Re: [RFA] ARM BE8 support

["Doug Evans" <dje at google dot com>]

Just bite the bullet and add address spaces.
1/2 :-)

On Mon, Aug 4, 2008 at 8:10 AM, Stan Shebs <stan@codesourcery.com> wrote:
> ARM's BE8 format introduces yet another amusing variation on endianness, in
> which the data is big-endian while the code is little-endian. The bits for
> binutils went in a while ago, this patch extends GDB. In theory, we should
> change functions like read_memory_unsigned_integer to have forms for both
> code and data; in lieu of such a sweeping change for what is rather a narrow
> use, I introduced macros to swap instruction bytes after reading.
> Fortunately, GDB doesn't often need to examine instructions! This was tested
> by passing --be8 to the linker and running under a hacked qemu simulator, no
> hardware being available yet.
>
> Review-wise, Richard Earnshaw is listed as ARM maintainer, not sure if he's
> active here?
>
> 2008-08-04  Stan Shebs  <stan@codesourcery.com>
>
>   ARM BE8 support.
>   * disasm.c (gdb_disassemble_info): Set endian_code.
>   * gdbarch.sh (gdbarch_info): New field byte_order_for_code.
>   * gdbarch.h, gdbarch.c: Regenerate.
>   * arch-utils.c (initialize_current_architecture): Set the
>   default byte_order_for_code.
>   (gdbarch_info_init): Ditto.
>   (gdbarch_info_fill): Ditto.
>   * arm-tdep.c (SWAP_INT, SWAP_SHORT): New macros.
>   (thumb_analyze_prologue): Swap halfword if code endianness is
>   different from general endianness.
>   (arm_skip_prologue): Similarly.
>   (arm_scan_prologue): Ditto.
>   (thumb_get_next_pc): Ditto.
>   (arm_get_next_pc): Ditto.
>   (arm_gdbarch_init): Set byte_order_for_code from BE8 flag,
>   choose correct endianness for breakpoints.
>
>
>
>
> Index: arch-utils.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/arch-utils.c,v
> retrieving revision 1.169
> diff -u -p -r1.169 arch-utils.c
> --- arch-utils.c        4 May 2008 15:21:05 -0000       1.169
> +++ arch-utils.c        4 Aug 2008 00:37:56 -0000
> @@ -629,6 +629,7 @@ initialize_current_architecture (void)
>     }
>
>   info.byte_order = default_byte_order;
> +  info.byte_order_for_code = info.byte_order;
>
>   if (! gdbarch_update_p (info))
>     internal_error (__FILE__, __LINE__,
> @@ -667,6 +668,7 @@ gdbarch_info_init (struct gdbarch_info *
>  {
>   memset (info, 0, sizeof (struct gdbarch_info));
>   info->byte_order = BFD_ENDIAN_UNKNOWN;
> +  info->byte_order_for_code = info->byte_order;
>   info->osabi = GDB_OSABI_UNINITIALIZED;
>  }
>
> @@ -708,6 +710,7 @@ gdbarch_info_fill (struct gdbarch_info *
>   /* From the default.  */
>   if (info->byte_order == BFD_ENDIAN_UNKNOWN)
>     info->byte_order = default_byte_order;
> +  info->byte_order_for_code = info->byte_order;
>
>   /* "(gdb) set osabi ...".  Handled by gdbarch_lookup_osabi.  */
>   if (info->osabi == GDB_OSABI_UNINITIALIZED)
> Index: arm-tdep.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/arm-tdep.c,v
> retrieving revision 1.266
> diff -u -p -r1.266 arm-tdep.c
> --- arm-tdep.c  19 May 2008 15:50:09 -0000      1.266
> +++ arm-tdep.c  4 Aug 2008 00:37:57 -0000
> @@ -69,6 +69,19 @@ static int arm_debug;
>  #define MSYMBOL_IS_SPECIAL(msym)                               \
>        (((long) MSYMBOL_INFO (msym) & 0x80000000) != 0)
>
> +/* Macros for swapping shorts and ints. In the unlikely case that anybody
> else needs these,
> +   move to a general header. (A better solution might be to define memory
> read routines that
> +   know whether they are reading code or data.)  */
> +
> +#define SWAP_SHORT(x) \
> +  ((((x) & 0xff00) >> 8) | (((x) & 0x00ff) << 8));
> +
> +#define SWAP_INT(x) \
> +  (  ((x & 0xff000000) >> 24) \
> +   | ((x & 0x00ff0000) >> 8)  \
> +   | ((x & 0x0000ff00) << 8)  \
> +   | ((x & 0x000000ff) << 24))
> +
>  /* Per-objfile data used for mapping symbols.  */
