Support for accessing arbitrary MIPS stack frames in memory.

* blockframe.c (get_prev_frame_info):  If INIT_FRAME_PC_FIRST is
set, run it before INIT_EXTRA_FRAME_INFO.
* stack.c (frame_info):  If PRINT_EXTRA_FRAME_INFO defined, call it.

* mips-tdep.c (init_extra_frame_info): Only clobber the `frame'
(FP) value in the frame_info struct if it is zero (as from top of
execution stack).
(setup_arbitrary_frame):  Implement FRAME_SPECIFICATION_DYADIC.

* mips-xdep.c (fetch_inferior_registers):  ZERO_REGNUM always
comes back as zero.  So does FP_REGNUM, as a trigger for
init_extra_frame_info.

* tm-mips.h (INIT_FRAME_PC_FIRST):  Kludge, FIXME, defined to get
the program counter set before INIT_EXTRA_FRAME_INFO is run.
(INIT_FRAME_PC):  Defined to null.
(PRINT_EXTRA_FRAME_INFO): print frame pointer location via symtab.
(FRAME_SPECIFICATION_DYADIC):  Ask for two args in frame command.
Briefly explain MIPS stacks in GDB.

3 files changed, 58 insertions, 0 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 1ff89d4..0242843 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,27 @@
+Fri Sep 18 02:07:39 1992  John Gilmore  (gnu@cygnus.com)
+
+	Support for accessing arbitrary MIPS stack frames in memory.
+
+	* blockframe.c (get_prev_frame_info):  If INIT_FRAME_PC_FIRST is
+	set, run it before INIT_EXTRA_FRAME_INFO.
+	* stack.c (frame_info):  If PRINT_EXTRA_FRAME_INFO defined, call it.
+
+	* mips-tdep.c (init_extra_frame_info): Only clobber the `frame'
+	(FP) value in the frame_info struct if it is zero (as from top of
+	execution stack).
+	(setup_arbitrary_frame):  Implement FRAME_SPECIFICATION_DYADIC.
+
+	* mips-xdep.c (fetch_inferior_registers):  ZERO_REGNUM always
+	comes back as zero.  So does FP_REGNUM, as a trigger for
+	init_extra_frame_info.
+
+	* tm-mips.h (INIT_FRAME_PC_FIRST):  Kludge, FIXME, defined to get
+	the program counter set before INIT_EXTRA_FRAME_INFO is run.
+	(INIT_FRAME_PC):  Defined to null.
+	(PRINT_EXTRA_FRAME_INFO): print frame pointer location via symtab.
+	(FRAME_SPECIFICATION_DYADIC):  Ask for two args in frame command.
+	Briefly explain MIPS stacks in GDB.
+
 Thu Sep 17 03:49:59 1992  John Gilmore  (gnu@cygnus.com)
 
 	* copying.awk, copying.c (show_copying_command,
diff --git a/gdb/mips-xdep.c b/gdb/mips-xdep.c
index 6c0e519..e314bf7 100644
--- a/gdb/mips-xdep.c
+++ b/gdb/mips-xdep.c
@@ -81,6 +81,8 @@ store_inferior_registers (regno)
   : regno >= FP0_REGNUM ?	FPR_BASE + (regno - FP0_REGNUM) \
   : 0)
 
+static const char zerobuf[MAX_REGISTER_RAW_SIZE];
+
 /* Get all registers from the inferior */
 
 void
@@ -104,6 +106,10 @@ fetch_inferior_registers (regno)
  	}
       supply_register (regno, buf);
     }
+
+  supply_register (ZERO_REGNUM, zerobuf);
+  /* Frame ptr reg must appear to be 0; it is faked by stack handling code. */
+  supply_register (FP_REGNUM, zerobuf);
 }
 
 /* Store our register values back into the inferior.
diff --git a/gdb/tm-mips.h b/gdb/tm-mips.h
index b8d8016..0604ddb 100644
--- a/gdb/tm-mips.h
+++ b/gdb/tm-mips.h
@@ -318,6 +318,15 @@ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
   (((int*)dummyname)[11] |= (((unsigned long)(fun)) >> 16), \
    ((int*)dummyname)[12] |= (unsigned short)(fun))
 
+/* There's a mess in stack frame creation.  See comments in blockframe.c
+   near reference to INIT_FRAME_PC_FIRST.  */
+
+#define	INIT_FRAME_PC(fromleaf, prev) /* nada */
+
+#define INIT_FRAME_PC_FIRST(fromleaf, prev) \
+  (prev)->pc = ((fromleaf) ? SAVED_PC_AFTER_CALL ((prev)->next) : \
+	      (prev)->next ? FRAME_SAVED_PC ((prev)->next) : read_pc ());
+
 /* Specific information about a procedure.
    This overlays the MIPS's PDR records, 
    mipsread.c (ab)uses this to save memory */
@@ -334,6 +343,25 @@ typedef struct mips_extra_func_info {
 
 #define INIT_EXTRA_FRAME_INFO(fromleaf, fci) init_extra_frame_info(fci)
 
+#define	PRINT_EXTRA_FRAME_INFO(fi) \
+  { \
+    if (fi && fi->proc_desc && fi->proc_desc->pdr.framereg < NUM_REGS) \
+      printf_filtered (" frame pointer is at %s+%d\n", \
+                       reg_names[fi->proc_desc->pdr.framereg], \
+                                 fi->proc_desc->pdr.frameoffset); \
+  }
+
+/* It takes two values to specify a frame (at least!) on the MIPS.  Sigh.
+
+   In fact, at the moment, the *PC* is the primary value that sets up
+   a frame.  The PC is looked up to see what function it's in; symbol
+   information from that function tells us which register is the frame
+   pointer base, and what offset from there is the "virtual frame pointer".
+   (This is usually an offset from SP.)  FIXME -- this should be cleaned
+   up so that the primary value is the SP, and the PC is used to disambiguate
+   multiple functions with the same SP that are at different stack levels. */
+#define	FRAME_SPECIFICATION_DYADIC
+
 #define STAB_REG_TO_REGNUM(num) ((num) < 32 ? (num) : (num)+FP0_REGNUM-32)
 
 /* Size of elements in jmpbuf */