Commit 80d4c477 authored by Marco Elver's avatar Marco Elver Committed by Ingo Molnar
Browse files

kcsan: Expose core configuration parameters as module params 



This adds early_boot, udelay_{task,interrupt}, and skip_watch as module
params. The latter parameters are useful to modify at runtime to tune
KCSAN's performance on new systems. This will also permit auto-tuning
these parameters to maximize overall system performance and KCSAN's race
detection ability.

None of the parameters are used in the fast-path and referring to them
via static variables instead of CONFIG constants will not affect
performance.

Signed-off-by: default avatarMarco Elver <elver@google.com>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: Qian Cai <cai@lca.pw>
parent a3120135

kernel/kcsan/core.c

+19 −5
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ 
#include <linux/export.h>

#include <linux/init.h>

#include <linux/kernel.h>

#include <linux/moduleparam.h>

#include <linux/percpu.h>

#include <linux/preempt.h>

#include <linux/random.h>
@@ -16,6 +17,20 @@ 
#include "encoding.h"

#include "kcsan.h"



static bool kcsan_early_enable = IS_ENABLED(CONFIG_KCSAN_EARLY_ENABLE);

static unsigned int kcsan_udelay_task = CONFIG_KCSAN_UDELAY_TASK;

static unsigned int kcsan_udelay_interrupt = CONFIG_KCSAN_UDELAY_INTERRUPT;

static long kcsan_skip_watch = CONFIG_KCSAN_SKIP_WATCH;



#ifdef MODULE_PARAM_PREFIX

#undef MODULE_PARAM_PREFIX

#endif

#define MODULE_PARAM_PREFIX "kcsan."

module_param_named(early_enable, kcsan_early_enable, bool, 0);

module_param_named(udelay_task, kcsan_udelay_task, uint, 0644);

module_param_named(udelay_interrupt, kcsan_udelay_interrupt, uint, 0644);

module_param_named(skip_watch, kcsan_skip_watch, long, 0644);



bool kcsan_enabled;



/* Per-CPU kcsan_ctx for interrupts */
@@ -239,9 +254,9 @@ should_watch(const volatile void *ptr, size_t size, int type) 


static inline void reset_kcsan_skip(void)

{

	long skip_count = CONFIG_KCSAN_SKIP_WATCH -

	long skip_count = kcsan_skip_watch -

			  (IS_ENABLED(CONFIG_KCSAN_SKIP_WATCH_RANDOMIZE) ?

				   prandom_u32_max(CONFIG_KCSAN_SKIP_WATCH) :

				   prandom_u32_max(kcsan_skip_watch) :

				   0);

	this_cpu_write(kcsan_skip, skip_count);

}
@@ -253,8 +268,7 @@ static __always_inline bool kcsan_is_enabled(void) 


static inline unsigned int get_delay(void)

{

	unsigned int delay = in_task() ? CONFIG_KCSAN_UDELAY_TASK :

					 CONFIG_KCSAN_UDELAY_INTERRUPT;

	unsigned int delay = in_task() ? kcsan_udelay_task : kcsan_udelay_interrupt;

	return delay - (IS_ENABLED(CONFIG_KCSAN_DELAY_RANDOMIZE) ?

				prandom_u32_max(delay) :

				0);
@@ -527,7 +541,7 @@ void __init kcsan_init(void) 
	 * We are in the init task, and no other tasks should be running;

	 * WRITE_ONCE without memory barrier is sufficient.

	 */

	if (IS_ENABLED(CONFIG_KCSAN_EARLY_ENABLE))

	if (kcsan_early_enable)

		WRITE_ONCE(kcsan_enabled, true);

}