Re: [RFA] ARM BE8 support

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

On Mon, Aug 4, 2008 at 10:43 AM, Stan Shebs <stan@codesourcery.com> wrote:
> Doug Evans wrote:
>>
>> Just bite the bullet and add address spaces.
>> 1/2 :-)
>>
>>
>
> Heh, although in this case address spaces probably can't help; on ARM code
> and data can easily be mixed down to a per-word level by using the $a etc
> symbols. Having two "address spaces" with exactly matching ranges might be
> made to work - but that solution seems more horrible than the problem it is
> solving!

I was just kibitzing, but for reference sake since you mention it,
there are targets (x86 even) where there is a range of addresses where
it matters whether you are doing an instruction fetch or a "normal"
memory read, and the answer you get back depends on what kind of
memory read you are doing.  I forget the details, but the APIC rings a
bell.  A colleague tells me SMRAM has a similar property.


>> 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;
>>>
>>>
>>>
>>>
>>
>>
>
>