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authorGravatar Denis Vlasenko <vda.linux@googlemail.com>2007-09-28 11:21:47 +0000
committerGravatar Denis Vlasenko <vda.linux@googlemail.com>2007-09-28 11:21:47 +0000
commita7bc9ac8f8a398fd11d10104a7aa26edd9b2f5a7 (patch)
treed5e2b8137c863fc5f4cf3193581051125c1efe7e /miscutils/hdparm.c
parentb9256054419582dc35917b1cb39c7e09f489dfad (diff)
downloadbusybox-a7bc9ac8f8a398fd11d10104a7aa26edd9b2f5a7.tar.gz
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hdparm: reduce possibility of numeric overflow in -T.
do_time 386 410 +24 ------------------------------------------------------------------------------ (add/remove: 0/0 grow/shrink: 1/0 up/down: 24/0) Total: 24 bytes
Diffstat (limited to 'miscutils/hdparm.c')
-rw-r--r--miscutils/hdparm.c20
1 files changed, 14 insertions, 6 deletions
diff --git a/miscutils/hdparm.c b/miscutils/hdparm.c
index 8a7204f29..1f85644d6 100644
--- a/miscutils/hdparm.c
+++ b/miscutils/hdparm.c
@@ -1375,10 +1375,13 @@ static void print_timing(unsigned long m, unsigned elapsed_us)
printf("%5lu MB in %u.%02u seconds = %lu kB/s\n",
m, sec, hs,
/* Trying to not overflow 32-bit arith in m * CONST
- * by keeping CONST not so big. + 1 prevents div-by-0. */
- (m * (1024 * 1000000 / (64*1024))) / (elapsed_us / (64*1024) + 1)
- // ~= (m * 1024 * 1000000) / elapsed_ms
- // = (m * 1024) / (elapsed_ms / 1000000)
+ * by keeping CONST not so big. But elapsed_us / CONST2
+ * also should not introduce big errors. Currently,
+ * 16000us is ~1.6% of 1 second.
+ * "+ 1" prevents div-by-0. */
+ (m * (1024 * 1000000 / (16*1024))) / (elapsed_us / (16*1024) + 1)
+ // ~= (m * 1024 * 1000000) / elapsed_us
+ // = (m * 1024) / (elapsed_us / 1000000)
// = kb / elapsed_sec
);
}
@@ -1418,6 +1421,11 @@ static void do_time(int cache /*,int fd*/)
/* Now do the timing */
iterations = 0;
+ /* Max time to run (small for cache, avoids getting
+ * huge total_MB which can overlow on print_timing) */
+ elapsed2 = 510000; /* cache */
+ if (!cache)
+ elapsed2 = 3000000; /* not cache */
start = monotonic_us();
do {
if (cache)
@@ -1425,11 +1433,11 @@ static void do_time(int cache /*,int fd*/)
read_big_block(buf);
elapsed = (unsigned)monotonic_us() - start;
++iterations;
- } while (elapsed < 3000000 && iterations < max_iterations);
+ } while (elapsed < elapsed2 && iterations < max_iterations);
total_MB = (unsigned long)iterations * TIMING_BUF_MB;
//printf(" elapsed:%u iterations:%u ", elapsed, iterations);
if (cache) {
- /* Now remove the lseek() and monotonic_us() overheads
+ /* Cache: remove lseek() and monotonic_us() overheads
* from elapsed */
start = monotonic_us();
do {