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f4f4caab0e
I wanted a tiny scriptable meltdown proof way to run userspace programs and visualize how program execution impacts memory. It helps to explain how things like Actually Portable Executable works. It can show you how the GCC generated code is going about manipulating matrices and more. I didn't feel fully comfortable with Qemu and Bochs because I'm not smart enough to understand them. I wanted something like gVisor but with much stronger levels of assurances. I wanted a single binary that'll run, on all major operating systems with an embedded GPL barrier ZIP filesystem that is tiny enough to transpile to JavaScript and run in browsers too. https://justine.storage.googleapis.com/emulator625.mp4
44 lines
2.7 KiB
ArmAsm
44 lines
2.7 KiB
ArmAsm
/*-*- mode:unix-assembly; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
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│vi: set et ft=asm ts=8 tw=8 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ This program is free software; you can redistribute it and/or modify │
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│ it under the terms of the GNU General Public License as published by │
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│ the Free Software Foundation; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ 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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│ General Public License for more details. │
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│ │
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│ You should have received a copy of the GNU General Public License │
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│ along with this program; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/macros.h"
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.source __FILE__
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/ Performs raw System Five system call.
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/
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/ This function provides a direct path into system call support
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/ that's friendly to C code, since it doesn't need an intermediate
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/ thunk. It only supports arities up to six, since there's no way
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/ to do more safely; this isn't a problem with Linux, although
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/ certain BSD calls may not be available.
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/
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/ @param %rdi is system call ordinal, which isn't translated,
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/ and must be correct for the underlying host system
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/ @param %rsi,%rdx,%rcx,%r8,%r9 may supply parameters 1 through 5
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/ @param sixth is optionally pushed on the stack before call
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/ @return %rax has result, or -1 w/ errno on failure
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syscall:mov %rdi,%rax
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mov %rsi,%rdi
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mov %rdx,%rsi
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mov %rcx,%rdx
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mov %r8,%rcx # ← intended
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mov %r9,%r8
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mov 8(%rsp),%r9
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jmp *systemfive(%rip)
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.endfn syscall,globl
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