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SubjectRe: [PATCH 1/3] printk: Fix kdb_trap_printk placement
On Thu, 28 Sep 2017 14:18:24 +0200
Peter Zijlstra <peterz@infradead.org> wrote:

> 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?

I believe the vprintk_nmi() just buffers the prints, and doesn't send
it out. I'm guessing not then.

>
> Cc: Jason Wessel <jason.wessel@windriver.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
> 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;

Hmm, what was with the return r before??

Anyway,

Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> + return vprintk_emit(0, LOGLEVEL_DEFAULT, NULL, 0, fmt, args);
> }
> EXPORT_SYMBOL_GPL(vprintk_default);
>
>

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