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Subject[PATCH v2] printk: report console names during cut-over
This reports the names of consoles as they're being disabled to help
identify which is which during cut-over. Helps answer the question
"which boot console actually got activated?" once the regular console
is running, mostly when debugging boot console failures.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
v2:
- move disable message into unregister_console, suggested by Frederic
Weisbecker.
---
kernel/printk/printk.c | 19 +++++++++----------
1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index b4e8500..555ad2d 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2358,21 +2358,18 @@ void register_console(struct console *newcon)
* users know there might be something in the kernel's log buffer that
* went to the bootconsole (that they do not see on the real console)
*/
+ printk(KERN_INFO "%sconsole [%s%d] enabled\n",
+ (newcon->flags & CON_BOOT) ? "boot" : "" ,
+ newcon->name, newcon->index);
if (bcon &&
((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
!keep_bootcon) {
- /* we need to iterate through twice, to make sure we print
- * everything out, before we unregister the console(s)
+ /* We need to iterate through all boot consoles, to make
+ * sure we print everything out, before we unregister them.
*/
- printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
- newcon->name, newcon->index);
for_each_console(bcon)
if (bcon->flags & CON_BOOT)
unregister_console(bcon);
- } else {
- printk(KERN_INFO "%sconsole [%s%d] enabled\n",
- (newcon->flags & CON_BOOT) ? "boot" : "" ,
- newcon->name, newcon->index);
}
}
EXPORT_SYMBOL(register_console);
@@ -2382,6 +2379,10 @@ int unregister_console(struct console *console)
struct console *a, *b;
int res;

+ printk(KERN_INFO "%sconsole [%s%d] disabled\n",
+ (console->flags & CON_BOOT) ? "boot" : "" ,
+ console->name, console->index);
+
res = _braille_unregister_console(console);
if (res)
return res;
@@ -2421,8 +2422,6 @@ static int __init printk_late_init(void)

for_each_console(con) {
if (!keep_bootcon && con->flags & CON_BOOT) {
- printk(KERN_INFO "turn off boot console %s%d\n",
- con->name, con->index);
unregister_console(con);
}
}
--
1.7.9.5

--
Kees Cook
Chrome OS Security


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