gcc/config/arm/netbsd-elf.h

   1 /* Definitions of target machine for GNU compiler, NetBSD/arm ELF version.
   2    Copyright (C) 2002-2024 Free Software Foundation, Inc.
   3    Contributed by Wasabi Systems, Inc.
   4
   5    This file is part of GCC.
   6
   7    GCC is free software; you can redistribute it and/or modify it
   8    under the terms of the GNU General Public License as published
   9    by the Free Software Foundation; either version 3, or (at your
  10    option) any later version.
  11
  12    GCC is distributed in the hope that it will be useful, but WITHOUT
  13    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  14    or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
  15    License for more details.
  16
  17    Under Section 7 of GPL version 3, you are granted additional
  18    permissions described in the GCC Runtime Library Exception, version
  19    3.1, as published by the Free Software Foundation.
  20
  21    You should have received a copy of the GNU General Public License and
  22    a copy of the GCC Runtime Library Exception along with this program;
  23    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  24    <http://www.gnu.org/licenses/>.  */
  25
  26 /* Run-time Target Specification.  */
  27
  28 /* arm.h defaults to ARM6 CPU.  */
  29
  30 /* This defaults us to little-endian.  */
  31 #ifndef TARGET_ENDIAN_DEFAULT
  32 #define TARGET_ENDIAN_DEFAULT 0
  33 #endif
  34
  35 #undef MULTILIB_DEFAULTS
  36
  37 /* Default it to use ATPCS with soft-VFP.  */
  38 #undef TARGET_DEFAULT
  39 #define TARGET_DEFAULT                  \
  40   (MASK_APCS_FRAME                      \
  41    | TARGET_ENDIAN_DEFAULT)
  42
  43 #undef ARM_DEFAULT_ABI
  44 #define ARM_DEFAULT_ABI ARM_ABI_ATPCS
  45
  46 #undef TARGET_OS_CPP_BUILTINS
  47 #define TARGET_OS_CPP_BUILTINS()        \
  48   do                                    \
  49     {                                   \
  50       NETBSD_OS_CPP_BUILTINS_ELF();     \
  51     }                                   \
  52   while (0)
  53
  54 #undef SUBTARGET_CPP_SPEC
  55 #define SUBTARGET_CPP_SPEC NETBSD_CPP_SPEC
  56
  57 #undef SUBTARGET_EXTRA_ASM_SPEC
  58 #define SUBTARGET_EXTRA_ASM_SPEC        \
  59   "%{" FPIE_OR_FPIC_SPEC ":-k}"
  60
  61 /* Default to full VFP if -mfloat-abi=hard is specified.  */
  62 #undef SUBTARGET_ASM_FLOAT_SPEC
  63 #define SUBTARGET_ASM_FLOAT_SPEC        \
  64   "%{mfloat-abi=hard:{!mfpu=*:-mfpu=vfp}}"
  65
  66 #undef SUBTARGET_EXTRA_SPECS
  67 #define SUBTARGET_EXTRA_SPECS                           \
  68   { "subtarget_extra_asm_spec", SUBTARGET_EXTRA_ASM_SPEC }, \
  69   { "subtarget_asm_float_spec", SUBTARGET_ASM_FLOAT_SPEC }, \
  70   { "netbsd_link_spec",         NETBSD_LINK_SPEC_ELF }, \
  71   { "netbsd_entry_point",       NETBSD_ENTRY_POINT },
  72
  73 #define NETBSD_ENTRY_POINT "__start"
  74
  75 #undef LINK_SPEC
  76 #define LINK_SPEC \
  77   "-X %{mbig-endian:-EB} %{mlittle-endian:-EL} \
  78    %(netbsd_link_spec)"
  79
  80 /* Make GCC agree with <machine/ansi.h>.  */
  81
  82 #undef SIZE_TYPE
  83 #define SIZE_TYPE "long unsigned int"
  84
  85 #undef PTRDIFF_TYPE
  86 #define PTRDIFF_TYPE "long int"
  87
  88 /* NetBSD does its profiling differently to the Acorn compiler. We
  89    don't need a word following the mcount call; and to skip it
  90    requires either an assembly stub or use of fomit-frame-pointer when
  91    compiling the profiling functions.  Since we break Acorn CC
  92    compatibility below a little more won't hurt.  */
  93
  94 #undef ARM_FUNCTION_PROFILER
  95 #define ARM_FUNCTION_PROFILER(STREAM,LABELNO)           \
  96 {                                                       \
  97   asm_fprintf (STREAM, "\tmov\t%Rip, %Rlr\n");          \
  98   asm_fprintf (STREAM, "\tbl\t__mcount%s\n",            \
  99                (TARGET_ARM && NEED_PLT_RELOC)           \
 100                ? "(PLT)" : "");                         \
 101 }
 102
 103 /* VERY BIG NOTE: Change of structure alignment for NetBSD/arm.
 104    There are consequences you should be aware of...
 105
 106    Normally GCC/arm uses a structure alignment of 32 for compatibility
 107    with armcc.  This means that structures are padded to a word
 108    boundary.  However this causes problems with bugged NetBSD kernel
 109    code (possibly userland code as well - I have not checked every
 110    binary).  The nature of this bugged code is to rely on sizeof()
 111    returning the correct size of various structures rounded to the
 112    nearest byte (SCSI and ether code are two examples, the vm system
 113    is another).  This code breaks when the structure alignment is 32
 114    as sizeof() will report a word=rounded size.  By changing the
 115    structure alignment to 8. GCC will conform to what is expected by
 116    NetBSD.
 117
 118    This has several side effects that should be considered.
 119    1. Structures will only be aligned to the size of the largest member.
 120       i.e. structures containing only bytes will be byte aligned.
 121            structures containing shorts will be half word aligned.
 122            structures containing ints will be word aligned.
 123
 124       This means structures should be padded to a word boundary if
 125       alignment of 32 is required for byte structures etc.
 126
 127    2. A potential performance penalty may exist if strings are no longer
 128       word aligned.  GCC will not be able to use word load/stores to copy
 129       short strings.
 130
 131    This modification is not encouraged but with the present state of the
 132    NetBSD source tree it is currently the only solution that meets the
 133    requirements.  */
 134
 135 #undef DEFAULT_STRUCTURE_SIZE_BOUNDARY
 136 #define DEFAULT_STRUCTURE_SIZE_BOUNDARY 8
 137
 138 #define SYSARCH_ARM_SYNC_ICACHE 0
 139
 140 /* Clear the instruction cache from `BEG' to `END'.  This makes a
 141    call to the ARM_SYNC_ICACHE architecture specific syscall.  */
 142 #define CLEAR_INSN_CACHE(BEG, END)                                      \
 143 do                                                                      \
 144   {                                                                     \
 145     extern int sysarch(int number, void *args);                         \
 146     struct                                                              \
 147       {                                                                 \
 148         unsigned int addr;                                              \
 149         int          len;                                               \
 150       } s;                                                              \
 151     s.addr = (unsigned int)(BEG);                                       \
 152     s.len = (END) - (BEG);                                              \
 153     (void) sysarch (SYSARCH_ARM_SYNC_ICACHE, &s);                       \
 154   }                                                                     \
 155 while (0)