2 files changed, 29 insertions, 7 deletions

diff --git a/Documentation/DocBook/kgdb.tmpl b/Documentation/DocBook/kgdb.tmpl
index 54d3b15..372dec2 100644
--- a/Documentation/DocBook/kgdb.tmpl
+++ b/Documentation/DocBook/kgdb.tmpl
@@ -106,6 +106,16 @@
     while debugging the kernel.
     </para>
     <para>
+    If the architecture that you are using supports the kernel option
+    CONFIG_DEBUG_RODATA, you should consider turning it off.  This
+    option will prevent the use of software breakpoints because it
+    marks certain regions of the kernel's memory space as read-only.
+    If kgdb supports it for the architecture you are using, you can
+    use hardware breakpoints if you desire to run with the
+    CONFIG_DEBUG_RODATA option turned on, else you need to turn off
+    this option.
+    </para>
+    <para>
     Next you should choose one of more I/O drivers to interconnect debugging
     host and debugged target.  Early boot debugging requires a KGDB
     I/O driver that supports early debugging and the driver must be
diff --git a/kernel/kgdb.c b/kernel/kgdb.c
index 3ec23c3..c0d45b2 100644
--- a/kernel/kgdb.c
+++ b/kernel/kgdb.c
@@ -166,13 +166,6 @@ early_param("nokgdbroundup", opt_nokgdbroundup);
  * Weak aliases for breakpoint management,
  * can be overriden by architectures when needed:
  */
-int __weak kgdb_validate_break_address(unsigned long addr)
-{
-	char tmp_variable[BREAK_INSTR_SIZE];
-
-	return probe_kernel_read(tmp_variable, (char *)addr, BREAK_INSTR_SIZE);
-}
-
 int __weak kgdb_arch_set_breakpoint(unsigned long addr, char *saved_instr)
 {
 	int err;
@@ -191,6 +184,25 @@ int __weak kgdb_arch_remove_breakpoint(unsigned long addr, char *bundle)
 				  (char *)bundle, BREAK_INSTR_SIZE);
 }
 
+int __weak kgdb_validate_break_address(unsigned long addr)
+{
+	char tmp_variable[BREAK_INSTR_SIZE];
+	int err;
+	/* Validate setting the breakpoint and then removing it.  In the
+	 * remove fails, the kernel needs to emit a bad message because we
+	 * are deep trouble not being able to put things back the way we
+	 * found them.
+	 */
+	err = kgdb_arch_set_breakpoint(addr, tmp_variable);
+	if (err)
+		return err;
+	err = kgdb_arch_remove_breakpoint(addr, tmp_variable);
+	if (err)
+		printk(KERN_ERR "KGDB: Critical breakpoint error, kernel "
+		   "memory destroyed at: %lx", addr);
+	return err;
+}
+
 unsigned long __weak kgdb_arch_pc(int exception, struct pt_regs *regs)
 {
 	return instruction_pointer(regs);