Re: [RFA/commit] Port GDB to powerpc-lynx178.

[Yao Qi <yao@codesourcery.com>]

On 12/18/2012 01:18 AM, Joel Brobecker wrote:
> diff --git a/gdb/rs6000-lynx178-tdep.c b/gdb/rs6000-lynx178-tdep.c
> new file mode 100644
> index 0000000..21d6d84
> --- /dev/null
> +++ b/gdb/rs6000-lynx178-tdep.c
> @@ -0,0 +1,420 @@
> +/* Copyright (C) 2006-2012 Free Software Foundation, Inc.
> +
> +   This file is part of GDB.
> +
> +   This program is free software; you can redistribute it and/or modify
> +   it under the terms of the GNU General Public License as published by
> +   the Free Software Foundation; either version 3 of the License, or
> +   (at your option) any later version.
> +
> +   This program is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +   GNU General Public License for more details.
> +
> +   You should have received a copy of the GNU General Public License
> +   along with this program.  If not, see<http://www.gnu.org/licenses/>.  */
> +
> +#include "defs.h"
> +#include "osabi.h"
> +#include "regcache.h"
> +#include "gdbcore.h"
> +#include "gdbtypes.h"
> +#include "infcall.h"
> +#include "ppc-tdep.h"
> +#include "value.h"
> +#include "xcoffread.h"
> +
> +/* Implement the "push_dummy_call" gdbarch method.  */
> +
> +static CORE_ADDR
> +rs6000_lynx178_push_dummy_call (struct gdbarch *gdbarch, struct value *function,
> +			struct regcache *regcache, CORE_ADDR bp_addr,
> +			int nargs, struct value **args, CORE_ADDR sp,
> +			int struct_return, CORE_ADDR struct_addr)
> +{
> +  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
> +  enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
> +  int ii;
> +  int len = 0;
> +  int argno;			/* current argument number */
> +  int argbytes;			/* current argument byte */
> +  gdb_byte tmp_buffer[50];
> +  int f_argno = 0;		/* current floating point argno */
> +  int wordsize = gdbarch_tdep (gdbarch)->wordsize;
> +  CORE_ADDR func_addr = find_function_addr (function, NULL);
> +
> +  struct value *arg = 0;
> +  struct type *type;
> +
> +  ULONGEST saved_sp;
> +
> +  /* The calling convention this function implements assumes the
> +     processor has floating-point registers.  We shouldn't be using it
> +     on PPC variants that lack them.  */
> +  gdb_assert (ppc_floating_point_unit_p (gdbarch));
> +
> +  /* The first eight words of ther arguments are passed in registers.
> +     Copy them appropriately.  */
> +  ii = 0;
> +
> +  /* If the function is returning a `struct', then the first word
> +     (which will be passed in r3) is used for struct return address.
> +     In that case we should advance one word and start from r4
> +     register to copy parameters.  */
> +  if (struct_return)
> +    {
> +      regcache_raw_write_unsigned (regcache, tdep->ppc_gp0_regnum + 3,
> +				   struct_addr);
> +      ii++;
> +    }
> +
> +  /* Effectively indirect call... gcc does...
> +
> +     return_val example( float, int);
> +
> +     eabi:
> +     float in fp0, int in r3
> +     offset of stack on overflow 8/16
> +     for varargs, must go by type.
> +     power open:
> +     float in r3&r4, int in r5
> +     offset of stack on overflow different
> +     both:
> +     return in r3 or f0.  If no float, must study how gcc emulates floats;
> +     pay attention to arg promotion.
> +     User may have to cast\args to handle promotion correctly
> +     since gdb won't know if prototype supplied or not.  */
> +
> +  for (argno = 0, argbytes = 0; argno < nargs && ii < 8; ++ii)
> +    {
> +      int reg_size = register_size (gdbarch, ii + 3);
> +
> +      arg = args[argno];
> +      type = check_typedef (value_type (arg));
> +      len = TYPE_LENGTH (type);
> +
> +      if (TYPE_CODE (type) == TYPE_CODE_FLT)
> +	{
> +
> +	  /* Floating point arguments are passed in fpr's, as well as gpr's.
> +	     There are 13 fpr's reserved for passing parameters.  At this point
> +	     there is no way we would run out of them.  */
> +
> +	  gdb_assert (len <= 8);
> +
> +	  regcache_cooked_write (regcache,
> +	                         tdep->ppc_fp0_regnum + 1 + f_argno,
> +	                         value_contents (arg));
> +	  ++f_argno;
> +	}
> +
> +      if (len > reg_size)
> +	{
> +
> +	  /* Argument takes more than one register.  */
> +	  while (argbytes < len)
> +	    {
> +	      gdb_byte word[MAX_REGISTER_SIZE];
> +	      memset (word, 0, reg_size);
> +	      memcpy (word,
> +		      ((char *) value_contents (arg)) + argbytes,
> +		      (len - argbytes) > reg_size
> +		        ? reg_size : len - argbytes);
> +	      regcache_cooked_write (regcache,
> +	                            tdep->ppc_gp0_regnum + 3 + ii,
> +				    word);
> +	      ++ii, argbytes += reg_size;
> +
> +	      if (ii >= 8)
> +		goto ran_out_of_registers_for_arguments;
> +	    }
> +	  argbytes = 0;
> +	  --ii;
> +	}
> +      else
> +	{
> +	  /* Argument can fit in one register.  No problem.  */
> +	  int adj = gdbarch_byte_order (gdbarch)
> +		    == BFD_ENDIAN_BIG ? reg_size - len : 0;
> +	  gdb_byte word[MAX_REGISTER_SIZE];
> +
> +	  memset (word, 0, reg_size);
> +	  memcpy (word, value_contents (arg), len);
> +	  regcache_cooked_write (regcache, tdep->ppc_gp0_regnum + 3 +ii, word);
> +	}
> +      ++argno;
> +    }
> +
> +ran_out_of_registers_for_arguments:
> +
> +  regcache_cooked_read_unsigned (regcache,
> +				 gdbarch_sp_regnum (gdbarch),
> +				 &saved_sp);
> +
> +  /* Location for 8 parameters are always reserved.  */
> +  sp -= wordsize * 8;
> +
> +  /* Another six words for back chain, TOC register, link register, etc.  */
> +  sp -= wordsize * 6;
> +
> +  /* Stack pointer must be quadword aligned.  */
> +  sp &= -16;

