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sysdep.h

/* Copyright (C) 1992,1993,1995-2000,2002,2003 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper, <drepper@gnu.org>, August 1995.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#ifndef _LINUX_I386_SYSDEP_H
#define _LINUX_I386_SYSDEP_H 1

/* There is some commonality.  */
#include <sysdeps/unix/i386/sysdep.h>
#include <bp-sym.h>
#include <bp-asm.h>
/* Defines RTLD_PRIVATE_ERRNO and USE_DL_SYSINFO.  */
#include <dl-sysdep.h>
#include <tls.h>


/* For Linux we can use the system call table in the header file
      /usr/include/asm/unistd.h
   of the kernel.  But these symbols do not follow the SYS_* syntax
   so we have to redefine the `SYS_ify' macro here.  */
#undef SYS_ify
#define SYS_ify(syscall_name) __NR_##syscall_name

#if defined USE_DL_SYSINFO \
    && (!defined NOT_IN_libc || defined IS_IN_libpthread)
# define I386_USE_SYSENTER    1
#else
# undef I386_USE_SYSENTER
#endif

#ifdef __ASSEMBLER__

/* Linux uses a negative return value to indicate syscall errors,
   unlike most Unices, which use the condition codes' carry flag.

   Since version 2.1 the return value of a system call might be
   negative even if the call succeeded.  E.g., the `lseek' system call
   might return a large offset.  Therefore we must not anymore test
   for < 0, but test for a real error by making sure the value in %eax
   is a real error number.  Linus said he will make sure the no syscall
   returns a value in -1 .. -4095 as a valid result so we can savely
   test with -4095.  */

/* We don't want the label for the error handle to be global when we define
   it here.  */
#ifdef PIC
# define SYSCALL_ERROR_LABEL 0f
#else
# define SYSCALL_ERROR_LABEL syscall_error
#endif

#undef      PSEUDO
#define     PSEUDO(name, syscall_name, args)                            \
  .text;                                                    \
  ENTRY (name)                                                    \
    DO_CALL (syscall_name, args);                                 \
    cmpl $-4095, %eax;                                            \
    jae SYSCALL_ERROR_LABEL;                                      \
  L(pseudo_end):

#undef      PSEUDO_END
#define     PSEUDO_END(name)                                      \
  SYSCALL_ERROR_HANDLER                                           \
  END (name)

#ifndef PIC
# define SYSCALL_ERROR_HANDLER      /* Nothing here; code in sysdep.S is used.  */
#else

# ifndef HAVE_HIDDEN
#  define SETUP_PIC_REG(reg) \
  call 1f;                                                  \
  .subsection 1;                                            \
1:movl (%esp), %e##reg;                                           \
  ret;                                                            \
  .previous
# else
#  define SETUP_PIC_REG(reg) \
  .section .gnu.linkonce.t.__i686.get_pc_thunk.reg,"ax",@progbits;            \
  .globl __i686.get_pc_thunk.reg;                                 \
  .hidden __i686.get_pc_thunk.reg;                                \
  .type __i686.get_pc_thunk.reg,@function;                              \
__i686.get_pc_thunk.reg:                                          \
  movl (%esp), %e##reg;                                           \
  ret;                                                            \
  .size __i686.get_pc_thunk.reg, . - __i686.get_pc_thunk.reg;                 \
  .previous;                                                      \
  call __i686.get_pc_thunk.reg
# endif

# if RTLD_PRIVATE_ERRNO
#  define SYSCALL_ERROR_HANDLER                                         \
0:SETUP_PIC_REG(cx);                                              \
  addl $_GLOBAL_OFFSET_TABLE_, %ecx;                                    \
  xorl %edx, %edx;                                                \
  subl %eax, %edx;                                                \
  movl %edx, errno@GOTOFF(%ecx);                                  \
  orl $-1, %eax;                                            \
  jmp L(pseudo_end);

