Add rtcwake.

Some of the bringup folks are debugging RTC issues and asked for this.

Rather than duplicate the weird xtzset dance with mktime, I've factored
that out into a new xmktime that takes a boolean for whether to use UTC
or local time.

Otherwise, the slight cleanup of hwclock.c is entirely optional. The
only functional change there is that util-linux 2.34's hwclock uses ISO
time format, which is the usual toybox preference anyway, so I've
switched it over to that rather than ctime(3).

Bug: http://b/152042947

3 files changed, 15 insertions, 0 deletions

diff --git a/lib/lib.h b/lib/lib.h
index 66b39d67..c528f190 100644
--- a/lib/lib.h
+++ b/lib/lib.h
@@ -188,6 +188,7 @@ void xsignal(int signal, void *handler);
 time_t xvali_date(struct tm *tm, char *str);
 void xparsedate(char *str, time_t *t, unsigned *nano, int endian);
 char *xgetline(FILE *fp, int *len);
+time_t xmktime(struct tm *tm, int utc);
 
 // lib.c
 void verror_msg(char *msg, int err, va_list va);
diff --git a/lib/portability.h b/lib/portability.h
index acc32fd4..41128958 100644
--- a/lib/portability.h
+++ b/lib/portability.h
@@ -175,6 +175,7 @@ void *memmem(const void *haystack, size_t haystack_length,
 // Linux headers not listed by POSIX or LSB
 #include <sys/mount.h>
 #ifdef __linux__
+#include <linux/rtc.h>
 #include <sys/statfs.h>
 #include <sys/swap.h>
 #include <sys/sysinfo.h>
diff --git a/lib/xwrap.c b/lib/xwrap.c
index 555fbd5e..5f18f295 100644
--- a/lib/xwrap.c
+++ b/lib/xwrap.c
@@ -1077,3 +1077,16 @@ char *xgetline(FILE *fp, int *len)
 
   return new;
 }
+
+time_t xmktime(struct tm *tm, int utc)
+{
+  char *old_tz = utc ? xtzset("UTC0") : 0;
+  time_t result;
+
+  if ((result = mktime(tm)) < 0) error_exit("mktime");
+  if (utc) {
+    free(xtzset(old_tz));
+    free(old_tz);
+  }
+  return result;
+}