78e5779b1e
1998-10-22 12:49 Ulrich Drepper <drepper@cygnus.com> * sysdeps/unix/sysv/linux/i386/sysdep.h: Drastically simplify and improve INLINE_SYSCALL using macro assembler magic.
275 lines
8.9 KiB
C
275 lines
8.9 KiB
C
/* Copyright (C) 1992, 93, 95, 96, 97, 98 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper, <drepper@gnu.ai.mit.edu>, August 1995.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If not,
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write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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#ifndef _LINUX_I386_SYSDEP_H
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#define _LINUX_I386_SYSDEP_H 1
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/* There is some commonality. */
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#include <sysdeps/unix/i386/sysdep.h>
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/* For Linux we can use the system call table in the header file
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/usr/include/asm/unistd.h
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of the kernel. But these symbols do not follow the SYS_* syntax
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so we have to redefine the `SYS_ify' macro here. */
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#undef SYS_ify
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#define SYS_ify(syscall_name) __NR_##syscall_name
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/* ELF-like local names start with `.L'. */
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#undef L
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#define L(name) .L##name
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#ifdef __ASSEMBLER__
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/* Linux uses a negative return value to indicate syscall errors,
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unlike most Unices, which use the condition codes' carry flag.
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Since version 2.1 the return value of a system call might be
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negative even if the call succeeded. E.g., the `lseek' system call
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might return a large offset. Therefore we must not anymore test
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for < 0, but test for a real error by making sure the value in %eax
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is a real error number. Linus said he will make sure the no syscall
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returns a value in -1 .. -4095 as a valid result so we can savely
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test with -4095. */
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/* We don't want the label for the error handle to be global when we define
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it here. */
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#ifdef PIC
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# define SYSCALL_ERROR_LABEL 0f
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#else
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# define SYSCALL_ERROR_LABEL syscall_error
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#endif
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#undef PSEUDO
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#define PSEUDO(name, syscall_name, args) \
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.text; \
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ENTRY (name) \
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DO_CALL (args, syscall_name); \
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cmpl $-4095, %eax; \
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jae SYSCALL_ERROR_LABEL; \
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L(pseudo_end):
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#undef PSEUDO_END
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#define PSEUDO_END(name) \
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SYSCALL_ERROR_HANDLER \
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END (name)
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#ifndef PIC
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#define SYSCALL_ERROR_HANDLER /* Nothing here; code in sysdep.S is used. */
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#else
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/* Store (- %eax) into errno through the GOT. */
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#ifdef _LIBC_REENTRANT
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#define SYSCALL_ERROR_HANDLER \
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0:pushl %ebx; \
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call 1f; \
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1:popl %ebx; \
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xorl %edx, %edx; \
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addl $_GLOBAL_OFFSET_TABLE_+[.-1b], %ebx; \
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subl %eax, %edx; \
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pushl %edx; \
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call __errno_location@PLT; \
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popl %ecx; \
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popl %ebx; \
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movl %ecx, (%eax); \
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orl $-1, %eax; \
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jmp L(pseudo_end);
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/* A quick note: it is assumed that the call to `__errno_location' does
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not modify the stack! */
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#else
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#define SYSCALL_ERROR_HANDLER \
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0:call 1f; \
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1:popl %ecx; \
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xorl %edx, %edx; \
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addl $_GLOBAL_OFFSET_TABLE_+[.-1b], %ecx; \
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subl %eax, %edx; \
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movl errno@GOT(%ecx), %ecx; \
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movl %edx, (%ecx); \
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orl $-1, %eax; \
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jmp L(pseudo_end);
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#endif /* _LIBC_REENTRANT */
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#endif /* PIC */
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/* Linux takes system call arguments in registers:
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syscall number %eax call-clobbered
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arg 1 %ebx call-saved
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arg 2 %ecx call-clobbered
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arg 3 %edx call-clobbered
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arg 4 %esi call-saved
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arg 5 %edi call-saved
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The stack layout upon entering the function is:
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20(%esp) Arg# 5
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16(%esp) Arg# 4
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12(%esp) Arg# 3
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8(%esp) Arg# 2
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4(%esp) Arg# 1
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(%esp) Return address
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(Of course a function with say 3 arguments does not have entries for
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arguments 4 and 5.)
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The following code tries hard to be optimal. A general assumption
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(which is true according to the data books I have) is that
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2 * xchg is more expensive than pushl + movl + popl
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Beside this a neat trick is used. The calling conventions for Linux
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tell that among the registers used for parameters %ecx and %edx need
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not be saved. Beside this we may clobber this registers even when
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they are not used for parameter passing.
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As a result one can see below that we save the content of the %ebx
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register in the %edx register when we have less than 3 arguments
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(2 * movl is less expensive than pushl + popl).
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Second unlike for the other registers we don't save the content of
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%ecx and %edx when we have more than 1 and 2 registers resp.
