timestamp.c: add some more error/warning messages

This might help to identify bugs/misbehaving systems
or attempts to mess with timestamp files.

diff --git a/timestamp.c b/timestamp.c
index c90318dd71daf7ca6cc109ff2cad725949164ef4..38c89ffcf590c083fbc4a3ce15d2b4b05d0ded1d 100644 (file)
--- a/timestamp.c
+++ b/timestamp.c
@@ -98,13 +98,16 @@ proc_info(pid_t pid, int *ttynr, unsigned long long *starttime)
        if (n < 0 || n >= (int)sizeof path)
                return -1;
 
-       if ((fd = open(path, O_RDONLY)) == -1)
+       if ((fd = open(path, O_RDONLY)) == -1) {
+               warn("failed to open: %s", path);
                return -1;
+       }
 
        while ((n = read(fd, p, buf + sizeof buf - p)) != 0) {
                if (n == -1) {
                        if (errno == EAGAIN || errno == EINTR)
                                continue;
+                       warn("read: %s", path);
                        close(fd);
                        return -1;
                }
@@ -115,7 +118,8 @@ proc_info(pid_t pid, int *ttynr, unsigned long long *starttime)
        close(fd);
 
        /* error if it contains NULL bytes */
-       if (n != 0 || memchr(buf, '\0', p - buf))
+       if (n != 0 || memchr(buf, '\0', p - buf)) {
+               warn("NUL in: %s", path);
                return -1;
 
        /* Get the 7th field, 5 fields after the last ')',
@@ -194,14 +198,18 @@ timestamp_check(int fd, int secs)
        struct stat st;
 
        if (fstat(fd, &st) == -1)
-               return 0;
+               err(1, "fstat");
 
-       if (!timespecisset(&st.st_atim) || !timespecisset(&st.st_mtim))
+       if (!timespecisset(&st.st_atim) || !timespecisset(&st.st_mtim)) {
+               warnx("timestamp atim or mtime not set");
                return 0;
+       }
 
        if (clock_gettime(CLOCK_BOOTTIME, &ts[0]) == -1 ||
-           clock_gettime(CLOCK_REALTIME, &ts[1]) == -1)
+           clock_gettime(CLOCK_REALTIME, &ts[1]) == -1) {
+               warn("clock_gettime");
                return 0;
+       }
 
        /* check if timestamp is too old */
        if (timespeccmp(&st.st_atim, &ts[0], <) ||
@@ -212,8 +220,10 @@ timestamp_check(int fd, int secs)
        timespecadd(&ts[0], &timeout, &ts[0]);
        timespecadd(&ts[1], &timeout, &ts[1]);
        if (timespeccmp(&st.st_atim, &ts[0], >) ||
-           timespeccmp(&st.st_mtim, &ts[1], >))
+           timespeccmp(&st.st_mtim, &ts[1], >)) {
+               warnx("timestamp too far in the future");
                return 0;
+       }
 
        return 1;
 }
@@ -249,6 +259,9 @@ timestamp_open(int *valid, int secs)
                char tmp[256];
                int n;
 
+               if (errno != ENOENT)
+                       err(1, "open: %s", path);
+
                n = snprintf(tmp, sizeof tmp, TIMESTAMP_DIR "/.tmp-%d", getpid());
                if (n < 0 || n >= (int)sizeof tmp)
                        return -1;