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

   1 /* Copyright (C) 1992,93,95,96,97,98,99,2000,02 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 #include <tls.h>
  28
  29 /* For Linux we can use the system call table in the header file
  30         /usr/include/asm/unistd.h
  31    of the kernel.  But these symbols do not follow the SYS_* syntax
  32    so we have to redefine the `SYS_ify' macro here.  */
  33 #undef SYS_ify
  34 #define SYS_ify(syscall_name)   __NR_##syscall_name
  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 %eax
  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 /* We don't want the label for the error handle to be global when we define
  50    it here.  */
  51 #ifdef PIC
  52 # define SYSCALL_ERROR_LABEL 0f
  53 #else
  54 # define SYSCALL_ERROR_LABEL syscall_error
  55 #endif
  56
  57 #undef  PSEUDO
  58 #define PSEUDO(name, syscall_name, args)                                      \
  59   .text;                                                                      \
  60   ENTRY (name)                                                                \
  61     DO_CALL (syscall_name, args);                                             \
  62     cmpl $-4095, %eax;                                                        \
  63     jae SYSCALL_ERROR_LABEL;                                                  \
  64   L(pseudo_end):
  65
  66 #undef  PSEUDO_END
  67 #define PSEUDO_END(name)                                                      \
  68   SYSCALL_ERROR_HANDLER                                                       \
  69   END (name)
  70
  71 #ifndef PIC
  72 # define SYSCALL_ERROR_HANDLER  /* Nothing here; code in sysdep.S is used.  */
  73 #else
  74
  75 # ifndef HAVE_HIDDEN
  76 #  define SETUP_PIC_REG(reg) \
  77   call 1f;                                                                    \
  78   .subsection 1;                                                              \
  79 1:movl (%esp), %e##reg;                                                       \
  80   ret;                                                                        \
  81   .previous
  82 # else
  83 #  define SETUP_PIC_REG(reg) \
  84   .section .gnu.linkonce.t.__i686.get_pc_thunk.reg,"ax",@progbits;            \
  85   .globl __i686.get_pc_thunk.reg;                                             \
  86   .hidden __i686.get_pc_thunk.reg;                                            \
  87   .type __i686.get_pc_thunk.reg,@function;                                    \
  88 __i686.get_pc_thunk.reg:                                                      \
  89   movl (%esp), %e##reg;                                                       \
  90   ret;                                                                        \
  91   .previous;                                                                  \
  92   call __i686.get_pc_thunk.reg
  93 # endif
  94
  95 /* Store (- %eax) into errno through the GOT.  */
  96 # ifdef _LIBC_REENTRANT
  97
  98 #  if USE_TLS && HAVE___THREAD
  99 #   define SYSCALL_ERROR_HANDLER                                              \
 100 0:SETUP_PIC_REG (cx);                                                         \
 101   addl $_GLOBAL_OFFSET_TABLE_, %ecx;                                          \
 102   movl errno@gotntpoff(%ecx), %ecx;                                           \
 103   xorl %edx, %edx;                                                            \
 104   subl %eax, %edx;                                                            \
 105   movl %edx, %gs:0(%ecx);                                                     \
 106   orl $-1, %eax;                                                              \
 107   jmp L(pseudo_end);
 108 #  else
 109 #   define SYSCALL_ERROR_HANDLER                                              \
 110 0:pushl %ebx;                                                                 \
 111   SETUP_PIC_REG (bx);                                                         \
 112   addl $_GLOBAL_OFFSET_TABLE_, %ebx;                                          \
 113   xorl %edx, %edx;                                                            \
 114   subl %eax, %edx;                                                            \
 115   pushl %edx;                                                                 \
 116   PUSH_ERRNO_LOCATION_RETURN;                                                 \
 117   call BP_SYM (__errno_location)@PLT;                                         \
 118   POP_ERRNO_LOCATION_RETURN;                                                  \
 119   popl %ecx;                                                                  \
 120   popl %ebx;                                                                  \
 121   movl %ecx, (%eax);                                                          \
 122   orl $-1, %eax;                                                              \
 123   jmp L(pseudo_end);
 124 /* A quick note: it is assumed that the call to `__errno_location' does
 125    not modify the stack!  */
 126 #  endif
 127 # else
 128 #  define SYSCALL_ERROR_HANDLER                                               \
 129 0:SETUP_PIC_REG(cx);                                                  \
 130   addl $_GLOBAL_OFFSET_TABLE_, %ecx;                                          \
 131   xorl %edx, %edx;                                                            \
 132   subl %eax, %edx;                                                            \
 133   movl errno@GOT(%ecx), %ecx;                                                 \
 134   movl %edx, (%ecx);                                                          \
 135   orl $-1, %eax;                                                              \
 136   jmp L(pseudo_end);
 137 # endif /* _LIBC_REENTRANT */
 138 #endif  /* PIC */
 139
 140 /* Linux takes system call arguments in registers:
 141
 142         syscall number  %eax         call-clobbered
 143         arg 1           %ebx         call-saved
 144         arg 2           %ecx         call-clobbered
 145         arg 3           %edx         call-clobbered
 146         arg 4           %esi         call-saved
 147         arg 5           %edi         call-saved
 148
 149    The stack layout upon entering the function is:
 150
 151         20(%esp)        Arg# 5
 152         16(%esp)        Arg# 4
 153         12(%esp)        Arg# 3
 154          8(%esp)        Arg# 2
 155          4(%esp)        Arg# 1
 156           (%esp)        Return address
 157
 158    (Of course a function with say 3 arguments does not have entries for
 159    arguments 4 and 5.)