# elif defined _LIBC_REENTRANT

#  if USE___THREAD
#   ifndef NOT_IN_libc
#    define SYSCALL_ERROR_ERRNO __libc_errno
#   else
#    define SYSCALL_ERROR_ERRNO errno
#   endif
#   define SYSCALL_ERROR_HANDLER                                  \
0:SETUP_PIC_REG (cx);                                             \
  addl $_GLOBAL_OFFSET_TABLE_, %ecx;                                    \
  movl SYSCALL_ERROR_ERRNO@GOTNTPOFF(%ecx), %ecx;                       \
  xorl %edx, %edx;                                                \
  subl %eax, %edx;                                                \
  movl %edx, %gs:0(%ecx);                                         \
  orl $-1, %eax;                                            \
  jmp L(pseudo_end);
#  else
#   define SYSCALL_ERROR_HANDLER                                  \
0:pushl %ebx;                                                     \
  SETUP_PIC_REG (bx);                                             \
  addl $_GLOBAL_OFFSET_TABLE_, %ebx;                                    \
  xorl %edx, %edx;                                                \
  subl %eax, %edx;                                                \
  pushl %edx;                                                     \
  PUSH_ERRNO_LOCATION_RETURN;                                     \
  call BP_SYM (__errno_location)@PLT;                                   \
  POP_ERRNO_LOCATION_RETURN;                                      \
  popl %ecx;                                                      \
  popl %ebx;                                                      \
  movl %ecx, (%eax);                                              \
  orl $-1, %eax;                                            \
  jmp L(pseudo_end);
/* A quick note: it is assumed that the call to `__errno_location' does
   not modify the stack!  */
#  endif
# else
/* Store (- %eax) into errno through the GOT.  */
#  define SYSCALL_ERROR_HANDLER                                         \
0:SETUP_PIC_REG(cx);                                        \
  addl $_GLOBAL_OFFSET_TABLE_, %ecx;                                    \
  xorl %edx, %edx;                                                \
  subl %eax, %edx;                                                \
  movl errno@GOT(%ecx), %ecx;                                     \
  movl %edx, (%ecx);                                              \
  orl $-1, %eax;                                            \
  jmp L(pseudo_end);
# endif     /* _LIBC_REENTRANT */
#endif      /* PIC */


/* The original calling convention for system calls on Linux/i386 is
   to use int $0x80.  */
#ifdef I386_USE_SYSENTER
# ifdef SHARED
#  define ENTER_KERNEL call *%gs:SYSINFO_OFFSET
# else
#  define ENTER_KERNEL call *_dl_sysinfo
# endif
#else
# define ENTER_KERNEL int $0x80
#endif

/* Linux takes system call arguments in registers:

      syscall number    %eax       call-clobbered
      arg 1       %ebx       call-saved
      arg 2       %ecx       call-clobbered
      arg 3       %edx       call-clobbered
      arg 4       %esi       call-saved
      arg 5       %edi       call-saved

   The stack layout upon entering the function is:

      20(%esp)    Arg# 5
      16(%esp)    Arg# 4
      12(%esp)    Arg# 3
       8(%esp)    Arg# 2
       4(%esp)    Arg# 1
        (%esp)    Return address

   (Of course a function with say 3 arguments does not have entries for
   arguments 4 and 5.)

   The following code tries hard to be optimal.  A general assumption
   (which is true according to the data books I have) is that

      2 * xchg    is more expensive than  pushl + movl + popl

   Beside this a neat trick is used.  The calling conventions for Linux
   tell that among the registers used for parameters %ecx and %edx need
   not be saved.  Beside this we may clobber this registers even when
   they are not used for parameter passing.

   As a result one can see below that we save the content of the %ebx
   register in the %edx register when we have less than 3 arguments
   (2 * movl is less expensive than pushl + popl).

   Second unlike for the other registers we don't save the content of
   %ecx and %edx when we have more than 1 and 2 registers resp.

   The code below might look a bit long but we have to take care for
   the pipelined processors (i586).  Here the `pushl' and `popl'
   instructions are marked as NP (not pairable) but the exception is
   two consecutive of these instruction.  This gives no penalty on
   other processors though.  */

#undef      DO_CALL
#define DO_CALL(syscall_name, args)                                     \
    PUSHARGS_##args                                               \
    DOARGS_##args                                           \
    movl $SYS_ify (syscall_name), %eax;                                 \
    ENTER_KERNEL                                            \
    POPARGS_##args

#define PUSHARGS_0      /* No arguments to push.  */
#define     DOARGS_0    /* No arguments to frob.  */
#define     POPARGS_0   /* No arguments to pop.  */
#define     _PUSHARGS_0 /* No arguments to push.  */
#define _DOARGS_0(n)    /* No arguments to frob.  */
#define     _POPARGS_0  /* No arguments to pop.  */

