[PATCH 1/3] printk: Fix kdb_trap_printk placement

From: Peter Zijlstra
Date: Thu Sep 28 2017 - 08:26:16 EST


Some people figured vprintk_emit() makes for a nice API and exported
it, bypassing the kdb trap.

This still leaves vprintk_nmi() outside of the kbd reach, should that
be fixed too?

Cc: Jason Wessel <jason.wessel@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
kernel/printk/printk.c | 18 ++++++------------
1 file changed, 6 insertions(+), 12 deletions(-)

--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1811,6 +1811,11 @@ asmlinkage int vprintk_emit(int facility
int printed_len;
bool in_sched = false;

+#ifdef CONFIG_KGDB_KDB
+ if (unlikely(kdb_trap_printk && kdb_printf_cpu < 0))
+ return vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
+#endif
+
if (level == LOGLEVEL_SCHED) {
level = LOGLEVEL_DEFAULT;
in_sched = true;
@@ -1903,18 +1908,7 @@ EXPORT_SYMBOL(printk_emit);

int vprintk_default(const char *fmt, va_list args)
{
- int r;
-
-#ifdef CONFIG_KGDB_KDB
- /* Allow to pass printk() to kdb but avoid a recursion. */
- if (unlikely(kdb_trap_printk && kdb_printf_cpu < 0)) {
- r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
- return r;
- }
-#endif
- r = vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
-
- return r;
+ return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
}
EXPORT_SYMBOL_GPL(vprintk_default);