sysdeps/unix/sysv/linux/m68k/sysdep.h

   1 /* Copyright (C) 1996 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3 Written by Andreas Schwab, <schwab@issan.informatik.uni-dortmund.de>,
   4 December 1995.
   5
   6 The GNU C Library is free software; you can redistribute it and/or
   7 modify it under the terms of the GNU Library General Public License as
   8 published by the Free Software Foundation; either version 2 of the
   9 License, or (at your option) any later version.
  10
  11 The GNU C Library is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 Library General Public License for more details.
  15
  16 You should have received a copy of the GNU Library General Public
  17 License along with the GNU C Library; see the file COPYING.LIB.  If
  18 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  19 Cambridge, MA 02139, USA.  */
  20
  21 #include <sysdeps/unix/sysdep.h>
  22
  23 /* For Linux we can use the system call table in the header file
  24         /usr/include/asm/unistd.h
  25    of the kernel.  But these symbols do not follow the SYS_* syntax
  26    so we have to redefine the `SYS_ify' macro here.  */
  27 #undef SYS_ify
  28 #ifdef __STDC__
  29 # define SYS_ify(syscall_name)  __NR_##syscall_name
  30 #else
  31 # define SYS_ify(syscall_name)  __NR_/**/syscall_name
  32 #endif
  33
  34 #ifdef ASSEMBLER
  35
  36 /* Define an entry point visible from C.  */
  37 #define ENTRY(name)                                                           \
  38   .globl name;                                                                \
  39   .type name, @function;                                                      \
  40   .align 4;                                                                   \
  41   C_LABEL(name)                                                               \
  42   CALL_MCOUNT
  43
  44 #undef END
  45 #define END(name) .size name, . - name
  46
  47 /* If compiled for profiling, call `_mcount' at the start of each function.  */
  48 #ifdef  PROF
  49 /* The mcount code relies on a normal frame pointer being on the stack
  50    to locate our caller, so push one just for its benefit.  */
  51 #define CALL_MCOUNT \
  52   move.l %fp, -(%sp); move.l %sp, %fp;                                        \
  53   jbsr JUMPTARGET (_mcount);                                                  \
  54   move.l (%sp)+, %fp;
  55 #else
  56 #define CALL_MCOUNT             /* Do nothing.  */
  57 #endif
  58
  59 #ifdef PIC
  60 #define JUMPTARGET(name)        name##@PLTPC
  61 #else
  62 #define JUMPTARGET(name)        name
  63 #endif
  64
  65 /* Since C identifiers are not normally prefixed with an underscore
  66    on this system, the asm identifier `syscall_error' intrudes on the
  67    C name space.  Make sure we use an innocuous name.  */
  68 #define syscall_error   __syscall_error
  69
  70 /* Linux uses a negative return value to indicate syscall errors, unlike
  71    most Unices, which use the condition codes' carry flag.
  72
  73    Since version 2.1 the return value of a system call might be negative
  74    even if the call succeeded.  E.g., the `lseek' system call might return
  75    a large offset.  Therefore we must not anymore test for < 0, but test
  76    for a real error by making sure the value in %d0 is a real error
  77    number.  Linus said he will make sure the no syscall returns a value
  78    in -1 .. -4095 as a valid result so we can savely test with -4095.  */
  79 #define PSEUDO(name, syscall_name, args)                                      \
  80   .text;                                                                      \
  81   ENTRY (name)                                                                \
  82     DO_CALL (&SYS_ify (syscall_name), args);                                  \
  83     cmp.l &-4095, %d0;                                                        \
  84     jcc syscall_error
  85
  86 #undef PSEUDO_END
  87 #define PSEUDO_END(name)                                                      \
  88   SYSCALL_ERROR_HANDLER;                                                      \
  89   END (name)
  90
  91 #ifdef PIC
  92 /* Store (- %d0) into errno through the GOT.  */
  93 #ifdef _LIBC_REENTRANT
  94 #define SYSCALL_ERROR_HANDLER                                                 \
  95 syscall_error:                                                                \
