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Commit 971a52d6 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

x86: delay CPA self-test and repeat it 



delay the CPA self-test so that any impact (corruption) of
user-space pagetables can be triggered. Repeat the test
every 30 seconds.

this would have prevented the bug fixed by 8cb2a7c1,
at its source.

Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent f1fbabb3

arch/x86/Kconfig.debug

+2 −2
Original line number Diff line number Diff line
@@ -220,9 +220,9 @@ config DEBUG_BOOT_PARAMS 
	  This option will cause struct boot_params to be exported via debugfs.



config CPA_DEBUG

	bool "CPA self test code"

	bool "CPA self-test code"

	depends on DEBUG_KERNEL

	help

	  Do change_page_attr self tests at boot.

	  Do change_page_attr() self-tests every 30 seconds.



endmenu

arch/x86/mm/pageattr-test.c

+51 −14
Original line number Diff line number Diff line
@@ -5,6 +5,7 @@ 
 * and compares page tables forwards and afterwards.

 */

#include <linux/bootmem.h>

#include <linux/kthread.h>

#include <linux/random.h>

#include <linux/kernel.h>

#include <linux/init.h>
@@ -14,8 +15,13 @@ 
#include <asm/pgtable.h>

#include <asm/kdebug.h>



/*

 * Only print the results of the first pass:

 */

static __read_mostly int print = 1;



enum {

	NTEST			= 4000,

	NTEST			= 400,

#ifdef CONFIG_X86_64

	LPS			= (1 << PMD_SHIFT),

#elif defined(CONFIG_X86_PAE)
@@ -31,7 +37,7 @@ struct split_state { 
	long min_exec, max_exec;

};



static __init int print_split(struct split_state *s)

static int print_split(struct split_state *s)

{

	long i, expected, missed = 0;

	int printed = 0;
@@ -82,10 +88,13 @@ static __init int print_split(struct split_state *s) 
				s->max_exec = addr;

		}

	}

	if (print) {

		printk(KERN_INFO

		"CPA mapping 4k %lu large %lu gb %lu x %lu[%lx-%lx] miss %lu\n",

			" 4k %lu large %lu gb %lu x %lu[%lx-%lx] miss %lu\n",

			s->spg, s->lpg, s->gpg, s->exec,

		s->min_exec != ~0UL ? s->min_exec : 0, s->max_exec, missed);

			s->min_exec != ~0UL ? s->min_exec : 0,

			s->max_exec, missed);

	}



	expected = (s->gpg*GPS + s->lpg*LPS)/PAGE_SIZE + s->spg + missed;

	if (expected != i) {
@@ -96,11 +105,11 @@ static __init int print_split(struct split_state *s) 
	return err;

}



static unsigned long __initdata addr[NTEST];

static unsigned int __initdata len[NTEST];

static unsigned long addr[NTEST];

static unsigned int len[NTEST];



/* Change the global bit on random pages in the direct mapping */

static __init int exercise_pageattr(void)

static int pageattr_test(void)

{

	struct split_state sa, sb, sc;

	unsigned long *bm;
@@ -110,7 +119,8 @@ static __init int exercise_pageattr(void) 
	int i, k;

	int err;



	printk(KERN_INFO "CPA exercising pageattr\n");

	if (print)

		printk(KERN_INFO "CPA self-test:\n");



	bm = vmalloc((max_pfn_mapped + 7) / 8);

	if (!bm) {
@@ -186,7 +196,6 @@ static __init int exercise_pageattr(void) 


	failed += print_split(&sb);



	printk(KERN_INFO "CPA reverting everything\n");

	for (i = 0; i < NTEST; i++) {

		if (!addr[i])

			continue;
@@ -214,12 +223,40 @@ static __init int exercise_pageattr(void) 
	failed += print_split(&sc);



	if (failed) {

		printk(KERN_ERR "CPA selftests NOT PASSED. Please report.\n");

		printk(KERN_ERR "NOT PASSED. Please report.\n");

		WARN_ON(1);

		return -EINVAL;

	} else {

		printk(KERN_INFO "CPA selftests PASSED\n");

		if (print)

			printk(KERN_INFO "ok.\n");

	}



	return 0;

}



static int do_pageattr_test(void *__unused)

{

	while (!kthread_should_stop()) {

		schedule_timeout_interruptible(HZ*30);

		if (pageattr_test() < 0)

			break;

		if (print)

			print--;

	}

	return 0;

}



static int start_pageattr_test(void)

{

	struct task_struct *p;



	p = kthread_create(do_pageattr_test, NULL, "pageattr-test");

	if (!IS_ERR(p))

		wake_up_process(p);

	else

		WARN_ON(1);



	return 0;

}

module_init(exercise_pageattr);
 


module_init(start_pageattr_test);