1 files changed, 128 insertions, 0 deletions
diff --git a/arch/um/os-Linux/start_up.c b/arch/um/os-Linux/start_up.c
index 829d6b0d8b02..32753131f8d8 100644
--- a/arch/um/os-Linux/start_up.c
+++ b/arch/um/os-Linux/start_up.c
@@ -3,6 +3,7 @@
  * Licensed under the GPL
  */
 
+#include <pty.h>
 #include <stdio.h>
 #include <stddef.h>
 #include <stdarg.h>
@@ -539,3 +540,130 @@ int __init parse_iomem(char *str, int *add)
 	return(1);
 }
 
+
+/* Changed during early boot */
+int pty_output_sigio = 0;
+int pty_close_sigio = 0;
+
+/* Used as a flag during SIGIO testing early in boot */
+static volatile int got_sigio = 0;
+
+static void __init handler(int sig)
+{
+	got_sigio = 1;
+}
+
+struct openpty_arg {
+	int master;
+	int slave;
+	int err;
+};
+
+static void openpty_cb(void *arg)
+{
+	struct openpty_arg *info = arg;
+
+	info->err = 0;
+	if(openpty(&info->master, &info->slave, NULL, NULL, NULL))
+		info->err = -errno;
+}
+
+static void __init check_one_sigio(void (*proc)(int, int))
+{
+	struct sigaction old, new;
+	struct openpty_arg pty = { .master = -1, .slave = -1 };
+	int master, slave, err;
+
+	initial_thread_cb(openpty_cb, &pty);
+	if(pty.err){
+		printk("openpty failed, errno = %d\n", -pty.err);
+		return;
+	}
+
+	master = pty.master;
+	slave = pty.slave;
+
+	if((master == -1) || (slave == -1)){
+		printk("openpty failed to allocate a pty\n");
+		return;
+	}
+
+	/* Not now, but complain so we now where we failed. */
+	err = raw(master);
+	if (err < 0)
+		panic("check_sigio : __raw failed, errno = %d\n", -err);
+
+	err = os_sigio_async(master, slave);
+	if(err < 0)
+		panic("tty_fds : sigio_async failed, err = %d\n", -err);
+
+	if(sigaction(SIGIO, NULL, &old) < 0)
+		panic("check_sigio : sigaction 1 failed, errno = %d\n", errno);
+	new = old;
+	new.sa_handler = handler;
+	if(sigaction(SIGIO, &new, NULL) < 0)
+		panic("check_sigio : sigaction 2 failed, errno = %d\n", errno);
+
+	got_sigio = 0;
+	(*proc)(master, slave);
+
+	close(master);
+	close(slave);
+
+	if(sigaction(SIGIO, &old, NULL) < 0)
+		panic("check_sigio : sigaction 3 failed, errno = %d\n", errno);
+}
+
+static void tty_output(int master, int slave)
+{
+	int n;
+	char buf[512];
+
+	printk("Checking that host ptys support output SIGIO...");
+
+	memset(buf, 0, sizeof(buf));
+
+	while(os_write_file(master, buf, sizeof(buf)) > 0) ;
+	if(errno != EAGAIN)
+		panic("check_sigio : write failed, errno = %d\n", errno);
+	while(((n = os_read_file(slave, buf, sizeof(buf))) > 0) && !got_sigio) ;
+
+	if(got_sigio){
+		printk("Yes\n");
+		pty_output_sigio = 1;
+	}
+	else if(n == -EAGAIN) printk("No, enabling workaround\n");
+	else panic("check_sigio : read failed, err = %d\n", n);
+}
+
+static void tty_close(int master, int slave)
+{
+	printk("Checking that host ptys support SIGIO on close...");
+
+	close(slave);
+	if(got_sigio){
+		printk("Yes\n");
+		pty_close_sigio = 1;
+	}
+	else printk("No, enabling workaround\n");
+}
+
+void __init check_sigio(void)
+{
+	if((os_access("/dev/ptmx", OS_ACC_R_OK) < 0) &&
+	   (os_access("/dev/ptyp0", OS_ACC_R_OK) < 0)){
+		printk("No pseudo-terminals available - skipping pty SIGIO "
+		       "check\n");
+		return;
+	}
+	check_one_sigio(tty_output);
+	check_one_sigio(tty_close);
+}
+
+void os_check_bugs(void)
+{
+	check_ptrace();
+	check_sigio();
+	check_devanon();
+}
+