eabi.h

gcc-you can use this code to learn something about gcc, and inquire further into linux,

/* Core target definitions for GNU compiler
   for IBM RS/6000 PowerPC targeted to embedded ELF systems.
   Copyright (C) 1995, 1996, 2000 Free Software Foundation, Inc.
   Contributed by Cygnus Support.

This file is part of GNU CC.

GNU CC 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 2, or (at your option)
any later version.

GNU CC 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 GNU CC; see the file COPYING.  If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

/* Add -meabi to target flags */
#undef TARGET_DEFAULT
#define TARGET_DEFAULT (MASK_POWERPC | MASK_NEW_MNEMONICS | MASK_EABI)

/* Invoke an initializer function to set up the GOT */
#define NAME__MAIN "__eabi"
#define INVOKE__main

#undef TARGET_VERSION
#define TARGET_VERSION fprintf (stderr, " (PowerPC Embedded)");

#undef TARGET_OS_CPP_BUILTINS
#define TARGET_OS_CPP_BUILTINS()          \
  do                                      \
    {                                     \
      builtin_define_std ("PPC");         \
      builtin_define ("__embedded__");    \
      builtin_assert ("system=embedded"); \
      builtin_assert ("cpu=powerpc");     \
      builtin_assert ("machine=powerpc"); \
    }                                     \
  while (0)

#undef TARGET_SPE_ABI
#undef TARGET_SPE
#undef TARGET_ISEL
#undef TARGET_FPRS

#define TARGET_SPE_ABI rs6000_spe_abi
#define TARGET_SPE (rs6000_cpu == PROCESSOR_PPC8540)
#define TARGET_ISEL rs6000_isel
#define TARGET_FPRS rs6000_fprs