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-rw-r--r--Documentation/DocBook/kgdb.tmpl10
-rw-r--r--kernel/kgdb.c26
2 files changed, 29 insertions, 7 deletions
diff --git a/Documentation/DocBook/kgdb.tmpl b/Documentation/DocBook/kgdb.tmpl
index 54d3b158d080..372dec20c8da 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 3ec23c3ec97f..c0d45b2c4d79 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);