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The code below might look a bit long but we have to take care for
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the pipelined processors (i586). Here the `pushl' and `popl'
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instructions are marked as NP (not pairable) but the exception is
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two consecutive of these instruction. This gives no penalty on
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other processors though. */
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#undef DO_CALL
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#define DO_CALL(args, syscall_name) \
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PUSHARGS_##args \
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DOARGS_##args \
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movl $SYS_ify (syscall_name), %eax; \
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int $0x80 \
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POPARGS_##args
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#define PUSHARGS_0 /* No arguments to push. */
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#define DOARGS_0 /* No arguments to frob. */
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#define POPARGS_0 /* No arguments to pop. */
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#define _PUSHARGS_0 /* No arguments to push. */
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#define _DOARGS_0(n) /* No arguments to frob. */
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#define _POPARGS_0 /* No arguments to pop. */
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#define PUSHARGS_1 movl %ebx, %edx; PUSHARGS_0
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#define DOARGS_1 _DOARGS_1 (4)
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#define POPARGS_1 POPARGS_0; movl %edx, %ebx
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#define _PUSHARGS_1 pushl %ebx; _PUSHARGS_0
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#define _DOARGS_1(n) movl n(%esp), %ebx; _DOARGS_0(n-4)
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#define _POPARGS_1 _POPARGS_0; popl %ebx
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#define PUSHARGS_2 PUSHARGS_1
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#define DOARGS_2 _DOARGS_2 (8)
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#define POPARGS_2 POPARGS_1
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#define _PUSHARGS_2 _PUSHARGS_1
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#define _DOARGS_2(n) movl n(%esp), %ecx; _DOARGS_1 (n-4)
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#define _POPARGS_2 _POPARGS_1
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#define PUSHARGS_3 _PUSHARGS_2
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#define DOARGS_3 _DOARGS_3 (16)
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#define POPARGS_3 _POPARGS_3
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#define _PUSHARGS_3 _PUSHARGS_2
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#define _DOARGS_3(n) movl n(%esp), %edx; _DOARGS_2 (n-4)
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#define _POPARGS_3 _POPARGS_2
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#define PUSHARGS_4 _PUSHARGS_4
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#define DOARGS_4 _DOARGS_4 (24)
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#define POPARGS_4 _POPARGS_4
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#define _PUSHARGS_4 pushl %esi; _PUSHARGS_3
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#define _DOARGS_4(n) movl n(%esp), %esi; _DOARGS_3 (n-4)
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#define _POPARGS_4 _POPARGS_3; popl %esi
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#define PUSHARGS_5 _PUSHARGS_5
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#define DOARGS_5 _DOARGS_5 (32)
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#define POPARGS_5 _POPARGS_5
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#define _PUSHARGS_5 pushl %edi; _PUSHARGS_4
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#define _DOARGS_5(n) movl n(%esp), %edi; _DOARGS_4 (n-4)
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#define _POPARGS_5 _POPARGS_4; popl %edi
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#else /* !__ASSEMBLER__ */
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/* We need some help from the assembler to generate optimal code. We
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define some macros here which later will be used. */
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asm ("__X'%ebx = 1\n\t"
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"__X'%ecx = 2\n\t"
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"__X'%edx = 2\n\t"
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"__X'%eax = 3\n\t"
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"__X'%esi = 3\n\t"
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"__X'%edi = 3\n\t"
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"__X'%ebp = 3\n\t"
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"__X'%esp = 3\n\t"
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".macro bpushl name reg\n\t"
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".if 1 - \\name\n\t"
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".if 2 - \\name\n\t"
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"pushl %ebx\n\t"
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".else\n\t"
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"xchgl \\reg, %ebx\n\t"
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".endif\n\t"
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".endif\n\t"
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".endm\n\t"
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".macro bpopl name reg\n\t"
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".if 1 - \\name\n\t"
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".if 2 - \\name\n\t"
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"popl %ebx\n\t"
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".else\n\t"
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"xchgl \\reg, %ebx\n\t"
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".endif\n\t"
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".endif\n\t"
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".endm\n\t"
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".macro bmovl name reg\n\t"
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".if 1 - \\name\n\t"
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".if 2 - \\name\n\t"
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"movl \\reg, %ebx\n\t"
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".endif\n\t"
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".endif\n\t"
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".endm\n\t");
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/* Define a macro which expands inline into the wrapper code for a system
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call. */
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#undef INLINE_SYSCALL
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#define INLINE_SYSCALL(name, nr, args...) \
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({ \
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unsigned int resultvar; \
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asm volatile ( \
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"bpushl __X'%k2, %k2\n\t" \
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"bmovl __X'%k2, %k2\n\t" \
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"movl %1, %%eax\n\t" \
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"int $0x80\n\t" \
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"bpopl __X'%k2, %k2\n\t" \
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: "=a" (resultvar) \
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: "i" (__NR_##name) ASMFMT_##nr(args) : "memory", "cc"); \
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if (resultvar >= 0xfffff001) \
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{ \
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__set_errno (-resultvar); \
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resultvar = 0xffffffff; \
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} \
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(int) resultvar; })
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#define ASMFMT_0()
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#define ASMFMT_1(arg1) \
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, "acdSD" (arg1)
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#define ASMFMT_2(arg1, arg2) \
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, "adCD" (arg1), "c" (arg2)
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#define ASMFMT_3(arg1, arg2, arg3) \
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, "aCD" (arg1), "c" (arg2), "d" (arg3)
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#define ASMFMT_4(arg1, arg2, arg3, arg4) \
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, "aD" (arg1), "c" (arg2), "d" (arg3), "S" (arg4)
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#define ASMFMT_5(arg1, arg2, arg3, arg4, arg5) \
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, "a" (arg1), "c" (arg2), "d" (arg3), "S" (arg4), "D" (arg5)
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#endif /* __ASSEMBLER__ */
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#endif /* linux/i386/sysdep.h */
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