Re: [RFA] ARM BE8 support

[Stan Shebs <stan@codesourcery.com>]

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!

Stan

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