 160
 161    The following code tries hard to be optimal.  A general assumption
 162    (which is true according to the data books I have) is that
 163
 164         2 * xchg        is more expensive than  pushl + movl + popl
 165
 166    Beside this a neat trick is used.  The calling conventions for Linux
 167    tell that among the registers used for parameters %ecx and %edx need
 168    not be saved.  Beside this we may clobber this registers even when
 169    they are not used for parameter passing.
 170
 171    As a result one can see below that we save the content of the %ebx
 172    register in the %edx register when we have less than 3 arguments
 173    (2 * movl is less expensive than pushl + popl).
 174
 175    Second unlike for the other registers we don't save the content of
 176    %ecx and %edx when we have more than 1 and 2 registers resp.
 177
 178    The code below might look a bit long but we have to take care for
 179    the pipelined processors (i586).  Here the `pushl' and `popl'
 180    instructions are marked as NP (not pairable) but the exception is
 181    two consecutive of these instruction.  This gives no penalty on
 182    other processors though.  */
 183
 184 #undef  DO_CALL
 185 #define DO_CALL(syscall_name, args)                                           \
 186     PUSHARGS_##args                                                           \
 187     DOARGS_##args                                                             \
 188     movl $SYS_ify (syscall_name), %eax;                                       \
 189     int $0x80                                                                 \
 190     POPARGS_##args
 191
 192 #define PUSHARGS_0      /* No arguments to push.  */
 193 #define DOARGS_0        /* No arguments to frob.  */
 194 #define POPARGS_0       /* No arguments to pop.  */
 195 #define _PUSHARGS_0     /* No arguments to push.  */
 196 #define _DOARGS_0(n)    /* No arguments to frob.  */
 197 #define _POPARGS_0      /* No arguments to pop.  */
 198
 199 #define PUSHARGS_1      movl %ebx, %edx; PUSHARGS_0
 200 #define DOARGS_1        _DOARGS_1 (4)
 201 #define POPARGS_1       POPARGS_0; movl %edx, %ebx
 202 #define _PUSHARGS_1     pushl %ebx; _PUSHARGS_0
 203 #define _DOARGS_1(n)    movl n(%esp), %ebx; _DOARGS_0(n-4)
 204 #define _POPARGS_1      _POPARGS_0; popl %ebx
 205
 206 #define PUSHARGS_2      PUSHARGS_1
 207 #define DOARGS_2        _DOARGS_2 (8)
 208 #define POPARGS_2       POPARGS_1
 209 #define _PUSHARGS_2     _PUSHARGS_1
 210 #define _DOARGS_2(n)    movl n(%esp), %ecx; _DOARGS_1 (n-4)
 211 #define _POPARGS_2      _POPARGS_1
 212
 213 #define PUSHARGS_3      _PUSHARGS_2
 214 #define DOARGS_3        _DOARGS_3 (16)
 215 #define POPARGS_3       _POPARGS_3
 216 #define _PUSHARGS_3     _PUSHARGS_2
 217 #define _DOARGS_3(n)    movl n(%esp), %edx; _DOARGS_2 (n-4)
 218 #define _POPARGS_3      _POPARGS_2
 219
 220 #define PUSHARGS_4      _PUSHARGS_4
 221 #define DOARGS_4        _DOARGS_4 (24)
 222 #define POPARGS_4       _POPARGS_4
 223 #define _PUSHARGS_4     pushl %esi; _PUSHARGS_3
 224 #define _DOARGS_4(n)    movl n(%esp), %esi; _DOARGS_3 (n-4)
 225 #define _POPARGS_4      _POPARGS_3; popl %esi
 226
 227 #define PUSHARGS_5      _PUSHARGS_5
 228 #define DOARGS_5        _DOARGS_5 (32)
 229 #define POPARGS_5       _POPARGS_5
 230 #define _PUSHARGS_5     pushl %edi; _PUSHARGS_4
 231 #define _DOARGS_5(n)    movl n(%esp), %edi; _DOARGS_4 (n-4)
 232 #define _POPARGS_5      _POPARGS_4; popl %edi
 233
 234 #else   /* !__ASSEMBLER__ */
 235
 236 /* We need some help from the assembler to generate optimal code.  We
