#
# 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
# are met:
#
# - Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# - Redistributions in binary form must reproduce the above copyright
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# - The name of the author may not be used to endorse or promote products
# derived from this software without specific prior written permission.
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# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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#include <abi/asmtool.h>
.data
OBJECT_BEGIN(__syscall_fast_func)
.long __syscall_slow
OBJECT_END(__syscall_fast_func)
.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.
*/
FUNCTION_BEGIN(__syscall_slow)
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
FUNCTION_END(__syscall_slow)
/** 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).
*/
FUNCTION_BEGIN(__syscall_fast)
pushl %ebx
pushl %esi
pushl %edi
pushl %ebp
mov %esp, %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 44(%esp), %eax # Syscall number.
call 1f
movw %cs, %cx
addw $8, %cx
movw %cx, %ds
movw %cx, %es
movw %cx, %fs
popl %ebp
popl %edi
popl %esi
popl %ebx
ret
/* Trampoline for entering kernel */
1:
pop %edi
sysenter
FUNCTION_END(__syscall_fast)