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#
# Copyright (c) 2007 Jakub Jermar
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
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.text

/** Syscall wrapper - INT $0x30 version.
 *
 * Mind the order of arguments. First two arguments and the syscall number go to
 * scratch registers. An optimized version of this wrapper for fewer arguments
 * could benefit from this and not save unused registers on the stack.
 */
.global __syscall_int
__syscall_int:
    pushl %ebx
    pushl %esi
    pushl %edi
    pushl %ebp
    movl 20(%esp), %edx # First argument.
    movl 24(%esp), %ecx # Second argument.
    movl 28(%esp), %ebx # Third argument.
    movl 32(%esp), %esi # Fourth argument.
    movl 36(%esp), %edi # Fifth argument.
    movl 40(%esp), %ebp # Sixth argument.
    movl 44(%esp), %eax # Syscall number.
    int $0x30
    popl %ebp
    popl %edi
    popl %esi
    popl %ebx
    ret


/** Syscall wrapper - SYSENTER version.
 *
 * This is an optimized version of syscall for four or less arguments.  Note
 * that EBP and EDI are used to remember user stack address and the return
 * address. The kernel part doesn't save DS, ES and FS so the handler restores
 * these to the selector immediately following CS (it must be the flat data
 * segment, otherwise the SYSENTER wouldn't work in the first place).
 */
.global __syscall_sysenter
__syscall_sysenter:
    pushl %ebx
    pushl %esi
    pushl %edi
    pushl %ebp
    mov %esp, %ebp
    lea ra, %edi
    movl 20(%esp), %edx # First argument.
    movl 24(%esp), %ecx # Second argument.
    movl 28(%esp), %ebx # Third argument.
    movl 32(%esp), %esi # Fourth argument.
    movl 44(%esp), %eax # Syscall number.
    sysenter
ra:
    movw %cs, %cx
    addw $8, %cx
    movw %cx, %ds
    movw %cx, %es
    movw %cx, %fs
    popl %ebp
    popl %edi
    popl %esi
    popl %ebx
    ret