Add the rt linux 4.1.3-rt3 as base

[kvmfornfv.git] / kernel / samples / hw_breakpoint / data_breakpoint.c

diff --git a/kernel/samples/hw_breakpoint/data_breakpoint.c b/kernel/samples/hw_breakpoint/data_breakpoint.c
new file mode 100644 (file)
index 0000000..ef7f322
--- /dev/null
+++ b/kernel/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 every time 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,
+                              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, NULL);
+       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");