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https://github.com/jart/cosmopolitan.git
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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
111 lines
4.5 KiB
C
111 lines
4.5 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 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/alg/bisectcarleft.h"
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#include "libc/bits/bits.h"
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#include "libc/bits/safemacros.h"
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#include "libc/calls/calls.h"
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#include "libc/calls/internal.h"
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#include "libc/calls/struct/sigset.h"
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#include "libc/dce.h"
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#include "libc/macros.h"
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#include "libc/nt/files.h"
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#include "libc/nt/runtime.h"
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#include "libc/nt/thunk/msabi.h"
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#include "libc/runtime/internal.h"
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#include "libc/runtime/missioncritical.h"
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#include "libc/runtime/runtime.h"
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#include "libc/runtime/symbols.h"
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#include "libc/sysv/consts/fileno.h"
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#include "libc/sysv/consts/nr.h"
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#include "libc/sysv/consts/prot.h"
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#include "libc/sysv/consts/sig.h"
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/**
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* @fileoverview Plain-text function call logging.
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*
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* Able to log ~2 million function calls per second, which is mostly
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* bottlenecked by system call overhead. Log size is reasonable if piped
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* into gzip.
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*/
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static char g_buf[512];
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static const char *g_lastsymbol;
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static struct SymbolTable *g_symbols;
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forceinline int getnestinglevel(struct StackFrame *frame) {
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int nesting = -2;
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while (frame) {
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++nesting;
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frame = frame->next;
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}
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return max(0, nesting);
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}
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/**
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* Prints name of function being called.
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*
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* We insert CALL instructions that point to this function, in the
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* prologues of other functions. We assume those functions behave
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* according to the System Five NexGen32e ABI.
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*/
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privileged interruptfn void ftrace_hook(void) {
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size_t i, j, nesting;
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const char *symbol;
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struct StackFrame *frame;
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LOAD_DEFAULT_RBX();
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if (g_symbols && !(g_runstate & RUNSTATE_BROKEN)) {
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frame = __builtin_frame_address(0);
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symbol =
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&g_symbols->name_base[g_symbols
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->symbols[bisectcarleft(
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(const int32_t(*)[2])g_symbols->symbols,
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g_symbols->count,
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frame->addr - g_symbols->addr_base)]
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.name_rva];
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if (symbol != g_lastsymbol &&
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(nesting = getnestinglevel(frame)) * 2 < ARRAYLEN(g_buf) - 3) {
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i = 2;
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j = 0;
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while (nesting--) {
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g_buf[i++] = ' ';
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g_buf[i++] = ' ';
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}
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while (i < ARRAYLEN(g_buf) - 2 && symbol[j]) {
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g_buf[i++] = symbol[j++];
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}
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g_buf[i++] = '\n';
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__print(g_buf, i);
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}
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g_lastsymbol = symbol;
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}
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RESTORE_RBX();
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}
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/**
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* Installs plaintext function tracer. Do not call.
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* @see libc/runtime/_init.S for documentation
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*/
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textstartup void ftrace_init(void) {
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g_buf[0] = '+';
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g_buf[1] = ' ';
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if ((g_symbols = opensymboltable(finddebugbinary()))) {
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__hook(ftrace_hook, g_symbols);
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}
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}
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