Messages in this thread Patch in this message | | | Date | Tue, 29 Nov 2016 14:54:33 +0100 | From | Petr Mladek <> | Subject | Re: [PATCH 1/3] printk: Fix kdb_trap_printk placement |
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On Tue 2016-10-18 19:08:31, Peter Zijlstra wrote: > Some people figured vprintk_emit() makes for a nice API and exported > it, bypassing the kdb trap.
I think that nobody saw this problem because kdb_trap_printk was used only for a limited number of printk's. It is just a trick how to use generic functions to print messages in the kdb context, e.g. for getting backtraces.
But the patch makes sense.
> This still leaves vprintk_nmi() outside of the kbd reach, should that > be fixed too?
It is perfectly fine. Messages from NMI context are not meant for kdb anyway.
> Cc: Jason Wessel <jason.wessel@windriver.com> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > --- > kernel/printk/printk.c | 19 ++++++++----------- > 1 file changed, 8 insertions(+), 11 deletions(-) > > --- a/kernel/printk/printk.c > +++ b/kernel/printk/printk.c > @@ -1750,6 +1750,13 @@ asmlinkage int vprintk_emit(int facility > /* cpu currently holding logbuf_lock in this function */ > static unsigned int logbuf_cpu = UINT_MAX; > > +#ifdef CONFIG_KGDB_KDB > + if (unlikely(kdb_trap_printk)) { > + r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args); > + return r;
r is not defined. It is fixed in the next patch but it breaks bisectability.
Please, find below an updated patch that also includes my Reviewed-by.
From 5adf18de45ba986ea3ae611446828238f4d65fe0 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra <peterz@infradead.org> Date: Tue, 18 Oct 2016 19:08:31 +0200 Subject: [PATCH 1/3] printk: Fix kdb_trap_printk placement
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@windriver.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Reviewed-by: Petr Mladek <pmladek@suse.com> --- kernel/printk/printk.c | 17 ++++++----------- 1 file changed, 6 insertions(+), 11 deletions(-)
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index f7a55e9ff2f7..541ce7705353 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1781,6 +1781,11 @@ asmlinkage int vprintk_emit(int facility, int level, /* cpu currently holding logbuf_lock in this function */ static unsigned int logbuf_cpu = UINT_MAX; +#ifdef CONFIG_KGDB_KDB + if (unlikely(kdb_trap_printk)) + return vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args); +#endif + if (level == LOGLEVEL_SCHED) { level = LOGLEVEL_DEFAULT; in_sched = true; @@ -1923,17 +1928,7 @@ asmlinkage int printk_emit(int facility, int level, int vprintk_default(const char *fmt, va_list args) { - int r; - -#ifdef CONFIG_KGDB_KDB - if (unlikely(kdb_trap_printk)) { - 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); -- 1.8.5.6
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