 237    define some macros here which later will be used.  */
 238 asm (".L__X'%ebx = 1\n\t"
 239      ".L__X'%ecx = 2\n\t"
 240      ".L__X'%edx = 2\n\t"
 241      ".L__X'%eax = 3\n\t"
 242      ".L__X'%esi = 3\n\t"
 243      ".L__X'%edi = 3\n\t"
 244      ".L__X'%ebp = 3\n\t"
 245      ".L__X'%esp = 3\n\t"
 246      ".macro bpushl name reg\n\t"
 247      ".if 1 - \\name\n\t"
 248      ".if 2 - \\name\n\t"
 249      "pushl %ebx\n\t"
 250      ".else\n\t"
 251      "xchgl \\reg, %ebx\n\t"
 252      ".endif\n\t"
 253      ".endif\n\t"
 254      ".endm\n\t"
 255      ".macro bpopl name reg\n\t"
 256      ".if 1 - \\name\n\t"
 257      ".if 2 - \\name\n\t"
 258      "popl %ebx\n\t"
 259      ".else\n\t"
 260      "xchgl \\reg, %ebx\n\t"
 261      ".endif\n\t"
 262      ".endif\n\t"
 263      ".endm\n\t"
 264      ".macro bmovl name reg\n\t"
 265      ".if 1 - \\name\n\t"
 266      ".if 2 - \\name\n\t"
 267      "movl \\reg, %ebx\n\t"
 268      ".endif\n\t"
 269      ".endif\n\t"
 270      ".endm\n\t");
 271
 272 /* Define a macro which expands inline into the wrapper code for a system
 273    call.  */
 274 #undef INLINE_SYSCALL
 275 #define INLINE_SYSCALL(name, nr, args...) \
 276   ({                                                                          \
 277     unsigned int resultvar;                                                   \
 278     asm volatile (                                                            \
 279     LOADARGS_##nr                                                             \
 280     "movl %1, %%eax\n\t"                                                      \
 281     "int $0x80\n\t"                                                           \
 282     RESTOREARGS_##nr                                                          \
 283     : "=a" (resultvar)                                                        \
 284     : "i" (__NR_##name) ASMFMT_##nr(args) : "memory", "cc");                  \
 285     if (resultvar >= 0xfffff001)                                              \
 286       {                                                                       \
 287         __set_errno (-resultvar);                                             \
 288         resultvar = 0xffffffff;                                               \
 289       }                                                                       \
 290     (int) resultvar; })
 291
 292 #define LOADARGS_0
 293 #define LOADARGS_1 \
 294     "bpushl .L__X'%k2, %k2\n\t"                                               \
 295     "bmovl .L__X'%k2, %k2\n\t"
 296 #define LOADARGS_2      LOADARGS_1
 297 #define LOADARGS_3      LOADARGS_1
 298 #define LOADARGS_4      LOADARGS_1
 299 #define LOADARGS_5      LOADARGS_1
 300
 301 #define RESTOREARGS_0
 302 #define RESTOREARGS_1 \
 303     "bpopl .L__X'%k2, %k2\n\t"
 304 #define RESTOREARGS_2   RESTOREARGS_1
 305 #define RESTOREARGS_3   RESTOREARGS_1
 306 #define RESTOREARGS_4   RESTOREARGS_1
 307 #define RESTOREARGS_5   RESTOREARGS_1
 308
 309 #define ASMFMT_0()
 310 #define ASMFMT_1(arg1) \
 311         , "acdSD" (arg1)
 312 #define ASMFMT_2(arg1, arg2) \
 313         , "adCD" (arg1), "c" (arg2)
 314 #define ASMFMT_3(arg1, arg2, arg3) \
 315         , "aCD" (arg1), "c" (arg2), "d" (arg3)
 316 #define ASMFMT_4(arg1, arg2, arg3, arg4) \
 317         , "aD" (arg1), "c" (arg2), "d" (arg3), "S" (arg4)
 318 #define ASMFMT_5(arg1, arg2, arg3, arg4, arg5) \
 319         , "a" (arg1), "c" (arg2), "d" (arg3), "S" (arg4), "D" (arg5)
 320
 321 #endif  /* __ASSEMBLER__ */
 322
 323 #endif /* linux/i386/sysdep.h */