  96     move.l (errno@GOTPC, %pc), %a0;                                           \
  97     neg.l %d0;                                                                \
  98     move.l %d0, (%a0);                                                        \
  99     move.l %d0, -(%sp);                                                       \
 100     jbsr __errno_location@PLTPC;                                              \
 101     move.l (%sp)+, (%a0);                                                     \
 102     move.l &-1, %d0;                                                          \
 103     /* Copy return value to %a0 for syscalls that are declared to return      \
 104        a pointer (e.g., mmap).  */                                            \
 105     move.l %d0, %a0;                                                          \
 106     rts;
 107 #else
 108 #define SYSCALL_ERROR_HANDLER                                                 \
 109 syscall_error:                                                                \
 110     move.l (errno@GOTPC, %pc), %a0;                                           \
 111     neg.l %d0;                                                                \
 112     move.l %d0, (%a0);                                                        \
 113     move.l &-1, %d0;                                                          \
 114     /* Copy return value to %a0 for syscalls that are declared to return      \
 115        a pointer (e.g., mmap).  */                                            \
 116     move.l %d0, %a0;                                                          \
 117     rts;
 118 #endif /* _LIBC_REENTRANT */
 119 #else
 120 #define SYSCALL_ERROR_HANDLER   /* Nothing here; code in sysdep.S is used.  */
 121 #endif /* PIC */
 122
 123 /* Linux takes system call arguments in registers:
 124
 125         syscall number  %d0          call-clobbered
 126         arg 1           %d1          call-clobbered
 127         arg 2           %d2          call-saved
 128         arg 3           %d3          call-saved
 129         arg 4           %d4          call-saved
 130         arg 5           %d5          call-saved
 131
 132    The stack layout upon entering the function is:
 133
 134         20(%sp)         Arg# 5
 135         16(%sp)         Arg# 4
 136         12(%sp)         Arg# 3
 137          8(%sp)         Arg# 2
 138          4(%sp)         Arg# 1
 139           (%sp)         Return address
 140
 141    (Of course a function with say 3 arguments does not have entries for
 142    arguments 4 and 5.)
 143
 144    Separate move's are faster than movem, but need more space.  Since
 145    speed is more important, we don't use movem.  Since %a0 and %a1 are
 146    scratch registers, we can use them for saving as well.  */
 147
 148 #define DO_CALL(syscall, args)                                                \
 149     move.l syscall, %d0;                                                      \
 150     DOARGS_##args                                                             \
 151     trap &0;                                                                  \
 152     UNDOARGS_##args
 153
 154 #define DOARGS_0        /* No arguments to frob.  */
 155 #define UNDOARGS_0      /* No arguments to unfrob.  */
 156 #define _DOARGS_0(n)    /* No arguments to frob.  */
 157
 158 #define DOARGS_1        _DOARGS_1 (4)
 159 #define _DOARGS_1(n)    move.l n(%sp), %d1; _DOARGS_0 (n)
 160 #define UNDOARGS_1      UNDOARGS_0
 161
 162 #define DOARGS_2        _DOARGS_2 (8)
 163 #define _DOARGS_2(n)    move.l %d2, %a0; move.l n(%sp), %d2; _DOARGS_1 (n-4)
 164 #define UNDOARGS_2      UNDOARGS_1; move.l %a0, %d2
 165
 166 #define DOARGS_3        _DOARGS_3 (12)
 167 #define _DOARGS_3(n)    move.l %d3, %a1; move.l n(%sp), %d3; _DOARGS_2 (n-4)
 168 #define UNDOARGS_3      UNDOARGS_2; move.l %a1, %d3
 169
 170 #define DOARGS_4        _DOARGS_4 (16)
 171 #define _DOARGS_4(n)    move.l %d4, -(%sp); move.l n+4(%sp), %d4; _DOARGS_3 (n)
 172 #define UNDOARGS_4      UNDOARGS_3; move.l (%sp)+, %d4
 173
 174 #define DOARGS_5        _DOARGS_5 (20)
 175 #define _DOARGS_5(n)    move.l %d5, -(%sp); move.l n+4(%sp), %d5; _DOARGS_4 (n)
 176 #define UNDOARGS_5      UNDOARGS_4; move.l (%sp)+, %d5
 177
 178
 179 #define ret     rts
 180 #if 0 /* Not used by Linux */
 181 #define r0      %d0
 182 #define r1      %d1
 183 #define MOVE(x,y)       movel x , y
 184 #endif
 185
 186 #endif  /* ASSEMBLER */