[PATCH] tools/misc: fix xenwatchdogd invocation

["zithro / Cyril Rébert" <slack@rabbit.lu>]

When xenwatchdogd is invoked with -h/--help (or any non-number), the
argument value is converted to 0, which immediately shutdowns dom0.

So make sure only numbers are passed to the program, otherwise fail.
For the help, use getopt_long as suggested.
While there, reformat the code a bit (s/tabs/spaces/, indentation, etc).

Bug fix only, no functional change intended.

Reported-by: Leigh Brown <leigh@solinno.co.uk>
Suggested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Cyril Rébert / zithro <slack@rabbit.lu>
---
- Not sure about the preprocessor stanzas, copied them from xentop.
- A small explanation about what the program does could be helpful,
  like some kind of synopsis ? Purpose, gotchas, etc. I can do the
  writing, but please be specific !
- Built on 4.17 and unstable, tested on 4.17.
---
 tools/misc/xenwatchdogd.c | 77 +++++++++++++++++++++++++++++----------
 1 file changed, 57 insertions(+), 20 deletions(-)

diff --git a/tools/misc/xenwatchdogd.c b/tools/misc/xenwatchdogd.c
index 254117b554..6ef5eaf45c 100644
--- a/tools/misc/xenwatchdogd.c
+++ b/tools/misc/xenwatchdogd.c
@@ -8,26 +8,34 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <signal.h>
+#include <string.h>
 #include <stdio.h>
 
+#define _GNU_SOURCE
+#include <getopt.h>
+#if !defined(__GNUC__) && !defined(__GNUG__)
+#define __attribute__(arg) /* empty */
+#endif
+
 xc_interface *h;
 int id = 0;
 
 void daemonize(void)
 {
     switch (fork()) {
-    case -1:
-	err(1, "fork");
-    case 0:
-	break;
-    default:
-	exit(0);
+        case -1:
+            err(1, "fork");
+        case 0:
+            break;
+        default:
+            exit(0);
     }
+
     umask(0);
     if (setsid() < 0)
-	err(1, "setsid");
+        err(1, "setsid");
     if (chdir("/") < 0)
-	err(1, "chdir /");
+        err(1, "chdir /");
     if (freopen("/dev/null", "r", stdin) == NULL)
         err(1, "reopen stdin");
     if(freopen("/dev/null", "w", stdout) == NULL)
@@ -52,39 +60,68 @@ void catch_usr1(int sig)
 
 int main(int argc, char **argv)
 {
+
     int t, s;
     int ret;
+    
+    char *usage = "usage: %s <timeout> <sleep>";
+    int opt, optind = 0;
+
+    struct option lopts[] = {
+        { "help",          no_argument,       NULL, 'h' },
+    };
+    const char *sopts = "h";
+
+    while ((opt = getopt_long(argc, argv, sopts, lopts, &optind)) != -1) {
+        switch (opt) {
+        case '?':
+        case 'h':
+            errx(1, usage, argv[0]);
+            break;
+        default:
+            errx(1, usage, argv[0]);
+        }
+    }
 
     if (argc < 2)
-	errx(1, "usage: %s <timeout> <sleep>", argv[0]);
+        errx(1, usage, argv[0]);
 
     daemonize();
 
     h = xc_interface_open(NULL, NULL, 0);
     if (h == NULL)
-	err(1, "xc_interface_open");
+        err(1, "xc_interface_open");
+
+    t = strtoul(argv[1], &argv[1], 0);
+    
+    // argv1 NaN
+    if ( *argv[1] != '\0' )
+        errx(1, "Error: timeout must be a number, got '%s'", argv[1]);
 
-    t = strtoul(argv[1], NULL, 0);
     if (t == ULONG_MAX)
-	err(1, "strtoul");
+        err(1, "strtoul");
 
     s = t / 2;
     if (argc == 3) {
-	s = strtoul(argv[2], NULL, 0);
-	if (s == ULONG_MAX)
-	    err(1, "strtoul");
+        s = strtoul(argv[2], &argv[2], 0);
+        // argv2 NaN
+        if ( *argv[2] != '\0' ){
+            errx(1, "Error: sleep must be a number, got '%s'", argv[2]);
+        }
+        if (s == ULONG_MAX)
+            err(1, "strtoul");
     }
 
     if (signal(SIGHUP, &catch_exit) == SIG_ERR)
-	err(1, "signal");
+        err(1, "signal");
     if (signal(SIGINT, &catch_exit) == SIG_ERR)
-	err(1, "signal");
+        err(1, "signal");
     if (signal(SIGQUIT, &catch_exit) == SIG_ERR)
-	err(1, "signal");
+        err(1, "signal");
     if (signal(SIGTERM, &catch_exit) == SIG_ERR)
-	err(1, "signal");
+        err(1, "signal");
     if (signal(SIGUSR1, &catch_usr1) == SIG_ERR)
-	err(1, "signal");
+        err(1, "signal");
 
     id = xc_watchdog(h, 0, t);
     if (id <= 0)
-- 
2.39.2