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53 lines
2.7 KiB
ArmAsm
53 lines
2.7 KiB
ArmAsm
/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
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│ vi: set noet ft=asm ts=8 sw=8 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2023 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/macros.h"
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// Invokes system call w/ arity of four.
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//
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// This function takes four params. The first four, are for
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// args passed along to the system call. The 5th is for the
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// the magic number, indicating which system call is called
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//
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// The return value follows the Linux Kernel (System V) ABI
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// where -errno is returned, rather than doing -1 w/ errno.
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//
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// This helper should not be used to do cancelation points.
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__syscall4:
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#ifdef __aarch64__
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mov x8,x4 // syscall number (linux)
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mov x16,x4 // syscall number (xnu)
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mov x9,0 // clear carry flag
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adds x9,x9,0 // clear carry flag
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svc 0
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bcs 1f
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ret
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1: neg x0,x0
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ret
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#elif defined(__x86_64__)
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mov %rcx,%r10 // avoid intel cx clobber
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mov %r8d,%eax // arg5 -> syscall number
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clc // linux saves carry flag
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syscall // bsds set carry on errs
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jnc 1f
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neg %rax // normalizes to system v
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1: ret
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#else
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#error "unsupported architecture"
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#endif
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.endfn __syscall4,globl
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