kdb,kgdb: Implement switch and pass buffer from kdb -> gdb

When switching from kdb mode to kgdb mode packets were getting lost
depending on the size of the fifo queue of the serial chip.  When gdb
initially connects if it is in kdb mode it should entirely send any
character buffer over to the gdbstub when switching connections.

Previously kdb was zero'ing out the character buffer and this could
lead to gdb failing to connect at all, or a lengthy pause could occur
on the initial connect.

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>

1 files changed, 15 insertions, 7 deletions

diff --git a/kernel/debug/gdbstub.c b/kernel/debug/gdbstub.c
index a11db956dd6..34872482315 100644
--- a/kernel/debug/gdbstub.c
+++ b/kernel/debug/gdbstub.c
@@ -42,6 +42,8 @@
 /* Our I/O buffers. */
 static char			remcom_in_buffer[BUFMAX];
 static char			remcom_out_buffer[BUFMAX];
+static int			gdbstub_use_prev_in_buf;
+static int			gdbstub_prev_in_buf_pos;
 
 /* Storage for the registers, in GDB format. */
 static unsigned long		gdb_regs[(NUMREGBYTES +
@@ -58,6 +60,13 @@ static int gdbstub_read_wait(void)
 	int ret = -1;
 	int i;
 
+	if (unlikely(gdbstub_use_prev_in_buf)) {
+		if (gdbstub_prev_in_buf_pos < gdbstub_use_prev_in_buf)
+			return remcom_in_buffer[gdbstub_prev_in_buf_pos++];
+		else
+			gdbstub_use_prev_in_buf = 0;
+	}
+
 	/* poll any additional I/O interfaces that are defined */
 	while (ret < 0)
 		for (i = 0; kdb_poll_funcs[i] != NULL; i++) {
@@ -109,7 +118,6 @@ static void get_packet(char *buffer)
 			buffer[count] = ch;
 			count = count + 1;
 		}
-		buffer[count] = 0;
 
 		if (ch == '#') {
 			xmitcsum = hex_to_bin(gdbstub_read_wait()) << 4;
@@ -124,6 +132,7 @@ static void get_packet(char *buffer)
 			if (dbg_io_ops->flush)
 				dbg_io_ops->flush();
 		}
+		buffer[count] = 0;
 	} while (checksum != xmitcsum);
 }
 
@@ -1082,12 +1091,11 @@ int gdbstub_state(struct kgdb_state *ks, char *cmd)
 	case 'c':
 		strcpy(remcom_in_buffer, cmd);
 		return 0;
-	case '?':
-		gdb_cmd_status(ks);
-		break;
-	case '\0':
-		strcpy(remcom_out_buffer, "");
-		break;
+	case '$':
+		strcpy(remcom_in_buffer, cmd);
+		gdbstub_use_prev_in_buf = strlen(remcom_in_buffer);
+		gdbstub_prev_in_buf_pos = 0;
+		return 0;
 	}
 	dbg_io_ops->write_char('+');
 	put_packet(remcom_out_buffer);