frv: extend gdbstub to support more features of gdb

Extend gdbstub to support more features of gdb remote protocol to keep
gdb-7 and emacs gud mode happy:

(*) The D command. Detach debugger.

(*) The H command. Handle setting the target thread by ignoring it.

(*) The qAttached command. Indicate we 'attached' to an existing process.

(*) The qC command. Indicate that the current thread ID is 0.

(*) The qOffsets command. Indicate that no relocation has been done.

(*) The qSymbol:: command. Indicate that we're not interested in looking up
any symbol addresses.

(*) The qSupported command. Indicate the maximum packet size and the fact
that reverse step and continue aren't supported.

(*) The vCont? command. Indicate that we don't support any of its variants.

Also make it possible to trace the commands and replies without tracing
the individual character I/O.

[[e-mail]: make gdbstub_handle_query() static]
Signed-off-by: David Howells <[e-mail]>
Cc: Jason Wessel <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/frv/include/asm/gdb-stub.h

···
 #ifndef __ASM_GDB_STUB_H
 #define __ASM_GDB_STUB_H
 
+#undef GDBSTUB_DEBUG_IO
 #undef GDBSTUB_DEBUG_PROTOCOL
 
 #include <asm/ptrace.h>
···
 extern void gdbstub_printk(const char *fmt, ...);
 extern void debug_to_serial(const char *p, int n);
 extern void console_set_baud(unsigned baud);
+
+#ifdef GDBSTUB_DEBUG_IO
+#define gdbstub_io(FMT,...) gdbstub_printk(FMT, ##__VA_ARGS__)
+#else
+#define gdbstub_io(FMT,...) ({ 0; })
+#endif
 
 #ifdef GDBSTUB_DEBUG_PROTOCOL
 #define gdbstub_proto(FMT,...) gdbstub_printk(FMT,##__VA_ARGS__)

arch/frv/kernel/gdb-io.c

···
 		return -EINTR;
 	}
 	else if (st & (UART_LSR_FE|UART_LSR_OE|UART_LSR_PE)) {
-		gdbstub_proto("### GDB Rx Error (st=%02x) ###\n",st);
+		gdbstub_io("### GDB Rx Error (st=%02x) ###\n",st);
 		return -EIO;
 	}
 	else {
-		gdbstub_proto("### GDB Rx %02x (st=%02x) ###\n",ch,st);
+		gdbstub_io("### GDB Rx %02x (st=%02x) ###\n",ch,st);
 		*_ch = ch & 0x7f;
 		return 0;
 	}

arch/frv/kernel/gdb-stub.c

···
 
 } /* end gdbstub_get_mmu_state() */
 
+/*
+ * handle general query commands of the form 'qXXXXX'
+ */
+static void gdbstub_handle_query(void)
+{
+	if (strcmp(input_buffer, "qAttached") == 0) {
+		/* return current thread ID */
+		sprintf(output_buffer, "1");
+		return;
+	}
+
+	if (strcmp(input_buffer, "qC") == 0) {
+		/* return current thread ID */
+		sprintf(output_buffer, "QC 0");
+		return;
+	}
+
+	if (strcmp(input_buffer, "qOffsets") == 0) {
+		/* return relocation offset of text and data segments */
+		sprintf(output_buffer, "Text=0;Data=0;Bss=0");
+		return;
+	}
+
+	if (strcmp(input_buffer, "qSymbol::") == 0) {
+		sprintf(output_buffer, "OK");
+		return;
+	}
+
+	if (strcmp(input_buffer, "qSupported") == 0) {
+		/* query of supported features */
+		sprintf(output_buffer, "PacketSize=%u;ReverseContinue-;ReverseStep-",
+			sizeof(input_buffer));
+		return;
+	}
+
+	gdbstub_strcpy(output_buffer,"E01");
+}
+
 /*****************************************************************************/
 /*
  * handle event interception and GDB remote protocol processing
···
 		case 'k' :
 			goto done;	/* just continue */
 
+			/* detach */
+		case 'D':
+			gdbstub_strcpy(output_buffer, "OK");
+			break;
 
 			/* reset the whole machine (FIXME: system dependent) */
 		case 'r':
···
 			__debug_regs->dcr |= DCR_SE;
 			__debug_status.dcr |= DCR_SE;
 			goto done;
+
+			/* extended command */
+		case 'v':
+			if (strcmp(input_buffer, "vCont?") == 0) {
+				output_buffer[0] = 0;
+				break;
+			}
+			goto unsupported_cmd;
 
 			/* set baud rate (bBB) */
 		case 'b':
···
 			gdbstub_strcpy(output_buffer,"OK");
 			break;
 
+			/* Thread-setting packet */
+		case 'H':
+			gdbstub_strcpy(output_buffer, "OK");
+			break;
+
+		case 'q':
+			gdbstub_handle_query();
+			break;
+
 		default:
+		unsupported_cmd:
 			gdbstub_proto("### GDB Unsupported Cmd '%s'\n",input_buffer);
+			gdbstub_strcpy(output_buffer,"E01");
 			break;
 		}