[rfa/arm] Handle bx and blx

Daniel Jacobowitz
2004-02-28T18:35:09Z

The software single-step implementation in GDB doesn't know either BX or
BLX. This results in losing control of the inferior when we single-step
over them. I based this on the ARM ARM, so I'm pretty sure I've got the
numbers correct.

OK to check in?

--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer

2004-02-28 Daniel Jacobowitz <drow@mvista.com>

* arm-tdep.c (thumb_get_next_pc): Handle BX.
(arm_get_next_pc): Handle BX and BLX.

Index: gdb/arm-tdep.c
===================================================================
RCS file: /big/fsf/rsync/src-cvs/src/gdb/arm-tdep.c,v
retrieving revision 1.164
diff -u -p -r1.164 arm-tdep.c
--- gdb/arm-tdep.c 16 Feb 2004 21:49:21 -0000 1.164
+++ gdb/arm-tdep.c 28 Feb 2004 03:37:18 -0000
@@ -1657,6 +1658,17 @@ thumb_get_next_pc (CORE_ADDR pc)
offset = (sbits (inst1, 0, 10) << 12) + (bits (inst2, 0, 10) << 1);
nextpc = pc_val + offset;
}
+ else if ((inst1 & 0xff80) == 0x4700) /* branch and exchange (bx) */
+ {
+ if (bits (inst1, 3, 6) == 0x0f)
+ nextpc = pc_val;
+ else
+ nextpc = read_register (bits (inst1, 3, 6));
+
+ nextpc = ADDR_BITS_REMOVE (nextpc);
+ if (nextpc == pc)
+ error ("Infinite loop detected");
+ }

return nextpc;
}
@@ -1697,6 +1709,20 @@ arm_get_next_pc (CORE_ADDR pc)
&& bits (this_instr, 4, 7) == 9) /* multiply */
error ("Illegal update to pc in instruction");

+ /* BX <reg>, BLX <reg> */
+ if (bits (this_instr, 4, 28) == 0x12fff1
+ || bits (this_instr, 4, 28) == 0x12fff3)
+ {
+ rn = bits (this_instr, 0, 3);
+ result = (rn == 15) ? pc_val + 8 : read_register (rn);
+ nextpc = (CORE_ADDR) ADDR_BITS_REMOVE (result);
+
+ if (nextpc == pc)
+ error ("Infinite loop detected");
+
+ return nextpc;
+ }
+
/* Multiply into PC */
c = (status & FLAG_C) ? 1 : 0;
rn = bits (this_instr, 16, 19);
@@ -1862,6 +1888,10 @@ arm_get_next_pc (CORE_ADDR pc)
{
nextpc = BranchDest (pc, this_instr);

+ /* BLX */
+ if (bits (this_instr, 28, 31) == INST_NV)
+ nextpc |= bit (this_instr, 24) << 1;
+
nextpc = ADDR_BITS_REMOVE (nextpc);
if (nextpc == pc)
error ("Infinite loop detected");