Re: [PATCH]: Handle sparc skipping unimp instruction with dwarf2

["Mark Kettenis" <mark dot kettenis at xs4all dot nl>]

>
>  This is a followon to my previous posting entitled:
>
>  [PATCH]: Setup sparc32 to support dwarf2 unwind sniffer
>
>  and this patch is relative to that one.
>
>  If you actually enable the dwarf2 unwind sniffer on sparc 32-bit
>  you'll hit a bunch of regressions in gdb.base/struct.exp, and
>  the reason is simple.  The dwarf2 unwinder doesn't know about the
>  convention where we should skip the caller's unimp instruction
>  when returning from a function that returns a structure.

Oh, it's coming back to me now.  That was another reason why I didn't
bother with the dwarf2 unwinder on 32-bit sparc yet.  Guess you don't
want to enable the dwarf2 unwinder for 32-bit Linux just yet ;-).

>  This is very easy to fix with just a little bit of infrastructure
>  adjustments.  What we do is we pass in the fs->pc to the dwarf2 reg
>  init function.  We use this PC to find out if the function we are
>  analyzing returns a struct or not.  If so, we adjust the PC and NPC
>  by 4.

Rather than passing the PC, I think you should actually pass down
NEXT_FRAME.  Other targets might have different requirements, and you
can unwind the PC from NEXT_FRAME in the sparc code.

Oh, and could you rename sparc32_dwarf2_struct_return_p() to
sparc32_struct_return_p() and make sparc32_frame_cache() use that function
too?  The check isn't really dwarf2-specific and duplication of code
is bad!

