Re: [RFA 1/2] mips: Switch inferior function calls to ON_STACK method.

["Maciej W. Rozycki" <macro@codesourcery.com>]

On Mon, 14 May 2012, Maciej W. Rozycki wrote:

>  I've lost track, sorry, however here is the promised update I will 
> include with the microMIPS change.  I used a local variable to hold the 
> address of the breakpoint slot after all lest the result be horrible.  No 
> regressions on mips-sde-elf or mips-linux-gnu, checked the usual set of 
> standard MIPS, MIPS16 and microMIPS multilibs.

 Hmm, I intended to fold this update into the original microMIPS change 
before committing, but somehow I did not.  I have checked it now instead.

2012-06-11  Maciej W. Rozycki  <macro@codesourcery.com>

	gdb/
	* mips-tdep.c (mips_push_dummy_code): Handle microMIPS code.

  Maciej

gdb-micromips-on-stack.diff
Index: gdb-fsf-trunk-quilt/gdb/mips-tdep.c
===================================================================
--- gdb-fsf-trunk-quilt.orig/gdb/mips-tdep.c	2012-05-12 21:21:38.000000000 +0100
+++ gdb-fsf-trunk-quilt/gdb/mips-tdep.c	2012-05-12 22:45:37.355619042 +0100
@@ -4198,11 +4198,18 @@ mips_push_dummy_code (struct gdbarch *gd
 		      CORE_ADDR *real_pc, CORE_ADDR *bp_addr,
 		      struct regcache *regcache)
 {
-  CORE_ADDR nop_addr;
   static gdb_byte nop_insn[] = { 0, 0, 0, 0 };
+  CORE_ADDR nop_addr;
+  CORE_ADDR bp_slot;
 
   /* Reserve enough room on the stack for our breakpoint instruction.  */
-  *bp_addr = sp - sizeof (nop_insn);
+  bp_slot = sp - sizeof (nop_insn);
+
+  /* Return to microMIPS mode if calling microMIPS code to avoid
+     triggering an address error exception on processors that only
+     support microMIPS execution.  */
+  *bp_addr = (mips_pc_is_micromips (gdbarch, funaddr)
+	      ? make_compact_addr (bp_slot) : bp_slot);
 
   /* The breakpoint layer automatically adjusts the address of
      breakpoints inserted in a branch delay slot.  With enough
@@ -4211,7 +4218,7 @@ mips_push_dummy_code (struct gdbarch *gd
      trigger the adjustement, and break the function call entirely.
      So, we reserve those 4 bytes and write a nop instruction
      to prevent that from happening.  */
-  nop_addr = *bp_addr - sizeof (nop_insn);
+  nop_addr = bp_slot - sizeof (nop_insn);
   write_memory (nop_addr, nop_insn, sizeof (nop_insn));
   sp = mips_frame_align (gdbarch, nop_addr);