Add support to break into the kernel on escape.

2 files changed, 53 insertions, 11 deletions

diff --git a/viengoos/bottom-half.c b/viengoos/bottom-half.c
index 50be852..3bb081f 100644
--- a/viengoos/bottom-half.c
+++ b/viengoos/bottom-half.c
@@ -26,25 +26,30 @@ void
 bottom_half_register (struct bottom_half *bh)
 {
   assert (! bh->next);
+  assert (bh != bottom_halves);
 
   do
     bh->next = bottom_halves;
-  while (! __sync_val_compare_and_swap (&bottom_halves, bh->next, bh));
+  while (__sync_val_compare_and_swap (&bottom_halves, bh->next, bh)
+	 != bh->next);
 }
 
 void
 bottom_half_run_hard (void)
 {
-  for (;;)
-    {
-      struct bottom_half *bh;
+  struct bottom_half *bh;
+
+  do
+    bh = bottom_halves;
+  while (bh && !__sync_val_compare_and_swap (&bottom_halves, bh, 0));
 
-      do
-	bh = bottom_halves;
-      while (bh && !__sync_val_compare_and_swap (&bottom_halves, bh, bh->next));
+  if (! bh)
+    return;
 
-      if (! bh)
-	break;
+  struct bottom_half *next = bh;
+  while ((bh = next))
+    {
+      next = bh->next;
 
       bh->next = 0;
       bh->callback (bh);
diff --git a/viengoos/sysdeps/generic/output-serial.c b/viengoos/sysdeps/generic/output-serial.c
index 3df0ddc..8d40887 100644
--- a/viengoos/sysdeps/generic/output-serial.c
+++ b/viengoos/sysdeps/generic/output-serial.c
@@ -28,6 +28,7 @@
 #include <errno.h>
 
 #include "output.h"
+#include "bottom-half.h"
 
 
 /* The base I/O ports for the serial device ports COM1 and COM2.  */
@@ -65,6 +66,11 @@
 #define UART_SPEED_DEFAULT	UART_SPEED_MAX
 
 
+static void check_for_escape_bottom_half_handler (struct bottom_half *bh);
+static struct bottom_half check_for_escape_bottom_half
+  = { .callback = check_for_escape_bottom_half_handler };
+static struct output_driver *driver;
+
 static void
 serial_init (struct output_driver *device, const char *driver_cfg)
 {
@@ -153,6 +159,12 @@ serial_init (struct output_driver *device, const char *driver_cfg)
   inb (UART_MCR);
   inb (UART_LSR);
   inb (UART_MSR);
+
+  if (! driver)
+    {
+      driver = device;
+      bottom_half_register (&check_for_escape_bottom_half);
+    }
 }
 
 
@@ -169,12 +181,22 @@ serial_putchar (struct output_driver *device, int chr)
 }
 
 static int
+serial_getchar_nonblocking (struct output_driver *device)
+{
+  if ((inb (UART_LSR)) & UART_LSR_DR)
+    return inb (UART_DR);
+
+  return -1;
+}
+
+static int
 serial_getchar (struct output_driver *device)
 {
-  while (!((inb (UART_LSR)) & UART_LSR_DR))
+  int c;
+  while ((c = serial_getchar_nonblocking (device)) == -1)
     ;
 
-  return inb (UART_DR);
+  return c;
 }
 
 struct output_driver serial_output =
@@ -185,3 +207,18 @@ struct output_driver serial_output =
     serial_putchar,
     serial_getchar
   };
+
+static void
+check_for_escape_bottom_half_handler (struct bottom_half *bh)
+{
+  assert (bh == &check_for_escape_bottom_half);
+  assert (driver);
+
+  int c;
+  if (unlikely ((c = serial_getchar_nonblocking (driver)))
+      && unlikely (c == 0x1b))
+    vg_debugger ();
+
+  bottom_half_register (bh);
+}
+