mirror of
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
227 lines
7.6 KiB
C
227 lines
7.6 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/log/log.h"
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#include "libc/macros.h"
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#include "libc/runtime/runtime.h"
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#include "tool/build/lib/alu.h"
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#include "tool/build/lib/endian.h"
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#include "tool/build/lib/flags.h"
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#include "tool/build/lib/ioports.h"
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#include "tool/build/lib/machine.h"
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#include "tool/build/lib/memory.h"
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#include "tool/build/lib/modrm.h"
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#include "tool/build/lib/string.h"
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#include "tool/build/lib/throw.h"
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static uint64_t ReadInt(uint8_t p[8], unsigned long w) {
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switch (w) {
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case 0:
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return Read8(p);
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case 1:
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return Read16(p);
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case 2:
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return Read32(p);
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case 3:
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return Read64(p);
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default:
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unreachable;
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}
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}
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static void WriteInt(uint8_t p[8], uint64_t x, unsigned long w) {
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switch (w) {
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case 0:
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Write8(p, x);
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break;
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case 1:
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Write16(p, x);
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break;
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case 2:
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Write64(p, x);
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break;
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case 3:
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Write64(p, x);
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break;
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default:
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unreachable;
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}
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}
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void OpString(struct Machine *m, int op) {
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void *p[2];
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bool compare;
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int64_t sgn, v;
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uint8_t s[3][8];
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unsigned n, lg2;
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uint64_t asz, seg;
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sgn = GetFlag(m->flags, FLAGS_DF) ? -1 : 1;
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asz = Asz(m->xedd) ? 0xffffffff : 0xffffffffffffffff;
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seg = GetSegment(m);
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lg2 = RegLog2(m->xedd);
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n = 1 << lg2;
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for (;;) {
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if (m->xedd->op.rep && !Read64(m->cx)) break;
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v = 0;
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*p = NULL;
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compare = false;
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switch (op) {
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case STRING_CMPS:
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Alu(lg2, ALU_SUB,
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ReadInt(Load(m, (Read64(m->si) + seg) & asz, n, s[2]), lg2),
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ReadInt(Load(m, Read64(m->di) & asz, n, s[1]), lg2), &m->flags);
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Write64(m->di, (Read64(m->di) + sgn * n) & asz);
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Write64(m->si, (Read64(m->si) + sgn * n) & asz);
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compare = true;
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break;
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case STRING_MOVS:
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memcpy(BeginStore(m, (v = Read64(m->di) & asz), n, p, s[0]),
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Load(m, (Read64(m->si) + seg) & asz, n, s[1]), n);
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Write64(m->di, (Read64(m->di) + sgn * n) & asz);
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Write64(m->si, (Read64(m->si) + sgn * n) & asz);
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break;
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case STRING_STOS:
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memcpy(BeginStore(m, (v = Read64(m->di) & asz), n, p, s[0]), m->ax, n);
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Write64(m->di, (Read64(m->di) + sgn * n) & asz);
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break;
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case STRING_LODS:
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memcpy(m->ax, Load(m, (Read64(m->si) + seg) & asz, n, s[1]), n);
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Write64(m->si, (Read64(m->si) + sgn * n) & asz);
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break;
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case STRING_SCAS:
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Alu(lg2, ALU_SUB, ReadInt(Load(m, Read64(m->di) & asz, n, s[1]), lg2),
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ReadInt(m->ax, lg2), &m->flags);
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Write64(m->di, (Read64(m->di) + sgn * n) & asz);
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compare = true;
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break;
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case STRING_OUTS:
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OpOut(m, Read16(m->dx),
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ReadInt(Load(m, (Read64(m->si) + seg) & asz, n, s[1]), lg2));
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Write64(m->si, (Read64(m->si) + sgn * n) & asz);
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break;
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case STRING_INS:
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WriteInt(BeginStore(m, (v = Read64(m->di) & asz), n, p, s[0]),
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OpIn(m, Read16(m->dx)), lg2);
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Write64(m->di, (Read64(m->di) + sgn * n) & asz);