>  static const struct objfile_data *arm_objfile_data_key;
>
> @@ -391,6 +404,9 @@ thumb_analyze_prologue (struct gdbarch *
>
>       insn = read_memory_unsigned_integer (start, 2);
>
> +      if (gdbarch_byte_order_for_code (gdbarch) != gdbarch_byte_order
> (gdbarch))
> +       insn = SWAP_SHORT (insn);
> +
>       if ((insn & 0xfe00) == 0xb400)           /* push { rlist } */
>        {
>          int regno;
> @@ -559,6 +575,9 @@ arm_skip_prologue (struct gdbarch *gdbar
>     {
>       inst = read_memory_unsigned_integer (skip_pc, 4);
>
> +      if (gdbarch_byte_order_for_code (gdbarch) != gdbarch_byte_order
> (gdbarch))
> +       inst = SWAP_INT (inst);
> +
>       /* "mov ip, sp" is no longer a required part of the prologue.  */
>       if (inst == 0xe1a0c00d)                  /* mov ip, sp */
>        continue;
> @@ -855,6 +874,9 @@ arm_scan_prologue (struct frame_info *th
>     {
>       unsigned int insn = read_memory_unsigned_integer (current_pc, 4);
>
> +      if (gdbarch_byte_order_for_code (gdbarch) != gdbarch_byte_order
> (gdbarch))
> +       insn = SWAP_INT (insn);
> +
>       if (insn == 0xe1a0c00d)          /* mov ip, sp */
>        {
>          regs[ARM_IP_REGNUM] = regs[ARM_SP_REGNUM];
> @@ -1812,6 +1834,9 @@ thumb_get_next_pc (struct frame_info *fr
>   CORE_ADDR nextpc = pc + 2;           /* default is next instruction */
>   unsigned long offset;
>
> +  if (gdbarch_byte_order_for_code (gdbarch) != gdbarch_byte_order
> (gdbarch))
> +    inst1 = SWAP_SHORT (inst1);
> +
>   if ((inst1 & 0xff00) == 0xbd00)      /* pop {rlist, pc} */
>     {
>       CORE_ADDR sp;
> @@ -1839,6 +1864,8 @@ thumb_get_next_pc (struct frame_info *fr
>   else if ((inst1 & 0xf800) == 0xf000) /* long branch with link, and blx */
>     {
>       unsigned short inst2 = read_memory_unsigned_integer (pc + 2, 2);
> +      if (gdbarch_byte_order_for_code (gdbarch) != gdbarch_byte_order
> (gdbarch))
> +       inst2 = SWAP_SHORT (inst2);
>       offset = (sbits (inst1, 0, 10) << 12) + (bits (inst2, 0, 10) << 1);
>       nextpc = pc_val + offset;
>       /* For BLX make sure to clear the low bits.  */
> @@ -1874,6 +1901,10 @@ arm_get_next_pc (struct frame_info *fram
>
>   pc_val = (unsigned long) pc;
>   this_instr = read_memory_unsigned_integer (pc, 4);
> +
> +  if (gdbarch_byte_order_for_code (gdbarch) != gdbarch_byte_order
> (gdbarch))
> +    this_instr = SWAP_INT (this_instr);
> +
>   status = get_frame_register_unsigned (frame, ARM_PS_REGNUM);
>   nextpc = (CORE_ADDR) (pc_val + 4);   /* Default case */
>
> @@ -3150,6 +3181,10 @@ arm_gdbarch_init (struct gdbarch_info in
>                  break;
>                }
>            }
> +
> +         if (e_flags & EF_ARM_BE8)
> +           info.byte_order_for_code = BFD_ENDIAN_LITTLE;
> +
>          break;
>
>        default:
> @@ -3192,7 +3227,7 @@ arm_gdbarch_init (struct gdbarch_info in
>   tdep->have_fpa_registers = have_fpa_registers;
>
>   /* Breakpoints.  */
> -  switch (info.byte_order)
> +  switch (info.byte_order_for_code)
>     {
>     case BFD_ENDIAN_BIG:
>       tdep->arm_breakpoint = arm_default_arm_be_breakpoint;
> Index: disasm.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/disasm.c,v
> retrieving revision 1.27
> diff -u -p -r1.27 disasm.c
> --- disasm.c    1 Jan 2008 22:53:09 -0000       1.27
> +++ disasm.c    4 Aug 2008 00:37:57 -0000
> @@ -343,6 +343,7 @@ gdb_disassemble_info (struct gdbarch *gd
>   di.arch = gdbarch_bfd_arch_info (gdbarch)->arch;
>   di.mach = gdbarch_bfd_arch_info (gdbarch)->mach;
>   di.endian = gdbarch_byte_order (gdbarch);
> +  di.endian_code = gdbarch_byte_order_for_code (gdbarch);
>   disassemble_init_for_target (&di);
>   return di;
>  }
> Index: gdbarch.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/gdbarch.c,v
> retrieving revision 1.431
