sysdeps/unix/sysv/linux/i386/sysdep.h

   1 /* Copyright (C) 1992, 1993, 1995-2000, 2002 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper, <drepper@gnu.org>, August 1995.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #ifndef _LINUX_I386_SYSDEP_H
  21 #define _LINUX_I386_SYSDEP_H 1
  22
  23 /* There is some commonality.  */
  24 #include <sysdeps/unix/i386/sysdep.h>
  25 #include <bp-sym.h>
  26 #include <bp-asm.h>
  27
  28 /* For Linux we can use the system call table in the header file
  29         /usr/include/asm/unistd.h
  30    of the kernel.  But these symbols do not follow the SYS_* syntax
  31    so we have to redefine the `SYS_ify' macro here.  */
  32 #undef SYS_ify
  33 #define SYS_ify(syscall_name)   __NR_##syscall_name
  34
  35 /* ELF-like local names start with `.L'.  */
  36 #undef L
  37 #define L(name) .L##name
  38
  39 #ifdef __ASSEMBLER__
  40
  41 /* Linux uses a negative return value to indicate syscall errors,
  42    unlike most Unices, which use the condition codes' carry flag.
  43
  44    Since version 2.1 the return value of a system call might be
  45    negative even if the call succeeded.  E.g., the `lseek' system call
  46    might return a large offset.  Therefore we must not anymore test
  47    for < 0, but test for a real error by making sure the value in %eax
  48    is a real error number.  Linus said he will make sure the no syscall
  49    returns a value in -1 .. -4095 as a valid result so we can savely
  50    test with -4095.  */
  51
  52 /* We don't want the label for the error handle to be global when we define
  53    it here.  */
  54 #ifdef PIC
  55 # define SYSCALL_ERROR_LABEL 0f
  56 #else
  57 # define SYSCALL_ERROR_LABEL syscall_error
  58 #endif
  59
  60 #undef  PSEUDO
  61 #define PSEUDO(name, syscall_name, args)                                      \
  62   .text;                                                                      \
  63   ENTRY (name)                                                                \
  64     DO_CALL (args, syscall_name);                                             \
  65     cmpl $-4095, %eax;                                                        \
  66     jae SYSCALL_ERROR_LABEL;                                                  \
  67   L(pseudo_end):
  68
  69 #undef  PSEUDO_END
  70 #define PSEUDO_END(name)                                                      \
  71   SYSCALL_ERROR_HANDLER                                                       \
  72   END (name)
  73
  74 #ifndef PIC
  75 #define SYSCALL_ERROR_HANDLER   /* Nothing here; code in sysdep.S is used.  */
  76 #else
  77 /* Store (- %eax) into errno through the GOT.  */
  78 #ifdef _LIBC_REENTRANT
  79 #define SYSCALL_ERROR_HANDLER                                                 \
  80 0:pushl %ebx;                                                                 \
  81   call 1f;                                                                    \
  82   .subsection 1;                                                              \
  83 1:movl (%esp), %ebx;                                                          \
  84   ret;                                                                        \
  85   .previous;                                                                  \
  86   addl $_GLOBAL_OFFSET_TABLE_, %ebx;                                          \
  87   xorl %edx, %edx;                                                            \
  88   subl %eax, %edx;                                                            \
  89   pushl %edx;                                                                 \
  90   PUSH_ERRNO_LOCATION_RETURN;                                                 \
  91   call BP_SYM (__errno_location)@PLT;                                         \
  92   POP_ERRNO_LOCATION_RETURN;                                                  \
  93   popl %ecx;                                                                  \
  94   popl %ebx;                                                                  \
  95   movl %ecx, (%eax);                                                          \
  96   orl $-1, %eax;                                                              \
  97   jmp L(pseudo_end);
  98 /* A quick note: it is assumed that the call to `__errno_location' does
  99    not modify the stack!  */
 100 #else
 101 #define SYSCALL_ERROR_HANDLER                                                 \
 102 0:call 1f;                                                                    \
 103   .subsection 1;                                                              \
 104 1:movl (%esp), %ecx;                                                          \
 105   ret;                                                                        \
 106   .previous;                                                                  \
 107   addl $_GLOBAL_OFFSET_TABLE_, %ecx;                                          \
 108   xorl %edx, %edx;                                                            \
 109   subl %eax, %edx;                                                            \
 110   movl errno@GOT(%ecx), %ecx;                                                 \
 111   movl %edx, (%ecx);                                                          \
 112   orl $-1, %eax;                                                              \
 113   jmp L(pseudo_end);
 114 #endif  /* _LIBC_REENTRANT */
 115 #endif  /* PIC */
 116
 117 /* Linux takes system call arguments in registers:
 118
 119         syscall number  %eax         call-clobbered
 120         arg 1           %ebx         call-saved
 121         arg 2           %ecx         call-clobbered
 122         arg 3           %edx         call-clobbered
 123         arg 4           %esi         call-saved
 124         arg 5           %edi         call-saved
 125
 126    The stack layout upon entering the function is:
 127
 128         20(%esp)        Arg# 5
 129         16(%esp)        Arg# 4
 130         12(%esp)        Arg# 3
 131          8(%esp)        Arg# 2
 132          4(%esp)        Arg# 1
 133           (%esp)        Return address
 134
 135    (Of course a function with say 3 arguments does not have entries for
 136    arguments 4 and 5.)
