cancellation support for a large amount of the required syscalls

Signed-off-by: Austin Foxley <austinf@cetoncorp.com>

1 files changed, 201 insertions, 0 deletions

diff --git a/libc/stdlib/system.c b/libc/stdlib/system.c
index 99f7970c8..aa1f83676 100644
--- a/libc/stdlib/system.c
+++ b/libc/stdlib/system.c
@@ -10,8 +10,15 @@
 #include <unistd.h>
 #include <sys/wait.h>
 #include <stdlib.h>
+#ifdef __UCLIBC_HAS_THREADS_NATIVE__
+#include <sched.h>
+#include <errno.h>
+#include <bits/libc-lock.h>
+#include <sysdep-cancel.h>
+#endif
 
 
+#if !defined __UCLIBC_HAS_THREADS_NATIVE__
 /* uClinux-2.0 has vfork, but Linux 2.0 doesn't */
 #include <sys/syscall.h>
 #ifndef __NR_vfork
@@ -61,4 +68,198 @@ int __libc_system(const char *command)
 	signal(SIGCHLD, save_chld);
 	return wait_val;
 }
+#else
+/* We have to and actually can handle cancelable system().  The big
+   problem: we have to kill the child process if necessary.  To do
+   this a cleanup handler has to be registered and is has to be able
+   to find the PID of the child.  The main problem is to reliable have
+   the PID when needed.  It is not necessary for the parent thread to
+   return.  It might still be in the kernel when the cancellation
+   request comes.  Therefore we have to use the clone() calls ability
+   to have the kernel write the PID into the user-level variable.  */
+
+libc_hidden_proto(sigaction)
+libc_hidden_proto(waitpid)
+      
+#if defined __ia64__
+# define FORK() \
+  INLINE_SYSCALL (clone2, 6, CLONE_PARENT_SETTID | SIGCHLD, NULL, 0, \
+		  &pid, NULL, NULL)
+#elif defined __sparc__
+# define FORK() \
+  INLINE_CLONE_SYSCALL (CLONE_PARENT_SETTID | SIGCHLD, 0, &pid, NULL, NULL)
+#elif defined __s390__
+# define FORK() \
+  INLINE_SYSCALL (clone, 3, 0, CLONE_PARENT_SETTID | SIGCHLD, &pid)
+#else
+# define FORK() \
+  INLINE_SYSCALL (clone, 3, CLONE_PARENT_SETTID | SIGCHLD, 0, &pid)
+#endif
+
+static void cancel_handler (void *arg);
+
+# define CLEANUP_HANDLER \
+  __libc_cleanup_region_start (1, cancel_handler, &pid)
+
+# define CLEANUP_RESET \
+  __libc_cleanup_region_end (0)
+
+static struct sigaction intr, quit;
+static int sa_refcntr;
+__libc_lock_define_initialized (static, lock);
+
+# define DO_LOCK() __libc_lock_lock (lock)
+# define DO_UNLOCK() __libc_lock_unlock (lock)
+# define INIT_LOCK() ({ __libc_lock_init (lock); sa_refcntr = 0; })
+# define ADD_REF() sa_refcntr++
+# define SUB_REF() --sa_refcntr
+
+/* Execute LINE as a shell command, returning its status.  */
+static int
+do_system (const char *line)
+{
+  int status, save;
+  pid_t pid;
+  struct sigaction sa;
+  sigset_t omask;
+
+  sa.sa_handler = SIG_IGN;
+  sa.sa_flags = 0;
+  __sigemptyset (&sa.sa_mask);
+
+  DO_LOCK ();
+  if (ADD_REF () == 0)
+    {
+      if (sigaction (SIGINT, &sa, &intr) < 0)
+	{
+	  SUB_REF ();
+	  goto out;
+	}
+      if (sigaction (SIGQUIT, &sa, &quit) < 0)
+	{
+	  save = errno;
+	  SUB_REF ();
+	  goto out_restore_sigint;
+	}
+    }
+  DO_UNLOCK ();
+
+  /* We reuse the bitmap in the 'sa' structure.  */
+  __sigaddset (&sa.sa_mask, SIGCHLD);
+  save = errno;
+  if (sigprocmask (SIG_BLOCK, &sa.sa_mask, &omask) < 0)
+    {
+	{
+	  DO_LOCK ();
+	  if (SUB_REF () == 0)
+	    {
+	      save = errno;
+	      (void) sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
+	    out_restore_sigint:
+	      (void) sigaction (SIGINT, &intr, (struct sigaction *) NULL);
+	      __set_errno (save);
+	    }
+	out:
+	  DO_UNLOCK ();
+	  return -1;
+	}
+    }
+
+  CLEANUP_HANDLER;
+
+  pid = FORK ();
+  if (pid == (pid_t) 0)
+    {
+      /* Child side.  */
+      const char *new_argv[4];
+      new_argv[0] = "/bin/sh";
+      new_argv[1] = "-c";
+      new_argv[2] = line;
+      new_argv[3] = NULL;
+
+      /* Restore the signals.  */
+      (void) sigaction (SIGINT, &intr, (struct sigaction *) NULL);
+      (void) sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
+      (void) sigprocmask (SIG_SETMASK, &omask, (sigset_t *) NULL);
+      INIT_LOCK ();
+
+      /* Exec the shell.  */
+      (void) execve ("/bin/sh", (char *const *) new_argv, __environ);
+      _exit (127);
+    }
+  else if (pid < (pid_t) 0)
+    /* The fork failed.  */
+    status = -1;
+  else
+    /* Parent side.  */
+    {
+      /* Note the system() is a cancellation point.  But since we call
+	 waitpid() which itself is a cancellation point we do not
+	 have to do anything here.  */
+      if (TEMP_FAILURE_RETRY (waitpid (pid, &status, 0)) != pid)
+	status = -1;
+    }
+
+  CLEANUP_RESET;
+
+  save = errno;
+  DO_LOCK ();
+  if ((SUB_REF () == 0
+       && (sigaction (SIGINT, &intr, (struct sigaction *) NULL)
+	   | sigaction (SIGQUIT, &quit, (struct sigaction *) NULL)) != 0)
+      || sigprocmask (SIG_SETMASK, &omask, (sigset_t *) NULL) != 0)
+    {
+	status = -1;
+    }
+  DO_UNLOCK ();
+
+  return status;
+}
+
+
+int
+__libc_system (const char *line)
+{
+  if (line == NULL)
+    /* Check that we have a command processor available.  It might
+       not be available after a chroot(), for example.  */
+    return do_system ("exit 0") == 0;
+
+  if (SINGLE_THREAD_P)
+    return do_system (line);
+
+  int oldtype = LIBC_CANCEL_ASYNC ();
+
+  int result = do_system (line);
+
+  LIBC_CANCEL_RESET (oldtype);
+
+  return result;
+}
+
+
+/* The cancellation handler.  */
+static void
+cancel_handler (void *arg)
+{
+  pid_t child = *(pid_t *) arg;
+
+  INTERNAL_SYSCALL_DECL (err);
+  INTERNAL_SYSCALL (kill, err, 2, child, SIGKILL);
+
+  TEMP_FAILURE_RETRY (waitpid (child, NULL, 0));
+
+  DO_LOCK ();
+
+  if (SUB_REF () == 0)
+    {
+      (void) sigaction (SIGQUIT, &quit, (struct sigaction *) NULL);
+      (void) sigaction (SIGINT, &intr, (struct sigaction *) NULL);
+    }
+
+  DO_UNLOCK ();
+}
+#endif
+#ifdef IS_IN_libc
 weak_alias(__libc_system,system)
+#endif