#define PUSHARGS_1      movl %ebx, %edx; PUSHARGS_0
#define     DOARGS_1    _DOARGS_1 (4)
#define     POPARGS_1   POPARGS_0; movl %edx, %ebx
#define     _PUSHARGS_1 pushl %ebx; _PUSHARGS_0
#define _DOARGS_1(n)    movl n(%esp), %ebx; _DOARGS_0(n-4)
#define     _POPARGS_1  _POPARGS_0; popl %ebx

#define PUSHARGS_2      PUSHARGS_1
#define     DOARGS_2    _DOARGS_2 (8)
#define     POPARGS_2   POPARGS_1
#define _PUSHARGS_2     _PUSHARGS_1
#define     _DOARGS_2(n)      movl n(%esp), %ecx; _DOARGS_1 (n-4)
#define     _POPARGS_2  _POPARGS_1

#define PUSHARGS_3      _PUSHARGS_2
#define DOARGS_3  _DOARGS_3 (16)
#define POPARGS_3 _POPARGS_3
#define _PUSHARGS_3     _PUSHARGS_2
#define _DOARGS_3(n)    movl n(%esp), %edx; _DOARGS_2 (n-4)
#define _POPARGS_3      _POPARGS_2

#define PUSHARGS_4      _PUSHARGS_4
#define DOARGS_4  _DOARGS_4 (24)
#define POPARGS_4 _POPARGS_4
#define _PUSHARGS_4     pushl %esi; _PUSHARGS_3
#define _DOARGS_4(n)    movl n(%esp), %esi; _DOARGS_3 (n-4)
#define _POPARGS_4      _POPARGS_3; popl %esi

#define PUSHARGS_5      _PUSHARGS_5
#define DOARGS_5  _DOARGS_5 (32)
#define POPARGS_5 _POPARGS_5
#define _PUSHARGS_5     pushl %edi; _PUSHARGS_4
#define _DOARGS_5(n)    movl n(%esp), %edi; _DOARGS_4 (n-4)
#define _POPARGS_5      _POPARGS_4; popl %edi

#else /* !__ASSEMBLER__ */

/* We need some help from the assembler to generate optimal code.  We
   define some macros here which later will be used.  */
asm (".L__X'%ebx = 1\n\t"
     ".L__X'%ecx = 2\n\t"
     ".L__X'%edx = 2\n\t"
     ".L__X'%eax = 3\n\t"
     ".L__X'%esi = 3\n\t"
     ".L__X'%edi = 3\n\t"
     ".L__X'%ebp = 3\n\t"
     ".L__X'%esp = 3\n\t"
     ".macro bpushl name reg\n\t"
     ".if 1 - \\name\n\t"
     ".if 2 - \\name\n\t"
     "pushl %ebx\n\t"
     ".else\n\t"
     "xchgl \\reg, %ebx\n\t"
     ".endif\n\t"
     ".endif\n\t"
     ".endm\n\t"
     ".macro bpopl name reg\n\t"
     ".if 1 - \\name\n\t"
     ".if 2 - \\name\n\t"
     "popl %ebx\n\t"
     ".else\n\t"
     "xchgl \\reg, %ebx\n\t"
     ".endif\n\t"
     ".endif\n\t"
     ".endm\n\t"
     ".macro bmovl name reg\n\t"
     ".if 1 - \\name\n\t"
     ".if 2 - \\name\n\t"
     "movl \\reg, %ebx\n\t"
     ".endif\n\t"
     ".endif\n\t"
     ".endm\n\t");

/* Define a macro which expands inline into the wrapper code for a system
   call.  */
#undef INLINE_SYSCALL
#define INLINE_SYSCALL(name, nr, args...) \
  ({                                                        \
    unsigned int resultvar = INTERNAL_SYSCALL (name, , nr, args);       \
    if (__builtin_expect (INTERNAL_SYSCALL_ERROR_P (resultvar, ), 0))         \
      {                                                           \
      __set_errno (INTERNAL_SYSCALL_ERRNO (resultvar, ));               \
      resultvar = 0xffffffff;                                     \
      }                                                           \
    (int) resultvar; })

