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https://github.com/jart/cosmopolitan.git
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d38700687a
- use PAGE_RSRV bit (originally only for blinkenlights), rather than PAGE_V bit, to indicate that a virtual address page has been reserved — this should allow a program to create & reserve inaccessible "guard pages" - mark page table entries for non-code pages with PAGE_XD bit, which should be supported on (circa) post-2004 x86-64 CPUs
73 lines
3.4 KiB
C
73 lines
3.4 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 2021 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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#include "libc/calls/calls.h"
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#include "libc/macros.internal.h"
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#include "libc/runtime/directmap.internal.h"
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#include "libc/runtime/pc.internal.h"
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#include "libc/str/str.h"
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#include "libc/sysv/consts/map.h"
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#include "libc/sysv/consts/prot.h"
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#include "libc/sysv/errfuns.h"
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static uint64_t sys_mmap_metal_break;
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noasan struct DirectMap sys_mmap_metal(void *paddr, size_t size, int prot,
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int flags, int fd, int64_t off) {
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/* asan runtime depends on this function */
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size_t i;
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struct mman *mm;
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struct DirectMap res;
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uint64_t addr, page, *pte, *pml4t;
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mm = (struct mman *)(BANE + 0x0500);
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pml4t = __get_pml4t();
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size = ROUNDUP(size, 4096);
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addr = (uint64_t)paddr;
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if (!(flags & MAP_FIXED)) {
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if (!addr)
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addr = 4096;
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for (i = 0; i < size; i += 4096) {
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pte = __get_virtual(mm, pml4t, addr + i, false);
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if (pte && (*pte & (PAGE_V | PAGE_RSRV))) {
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addr = MAX(addr, sys_mmap_metal_break) + i + 4096;
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i = 0;
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}
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}
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sys_mmap_metal_break = MAX(addr + size, sys_mmap_metal_break);
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}
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for (i = 0; i < size; i += 4096) {
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page = __new_page(mm);
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pte = __get_virtual(mm, pml4t, addr + i, true);
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if (pte && page) {
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__clear_page(BANE + page);
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page |= PAGE_RSRV | PAGE_U;
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if ((prot & PROT_WRITE))
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page |= PAGE_V | PAGE_RW;
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else if ((prot & (PROT_READ | PROT_EXEC)))
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page |= PAGE_V;
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if (!(prot & PROT_EXEC)) page |= PAGE_XD;
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*pte = page;
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} else {
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addr = -1;
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break;
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}
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}
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res.addr = (void *)addr;
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res.maphandle = -1;
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return res;
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}
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