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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
259 lines
11 KiB
C
259 lines
11 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/arraylist.h"
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#include "libc/assert.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/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/runtime/gc.h"
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#include "libc/runtime/memtrack.h"
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#include "libc/runtime/runtime.h"
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#include "libc/sysv/consts/map.h"
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#include "libc/sysv/consts/mremap.h"
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#include "libc/sysv/consts/o.h"
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#include "libc/sysv/consts/ok.h"
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#include "libc/sysv/consts/prot.h"
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#include "libc/x/x.h"
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#include "tool/build/lib/elfwriter.h"
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#include "tool/build/lib/interner.h"
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static const Elf64_Ehdr kObjHeader = {
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.e_ident = {ELFMAG0, ELFMAG1, ELFMAG2, ELFMAG3, ELFCLASS64, ELFDATA2LSB, 1,
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ELFOSABI_NONE},
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.e_type = ET_REL,
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.e_machine = EM_NEXGEN32E,
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.e_version = 1,
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.e_ehsize = sizeof(Elf64_Ehdr),
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.e_shentsize = sizeof(Elf64_Shdr)};
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static size_t AppendSection(struct ElfWriter *elf, const char *name,
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int sh_type, int sh_flags) {
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ssize_t section =
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append(elf->shdrs,
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(&(Elf64_Shdr){.sh_type = sh_type,
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.sh_flags = sh_flags,
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.sh_entsize = elf->entsize,
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.sh_addralign = elf->addralign,
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.sh_offset = sh_type != SHT_NULL ? elf->wrote : 0,
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.sh_name = intern(elf->shstrtab, name)}));
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CHECK_NE(-1, section);
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return section;
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}
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static size_t FinishSection(struct ElfWriter *elf) {
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size_t section = elf->shdrs->i - 1;
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elf->shdrs->p[section].sh_size =
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elf->wrote - elf->shdrs->p[section].sh_offset;
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return section;
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}
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static struct ElfWriterSymRef AppendSymbol(struct ElfWriter *elf,
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const char *name, int st_info,
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int st_other, size_t st_value,
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size_t st_size, size_t st_shndx,
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enum ElfWriterSymOrder slg) {
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ssize_t sym =
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append(elf->syms[slg], (&(Elf64_Sym){.st_info = st_info,
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.st_size = st_size,
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.st_value = st_value,
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.st_other = st_other,
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.st_name = intern(elf->strtab, name),
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.st_shndx = st_shndx}));
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CHECK_NE(-1, sym);
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return (struct ElfWriterSymRef){.slg = slg, .sym = sym};
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}
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static void MakeRelaSection(struct ElfWriter *elf, size_t section) {
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size_t shdr, size;
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size = (elf->relas->i - elf->relas->j) * sizeof(Elf64_Rela);
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elfwriter_align(elf, alignof(Elf64_Rela), sizeof(Elf64_Rela));
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shdr = elfwriter_startsection(
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elf,
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gc(xasprintf("%s%s", ".rela",
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&elf->shstrtab->p[elf->shdrs->p[section].sh_name])),
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SHT_RELA, SHF_INFO_LINK);
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elf->shdrs->p[shdr].sh_info = section;
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elfwriter_reserve(elf, size);
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elfwriter_commit(elf, size);
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FinishSection(elf);
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elf->relas->j = elf->relas->i;
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}
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static void WriteRelaSections(struct ElfWriter *elf, size_t symtab) {
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uint32_t sym;
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size_t i, j, k;
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Elf64_Rela *rela;
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for (j = 0, i = 0; i < elf->shdrs->i; ++i) {
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if (elf->shdrs->p[i].sh_type == SHT_RELA) {
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elf->shdrs->p[i].sh_link = symtab;
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for (rela = (Elf64_Rela *)((char *)elf->map + elf->shdrs->p[i].sh_offset);
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rela <
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(Elf64_Rela *)((char *)elf->map + (elf->shdrs->p[i].sh_offset +
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elf->shdrs->p[i].sh_size));
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rela++, j++) {
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sym = elf->relas->p[j].symkey.sym;
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for (k = 0; k < elf->relas->p[j].symkey.slg; ++k) {
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sym += elf->syms[k]->i;
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}
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rela->r_offset = elf->relas->p[j].offset;
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rela->r_info = ELF64_R_INFO(sym, elf->relas->p[j].type);
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rela->r_addend = elf->relas->p[j].addend;
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}
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}
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}
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assert(j == elf->relas->i);
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}
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static size_t FlushStrtab(struct ElfWriter *elf, const char *name,
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struct Interner *strtab) {
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size_t size = strtab->i * sizeof(strtab->p[0]);
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elfwriter_align(elf, 1, 0);
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AppendSection(elf, ".strtab", SHT_STRTAB, 0);
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mempcpy(elfwriter_reserve(elf, size), strtab->p, size);
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elfwriter_commit(elf, size);
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return FinishSection(elf);
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}
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static void FlushTables(struct ElfWriter *elf) {
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size_t i, size, symtab;
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elfwriter_align(elf, alignof(Elf64_Sym), sizeof(Elf64_Sym));
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symtab = AppendSection(elf, ".symtab", SHT_SYMTAB, 0);
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for (i = 0; i < ARRAYLEN(elf->syms); ++i) {
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size = elf->syms[i]->i * sizeof(Elf64_Sym);
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memcpy(elfwriter_reserve(elf, size), elf->syms[i]->p, size);
