Re: Fix ARM stepping over Thumb-mode "bx pc" or "blx pc"

["Joseph S. Myers" <joseph@codesourcery.com>]

On Sat, 11 Aug 2012, Yao Qi wrote:

> I don't have any preference on clearing either the last one bit in
> address or the last two bits.  Looks like two ways coexist in arm-tdep.c
> nowadays.  As 'pc_val' is set by MAKE_THUMB_ADDR at the beginning, it is
> better to revert its change by using UNMAKE_THUMB_ADDR (which only
> clears the last one bit of address).

This version uses UNMAKE_THUMB_ADDR as requested.  Tested with no
regressions with cross to arm-none-linux-gnueabi.

2012-08-13  Joseph Myers  <joseph@codesourcery.com>

	* arm-tdep.c (thumb_get_next_pc_raw): Mask off low bits for bx pc
	and blx pc.

testsuite:
2012-08-13  Joseph Myers  <joseph@codesourcery.com>

	* gdb.arch/thumb-bx-pc.S: New file.
	* gdb.arch/thumb-bx-pc.exp: New file.

Index: gdb/arm-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/arm-tdep.c,v
retrieving revision 1.365
diff -u -r1.365 arm-tdep.c
--- gdb/arm-tdep.c	25 Jun 2012 12:32:45 -0000	1.365
+++ gdb/arm-tdep.c	13 Aug 2012 13:56:04 -0000
@@ -4541,7 +4541,7 @@
   else if ((inst1 & 0xff00) == 0x4700)	/* bx REG, blx REG */
     {
       if (bits (inst1, 3, 6) == 0x0f)
-	nextpc = pc_val;
+	nextpc = UNMAKE_THUMB_ADDR (pc_val);
       else
 	nextpc = get_frame_register_unsigned (frame, bits (inst1, 3, 6));
     }
Index: gdb/testsuite/gdb.arch/thumb-bx-pc.S
===================================================================
RCS file: gdb/testsuite/gdb.arch/thumb-bx-pc.S
diff -N gdb/testsuite/gdb.arch/thumb-bx-pc.S
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ gdb/testsuite/gdb.arch/thumb-bx-pc.S	13 Aug 2012 13:56:05 -0000
@@ -0,0 +1,34 @@
+/* Test PC adjustment from Thumb-mode "bx pc" instruction.
+
+   Copyright 2012 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+	.syntax unified
+	.thumb
+	.text
+	.p2align 2
+	.global	main
+	.thumb
+	.thumb_func
+	.type main, %function
+main:
+	bx	pc
+	nop
+.code 32
+	mov	r0, #0
+	bx	lr
+	.size	main, .-main
Index: gdb/testsuite/gdb.arch/thumb-bx-pc.exp
===================================================================
RCS file: gdb/testsuite/gdb.arch/thumb-bx-pc.exp
diff -N gdb/testsuite/gdb.arch/thumb-bx-pc.exp
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ gdb/testsuite/gdb.arch/thumb-bx-pc.exp	13 Aug 2012 13:56:05 -0000
@@ -0,0 +1,41 @@
+# Copyright 2012 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test PC adjustment from Thumb-mode "bx pc" instruction.
+
+if {![istarget arm*-*]} then {
+    verbose "Skipping ARM tests."
+    return
+}
+
+set testfile "thumb-bx-pc"
+set srcfile ${testfile}.S
+set opts {}
+
+if [prepare_for_testing ${testfile}.exp ${testfile} ${srcfile} $opts] {
+    untested ${testfile}.exp
+    return -1
+}
+
+if ![runto_main] then {
+    untested ${testfile}.exp
+    return -1
+}
+
+gdb_test "stepi" "0x\[0-9a-fA-F\]+ in main \\(\\)" "stepi for bx pc"
+
+gdb_test "x /i \$pc" \
+    "0x\[0-9a-fA-F\]+ <main\\+4>:\[ \t\]+mov\[ \t\]+r0,\[ \t\]+#0.*" \
+    "stepi reached correct instruction"

-- 
Joseph S. Myers
joseph@codesourcery.com