debug: Add _ONCE() logic to report_bug()
Josh suggested moving the _ONCE logic inside the trap handler, using a
bit in the bug_entry::flags field, avoiding the need for the extra
variable.
Sadly this only works for WARN_ON_ONCE(), since the others have
printk() statements prior to triggering the trap.
Still, this saves a fair amount of text and some data:
text data filename
10682460 4530992 defconfig-build/vmlinux.orig
10665111 4530096 defconfig-build/vmlinux.patched
Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/lib/bug.c b/lib/bug.c
index 06edbbe..a6a1137 100644
--- a/lib/bug.c
+++ b/lib/bug.c
@@ -47,7 +47,7 @@
#include <linux/sched.h>
#include <linux/rculist.h>
-extern const struct bug_entry __start___bug_table[], __stop___bug_table[];
+extern struct bug_entry __start___bug_table[], __stop___bug_table[];
static inline unsigned long bug_addr(const struct bug_entry *bug)
{
@@ -62,10 +62,10 @@
/* Updates are protected by module mutex */
static LIST_HEAD(module_bug_list);
-static const struct bug_entry *module_find_bug(unsigned long bugaddr)
+static struct bug_entry *module_find_bug(unsigned long bugaddr)
{
struct module *mod;
- const struct bug_entry *bug = NULL;
+ struct bug_entry *bug = NULL;
rcu_read_lock_sched();
list_for_each_entry_rcu(mod, &module_bug_list, bug_list) {
@@ -122,15 +122,15 @@
#else
-static inline const struct bug_entry *module_find_bug(unsigned long bugaddr)
+static inline struct bug_entry *module_find_bug(unsigned long bugaddr)
{
return NULL;
}
#endif
-const struct bug_entry *find_bug(unsigned long bugaddr)
+struct bug_entry *find_bug(unsigned long bugaddr)
{
- const struct bug_entry *bug;
+ struct bug_entry *bug;
for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
if (bugaddr == bug_addr(bug))
@@ -141,9 +141,9 @@
enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
{
- const struct bug_entry *bug;
+ struct bug_entry *bug;
const char *file;
- unsigned line, warning;
+ unsigned line, warning, once, done;
if (!is_valid_bugaddr(bugaddr))
return BUG_TRAP_TYPE_NONE;
@@ -164,6 +164,18 @@
line = bug->line;
#endif
warning = (bug->flags & BUGFLAG_WARNING) != 0;
+ once = (bug->flags & BUGFLAG_ONCE) != 0;
+ done = (bug->flags & BUGFLAG_DONE) != 0;
+
+ if (warning && once) {
+ if (done)
+ return BUG_TRAP_TYPE_WARN;
+
+ /*
+ * Since this is the only store, concurrency is not an issue.
+ */
+ bug->flags |= BUGFLAG_DONE;
+ }
}
if (warning) {