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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
122 lines
4.3 KiB
C
122 lines
4.3 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/assert.h"
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#include "libc/bits/weaken.h"
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#include "libc/macros.h"
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#include "libc/mem/mem.h"
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#include "libc/nexgen32e/bsf.h"
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#include "libc/nexgen32e/bsr.h"
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#include "libc/runtime/runtime.h"
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#include "libc/sysv/errfuns.h"
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static struct CxaAtexitBlocks {
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struct CxaAtexitBlock {
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unsigned mask;
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struct CxaAtexitBlock *next;
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struct CxaAtexit {
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void *fp;
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void *arg;
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void *pred;
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} p[ATEXIT_MAX];
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} * p, root;
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} __cxa_blocks;
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/**
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* Adds global destructor.
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*
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* Destructors are called in reverse order. They won't be called if the
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* program aborts or _exit() is called. Invocations of this function are
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* usually generated by the C++ compiler. Behavior is limitless if you
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* choose to link calloc() and free().
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*
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* @param fp is void(*)(T)
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* @param arg is passed to callback
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* @param pred can be non-null for things like dso modules
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* @return 0 on success or nonzero w/ errno
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* @note folks have forked libc in past just to unbloat atexit()
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*/
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int __cxa_atexit(void *fp, void *arg, void *pred) {
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unsigned i;
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struct CxaAtexitBlock *b, *b2;
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b = __cxa_blocks.p;
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if (!b) b = __cxa_blocks.p = &__cxa_blocks.root;
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if (!~b->mask) {
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if (weaken(calloc) &&
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(b2 = weaken(calloc)(1, sizeof(struct CxaAtexitBlock)))) {
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b2->next = b;
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__cxa_blocks.p = b = b2;
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} else {
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return enomem();
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}
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}
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i = bsr(~b->mask);
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assert(i < ARRAYLEN(b->p));
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b->mask |= 1u << i;
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b->p[i].fp = fp;
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b->p[i].arg = arg;
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b->p[i].pred = pred;
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return 0;
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}
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/**
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* Triggers global destructors.
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*
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* @param pred can be null to match all
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* @note reentrant emptor
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*/
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void __cxa_finalize(void *pred) {
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unsigned i;
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unsigned long mask;
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struct CxaAtexitBlock *b, *b2;
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StartOver:
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if ((b = __cxa_blocks.p)) {
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for (;;) {
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mask = b->mask;
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while (mask) {
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i = bsf(mask);
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mask &= ~(1u << i);
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if (!pred || pred == b->p[i].pred) {
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b->mask &= ~(1u << i);
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if (b->p[i].fp) {
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((void (*)(void *))b->p[i].fp)(b->p[i].arg);
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goto StartOver;
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}
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}
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}
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if (!pred) {
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b2 = b->next;
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if (b2) {
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assert(b != &__cxa_blocks.root);
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if (weaken(free)) {
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weaken(free)(b);
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}
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}
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__cxa_blocks.p = b2;
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goto StartOver;
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} else {
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if (b->next) {
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b = b->next;
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} else {
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break;
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}
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}
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}
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}
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}
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