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

   1 /* Copyright (C) 1992, 93, 95, 96, 97, 98 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper, <drepper@gnu.ai.mit.edu>, August 1995.
   4    ARM changes by Philip Blundell, <pjb27@cam.ac.uk>, May 1997.
   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 not,
  18    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #ifndef _LINUX_ARM_SYSDEP_H
  22 #define _LINUX_ARM_SYSDEP_H 1
  23
  24 /* There is some commonality.  */
  25 #include <sysdeps/unix/arm/sysdep.h>
  26
  27 /* For Linux we can use the system call table in the header file
  28         /usr/include/asm/unistd.h
  29    of the kernel.  But these symbols do not follow the SYS_* syntax
  30    so we have to redefine the `SYS_ify' macro here.  */
  31 #undef SYS_ify
  32 #define SWI_BASE  (0x900000)
  33 #define SYS_ify(syscall_name)   (__NR_##syscall_name)
  34
  35
  36 #ifdef __ASSEMBLER__
  37
  38 /* Linux uses a negative return value to indicate syscall errors,
  39    unlike most Unices, which use the condition codes' carry flag.
  40
  41    Since version 2.1 the return value of a system call might be
  42    negative even if the call succeeded.  E.g., the `lseek' system call
  43    might return a large offset.  Therefore we must not anymore test
  44    for < 0, but test for a real error by making sure the value in R0
  45    is a real error number.  Linus said he will make sure the no syscall
  46    returns a value in -1 .. -4095 as a valid result so we can savely
  47    test with -4095.  */
  48
  49 #undef  PSEUDO
  50 #define PSEUDO(name, syscall_name, args)                                      \
  51   .text;                                                                      \
  52   .type syscall_error,%function;                                              \
  53   ENTRY (name);                                                               \
  54     DO_CALL (args, syscall_name);                                             \
  55     cmn r0, $4096;                                                            \
  56     bhs PLTJMP(C_SYMBOL_NAME(__syscall_error));
  57
  58 #undef  PSEUDO_END
  59 #define PSEUDO_END(name)                                                      \
  60   SYSCALL_ERROR_HANDLER                                                       \
  61   END (name)
  62
  63 #define SYSCALL_ERROR_HANDLER   /* Nothing here; code in sysdep.S is used.  */
  64
  65 /* Linux takes system call args in registers:
  66         syscall number  in the SWI instruction
  67         arg 1           r0
  68         arg 2           r1
  69         arg 3           r2
  70         arg 4           r3
  71         arg 5           r4      (this is different from the APCS convention)
  72
  73    The compiler is going to form a call by coming here, through PSEUDO, with
  74    arguments
  75         syscall number  in the DO_CALL macro
  76         arg 1           r0
  77         arg 2           r1
  78         arg 3           r2
  79         arg 4           r3
  80         arg 5           [sp]
  81
  82    We need to shuffle values between R4 and the stack so that the caller's
  83    R4 is not corrupted, and the kernel sees the right argument there.
  84
  85 */
  86
  87 #undef  DO_CALL
  88 #define DO_CALL(args, syscall_name)             \
  89     DOARGS_##args                               \
  90     swi SYS_ify (syscall_name);                 \
  91     UNDOARGS_##args
  92
  93 #define DOARGS_0 /* nothing */
  94 #define DOARGS_1 /* nothing */
  95 #define DOARGS_2 /* nothing */
  96 #define DOARGS_3 /* nothing */
  97 #define DOARGS_4 /* nothing */
  98 #define DOARGS_5 ldr ip, [sp]; str r4, [sp]; mov r4, ip;
  99
 100 #define UNDOARGS_0 /* nothing */
 101 #define UNDOARGS_1 /* nothing */
 102 #define UNDOARGS_2 /* nothing */
 103 #define UNDOARGS_3 /* nothing */
 104 #define UNDOARGS_4 /* nothing */
 105 #define UNDOARGS_5 ldr r4, [sp];
 106
 107 #endif  /* __ASSEMBLER__ */
 108
 109 #endif /* linux/arm/sysdep.h */