 137
 138    The following code tries hard to be optimal.  A general assumption
 139    (which is true according to the data books I have) is that
 140
 141         2 * xchg        is more expensive than  pushl + movl + popl
 142
 143    Beside this a neat trick is used.  The calling conventions for Linux
 144    tell that among the registers used for parameters %ecx and %edx need
 145    not be saved.  Beside this we may clobber this registers even when
 146    they are not used for parameter passing.
 147
 148    As a result one can see below that we save the content of the %ebx
 149    register in the %edx register when we have less than 3 arguments
 150    (2 * movl is less expensive than pushl + popl).
 151
 152    Second unlike for the other registers we don't save the content of
 153    %ecx and %edx when we have more than 1 and 2 registers resp.
 154
 155    The code below might look a bit long but we have to take care for
 156    the pipelined processors (i586).  Here the `pushl' and `popl'
 157    instructions are marked as NP (not pairable) but the exception is
 158    two consecutive of these instruction.  This gives no penalty on
 159    other processors though.  */
 160
 161 #undef  DO_CALL
 162 #define DO_CALL(args, syscall_name)                                           \
 163     PUSHARGS_##args                                                           \
 164     DOARGS_##args                                                             \
 165     movl $SYS_ify (syscall_name), %eax;                                       \
 166     int $0x80                                                                 \
 167     POPARGS_##args
 168
 169 #define PUSHARGS_0      /* No arguments to push.  */
 170 #define DOARGS_0        /* No arguments to frob.  */
 171 #define POPARGS_0       /* No arguments to pop.  */
 172 #define _PUSHARGS_0     /* No arguments to push.  */
 173 #define _DOARGS_0(n)    /* No arguments to frob.  */
 174 #define _POPARGS_0      /* No arguments to pop.  */
 175
 176 #define PUSHARGS_1      movl %ebx, %edx; PUSHARGS_0
 177 #define DOARGS_1        _DOARGS_1 (4)
 178 #define POPARGS_1       POPARGS_0; movl %edx, %ebx
 179 #define _PUSHARGS_1     pushl %ebx; _PUSHARGS_0
 180 #define _DOARGS_1(n)    movl n(%esp), %ebx; _DOARGS_0(n-4)
 181 #define _POPARGS_1      _POPARGS_0; popl %ebx
 182
 183 #define PUSHARGS_2      PUSHARGS_1
 184 #define DOARGS_2        _DOARGS_2 (8)
 185 #define POPARGS_2       POPARGS_1
 186 #define _PUSHARGS_2     _PUSHARGS_1
 187 #define _DOARGS_2(n)    movl n(%esp), %ecx; _DOARGS_1 (n-4)
 188 #define _POPARGS_2      _POPARGS_1
 189
 190 #define PUSHARGS_3      _PUSHARGS_2
 191 #define DOARGS_3        _DOARGS_3 (16)
 192 #define POPARGS_3       _POPARGS_3
 193 #define _PUSHARGS_3     _PUSHARGS_2
 194 #define _DOARGS_3(n)    movl n(%esp), %edx; _DOARGS_2 (n-4)
 195 #define _POPARGS_3      _POPARGS_2
 196
 197 #define PUSHARGS_4      _PUSHARGS_4
 198 #define DOARGS_4        _DOARGS_4 (24)
 199 #define POPARGS_4       _POPARGS_4
 200 #define _PUSHARGS_4     pushl %esi; _PUSHARGS_3
 201 #define _DOARGS_4(n)    movl n(%esp), %esi; _DOARGS_3 (n-4)
 202 #define _POPARGS_4      _POPARGS_3; popl %esi
 203
 204 #define PUSHARGS_5      _PUSHARGS_5
 205 #define DOARGS_5        _DOARGS_5 (32)
 206 #define POPARGS_5       _POPARGS_5
 207 #define _PUSHARGS_5     pushl %edi; _PUSHARGS_4
 208 #define _DOARGS_5(n)    movl n(%esp), %edi; _DOARGS_4 (n-4)
 209 #define _POPARGS_5      _POPARGS_4; popl %edi
 210
 211 #else   /* !__ASSEMBLER__ */
 212
 213 /* We need some help from the assembler to generate optimal code.  We
