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71 lines
2.1 KiB
ArmAsm
71 lines
2.1 KiB
ArmAsm
/* Copyright (C) 1996-2020 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by David Mosberger <davidm@azstarnet.com>, 1996.
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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 Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the 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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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library. If not, see
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<https://www.gnu.org/licenses/>. */
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#include <sysdep.h>
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/*
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* This is for COMPATIBILITY with Linux/x86 only. Linux/Alpha system
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* calls return an error indication in a3. This allows arbitrary 64bit
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* values to be returned in v0 (because negative values are not
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* mistaken as error numbers). However, C allows only one value to
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* be returned, so the interface below folds the error indication passed in
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* a3 back into v0: it sets v0 to -errno if an error occurs. Thus,
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* no negative 64bit numbers can be returned. To avoid this problem,
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* use assembly stubs wherever possible/convenient.
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*
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* Usage:
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*
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* long syscall(syscall_number, arg1, arg2, arg3, arg4, arg5, arg6)
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*
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* syscall_number = the index of the system call we're invoking
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* arg1-arg6 = up to 6 integer arguments to the system call
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*
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* We need to do some arg shifting: the kernel expects the
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* syscall number in v0 and the first six args in a0-a5.
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*
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*/
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LEAF(__syscall, 0)
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#ifdef PROF
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ldgp gp, 0(pv)
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.set noat
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lda AT, _mcount
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jsr AT, (AT), _mcount
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.set at
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.prologue 1
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#else
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.prologue 0
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#endif
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mov a0, v0 /* Syscall number -> v0 */
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mov a1, a0 /* arg1-arg5 -> a0-a4 */
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mov a2, a1
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mov a3, a2
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mov a4, a3
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mov a5, a4
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ldq a5,0(sp) /* arg6 -> a5 */
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call_pal PAL_callsys /* Invoke system call */
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bne a3, SYSCALL_ERROR_LABEL
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ret
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PSEUDO_END(__syscall)
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weak_alias (__syscall, syscall)
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