/* Define a macro which expands inline into the wrapper code for a system
   call.  This use is for internal calls that do not need to handle errors
   normally.  It will never touch errno.  This returns just what the kernel
   gave back.  */
#undef INTERNAL_SYSCALL
#ifdef I386_USE_SYSENTER
# ifdef SHARED
#  define INTERNAL_SYSCALL(name, err, nr, args...) \
  ({                                                        \
    unsigned int resultvar;                                       \
    asm volatile (                                                \
    LOADARGS_##nr                                           \
    "movl %1, %%eax\n\t"                                          \
    "call *%%gs:%P2\n\t"                                          \
    RESTOREARGS_##nr                                              \
    : "=a" (resultvar)                                            \
    : "i" (__NR_##name), "i" (offsetof (tcbhead_t, sysinfo))                  \
      ASMFMT_##nr(args) : "memory", "cc");                              \
    (int) resultvar; })
# else
#  define INTERNAL_SYSCALL(name, err, nr, args...) \
  ({                                                        \
    unsigned int resultvar;                                       \
    asm volatile (                                                \
    LOADARGS_##nr                                           \
    "movl %1, %%eax\n\t"                                          \
    "call *_dl_sysinfo\n\t"                                       \
    RESTOREARGS_##nr                                              \
    : "=a" (resultvar)                                            \
    : "i" (__NR_##name) ASMFMT_##nr(args) : "memory", "cc");                  \
    (int) resultvar; })
# endif
#else
# define INTERNAL_SYSCALL(name, err, nr, args...) \
  ({                                                        \
    unsigned int resultvar;                                       \
    asm volatile (                                                \
    LOADARGS_##nr                                           \
    "movl %1, %%eax\n\t"                                          \
    "int $0x80\n\t"                                         \
    RESTOREARGS_##nr                                              \
    : "=a" (resultvar)                                            \
    : "i" (__NR_##name) ASMFMT_##nr(args) : "memory", "cc");                  \
    (int) resultvar; })
#endif

#undef INTERNAL_SYSCALL_DECL
#define INTERNAL_SYSCALL_DECL(err) do { } while (0)

#undef INTERNAL_SYSCALL_ERROR_P
#define INTERNAL_SYSCALL_ERROR_P(val, err) \
  ((unsigned int) (val) >= 0xfffff001u)

#undef INTERNAL_SYSCALL_ERRNO
#define INTERNAL_SYSCALL_ERRNO(val, err)  (-(val))

#define LOADARGS_0
#if defined I386_USE_SYSENTER && defined SHARED
# define LOADARGS_1 \
    "bpushl .L__X'%k3, %k3\n\t"                                         \
    "bmovl .L__X'%k3, %k3\n\t"
#else
# define LOADARGS_1 \
    "bpushl .L__X'%k2, %k2\n\t"                                         \
    "bmovl .L__X'%k2, %k2\n\t"
#endif
#define LOADARGS_2      LOADARGS_1
#define LOADARGS_3      LOADARGS_1
#define LOADARGS_4      LOADARGS_1
#define LOADARGS_5      LOADARGS_1

#define RESTOREARGS_0
#if defined I386_USE_SYSENTER && defined SHARED
# define RESTOREARGS_1 \
    "bpopl .L__X'%k3, %k3\n\t"
#else
# define RESTOREARGS_1 \
    "bpopl .L__X'%k2, %k2\n\t"
#endif
#define RESTOREARGS_2   RESTOREARGS_1
#define RESTOREARGS_3   RESTOREARGS_1
#define RESTOREARGS_4   RESTOREARGS_1
#define RESTOREARGS_5   RESTOREARGS_1

#define ASMFMT_0()
#define ASMFMT_1(arg1) \
      , "acdSD" (arg1)
#define ASMFMT_2(arg1, arg2) \
      , "adSD" (arg1), "c" (arg2)
#define ASMFMT_3(arg1, arg2, arg3) \
      , "aSD" (arg1), "c" (arg2), "d" (arg3)
#define ASMFMT_4(arg1, arg2, arg3, arg4) \
      , "aD" (arg1), "c" (arg2), "d" (arg3), "S" (arg4)
#define ASMFMT_5(arg1, arg2, arg3, arg4, arg5) \
      , "a" (arg1), "c" (arg2), "d" (arg3), "S" (arg4), "D" (arg5)

#endif      /* __ASSEMBLER__ */

#endif /* linux/i386/sysdep.h */

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