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Add x86_64-linux-gnu emulator
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
This commit is contained in:
Justine Tunney
parent
467504308a
commit
f4f4caab0e
1052 changed files with 65667 additions and 7825 deletions
218
tool/build/lib/pml4t.c
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218
tool/build/lib/pml4t.c
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/*-*- 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/log/check.h"
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#include "libc/macros.h"
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#include "libc/mem/mem.h"
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#include "libc/str/str.h"
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#include "libc/sysv/errfuns.h"
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#include "tool/build/lib/memory.h"
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#include "tool/build/lib/pml4t.h"
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static int64_t MakeAddress(unsigned short a[4]) {
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uint64_t x;
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x = 0;
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x |= a[0];
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x <<= 9;
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x |= a[1];
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x <<= 9;
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x |= a[2];
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x <<= 9;
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x |= a[3];
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x <<= 12;
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return SignExtendAddr(x);
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}
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static uint64_t *GetPageTable(pml4t_t p, long i, void *NewPhysicalPage(void)) {
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uint64_t *res;
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DCHECK_ALIGNED(4096, p);
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DCHECK(0 <= i && i < 512);
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if (IsValidPage(p[i])) {
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res = UnmaskPageAddr(p[i]);
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} else if ((res = NewPhysicalPage())) {
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DCHECK_ALIGNED(4096, res);
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p[i] = MaskPageAddr(res) | 0b11;
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}
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return res;
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}
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/**
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* Maps virtual page region to system memory region.
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*
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* @param pml4t is root of 48-bit page tables
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* @param v is fixed page-aligned virtual address, rounded down
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* @param r is real memory address, rounded down
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* @param n is number of bytes needed, rounded up
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* @return 0 on success, or -1 w/ errno
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* @note existing pages are overwritten
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*/
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int RegisterPml4t(pml4t_t pml4t, int64_t v, int64_t r, size_t n,
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void *NewPhysicalPage(void)) {
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unsigned i, j, k, l;
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uint64_t *pdpt, *pdt, *pd, u;
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if (!n) return 0;
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u = ROUNDDOWN(r, 4096);
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n = ROUNDUP(n, 4096) >> 12;
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i = (v >> 39) & 511;
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j = (v >> 30) & 511;
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k = (v >> 21) & 511;
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l = (v >> 12) & 511;
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if (u + n > 0x800000000000) return eoverflow();
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if (r + n > 0x800000000000) return eoverflow();
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for (; i < 512; ++i) {
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if (!(pdpt = GetPageTable(pml4t, i, NewPhysicalPage))) return -1;
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for (; j < 512; ++j) {
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if (!(pdt = GetPageTable(pdpt, j, NewPhysicalPage))) return -1;
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for (; k < 512; ++k) {
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if (!(pd = GetPageTable(pdt, k, NewPhysicalPage))) return -1;
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for (; l < 512; ++l) {
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pd[l] = MaskPageAddr(u) | 0b11;
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if (!--n) return 0;
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u += 4096;
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}
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l = 0;
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}
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k = 0;
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}
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j = 0;
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}
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return enomem();
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}
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/**
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* Locates free memory range.