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elfwriter_commit(elf, size);
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}
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FinishSection(elf);
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elf->shdrs->p[symtab].sh_link = FlushStrtab(elf, ".strtab", elf->strtab);
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elf->ehdr->e_shstrndx = FlushStrtab(elf, ".shstrtab", elf->shstrtab);
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WriteRelaSections(elf, symtab);
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size = elf->shdrs->i * sizeof(elf->shdrs->p[0]);
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elfwriter_align(elf, alignof(elf->shdrs->p[0]), sizeof(elf->shdrs->p[0]));
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elf->ehdr->e_shoff = elf->wrote;
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elf->ehdr->e_shnum = elf->shdrs->i;
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elf->shdrs->p[symtab].sh_info =
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elf->syms[kElfWriterSymSection]->i + elf->syms[kElfWriterSymLocal]->i;
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mempcpy(elfwriter_reserve(elf, size), elf->shdrs->p, size);
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elfwriter_commit(elf, size);
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}
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struct ElfWriter *elfwriter_open(const char *path, int mode) {
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struct ElfWriter *elf;
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CHECK_NOTNULL((elf = calloc(1, sizeof(struct ElfWriter))));
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CHECK_NOTNULL((elf->path = strdup(path)));
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CHECK_NE(-1, asprintf(&elf->tmppath, "%s.%d", elf->path, getpid()));
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CHECK_NE(-1, (elf->fd = open(elf->tmppath,
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O_CREAT | O_TRUNC | O_RDWR | O_EXCL, mode)));
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CHECK_NE(-1, ftruncate(elf->fd, (elf->mapsize = FRAMESIZE)));
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CHECK_NE(MAP_FAILED, (elf->map = mmap((void *)(intptr_t)kFixedMappingsStart,
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elf->mapsize, PROT_READ | PROT_WRITE,
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MAP_SHARED | MAP_FIXED, elf->fd, 0)));
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elf->ehdr = memcpy(elf->map, &kObjHeader, (elf->wrote = sizeof(kObjHeader)));
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elf->strtab = newinterner();
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elf->shstrtab = newinterner();
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return elf;
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}
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void elfwriter_close(struct ElfWriter *elf) {
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size_t i;
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FlushTables(elf);
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CHECK_NE(-1, munmap(elf->map, elf->mapsize));
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CHECK_NE(-1, ftruncate(elf->fd, elf->wrote));
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CHECK_NE(-1, close(elf->fd));
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CHECK_NE(-1, rename(elf->tmppath, elf->path));
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freeinterner(elf->shstrtab);
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freeinterner(elf->strtab);
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free(elf->shdrs->p);
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free(elf->relas->p);
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for (i = 0; i < ARRAYLEN(elf->syms); ++i) free(elf->syms[i]->p);
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free(elf);
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}
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void elfwriter_align(struct ElfWriter *elf, size_t addralign, size_t entsize) {
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elf->entsize = entsize;
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elf->addralign = addralign;
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elf->wrote = roundup(elf->wrote, addralign);
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}
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size_t elfwriter_startsection(struct ElfWriter *elf, const char *name,
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int sh_type, int sh_flags) {
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size_t shdr = AppendSection(elf, name, sh_type, sh_flags);
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AppendSymbol(elf, "",
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sh_type != SHT_NULL ? ELF64_ST_INFO(STB_LOCAL, STT_SECTION)
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: ELF64_ST_INFO(STB_LOCAL, STT_NOTYPE),
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STV_DEFAULT, 0, 0, shdr, kElfWriterSymSection);
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return shdr;
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}
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void *elfwriter_reserve(struct ElfWriter *elf, size_t size) {
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size_t need, greed;
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need = elf->wrote + size;
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greed = elf->mapsize;
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if (need > greed) {
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do {
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greed = greed + (greed >> 1);
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} while (need > greed);
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greed = roundup(greed, FRAMESIZE);
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CHECK_NE(-1, ftruncate(elf->fd, greed));
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CHECK_NE(MAP_FAILED, mmap((char *)elf->map + elf->mapsize,
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greed - elf->mapsize, PROT_READ | PROT_WRITE,
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MAP_SHARED | MAP_FIXED, elf->fd, elf->mapsize));
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elf->mapsize = greed;
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}
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return (char *)elf->map + elf->wrote;
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}
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void elfwriter_commit(struct ElfWriter *elf, size_t size) {
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elf->wrote += size;
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}
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void elfwriter_finishsection(struct ElfWriter *elf) {
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size_t section = FinishSection(elf);
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if (elf->relas->j < elf->relas->i) MakeRelaSection(elf, section);
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}
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struct ElfWriterSymRef elfwriter_appendsym(struct ElfWriter *elf,
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const char *name, int st_info,
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int st_other, size_t st_value,
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size_t st_size) {
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return AppendSymbol(
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elf, name, st_info, st_other, st_value, st_size, elf->shdrs->i - 1,
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ELF64_ST_BIND(st_info) == STB_LOCAL ? kElfWriterSymLocal
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: kElfWriterSymGlobal);
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}
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struct ElfWriterSymRef elfwriter_linksym(struct ElfWriter *elf,
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const char *name, int st_info,
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int st_other) {
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return AppendSymbol(elf, name, st_info, st_other, 0, 0, 0,
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kElfWriterSymGlobal);
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}
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void elfwriter_appendrela(struct ElfWriter *elf, uint64_t r_offset,
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struct ElfWriterSymRef symkey, uint32_t type,
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int64_t r_addend) {
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CHECK_NE(-1,
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append(elf->relas, (&(struct ElfWriterRela){.type = type,
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.symkey = symkey,
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.offset = r_offset,
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.addend = r_addend})));
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}
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