN_4;
+        attr.bp_type = HW_BREAKPOINT_W | HW_BREAKPOINT_R;
+
+        sample_hbp = register_wide_hw_breakpoint(&attr, sample_hbp_handler);
+        if (IS_ERR((void __force *)sample_hbp)) {
+                ret = PTR_ERR((void __force *)sample_hbp);
+                goto fail;
+        }
+
+        printk(KERN_INFO "HW Breakpoint for %s write installed\n", ksym_name);
+
+        return 0;
+
+fail:
+        printk(KERN_INFO "Breakpoint registration failed\n");
+
+        return ret;
+}
+
+static void __exit hw_break_module_exit(void)
+{
+        unregister_wide_hw_breakpoint(sample_hbp);
+        printk(KERN_INFO "HW Breakpoint for %s write uninstalled\n", ksym_name);
+}
+
+module_init(hw_break_module_init);
+module_exit(hw_break_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("K.Prasad");
+MODULE_DESCRIPTION("ksym breakpoint");
diff --git a/samples/kobject/kobject-example.c b/samples/kobject/kobject-example.c
index 8d9b55a12023..86ea0c3ad975 100644
--- a/samples/kobject/kobject-example.c
+++ b/samples/kobject/kobject-example.c
@@ -44,7 +44,7 @@ static struct kobj_attribute foo_attribute =
         __ATTR(foo, 0666, foo_show, foo_store);
 
 /*
- * More complex function where we determine which varible is being accessed by
+ * More complex function where we determine which variable is being accessed by
  * looking at the attribute for the "baz" and "bar" files.
  */
 static ssize_t b_show(struct kobject *kobj, struct kobj_attribute *attr,
@@ -79,7 +79,7 @@ static struct kobj_attribute bar_attribute =
 
 
 /*
- * Create a group of attributes so that we can create and destory them all
+ * Create a group of attributes so that we can create and destroy them all
  * at once.
  */
 static struct attribute *attrs[] = {
diff --git a/samples/kobject/kset-example.c b/samples/kobject/kset-example.c
index 45b7d56fb541..d0c687fd9802 100644
--- a/samples/kobject/kset-example.c
+++ b/samples/kobject/kset-example.c
@@ -10,6 +10,7 @@
 #include <linux/kobject.h>
 #include <linux/string.h>
 #include <linux/sysfs.h>
+#include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/init.h>
 
@@ -87,7 +88,7 @@ static ssize_t foo_attr_store(struct kobject *kobj,
 }
 
 /* Our custom sysfs_ops that we will associate with our ktype later on */
-static struct sysfs_ops foo_sysfs_ops = {
+static const struct sysfs_ops foo_sysfs_ops = {
         .show = foo_attr_show,
         .store = foo_attr_store,
 };
@@ -127,7 +128,7 @@ static struct foo_attribute foo_attribute =
         __ATTR(foo, 0666, foo_show, foo_store);
 
 /*
- * More complex function where we determine which varible is being accessed by
+ * More complex function where we determine which variable is being accessed by
  * looking at the attribute for the "baz" and "bar" files.
  */
 static ssize_t b_show(struct foo_obj *foo_obj, struct foo_attribute *attr,
@@ -161,7 +162,7 @@ static struct foo_attribute bar_attribute =
         __ATTR(bar, 0666, b_show, b_store);
 
 /*
- * Create a group of attributes so that we can create and destory them all
+ * Create a group of attributes so that we can create and destroy them all
  * at once.
  */
 static struct attribute *foo_default_attrs[] = {