kasan: increase the number of bits to shift when recording extra timestamps

In 5d4c6ac94694 ("kasan: record and report more information") I thought
that printk only displays a maximum of 99999 seconds, but actually printk
can display a larger number of seconds.

So increase the number of bits to shift when recording the extra timestamp
(44 bits), without affecting the precision, shift it right by 9 bits,
discarding all bits that do not affect the microsecond part (nanoseconds
will not be shown).

Currently the maximum time that can be displayed is 9007199.254740s,
because

11111111111111111111111111111111111111111111 (44 bits) << 9
= 11111111111111111111111111111111111111111111000000000
= 9007199.254740

Link: https://lkml.kernel.org/r/AM6PR03MB58481629F2F28CE007412139994D2@AM6PR03MB5848.eurprd03.prod.outlook.com
Fixes: 5d4c6ac94694 ("kasan: record and report more information")
Signed-off-by: Juntong Deng <juntong.deng@outlook.com>
Acked-by: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 610efae912209472d818628778f1ebce5b0e2cc1..f2747ed30da084411658211d59fb9f1eeab1d0ec 100644 (file)
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -55,7 +55,7 @@ void kasan_set_track(struct kasan_track *track, depot_stack_handle_t stack)
        u64 ts_nsec = local_clock();
 
        track->cpu = cpu;
-       track->timestamp = ts_nsec >> 3;
+       track->timestamp = ts_nsec >> 9;
 #endif /* CONFIG_KASAN_EXTRA_INFO */
        track->pid = current->pid;
        track->stack = stack;

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index 7afa4feb03e18f32e37f67c0131d2678249776d3..b48c768acc84d29700fe8196e77850920f72e641 100644 (file)
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -267,7 +267,7 @@ static void print_track(struct kasan_track *track, const char *prefix)
        u64 ts_nsec = track->timestamp;
        unsigned long rem_usec;
 
-       ts_nsec <<= 3;
+       ts_nsec <<= 9;
        rem_usec = do_div(ts_nsec, NSEC_PER_SEC) / 1000;
 
        pr_err("%s by task %u on cpu %d at %lu.%06lus:\n",