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*
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* @param hint specifies signedness and around where to start searching
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* @return virtual page address with size bytes free, or -1 w/ errno
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*/
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int64_t FindPml4t(pml4t_t pml4t, int64_t hint, uint64_t size,
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void *NewPhysicalPage(void)) {
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int64_t res;
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unsigned short a[4], b[4];
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uint64_t *pdpt, *pdt, *pd, have;
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if (!size) return einval();
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have = 0;
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size = ROUNDUP(size, 4096) >> 12;
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b[0] = a[0] = (hint >> 39) & 511;
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b[1] = a[1] = (hint >> 30) & 511;
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b[2] = a[2] = (hint >> 21) & 511;
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a[3] = 0;
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for (; b[0] < 512; ++b[0]) {
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if (!(pdpt = GetPageTable(pml4t, b[0], NewPhysicalPage))) return -1;
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for (; b[1] < 512; ++b[1]) {
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if (!(pdt = GetPageTable(pdpt, b[1], NewPhysicalPage))) return -1;
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for (; b[2] < 512; ++b[2]) {
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if (!IsValidPage(pdt[b[2]])) {
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if ((have += 512) >= size) {
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return MakeAddress(a);
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}
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} else if (size < 0x200) {
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pd = UnmaskPageAddr(pdt[b[2]]);
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for (b[3] = 0; b[3] < 512; ++b[3]) {
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if (!IsValidPage(pd[b[3]])) {
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if ((have += 1) >= size) {
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return MakeAddress(a);
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}
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} else {
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have = 0;
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a[0] = b[0];
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a[1] = b[1];
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a[2] = b[2];
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a[3] = b[3];
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if ((a[3] += 1) == 512) {
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a[3] = 0;
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if ((a[2] += 1) == 512) {
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a[2] = 0;
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if ((a[1] += 1) == 512) {
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a[1] = 0;
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a[0] += 1;
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if (a[0] == 256 || a[0] == 512) {
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return eoverflow();
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}
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}
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}
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}
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}
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}
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}
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}
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a[2] = 0;
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}
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a[1] = 0;
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}
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return enomem();
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}
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/**
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* Unmaps pages and frees page tables.
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*/
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int FreePml4t(pml4t_t pml4t, int64_t addr, uint64_t size,
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void FreePhysicalPageTable(void *),
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int FreePhysicalPages(void *, size_t)) {
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int rc;
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char *pages;
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uint64_t i, *pdpt, *pdt, *pd;
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unsigned short r, s[4], a[4], R[2][2] = {{256, 512}, {0, 256}};
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a[0] = addr >> 39;
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a[1] = addr >> 30;
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a[2] = addr >> 21;
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a[3] = addr >> 12;
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size = ROUNDUP(size, 4096) >> 12;
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for (rc = r = 0; r < ARRAYLEN(R); ++r) {
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for (a[0] &= 511; size && R[r][0] <= a[0] && a[0] < R[r][1]; ++a[0]) {
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if (!IsValidPage(pml4t[a[0]])) continue;
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pdpt = UnmaskPageAddr(pml4t[a[0]]);
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for (s[1] = (a[1] &= 511); size && a[1] < 512; ++a[1]) {
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if (!IsValidPage(pdpt[a[1]])) continue;
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pdt = UnmaskPageAddr(pdpt[a[1]]);
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for (s[2] = (a[2] &= 511); size && a[2] < 512; ++a[2]) {
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if (!IsValidPage(pdt[a[2]])) continue;
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pd = UnmaskPageAddr(pdt[a[2]]);
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for (s[3] = (a[3] &= 511); size && a[3] < 512; ++a[3]) {
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if (IsValidPage(pd[a[3]])) {
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pages = UnmaskPageAddr(pd[a[3]]);
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pd[a[3]] = 0;
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for (i = 1; i + 1 < size && a[3] + i < 512; ++i) {
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if (!IsValidPage(pd[a[3] + i])) break;
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if (UnmaskPageAddr(pd[a[3] + i]) != pages + i * 4096) break;
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pd[a[3] + i] = 0;
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}
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FreePhysicalPages(pages, i * 4096);
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a[3] += i - 1;
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size -= i;
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}
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}
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if (s[3] == 0 && a[3] == 512) {
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FreePhysicalPageTable(pd);
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pdt[a[2]] = 0;
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}
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}
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if (s[2] == 0 && a[2] == 512) {
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FreePhysicalPageTable(pdt);
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pdpt[a[1]] = 0;
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}
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}
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if (s[1] == 0 && a[1] == 512) {
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FreePhysicalPageTable(pdpt);
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pml4t[a[0]] = 0;
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}
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}
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}
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return 0;
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}
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