mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-26 19:00:25 +00:00
![Frederic Weisbecker](/assets/img/avatar_default.png)
Context tracking recursion can happen when an exception triggers in the middle of a call to a context tracking probe. This special case can be caused by vmalloc faults. If an access to a memory area allocated by vmalloc happens in the middle of context_tracking_enter(), we may run into an endless fault loop because the exception in turn calls context_tracking_enter() which faults on the same vmalloc'ed memory, triggering an exception again, etc... Some rare crashes have been reported so lets protect against this with a recursion counter. Reported-by: Dave Jones <davej@redhat.com> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Reviewed-by: Rik van Riel <riel@redhat.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris Metcalf <cmetcalf@ezchip.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Mike Galbraith <umgwanakikbuti@gmail.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Rafael J . Wysocki <rafael.j.wysocki@intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1430928266-24888-2-git-send-email-fweisbec@gmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
48 lines
1.3 KiB
C
48 lines
1.3 KiB
C
#ifndef _LINUX_CONTEXT_TRACKING_STATE_H
|
|
#define _LINUX_CONTEXT_TRACKING_STATE_H
|
|
|
|
#include <linux/percpu.h>
|
|
#include <linux/static_key.h>
|
|
|
|
struct context_tracking {
|
|
/*
|
|
* When active is false, probes are unset in order
|
|
* to minimize overhead: TIF flags are cleared
|
|
* and calls to user_enter/exit are ignored. This
|
|
* may be further optimized using static keys.
|
|
*/
|
|
bool active;
|
|
int recursion;
|
|
enum ctx_state {
|
|
CONTEXT_KERNEL = 0,
|
|
CONTEXT_USER,
|
|
CONTEXT_GUEST,
|
|
} state;
|
|
};
|
|
|
|
#ifdef CONFIG_CONTEXT_TRACKING
|
|
extern struct static_key context_tracking_enabled;
|
|
DECLARE_PER_CPU(struct context_tracking, context_tracking);
|
|
|
|
static inline bool context_tracking_is_enabled(void)
|
|
{
|
|
return static_key_false(&context_tracking_enabled);
|
|
}
|
|
|
|
static inline bool context_tracking_cpu_is_enabled(void)
|
|
{
|
|
return __this_cpu_read(context_tracking.active);
|
|
}
|
|
|
|
static inline bool context_tracking_in_user(void)
|
|
{
|
|
return __this_cpu_read(context_tracking.state) == CONTEXT_USER;
|
|
}
|
|
#else
|
|
static inline bool context_tracking_in_user(void) { return false; }
|
|
static inline bool context_tracking_active(void) { return false; }
|
|
static inline bool context_tracking_is_enabled(void) { return false; }
|
|
static inline bool context_tracking_cpu_is_enabled(void) { return false; }
|
|
#endif /* CONFIG_CONTEXT_TRACKING */
|
|
|
|
#endif
|