From: Martin Mares <mj@ucw.cz>
Date: Sat, 28 Mar 2009 16:21:53 +0000 (+0100)
Subject: Box: Use SIGSTOP to notify the parent that the child is ready to be traced
X-Git-Tag: python-dummy-working~109
X-Git-Url: http://mj.ucw.cz/gitweb/?a=commitdiff_plain;h=60df4f1d5b7aa59fdf47d87e8352e108b35ffca2;p=moe.git

Box: Use SIGSTOP to notify the parent that the child is ready to be traced
instead of SIGCHLD. This should be safer.
---

diff --git a/box/box.c b/box/box.c
index da7dfc1..f574f86 100644
--- a/box/box.c
+++ b/box/box.c
@@ -944,6 +944,11 @@ boxkeeper(void)
 		msg("= %ld\n", u.regs.eax);
 	      ptrace(PTRACE_SYSCALL, box_pid, 0, 0);
 	    }
+	  else if (sig == SIGSTOP)
+	    {
+	      msg(">> SIGSTOP\n");
+	      ptrace(PTRACE_SYSCALL, box_pid, 0, 0);
+	    }
 	  else if (sig != SIGSTOP && sig != SIGXCPU && sig != SIGXFSZ)
 	    {
 	      msg(">> Signal %d\n", sig);
@@ -1007,8 +1012,7 @@ box_inside(int argc, char **argv)
       if (ptrace(PTRACE_TRACEME) < 0)
 	die("ptrace(PTRACE_TRACEME): %m");
       /* Trick: Make sure that we are stopped until the boxkeeper wakes up. */
-      signal(SIGCHLD, SIG_IGN);
-      raise(SIGCHLD);
+      raise(SIGSTOP);
     }
   execve(args[0], args, env);
   die("execve(\"%s\"): %m", args[0]);