Thanks,

Mark

>  2006-04-04  David S. Miller  <davem@sunset.davemloft.net>
>
>  	* dwarf2-frame.c (dwarf2_frame_ops init_reg): Add CORE_ADDR "pc"
>  	argument.
>  	(dwarf2_frame_default_init_reg): Likewise.
>  	(dwarf2_frame_set_init_reg): Update init_reg arg.
>  	(dwarf2_frame_init_reg): Take "pc" and pass it to ops->init_reg().
>  	(dwarf2_frame_cache): Pass fs->pc to dwarf2_frame_init_reg.
>  	* dwarf2-frame.h (dwarf2-frame_set_init_reg): Update declaration.
>  	* cris-tdep.c (cris_dwarf2_frame_init_reg): Add "pc" argument.
>  	* s390-tdep.c (s390_dwarf2_frame_init_reg): Likewise.
>  	* sh-tdep.c (sh_dwarf2_frame_init_reg): Likewise.
>  	* sparc64-tdep.c (sparc64_dwarf2_frame_init_reg): Likewise.
>  	* sparc-tdep.c (sparc_dwarf2_frame_init_reg): Likewise, and use
>  	it to determine if the function returns a structure and thus we
>  	have to indicate the return PC and NPC are 4 bytes later than
>  	usual.
>
>  --- dwarf2-frame.h.~1~	2006-02-25 15:04:58.000000000 -0800
>  +++ dwarf2-frame.h	2006-04-04 21:35:50.000000000 -0700
>  @@ -79,7 +79,8 @@ struct dwarf2_frame_state_reg
>
>   extern void dwarf2_frame_set_init_reg (struct gdbarch *gdbarch,
>   				       void (*init_reg) (struct gdbarch *, int,
>  -					     struct dwarf2_frame_state_reg *));
>  +					     struct dwarf2_frame_state_reg *,
>  +					     CORE_ADDR));
>
>   /* Set the architecture-specific signal trampoline recognition
>      function for GDBARCH to SIGNAL_FRAME_P.  */
>  --- dwarf2-frame.c.~1~	2006-02-25 15:04:58.000000000 -0800
>  +++ dwarf2-frame.c	2006-04-04 21:36:40.000000000 -0700
>  @@ -506,7 +506,8 @@ static struct gdbarch_data *dwarf2_frame
>   struct dwarf2_frame_ops
>   {
>     /* Pre-initialize the register state REG for register REGNUM.  */
>  -  void (*init_reg) (struct gdbarch *, int, struct dwarf2_frame_state_reg
>  *);
>  +  void (*init_reg) (struct gdbarch *, int, struct dwarf2_frame_state_reg
>  *,
>  +		    CORE_ADDR);
>
>     /* Check whether the frame preceding NEXT_FRAME will be a signal
>        trampoline.  */
>  @@ -518,7 +519,8 @@ struct dwarf2_frame_ops
>
>   static void
>   dwarf2_frame_default_init_reg (struct gdbarch *gdbarch, int regnum,
>  -			       struct dwarf2_frame_state_reg *reg)
>  +			       struct dwarf2_frame_state_reg *reg,
>  +			       CORE_ADDR pc)
>   {
>     /* If we have a register that acts as a program counter, mark it as
>        a destination for the return address.  If we have a register that
>  @@ -570,7 +572,8 @@ dwarf2_frame_init (struct obstack *obsta
>   void
>   dwarf2_frame_set_init_reg (struct gdbarch *gdbarch,
>   			   void (*init_reg) (struct gdbarch *, int,
>  -					     struct dwarf2_frame_state_reg *))
>  +					     struct dwarf2_frame_state_reg *,
>  +					     CORE_ADDR))
>   {
>     struct dwarf2_frame_ops *ops = gdbarch_data (gdbarch,
>  dwarf2_frame_data);
>
>  @@ -581,11 +584,12 @@ dwarf2_frame_set_init_reg (struct gdbarc
>
>   static void
>   dwarf2_frame_init_reg (struct gdbarch *gdbarch, int regnum,
>  -		       struct dwarf2_frame_state_reg *reg)
>  +		       struct dwarf2_frame_state_reg *reg,
>  +		       CORE_ADDR pc)
>   {
>     struct dwarf2_frame_ops *ops = gdbarch_data (gdbarch,
>  dwarf2_frame_data);
>
>  -  ops->init_reg (gdbarch, regnum, reg);
>  +  ops->init_reg (gdbarch, regnum, reg, pc);
>   }
>
>   /* Set the architecture-specific signal trampoline recognition
>  @@ -713,7 +717,7 @@ dwarf2_frame_cache (struct frame_info *n
>       int regnum;
>
>       for (regnum = 0; regnum < num_regs; regnum++)
>  -      dwarf2_frame_init_reg (gdbarch, regnum, &cache->reg[regnum]);
>  +      dwarf2_frame_init_reg (gdbarch, regnum, &cache->reg[regnum],
>  fs->pc);
>     }
>
>     /* Go through the DWARF2 CFI generated table and save its register
>  --- cris-tdep.c.~1~	2006-02-25 15:04:58.000000000 -0800
>  +++ cris-tdep.c	2006-04-04 21:36:50.000000000 -0700
>  @@ -1852,7 +1852,8 @@ cris_dwarf2_reg_to_regnum (int reg)
>
>   static void
>   cris_dwarf2_frame_init_reg (struct gdbarch *gdbarch, int regnum,
>  -                            struct dwarf2_frame_state_reg *reg)
>  +                            struct dwarf2_frame_state_reg *reg,
>  +			    CORE_ADDR pc)
>   {
>     /* The return address column.  */
>     if (regnum == PC_REGNUM)
>  --- s390-tdep.c.~1~	2006-02-25 15:05:02.000000000 -0800
>  +++ s390-tdep.c	2006-04-04 21:36:56.000000000 -0700
>  @@ -2279,7 +2279,8 @@ s390_unwind_sp (struct gdbarch *gdbarch,
>
>   static void
>   s390_dwarf2_frame_init_reg (struct gdbarch *gdbarch, int regnum,
>  -                            struct dwarf2_frame_state_reg *reg)
>  +                            struct dwarf2_frame_state_reg *reg,
>  +			    CORE_ADDR pc)
>   {
>     struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
>
>  --- sh-tdep.c.~1~	2006-04-04 14:52:27.000000000 -0700
>  +++ sh-tdep.c	2006-04-04 21:37:07.000000000 -0700
>  @@ -2123,7 +2123,8 @@ sh_sh2a_register_sim_regno (int nr)
>
>   static void
>   sh_dwarf2_frame_init_reg (struct gdbarch *gdbarch, int regnum,
>  -                          struct dwarf2_frame_state_reg *reg)
>  +                          struct dwarf2_frame_state_reg *reg,
>  +			  CORE_ADDR pc)
>   {
>     /* Mark the PC as the destination for the return address.  */
>     if (regnum == PC_REGNUM)
>  --- sparc64-tdep.c.~1~	2006-02-25 15:05:03.000000000 -0800
>  +++ sparc64-tdep.c	2006-04-04 21:37:16.000000000 -0700
>  @@ -1106,7 +1106,8 @@ sparc64_return_value (struct gdbarch *gd
>
>   static void
>   sparc64_dwarf2_frame_init_reg (struct gdbarch *gdbarch, int regnum,
>  -			       struct dwarf2_frame_state_reg *reg)
>  +			       struct dwarf2_frame_state_reg *reg,
>  +			       CORE_ADDR pc)
>   {
>     switch (regnum)
>       {
>  --- sparc-tdep.c.~2~	2006-04-04 20:19:46.000000000 -0700
>  +++ sparc-tdep.c	2006-04-04 21:35:29.000000000 -0700
>  @@ -995,9 +995,33 @@
>   	  || (sparc_floating_p (type) && TYPE_LENGTH (type) == 16));
>   }
>
>  +static int
>  +sparc32_dwarf2_struct_return_p (CORE_ADDR pc)
>  +{
>  +  struct symbol *sym;
>  +
>  +  sym = find_pc_function (pc);
>  +  if (sym)
>  +    {
>  +      struct type *type = check_typedef (SYMBOL_TYPE (sym));
>  +      enum type_code code = TYPE_CODE (type);
>  +
>  +      if (code == TYPE_CODE_FUNC || code == TYPE_CODE_METHOD)
>  +	{
>  +	  type = check_typedef (TYPE_TARGET_TYPE (type));
>  +	  if (sparc_structure_or_union_p (type)
>  +	      || (sparc_floating_p (type) && TYPE_LENGTH (type) == 16))
>  +	    return 1;
>  +	}
>  +    }
>  +
>  +  return 0;
>  +}
>  +
>   static void
>   sparc32_dwarf2_frame_init_reg (struct gdbarch *gdbarch, int regnum,
>  -			       struct dwarf2_frame_state_reg *reg)
>  +			       struct dwarf2_frame_state_reg *reg,
>  +			       CORE_ADDR pc)
>   {
>     switch (regnum)
>       {
>  @@ -1012,11 +1036,11 @@
>         break;
>       case SPARC32_PC_REGNUM:
>         reg->how = DWARF2_FRAME_REG_RA_OFFSET;
>  -      reg->loc.offset = 8;
>  +      reg->loc.offset = (sparc32_dwarf2_struct_return_p (pc) ? 12 : 8);
>         break;
>       case SPARC32_NPC_REGNUM:
>         reg->how = DWARF2_FRAME_REG_RA_OFFSET;
>  -      reg->loc.offset = 12;
>  +      reg->loc.offset = (sparc32_dwarf2_struct_return_p (pc) ? 16 : 12);
>         break;
>       }
>   }
>