Re: [PATCH]: Setup sparc32 to support dwarf2 unwind sniffer

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

>
>  This doesn't actually enable the sniffer, it just adds the
>  necessary dwarf2_frame_set_init_reg() handler, similar to what
>  sparc64 already has implemented in sparc64-tdep.c
>
>  We can't unilaterally make use of the dwarf2 unwinder on all
>  sparc targets yet, because of the mentioned StackGhost issues
>  mentioned in the comment.
>
>  But after this patch, we can decide to enable dwarf2 unwinding on a
>  per-target basis.  And we can do so right now on targets that do not
>  support StackGhost.  Later if the StackGhost issue is resolved, we
>  can do this for all Sparc targets.
>
>  This is very desirable because many current Sparc bugs are due to
>  the fact that sparc_analyze_prologue() cannot deal at all with clever
>  assembler sequences, for example in cases where the save is deferred
>  to somewhere past the beginning of the function which is also a
>  valid compiler optimization.

Perhaps we should try to address those issues.  I never went through the
trouble of making the sparc and sparc64 prologue analyzers any smarter,
because I never encountered any code that made it fail.  This is probably
because OpenBSD/sparc64 uses GCC 3.3.5 (and OpenBSD/sparc uses an even
older compiler).  If you can post some disaambly of (real-life) prologues
that the current unwinder doesn't handle, I'll happiliy turn them into
testcases and try to improve the analyzer.

>  Ok to apply?

Yes, thanks!

I didn't do this before, because OpenBSD/sparc still uses stabs, so I
had no way to test this.

Don't hesitate to enable the dwarf2 unwinder on Linux.

Marl

>
>  2006-04-04  David S. Miller  <davem@sunset.davemloft.net>
>
>  	* sparc-tdep.c (sparc32_dwarf2_frame_init_reg): New.
>  	(sparc32_gdbarch_init): Pass it to dwarf2_frame_set_init_reg.
>  	* Makefile.in (sparc-tdep.o): Update dependencies.
>
>  --- sparc-tdep.c.~1~	2006-02-25 15:05:03.000000000 -0800
>  +++ sparc-tdep.c	2006-04-04 20:19:46.000000000 -0700
>  @@ -22,6 +22,7 @@
>   #include "defs.h"
>   #include "arch-utils.h"
>   #include "dis-asm.h"
>  +#include "dwarf2-frame.h"
>   #include "floatformat.h"
>   #include "frame.h"
>   #include "frame-base.h"
>  @@ -994,6 +995,32 @@
>   	  || (sparc_floating_p (type) && TYPE_LENGTH (type) == 16));
>   }
>
>  +static void
>  +sparc32_dwarf2_frame_init_reg (struct gdbarch *gdbarch, int regnum,
>  +			       struct dwarf2_frame_state_reg *reg)
>  +{
>  +  switch (regnum)
>  +    {
>  +    case SPARC_G0_REGNUM:
>  +      /* Since %g0 is always zero, there is no point in saving it, and
>  +	 people will be inclined omit it from the CFI.  Make sure we
>  +	 don't warn about that.  */
>  +      reg->how = DWARF2_FRAME_REG_SAME_VALUE;
>  +      break;
>  +    case SPARC_SP_REGNUM:
>  +      reg->how = DWARF2_FRAME_REG_CFA;
>  +      break;
>  +    case SPARC32_PC_REGNUM:
>  +      reg->how = DWARF2_FRAME_REG_RA_OFFSET;
>  +      reg->loc.offset = 8;
>  +      break;
>  +    case SPARC32_NPC_REGNUM:
>  +      reg->how = DWARF2_FRAME_REG_RA_OFFSET;
>  +      reg->loc.offset = 12;
>  +      break;
>  +    }
>  +}
>  +
>   
>   /* The SPARC Architecture doesn't have hardware single-step support,
>      and most operating systems don't implement it either, so we provide
>  @@ -1248,6 +1275,11 @@
>     /* Hook in ABI-specific overrides, if they have been registered.  */
>     gdbarch_init_osabi (info, gdbarch);
>
>  +  /* Hook in the DWARF CFI frame unwinder.  */
>  +  dwarf2_frame_set_init_reg (gdbarch, sparc32_dwarf2_frame_init_reg);
>  +  /* FIXME: kettenis/20050423: Don't enable the unwinder until the
>  +     StackGhost issues have been resolved.  */
>  +
>     frame_unwind_append_sniffer (gdbarch, sparc32_frame_sniffer);
>
>     /* If we have register sets, enable the generic core file support.  */
>  --- Makefile.in.~1~	2006-04-04 15:12:20.000000000 -0700
>  +++ Makefile.in	2006-04-04 20:23:16.000000000 -0700
>  @@ -2666,10 +2666,10 @@
>   	$(sparc_tdep_h) $(solib_svr4_h)
>   sparc-stub.o: sparc-stub.c
>   sparc-tdep.o: sparc-tdep.c $(defs_h) $(arch_utils_h) $(dis_asm_h) \
>  -	$(floatformat_h) $(frame_h) $(frame_base_h) $(frame_unwind_h) \
>  -	$(gdbcore_h) $(gdbtypes_h) $(inferior_h) $(symtab_h) $(objfiles_h) \
>  -	$(osabi_h) $(regcache_h) $(target_h) $(value_h) $(gdb_assert_h) \
>  -	$(gdb_string_h) $(sparc_tdep_h)
>  +	$(dwarf2_frame_h) $(floatformat_h) $(frame_h) $(frame_base_h) \
>  +	$(frame_unwind_h) $(gdbcore_h) $(gdbtypes_h) $(inferior_h) \
>  +	$(symtab_h) $(objfiles_h) $(osabi_h) $(regcache_h) $(target_h) \
>  +	$(value_h) $(gdb_assert_h) $(gdb_string_h) $(sparc_tdep_h)
>   stabsread.o: stabsread.c $(defs_h) $(gdb_string_h) $(bfd_h)
>  $(gdb_obstack_h) \
>   	$(symtab_h) $(gdbtypes_h) $(expression_h) $(symfile_h) $(objfiles_h) \
>   	$(aout_stab_gnu_h) $(libaout_h) $(aout_aout64_h) $(gdb_stabs_h) \
>