2011-02-15 Yao Qi <yao@codesourcery.com>

	PR tdep/12352
	* arm-tdep.c (copy_ldr_str_ldrb_strb): Replace PC with SP in
	order to store PC value on stack instead of text section.

2011-02-15  Yao Qi  <yao@codesourcery.com>

	PR tdep/12352
	* gdb.arch/arm-disp-step.S : New test for str instruction.
	* gdb.arch/arm-disp-step.exp : Likewise

5 files changed, 104 insertions, 11 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 10d816f..a02e058 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2011-02-15  Yao Qi  <yao@codesourcery.com>
+
+	PR tdep/12352
+	* arm-tdep.c (copy_ldr_str_ldrb_strb): Replace PC with SP in
+	order to store PC value on stack instead of text section.
+
 2011-02-15  Thiago Jung Bauermann  <bauerman@br.ibm.com>
 
 	* rs6000-tdep.c (IS_EFP_PSEUDOREG): Use correct constant for
diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index 9dfbf49..6a279d1 100644
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -5930,16 +5930,24 @@ copy_ldr_str_ldrb_strb (struct gdbarch *gdbarch, uint32_t insn,
 
   /* To write PC we can do:
 
-     scratch+0:  str pc, temp  (*temp = scratch + 8 + offset)
-     scratch+4:  ldr r4, temp
-     scratch+8:  sub r4, r4, pc  (r4 = scratch + 8 + offset - scratch - 8 - 8)
-     scratch+12: add r4, r4, #8  (r4 = offset)
-     scratch+16: add r0, r0, r4
-     scratch+20: str r0, [r2, #imm] (or str r0, [r2, r3])
-     scratch+24: <temp>
+     Before this sequence of instructions:
+     r0 is the PC value got from displaced_read_reg, so r0 = from + 8;
+     r2 is the Rn value got from dispalced_read_reg.
+
+     Insn1: push {pc} Write address of STR instruction + offset on stack
+     Insn2: pop  {r4} Read it back from stack, r4 = addr(Insn1) + offset
+     Insn3: sub r4, r4, pc   r4 = addr(Insn1) + offset - pc
+                                = addr(Insn1) + offset - addr(Insn3) - 8
+                                = offset - 16
+     Insn4: add r4, r4, #8   r4 = offset - 8
+     Insn5: add r0, r0, r4   r0 = from + 8 + offset - 8
+                                = from + offset
+     Insn6: str r0, [r2, #imm] (or str r0, [r2, r3])
 
      Otherwise we don't know what value to write for PC, since the offset is
-     architecture-dependent (sometimes PC+8, sometimes PC+12).  */
+     architecture-dependent (sometimes PC+8, sometimes PC+12).  More details
+     of this can be found in Section "Saving from r15" in
+     http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0204g/Cihbjifh.html */
 
   if (load || rt != 15)
     {
@@ -5960,9 +5968,8 @@ copy_ldr_str_ldrb_strb (struct gdbarch *gdbarch, uint32_t insn,
     {
       /* We need to use r4 as scratch.  Make sure it's restored afterwards.  */
       dsc->u.ldst.restore_r4 = 1;
-
-      dsc->modinsn[0] = 0xe58ff014;  /* str pc, [pc, #20].  */
-      dsc->modinsn[1] = 0xe59f4010;  /* ldr r4, [pc, #16].  */
+      dsc->modinsn[0] = 0xe92d8000;  /* push {pc} */
+      dsc->modinsn[1] = 0xe8bd0010;  /* pop  {r4} */
       dsc->modinsn[2] = 0xe044400f;  /* sub r4, r4, pc.  */
       dsc->modinsn[3] = 0xe2844008;  /* add r4, r4, #8.  */
       dsc->modinsn[4] = 0xe0800004;  /* add r0, r0, r4.  */
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 2ce11ab..7b26a01 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2011-02-15  Yao Qi  <yao@codesourcery.com>
+
+	PR tdep/12352
+	* gdb.arch/arm-disp-step.S : New test for str instruction.
+	* gdb.arch/arm-disp-step.exp : Likewise.
+
 2011-02-15  Thiago Jung Bauermann  <bauerman@br.ibm.com>
 
