sanitise results of stat()/lstat() on Solaris

Solaris 11 (possibly only 11.4) can return negative values for
st_atim.tv_nsec, st_mtim.tv_nsec and st_ctim.tv_nsec.

Gnulib already identifies this as an issue and works around it with
stat_time_normalize().  I've adapted that function for this patch,
omitting st_ctim (unused by rsync) and using only a very simple test for
time_t overflow.

The feature test macros used mean this code path will be used on _all_
Solaris builds, but this shouldn't be an issue; it would probably be
safe on anything that provides tv_nsec.

syscall.c

@@ -357,19 +357,29 @@ int do_mkstemp(char *template, mode_t perms)
 int do_stat(const char *path, STRUCT_STAT *st)
 {
 #ifdef USE_STAT64_FUNCS
-	return stat64(path, st);
+	int r = stat64(path, st);
 #else
-	return stat(path, st);
+	int r = stat(path, st);
+#endif
+#if defined __sun && defined HAVE_STRUCT_STAT_ST_MTIM_TV_NSEC
+	return stat_time_normalize(r, st);
+#else
+	return r;
 #endif
 }
 
 int do_lstat(const char *path, STRUCT_STAT *st)
 {
 #ifdef SUPPORT_LINKS
 # ifdef USE_STAT64_FUNCS
-	return lstat64(path, st);
+	int r = lstat64(path, st);
+# else
+	int r = lstat(path, st);
+# endif
+# if defined __sun && defined HAVE_STRUCT_STAT_ST_MTIM_TV_NSEC
+	return stat_time_normalize(r, st);
 # else
-	return lstat(path, st);
+	return r;
 # endif
 #else
 	return do_stat(path, st);

util2.c

@@ -143,3 +143,44 @@ const char *src_file(const char *file)
 		return file + prefix;
 	return file;
 }
+
+/* If a stat-like function returned RESULT, normalize the timestamps
+   in *ST, in case this platform suffers from the Solaris 11 bug where
+   tv_nsec might be negative.  Return the adjusted RESULT, setting
+   errno to EOVERFLOW if normalization overflowed.  This function
+   is intended to be private to this .h file.
+
+   This is adapted from Gnulib. */
+
+int stat_time_normalize(int result, STRUCT_STAT *st)
+{
+#if defined __sun && defined HAVE_STRUCT_STAT_ST_MTIM_TV_NSEC
+    if (result == 0) {
+        long int timespec_hz = 1000000000;
+        short int const ts_off[] = { offsetof (struct stat, st_atim),
+                                     offsetof (struct stat, st_mtim) };
+        unsigned i;
+        for (i = 0; i < sizeof ts_off / sizeof *ts_off; i++) {
+            struct timespec *ts = (struct timespec *)((char *) st + ts_off[i]);
+            long int q = ts->tv_nsec / timespec_hz;
+            long int r = ts->tv_nsec % timespec_hz;
+            if (r < 0) {
+                r += timespec_hz;
+                q--;
+            }
+            ts->tv_nsec = r;
+            /* Overflow is possible, as Solaris 11 stat can yield
+               tv_sec == TYPE_MINIMUM (time_t) && tv_nsec == -1000000000.  */
+            time_t sec = ts->tv_sec + q;
+            if ((q > 0 && sec < ts->tv_sec) || (q < 0 && sec > ts->tv_sec)) {
+                errno = EOVERFLOW;
+                return -1;
+            }
+            ts->tv_sec = sec;
+        }
+    }
+#else
+    (void)st;
+#endif
+    return result;
+}