Use GDB 'O' packets for console output if the serial line is shared

and GDB is attached.

It may be necessary for gdb and the console to share a serial port.
This patch utilises the GDB protocol to encode console output.

Based on a patch from Tony Breeds <tony@bakeyournoodle.com>
Signed-off-by: Keir Fraser <keir@xensource.com>

1 files changed, 42 insertions, 10 deletions

diff --git a/xen/common/gdbstub.c b/xen/common/gdbstub.c
index 8934122925..257547ed19 100644
--- a/xen/common/gdbstub.c
+++ b/xen/common/gdbstub.c
@@ -357,6 +357,25 @@ gdb_cmd_write_mem(unsigned long addr, unsigned long length,
     gdb_send_packet(ctx);
 }
 
+static void
+gdbstub_attach(struct gdb_context *ctx)
+{
+    static void gdbstub_console_puts(const char *str);
+    if ( ctx->currently_attached )
+        return;    
+    ctx->currently_attached = 1;
+    ctx->console_steal_id = console_steal(ctx->serhnd, gdbstub_console_puts);
+}
+
+static void
+gdbstub_detach(struct gdb_context *ctx)
+{
+    if ( !ctx->currently_attached )
+        return;
+    ctx->currently_attached = 0;
+    console_giveback(ctx->console_steal_id);
+}
+
 /* command dispatcher */
 static int 
 process_command(struct cpu_user_regs *regs, struct gdb_context *ctx)
@@ -427,7 +446,7 @@ process_command(struct cpu_user_regs *regs, struct gdb_context *ctx)
         gdb_arch_read_reg(addr, regs, ctx);
         break;
     case 'D':
-        ctx->currently_attached = 0;
+        gdbstub_detach(ctx);
         gdb_send_reply("OK", ctx);
         /* fall through */
     case 'k':
@@ -444,7 +463,7 @@ process_command(struct cpu_user_regs *regs, struct gdb_context *ctx)
              ctx->in_buf[1] )
             addr = str2ulong(&ctx->in_buf[1], sizeof(unsigned long));
         if ( ctx->in_buf[0] != 'D' )
-            ctx->currently_attached = 1;
+            gdbstub_attach(ctx);
         resume = 1;
         gdb_arch_resume(regs, addr, type, ctx);
         break;
@@ -459,17 +478,29 @@ process_command(struct cpu_user_regs *regs, struct gdb_context *ctx)
 
 static struct gdb_context
 __gdb_ctx = {
-    .serhnd             = -1,
-    .currently_attached = 0,
-    .running            = ATOMIC_INIT(1),
-    .connected          = 0,
-    .signum             = 1,
-    .in_bytes           = 0,
-    .out_offset         = 0,
-    .out_csum           = 0,
+    .serhnd  = -1,
+    .running = ATOMIC_INIT(1),
+    .signum  = 1
 };
 static struct gdb_context *gdb_ctx = &__gdb_ctx;
 
+static void
+gdbstub_console_puts(const char *str)
+{
+    const char *p;
+
+    gdb_start_packet(gdb_ctx);
+    gdb_write_to_packet_char('O', gdb_ctx);
+
+    for ( p = str; *p != '\0'; p++ )
+    {
+        gdb_write_to_packet_char(hex2char((*p>>4) & 0x0f), gdb_ctx );
+        gdb_write_to_packet_char(hex2char((*p) & 0x0f), gdb_ctx );
+    }
+
+    gdb_send_packet(gdb_ctx);
+}
+
 /* trap handler: main entry point */
 int 
 __trap_to_gdb(struct cpu_user_regs *regs, unsigned long cookie)
@@ -525,6 +556,7 @@ __trap_to_gdb(struct cpu_user_regs *regs, unsigned long cookie)
 
     gdb_arch_enter(regs);
     gdb_ctx->signum = gdb_arch_signal_num(regs, cookie);
+
     /* If gdb is already attached, tell it we've stopped again. */
     if ( gdb_ctx->currently_attached )
     {