3 files changed, 43 insertions, 0 deletions

diff --git a/libbb/Config.in b/libbb/Config.in
index a1ff7c056..0a3769df2 100644
--- a/libbb/Config.in
+++ b/libbb/Config.in
@@ -95,4 +95,14 @@ config FEATURE_EDITING_FANCY_PROMPT
           Setting this option allows for prompts to use things like \w and
           \$ and escape codes.
 
+config MONOTONIC_SYSCALL
+        bool "Use clock_gettime(CLOCK_MONOTONIC) syscall"
+        default y
+        help
+          Use clock_gettime(CLOCK_MONOTONIC) syscall for measuring
+          time intervals (time, ping, traceroute etc need this).
+          Probably requires Linux 2.6+. If not selected, gettimeofday
+          will be used instead (which gives wrong results if date/time
+          is reset).
+
 endmenu
diff --git a/libbb/Kbuild b/libbb/Kbuild
index e562f3222..693f6092c 100644
--- a/libbb/Kbuild
+++ b/libbb/Kbuild
@@ -78,6 +78,7 @@ lib-y += simplify_path.o
 lib-y += skip_whitespace.o
 lib-y += speed_table.o
 lib-y += str_tolower.o
+lib-y += time.o
 lib-y += trim.o
 lib-y += u_signal_names.o
 lib-y += udp_io.o
diff --git a/libbb/time.c b/libbb/time.c
new file mode 100644
index 000000000..f2a741521
--- /dev/null
+++ b/libbb/time.c
@@ -0,0 +1,32 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Utility routines.
+ *
+ * Copyright (C) 2007 Denis Vlasenko
+ *
+ * Licensed under GPL version 2, see file LICENSE in this tarball for details.
+ */
+
+#include "libbb.h"
+
+#if ENABLE_MONOTONIC_SYSCALL
+#include <sys/syscall.h>
+
+/* libc has incredibly messy way of doing this,
+ * typically requiring -lrt. We just skip all this mess */
+unsigned long long monotonic_us(void)
+{
+        struct timespec ts;
+        if (syscall(__NR_clock_gettime, CLOCK_MONOTONIC, &ts))
+                bb_error_msg_and_die("clock_gettime(MONOTONIC) failed");
+        return ts.tv_sec * 1000000ULL + ts.tv_nsec/1000;
+}
+#else
+unsigned long long monotonic_us(void)
+{
+        struct timeval tv;
+        if (gettimeofday(&tv, NULL))
+                bb_error_msg_and_die("gettimeofday failed");
+        return tv.tv_sec * 1000000ULL + tv_usec;
+}
+#endif