 	* gdb.arch/vsx-regs.exp: Add "vector_register1_vr" and
diff --git a/gdb/testsuite/gdb.arch/arm-disp-step.S b/gdb/testsuite/gdb.arch/arm-disp-step.S
index e1756e7..fb76974 100644
--- a/gdb/testsuite/gdb.arch/arm-disp-step.S
+++ b/gdb/testsuite/gdb.arch/arm-disp-step.S
@@ -48,6 +48,10 @@ test_ret_end:
 	bl test_ldm_stm_pc
 #endif
 
+	/* Test str in ARM mode and Thumb-2 */
+#if !defined(__thumb__)
+	bl test_str_pc
+#endif
 	/* Return */
 	mov     sp, r7
 	sub     sp, sp, #4
@@ -118,3 +122,36 @@ test_ldm_stm_pc_ret:
 	.word	test_ldm_stm_pc_ret
 	.size test_ldm_stm_pc, .-test_ldm_stm_pc
 #endif
+
+#if !defined(__thumb__)
+#if defined (__thumb2__)
+	.code   16
+	.thumb_func
+#endif
+	.global test_str_pc
+	.type test_str_pc, %function
+test_str_pc:
+	str     pc, [sp, #-4]
+	ldr	r0, [sp, #-4]
+	sub	r0, r0, pc
+	/* compute offset again without displaced stepping.  */
+	str     pc, [sp, #-4]
+	ldr	r1, [sp, #-4]
+	sub	r1, r1, pc
+
+	/* r0 should be equal to r1.  */
+	cmp	r0, r1
+	bne	pc_offset_wrong
+
+	.global pc_offset_right
+pc_offset_right:
+	b	test_str_pc_end
+
+	.global pc_offset_wrong
+pc_offset_wrong:
+	nop
+
+	.global test_str_pc_end
+test_str_pc_end:
+	bx lr
+#endif
diff --git a/gdb/testsuite/gdb.arch/arm-disp-step.exp b/gdb/testsuite/gdb.arch/arm-disp-step.exp
index 841bfce..3bea521 100644
--- a/gdb/testsuite/gdb.arch/arm-disp-step.exp
+++ b/gdb/testsuite/gdb.arch/arm-disp-step.exp
@@ -126,6 +126,42 @@ proc test_ldr_from_pc {} {
 	".*bx lr.*"
 }
 
+###########################################
+
+proc test_str_pc {} {
+    global srcfile
+    gdb_test_multiple "break *test_str_pc" "break test_str_pc" {
+	-re "Breakpoint.*at.* file .*$srcfile, line.*" {
+	    pass "break test_str_pc"
+	}
+	-re "No symbol.*" {
+	    pass "break test_str_pc"
+	    return
+	}
+    }
+    gdb_test "break *test_str_pc_end" \
+	"Breakpoint.*at.* file .*$srcfile, line.*" \
+	"break test_str_pc_end"
+
+    # Set breakpoint on both lables pc_offset_right and pc_offset_wrong
+    gdb_test "break *pc_offset_right" \
+	"Breakpoint.*at.* file .*$srcfile, line.*" \
+	"break pc_offset_right"
+    gdb_test "break *pc_offset_wrong" \
+	"Breakpoint.*at.* file .*$srcfile, line.*" \
+	"break pc_offset_wrong"
+
+    gdb_continue_to_breakpoint "continue to test_str_pc" \
+	".*str.*pc\,.*\[sp, #-4\].*"
+    # If breakpoint on lable pc_offset_wrong is hit, that means the offset
+    # computed in displaced stepping is different from offset computed
+    # without displaced stepping.  Report a failure.
+    gdb_continue_to_breakpoint "continue to pc_offset_right" \
+	".*b.*test_str_pc_end.*"
+    gdb_continue_to_breakpoint "continue to test_str_pc_end" \
+	".*bx lr.*"
+}
+
 # Get things started.
 
 clean_restart ${testfile}
@@ -165,6 +201,7 @@ test_ldr_from_pc
 
 test_ldm_stm_pc
 
+test_str_pc
 ##########################################
 
 # Done, run program to exit.