kernel debug: support resetting WARN_ONCE for all architectures

Some architectures store the WARN_ONCE state in the flags field of the
bug_entry.  Clear that one too when resetting once state through
/sys/kernel/debug/clear_warn_once

Pointed out by Michael Ellerman

Improves the earlier patch that add clear_warn_once.

[[email protected]: add a missing ifdef CONFIG_MODULES]
  Link: http://lkml.kernel.org/r/[email protected]
[[email protected]: fix unused var warning]
[[email protected]: Use 0200 for clear_warn_once file, per mpe]
[[email protected]: clear BUGFLAG_DONE in clear_once_table(), per mpe]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Andi Kleen <[email protected]>
Tested-by: Michael Ellerman <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

3 files changed, 30 insertions, 1 deletions

diff --git a/include/linux/bug.h b/include/linux/bug.h
index da4231c905c8..fe5916550da8 100644
--- a/include/linux/bug.h
+++ b/include/linux/bug.h
@@ -43,6 +43,8 @@ enum bug_trap_type report_bug(unsigned long bug_addr, struct pt_regs *regs);
 /* These are defined by the architecture */
 int is_valid_bugaddr(unsigned long addr);
 
+void generic_bug_clear_once(void);
+
 #else	/* !CONFIG_GENERIC_BUG */
 
 static inline enum bug_trap_type report_bug(unsigned long bug_addr,
@@ -51,6 +53,9 @@ static inline enum bug_trap_type report_bug(unsigned long bug_addr,
 	return BUG_TRAP_TYPE_BUG;
 }
 
+
+static inline void generic_bug_clear_once(void) {}
+
 #endif	/* CONFIG_GENERIC_BUG */
 
 /*
diff --git a/kernel/panic.c b/kernel/panic.c
index 672a91dc20fe..67cebf2a3b67 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -595,6 +595,7 @@ EXPORT_SYMBOL(warn_slowpath_null);
 
 static int clear_warn_once_set(void *data, u64 val)
 {
+	generic_bug_clear_once();
 	memset(__start_once, 0, __end_once - __start_once);
 	return 0;
 }
@@ -607,7 +608,7 @@ DEFINE_SIMPLE_ATTRIBUTE(clear_warn_once_fops,
 static __init int register_warn_debugfs(void)
 {
 	/* Don't care about failure */
-	debugfs_create_file("clear_warn_once", 0644, NULL,
+	debugfs_create_file("clear_warn_once", 0200, NULL,
 			    NULL, &clear_warn_once_fops);
 	return 0;
 }
diff --git a/lib/bug.c b/lib/bug.c
index 1e094408c893..f66be6bf6206 100644
--- a/lib/bug.c
+++ b/lib/bug.c
@@ -196,3 +196,26 @@ enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
 
 	return BUG_TRAP_TYPE_BUG;
 }
+
+static void clear_once_table(struct bug_entry *start, struct bug_entry *end)
+{
+	struct bug_entry *bug;
+
+	for (bug = start; bug < end; bug++)
+		bug->flags &= ~BUGFLAG_DONE;
+}
+
+void generic_bug_clear_once(void)
+{
+#ifdef CONFIG_MODULES
+	struct module *mod;
+
+	rcu_read_lock_sched();
+	list_for_each_entry_rcu(mod, &module_bug_list, bug_list)
+		clear_once_table(mod->bug_table,
+				 mod->bug_table + mod->num_bugs);
+	rcu_read_unlock_sched();
+#endif
+
+	clear_once_table(__start___bug_table, __stop___bug_table);
+}