> diff -u -p -r1.431 gdbarch.c
> --- gdbarch.c   25 Jul 2008 16:12:03 -0000      1.431
> +++ gdbarch.c   4 Aug 2008 00:37:57 -0000
> @@ -90,6 +90,7 @@ struct gdbarch
>   /* basic architectural information */
>   const struct bfd_arch_info * bfd_arch_info;
>   int byte_order;
> +  int byte_order_for_code;
>   enum gdb_osabi osabi;
>   const struct target_desc * target_desc;
>
> @@ -254,6 +255,7 @@ struct gdbarch startup_gdbarch =
>   /* basic architecture information */
>   &bfd_default_arch_struct,  /* bfd_arch_info */
>   BFD_ENDIAN_BIG,  /* byte_order */
> +  BFD_ENDIAN_BIG,  /* byte_order_for_code */
>   GDB_OSABI_UNKNOWN,  /* osabi */
>   0,  /* target_desc */
>   /* target specific vector and its dump routine */
> @@ -398,6 +400,7 @@ gdbarch_alloc (const struct gdbarch_info
>
>   gdbarch->bfd_arch_info = info->bfd_arch_info;
>   gdbarch->byte_order = info->byte_order;
> +  gdbarch->byte_order_for_code = info->byte_order_for_code;
>   gdbarch->osabi = info->osabi;
>   gdbarch->target_desc = info->target_desc;
>
> @@ -693,6 +696,9 @@ gdbarch_dump (struct gdbarch *gdbarch, s
>                       "gdbarch_dump: byte_order = %s\n",
>                       paddr_d (gdbarch->byte_order));
>   fprintf_unfiltered (file,
> +                      "gdbarch_dump: byte_order_for_code = %s\n",
> +                      paddr_d (gdbarch->byte_order_for_code));
> +  fprintf_unfiltered (file,
>                       "gdbarch_dump: call_dummy_location = %s\n",
>                       paddr_d (gdbarch->call_dummy_location));
>   fprintf_unfiltered (file,
> @@ -1122,6 +1128,15 @@ gdbarch_byte_order (struct gdbarch *gdba
>   return gdbarch->byte_order;
>  }
>
> +int
> +gdbarch_byte_order_for_code (struct gdbarch *gdbarch)
> +{
> +  gdb_assert (gdbarch != NULL);
> +  if (gdbarch_debug >= 2)
> +    fprintf_unfiltered (gdb_stdlog, "gdbarch_byte_order_for_code
> called\n");
> +  return gdbarch->byte_order_for_code;
> +}
> +
>  enum gdb_osabi
>  gdbarch_osabi (struct gdbarch *gdbarch)
>  {
> Index: gdbarch.h
> ===================================================================
> RCS file: /cvs/src/src/gdb/gdbarch.h,v
> retrieving revision 1.385
> diff -u -p -r1.385 gdbarch.h
> --- gdbarch.h   22 Jul 2008 02:10:13 -0000      1.385
> +++ gdbarch.h   4 Aug 2008 00:37:58 -0000
> @@ -64,6 +64,9 @@ extern const struct bfd_arch_info * gdba
>  extern int gdbarch_byte_order (struct gdbarch *gdbarch);
>  /* set_gdbarch_byte_order() - not applicable - pre-initialized. */
>
> +extern int gdbarch_byte_order_for_code (struct gdbarch *gdbarch);
> +/* set_gdbarch_byte_order_for_code() - not applicable - pre-initialized. */
> +
>  extern enum gdb_osabi gdbarch_osabi (struct gdbarch *gdbarch);
>  /* set_gdbarch_osabi() - not applicable - pre-initialized. */
>
> @@ -885,6 +888,8 @@ struct gdbarch_info
>   /* Use default: BFD_ENDIAN_UNKNOWN (NB: is not ZERO).  */
>   int byte_order;
>
> +  int byte_order_for_code;
> +
>   /* Use default: NULL (ZERO). */
>   bfd *abfd;
>
> Index: gdbarch.sh
> ===================================================================
> RCS file: /cvs/src/src/gdb/gdbarch.sh,v
> retrieving revision 1.472
> diff -u -p -r1.472 gdbarch.sh
> --- gdbarch.sh  25 Jul 2008 16:12:03 -0000      1.472
> +++ gdbarch.sh  4 Aug 2008 00:37:58 -0000
> @@ -339,6 +339,7 @@ function_list ()
>  i:const struct bfd_arch_info
> *:bfd_arch_info:::&bfd_default_arch_struct::::gdbarch_bfd_arch_info
> (gdbarch)->printable_name
>  #
>  i:int:byte_order:::BFD_ENDIAN_BIG
> +i:int:byte_order_for_code:::BFD_ENDIAN_BIG
>  #
>  i:enum gdb_osabi:osabi:::GDB_OSABI_UNKNOWN
>  #
> @@ -962,6 +963,8 @@ struct gdbarch_info
>   /* Use default: BFD_ENDIAN_UNKNOWN (NB: is not ZERO).  */
>   int byte_order;
>
> +  int byte_order_for_code;
> +
>   /* Use default: NULL (ZERO). */
>   bfd *abfd;
>
>
>