Rewrite bytes/sec calculation using fixed point math.

This makes signal handler safe on OpenBSD.

To avoid overflows the accuracy is scaled. Above 10 minutes run time
we only care about second accuracy. Between 1 seconds and 10 minutes
we use millisecond accuracy.

Below one second we use nanoseconds, but those numbers are probably
meaningless.

Signal handler problem pointed out by deraadt

OK deraadt, millert, tb

diff --git a/bin/dd/misc.c b/bin/dd/misc.c
index 68afbeb..cd0ba9f 100644 (file)
--- a/bin/dd/misc.c
+++ b/bin/dd/misc.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: misc.c,v 1.25 2024/07/12 14:30:27 deraadt Exp $       */
+/*     $OpenBSD: misc.c,v 1.26 2024/07/12 19:11:25 florian Exp $       */
 /*     $NetBSD: misc.c,v 1.4 1995/03/21 09:04:10 cgd Exp $     */
 
 /*-
@@ -51,16 +51,26 @@ sig_summary(int notused)
 {
        int save_errno = errno;
        struct timespec elapsed, now;
-       double nanosecs;
+       unsigned long long bps, msec;
 
        if (ddflags & C_NOINFO)
                return;
 
        clock_gettime(CLOCK_MONOTONIC, &now);
        timespecsub(&now, &st.start, &elapsed);
-       nanosecs = ((double)elapsed.tv_sec * 1000000000) + elapsed.tv_nsec;
-       if (nanosecs == 0)
-               nanosecs = 1;
+
+       if (elapsed.tv_sec > 600)
+               bps = st.bytes / elapsed.tv_sec;
+       else if (elapsed.tv_sec > 0) {
+               /* will overflow at ~ 30 exabytes / second */
+               msec = elapsed.tv_sec * 1000 + elapsed.tv_nsec / 1000000;
+               if (msec == 0)
+                       msec = 1;
+               bps = st.bytes * 1000 / msec;
+       } else if (elapsed.tv_nsec > 0)
+               bps = st.bytes * 1000000000 / elapsed.tv_nsec;
+       else
+               bps = st.bytes;
 
        /* Be async safe: use dprintf(3). */
        dprintf(STDERR_FILENO, "%zu+%zu records in\n%zu+%zu records out\n",
@@ -77,9 +87,8 @@ sig_summary(int notused)
        if (!(ddflags & C_NOXFER)) {
                dprintf(STDERR_FILENO,
                    "%lld bytes transferred in %lld.%03ld secs "
-                   "(%0.0f bytes/sec)\n", (long long)st.bytes,
-                   (long long)elapsed.tv_sec, elapsed.tv_nsec / 1000000,
-                   ((double)st.bytes * 1000000000) / nanosecs);
+                   "(%llu bytes/sec)\n", (long long)st.bytes,
+                   (long long)elapsed.tv_sec, elapsed.tv_nsec / 1000000, bps);
        }
        errno = save_errno;
 }