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Don't relocate file descriptor memory
This change fixes #496 where ASAN spotted a race condition that could happen in multithreaded programs, with more than OPEN_MAX descriptors when using ZipOS or Windows NT, which require tracking open file info and this change fixes that table so it never relocates, thus allowing us to continue to enjoy the benefits of avoiding locks while reading.
This commit is contained in:
Justine Tunney
parent
c3208eb9d5
commit
3265324e00
35 changed files with 297 additions and 152 deletions
160
libc/intrin/mman.greg.c
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160
libc/intrin/mman.greg.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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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╠──────────────────────────────────────────────────────────────────────────────╣
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╠──────────────────────────────────────────────────────▌▀▄─▐──▀▄─▐▄─▐▄▐▄─▐▄─▐▄─│
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│ αcτµαlly pδrταblε εxεcµταblε § no-frills virtual memory management │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "ape/relocations.h"
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#include "libc/elf/def.h"
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#include "libc/elf/struct/phdr.h"
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#include "libc/macros.internal.h"
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#include "libc/nexgen32e/uart.internal.h"
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#include "libc/runtime/e820.internal.h"
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#include "libc/runtime/metalprintf.internal.h"
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#include "libc/runtime/pc.internal.h"
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#include "libc/runtime/runtime.h"
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/**
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* Allocates new page of physical memory.
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*/
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noasan texthead uint64_t __new_page(struct mman *mm) {
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uint64_t p;
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if (mm->pdpi == mm->e820n) {
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/* TODO: reclaim free pages */
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return 0;
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}
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while (mm->pdp >= mm->e820[mm->pdpi].addr + mm->e820[mm->pdpi].size) {
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if (++mm->pdpi == mm->e820n) return 0;
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mm->pdp = mm->e820[mm->pdpi].addr;
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}
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p = mm->pdp;
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mm->pdp += 4096;
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return p;
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}
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/**
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* Returns pointer to page table entry for page at virtual address.
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* Additional page tables are allocated if needed as a side-effect.
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*/
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noasan textreal uint64_t *__get_virtual(struct mman *mm, uint64_t *t,
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int64_t vaddr, bool maketables) {
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uint64_t *e, p;
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unsigned char h;
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for (h = 39;; h -= 9) {
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e = t + ((vaddr >> h) & 511);
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if (h == 12) return e;
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if (!(*e & PAGE_V)) {
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if (!maketables) return NULL;
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if (!(p = __new_page(mm))) return NULL;
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*e = p | PAGE_V | PAGE_RW;
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}
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t = (uint64_t *)(BANE + (*e & PAGE_TA));
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}
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}
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/**
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* Sorts, rounds, and filters BIOS memory map.
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*/
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static noasan textreal void __normalize_e820(struct mman *mm) {
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uint64_t a, b;
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uint64_t x, y;
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unsigned i, j, n;
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for (n = i = 0; mm->e820[i].size; ++i) {
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mm->e820[n] = mm->e820[i];
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x = mm->e820[n].addr;
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y = mm->e820[n].addr + mm->e820[n].size;
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a = ROUNDUP(x, 4096);
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b = ROUNDDOWN(y, 4096) - a;
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if (b > 0 && mm->e820[i].type == kMemoryUsable) {
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mm->e820[n].addr = a;
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mm->e820[n].size = b;
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++n;
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}
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}
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for (i = 1; i < n; ++i) {
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for (j = i; j > 0 && mm->e820[i].addr < mm->e820[j - 1].addr; --j) {
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mm->e820[j] = mm->e820[j - 1];
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}
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mm->e820[j] = mm->e820[i];
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}
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mm->pdp = MAX(0x80000, mm->e820[0].addr);
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mm->pdpi = 0;
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mm->e820n = n;
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}
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/**
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* Identity maps all usable physical memory to its negative address.
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*/
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static noasan textreal void __invert_memory(struct mman *mm, uint64_t *pml4t) {
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uint64_t i, j, *m, p, pe;
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for (i = 0; i < mm->e820n; ++i) {
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for (p = mm->e820[i].addr, pe = mm->e820[i].addr + mm->e820[i].size;
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p + 0x200000 < pe; p += 4096) {
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m = __get_virtual(mm, pml4t, BANE + p, true);
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if (m && !(*m & PAGE_V)) {
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*m = p | PAGE_V | PAGE_RW;
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}
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}
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}
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}
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noasan textreal void __setup_mman(struct mman *mm, uint64_t *pml4t) {
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__normalize_e820(mm);
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__invert_memory(mm, pml4t);
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}
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/**
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* Maps APE-defined ELF program headers into memory and clears BSS.
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*/
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noasan textreal void __map_phdrs(struct mman *mm, uint64_t *pml4t, uint64_t b) {
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struct Elf64_Phdr *p;
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uint64_t i, f, v, m, *e;
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extern char ape_phdrs[] __attribute__((__weak__));
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extern char ape_phdrs_end[] __attribute__((__weak__));
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__setup_mman(mm, pml4t);
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for (p = (struct Elf64_Phdr *)REAL(ape_phdrs), m = 0;
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p < (struct Elf64_Phdr *)REAL(ape_phdrs_end); ++p) {
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if (p->p_type == PT_LOAD || p->p_type == PT_GNU_STACK) {
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f = PAGE_V | PAGE_U;
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if (p->p_flags & PF_W) f |= PAGE_RW;
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for (i = 0; i < p->p_memsz; i += 4096) {
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if (i < p->p_filesz) {
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v = b + p->p_offset + i;
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m = MAX(m, v);
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} else {
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v = __clear_page(__new_page(mm));
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}
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*__get_virtual(mm, pml4t, p->p_vaddr + i, true) = (v & PAGE_TA) | f;
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}
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}
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}
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mm->pdp = MAX(mm->pdp, m);
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}
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