How about 'sp = align_down (sp, 16);'?

> +
> +  /* If there are more arguments, allocate space for them in
> +     the stack, then push them starting from the ninth one.  */
> +
> +  if ((argno < nargs) || argbytes)
> +    {
> +      int space = 0, jj;
> +
> +      if (argbytes)
> +	{
> +	  space += ((len - argbytes + 3) & -4);
> +	  jj = argno + 1;
> +	}
> +      else
> +	jj = argno;
> +
> +      for (; jj < nargs; ++jj)
> +	{
> +	  struct value *val = args[jj];
> +	  space += ((TYPE_LENGTH (value_type (val))) + 3) & -4;
> +	}
> +
> +      /* Add location required for the rest of the parameters.  */
> +      space = (space + 15) & -16;

How about 'space = align_up (space, 16);'? and we may use
'align_up (XXX, 4)' somewhere else in this patch.

> +
> +/* PowerPC Lynx178 OSABI sniffer.  */
> +
> +static enum gdb_osabi
> +rs6000_lynx178_osabi_sniffer (bfd *abfd)
> +{
> +  if (bfd_get_flavour (abfd) != bfd_target_xcoff_flavour)
> +    return GDB_OSABI_UNKNOWN;
> +
> +  /* The only noticeable difference between Lynx178 XCOFF files and
> +     AIX XCOFF files comes from the fact that there are no shared
> +     libraries on Lynx178.  So if the number of import files is
> +     different from zero, it cannot be a Lynx178 binary.  */
> +  if (xcoff_get_n_import_files (abfd) != 0)
> +    return GDB_OSABI_UNKNOWN;

As your comments said, we need the function returning a flag indicating 
'the xcoff file has shared libraries or not', and looks the precise 
number of import files doesn't matter here.  I suggest that rename 
function 'xcoff_get_n_import_files' to 'xcoff_has_import_files'.

> +
> diff --git a/gdb/xcoffread.c b/gdb/xcoffread.c
> index 10c93cc..7838ac1 100644
> --- a/gdb/xcoffread.c
> +++ b/gdb/xcoffread.c
> @@ -3113,6 +3113,67 @@ static const struct sym_fns xcoff_sym_fns =
>     &psym_functions
>   };
>

> +
> +/* Return the number of import files (shared libraries) that the given
> +   BFD depends on.  Return -1 if this number could not be computed.  */
> +
> +extern int
> +xcoff_get_n_import_files (bfd *abfd)

As I said above, we can define this function:

int xcoff_has_import_files (bfd *abfd)

which returns 1 when the BFD has the import files and returns 0 when the 
BFD doesn't.  Returns -1 when it is unknown.

-- 
Yao (齐尧)