 214    define some macros here which later will be used.  */
 215 asm (".L__X'%ebx = 1\n\t"
 216      ".L__X'%ecx = 2\n\t"
 217      ".L__X'%edx = 2\n\t"
 218      ".L__X'%eax = 3\n\t"
 219      ".L__X'%esi = 3\n\t"
 220      ".L__X'%edi = 3\n\t"
 221      ".L__X'%ebp = 3\n\t"
 222      ".L__X'%esp = 3\n\t"
 223      ".macro bpushl name reg\n\t"
 224      ".if 1 - \\name\n\t"
 225      ".if 2 - \\name\n\t"
 226      "pushl %ebx\n\t"
 227      ".else\n\t"
 228      "xchgl \\reg, %ebx\n\t"
 229      ".endif\n\t"
 230      ".endif\n\t"
 231      ".endm\n\t"
 232      ".macro bpopl name reg\n\t"
 233      ".if 1 - \\name\n\t"
 234      ".if 2 - \\name\n\t"
 235      "popl %ebx\n\t"
 236      ".else\n\t"
 237      "xchgl \\reg, %ebx\n\t"
 238      ".endif\n\t"
 239      ".endif\n\t"
 240      ".endm\n\t"
 241      ".macro bmovl name reg\n\t"
 242      ".if 1 - \\name\n\t"
 243      ".if 2 - \\name\n\t"
 244      "movl \\reg, %ebx\n\t"
 245      ".endif\n\t"
 246      ".endif\n\t"
 247      ".endm\n\t");
 248
 249 /* Define a macro which expands inline into the wrapper code for a system
 250    call.  */
 251 #undef INLINE_SYSCALL
 252 #define INLINE_SYSCALL(name, nr, args...) \
 253   ({                                                                          \
 254     unsigned int resultvar;                                                   \
 255     asm volatile (                                                            \
 256     LOADARGS_##nr                                                             \
 257     "movl %1, %%eax\n\t"                                                      \
 258     "int $0x80\n\t"                                                           \
 259     RESTOREARGS_##nr                                                          \
 260     : "=a" (resultvar)                                                        \
 261     : "i" (__NR_##name) ASMFMT_##nr(args) : "memory", "cc");                  \
 262     if (resultvar >= 0xfffff001)                                              \
 263       {                                                                       \
 264         __set_errno (-resultvar);                                             \
 265         resultvar = 0xffffffff;                                               \
 266       }                                                                       \
 267     (int) resultvar; })
 268
 269 #define LOADARGS_0
 270 #define LOADARGS_1 \
 271     "bpushl .L__X'%k2, %k2\n\t"                                               \
 272     "bmovl .L__X'%k2, %k2\n\t"
 273 #define LOADARGS_2      LOADARGS_1
 274 #define LOADARGS_3      LOADARGS_1
 275 #define LOADARGS_4      LOADARGS_1
 276 #define LOADARGS_5      LOADARGS_1
 277
 278 #define RESTOREARGS_0
 279 #define RESTOREARGS_1 \
 280     "bpopl .L__X'%k2, %k2\n\t"
 281 #define RESTOREARGS_2   RESTOREARGS_1
 282 #define RESTOREARGS_3   RESTOREARGS_1
 283 #define RESTOREARGS_4   RESTOREARGS_1
 284 #define RESTOREARGS_5   RESTOREARGS_1
 285
 286 #define ASMFMT_0()
 287 #define ASMFMT_1(arg1) \
 288         , "acdSD" (arg1)
 289 #define ASMFMT_2(arg1, arg2) \
 290         , "adCD" (arg1), "c" (arg2)
 291 #define ASMFMT_3(arg1, arg2, arg3) \
 292         , "aCD" (arg1), "c" (arg2), "d" (arg3)
 293 #define ASMFMT_4(arg1, arg2, arg3, arg4) \
 294         , "aD" (arg1), "c" (arg2), "d" (arg3), "S" (arg4)
 295 #define ASMFMT_5(arg1, arg2, arg3, arg4, arg5) \
 296         , "a" (arg1), "c" (arg2), "d" (arg3), "S" (arg4), "D" (arg5)
 297
 298 #endif  /* __ASSEMBLER__ */
 299
 300 #endif /* linux/i386/sysdep.h */