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printk: Prepare for nested printk_nmi_enter()

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There is plenty of space in the printk_context variable. Reserve one byte
there for the NMI context to be on the safe side.

It should never overflow. The BUG_ON(in_nmi() == NMI_MASK) in nmi_enter()
will trigger much earlier.

Signed-off-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Link: https://lkml.kernel.org/r/20200505134100.681374113@linutronix.de
This commit is contained in:
Petr Mladek 2020-02-24 13:13:31 +01:00 committed by Thomas Gleixner
parent 1ed0948eea
commit 8c4e93c362
2 changed files with 7 additions and 5 deletions
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8
kernel/printk/internal.h
View file

@ -6,9 +6,11 @@
#ifdef CONFIG_PRINTK
#define PRINTK_SAFE_CONTEXT_MASK 0x3fffffff
#define PRINTK_NMI_DIRECT_CONTEXT_MASK 0x40000000
#define PRINTK_NMI_CONTEXT_MASK 0x80000000
#define PRINTK_SAFE_CONTEXT_MASK 0x007ffffff
#define PRINTK_NMI_DIRECT_CONTEXT_MASK 0x008000000
#define PRINTK_NMI_CONTEXT_MASK 0xff0000000
#define PRINTK_NMI_CONTEXT_OFFSET 0x010000000
extern raw_spinlock_t logbuf_lock;

4
kernel/printk/printk_safe.c
View file

@ -295,12 +295,12 @@ static __printf(1, 0) int vprintk_nmi(const char *fmt, va_list args)
void notrace printk_nmi_enter(void)
{
this_cpu_or(printk_context, PRINTK_NMI_CONTEXT_MASK);
this_cpu_add(printk_context, PRINTK_NMI_CONTEXT_OFFSET);
}
void notrace printk_nmi_exit(void)
{
this_cpu_and(printk_context, ~PRINTK_NMI_CONTEXT_MASK);
this_cpu_sub(printk_context, PRINTK_NMI_CONTEXT_OFFSET);
}
/*