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break;
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default:
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abort();
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}
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EndStore(m, v, n, p, s[0]);
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if (!m->xedd->op.rep) break;
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Write64(m->cx, Read64(m->cx) - 1);
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if (compare) {
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if (m->xedd->op.rep == 2 && GetFlag(m->flags, FLAGS_ZF)) break;
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if (m->xedd->op.rep == 3 && !GetFlag(m->flags, FLAGS_ZF)) break;
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}
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}
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}
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void OpRepMovsbEnhanced(struct Machine *m) {
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bool failed;
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uint8_t *direal, *sireal;
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unsigned diremain, siremain, i, n;
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uint64_t divirtual, sivirtual, diactual, siactual, failaddr, seg, asz, cx;
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if (!(cx = Read64(m->cx))) return;
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failed = false;
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failaddr = 0;
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seg = GetSegment(m);
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asz = Asz(m->xedd) ? 0xffffffff : 0xffffffffffffffff;
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divirtual = Read64(m->di) & asz;
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sivirtual = Read64(m->si) & asz;
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SetWriteAddr(m, (seg + divirtual) & asz, cx);
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SetReadAddr(m, (seg + sivirtual) & asz, cx);
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do {
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diactual = (seg + divirtual) & asz;
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siactual = (seg + sivirtual) & asz;
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if (!(direal = FindReal(m, diactual))) {
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failaddr = diactual;
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failed = true;
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break;
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}
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if (!(sireal = FindReal(m, siactual))) {
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failaddr = siactual;
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failed = true;
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break;
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}
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diremain = 0x1000 - (divirtual & 0xfff);
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siremain = 0x1000 - (sivirtual & 0xfff);
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n = MIN(cx, MIN(diremain, siremain));
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for (i = 0; i < n; ++i) {
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direal[i] = sireal[i];
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}
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cx -= n;
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divirtual = (divirtual + n) & asz;
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sivirtual = (sivirtual + n) & asz;
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} while (cx);
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Write64(m->cx, cx);
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Write64(m->di, divirtual);
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Write64(m->si, sivirtual);
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if (failed) ThrowSegmentationFault(m, failaddr);
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}
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void OpRepStosbEnhanced(struct Machine *m) {
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bool failed;
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uint8_t *direal, al;
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unsigned diremain, i, n;
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uint64_t divirtual, diactual, failaddr, seg, asz, cx;
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if (!(cx = Read64(m->cx))) return;
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failaddr = 0;
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failed = false;
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al = Read8(m->ax);
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seg = GetSegment(m);
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asz = Asz(m->xedd) ? 0xffffffff : 0xffffffffffffffff;
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divirtual = Read64(m->di) & asz;
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SetWriteAddr(m, (seg + divirtual) & asz, cx);
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do {
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diactual = (seg + divirtual) & asz;
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if (!(direal = FindReal(m, diactual))) {
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failaddr = diactual;
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failed = true;
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break;
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}
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diremain = 0x1000 - (divirtual & 0xfff);
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n = MIN(cx, diremain);
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for (i = 0; i < n; ++i) {
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direal[i] = al;
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}
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cx -= n;
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divirtual = (divirtual + n) & asz;
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} while (cx);
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Write64(m->cx, cx);
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Write64(m->di, divirtual);
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if (failed) ThrowSegmentationFault(m, failaddr);
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}
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void OpMovsb(struct Machine *m) {
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if (m->xedd->op.rep && !GetFlag(m->flags, FLAGS_DF)) {
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OpRepMovsbEnhanced(m);
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} else {
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OpString(m, STRING_MOVS);
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}
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}
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void OpStosb(struct Machine *m) {
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if (m->xedd->op.rep && !GetFlag(m->flags, FLAGS_DF)) {
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OpRepStosbEnhanced(m);
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} else {
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OpString(m, STRING_STOS);
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}
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}
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