mirror of
https://github.com/classilla/tenfourfox.git
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550 lines
17 KiB
C++
550 lines
17 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*/
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/* Code in this file needs to be kept in sync with code in nsPresArena.cpp.
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*
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* We want to use a fixed address for frame poisoning so that it is readily
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* identifiable in crash dumps. Whether such an address is available
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* without any special setup depends on the system configuration.
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*
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* All current 64-bit CPUs (with the possible exception of PowerPC64)
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* reserve the vast majority of the virtual address space for future
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* hardware extensions; valid addresses must be below some break point
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* between 2**48 and 2**54, depending on exactly which chip you have. Some
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* chips (notably amd64) also allow the use of the *highest* 2**48 -- 2**54
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* addresses. Thus, if user space pointers are 64 bits wide, we can just
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* use an address outside this range, and no more is required. To
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* accommodate the chips that allow very high addresses to be valid, the
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* value chosen is close to 2**63 (that is, in the middle of the space).
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*
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* In most cases, a purely 32-bit operating system must reserve some
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* fraction of the address space for its own use. Contemporary 32-bit OSes
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* tend to take the high gigabyte or so (0xC000_0000 on up). If we can
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* prove that high addresses are reserved to the kernel, we can use an
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* address in that region. Unfortunately, not all 32-bit OSes do this;
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* OSX 10.4 might not, and it is unclear what mobile OSes are like
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* (some 32-bit CPUs make it very easy for the kernel to exist in its own
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* private address space).
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*
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* Furthermore, when a 32-bit user space process is running on a 64-bit
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* kernel, the operating system has no need to reserve any of the space that
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* the process can see, and generally does not do so. This is the scenario
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* of greatest concern, since it covers all contemporary OSX iterations
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* (10.5+) as well as Windows Vista and 7 on newer amd64 hardware. Linux on
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* amd64 is generally run as a pure 64-bit environment, but its 32-bit
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* compatibility mode also has this property.
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*
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* Thus, when user space pointers are 32 bits wide, we need to validate
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* our chosen address, and possibly *make* it a good poison address by
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* allocating a page around it and marking it inaccessible. The algorithm
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* for this is:
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*
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* 1. Attempt to make the page surrounding the poison address a reserved,
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* inaccessible memory region using OS primitives. On Windows, this is
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* done with VirtualAlloc(MEM_RESERVE); on Unix, mmap(PROT_NONE).
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*
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* 2. If mmap/VirtualAlloc failed, there are two possible reasons: either
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* the region is reserved to the kernel and no further action is
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* required, or there is already usable memory in this area and we have
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* to pick a different address. The tricky part is knowing which case
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* we have, without attempting to access the region. On Windows, we
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* rely on GetSystemInfo()'s reported upper and lower bounds of the
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* application memory area. On Unix, there is nothing devoted to the
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* purpose, but seeing if madvise() fails is close enough (it *might*
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* disrupt someone else's use of the memory region, but not by as much
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* as anything else available).
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*
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* Be aware of these gotchas:
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*
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* 1. We cannot use mmap() with MAP_FIXED. MAP_FIXED is defined to
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* _replace_ any existing mapping in the region, if necessary to satisfy
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* the request. Obviously, as we are blindly attempting to acquire a
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* page at a constant address, we must not do this, lest we overwrite
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* someone else's allocation.
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*
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* 2. For the same reason, we cannot blindly use mprotect() if mmap() fails.
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*
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* 3. madvise() may fail when applied to a 'magic' memory region provided as
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* a kernel/user interface. Fortunately, the only such case I know about
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* is the "vsyscall" area (not to be confused with the "vdso" area) for
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* *64*-bit processes on Linux - and we don't even run this code for
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* 64-bit processes.
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*
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* 4. VirtualQuery() does not produce any useful information if
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* applied to kernel memory - in fact, it doesn't write its output
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* at all. Thus, it is not used here.
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*/
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#include "mozilla/IntegerPrintfMacros.h"
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// MAP_ANON(YMOUS) is not in any standard. Add defines as necessary.
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#define _GNU_SOURCE 1
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#define _DARWIN_C_SOURCE 1
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#include <stddef.h>
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#include <errno.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#ifdef _WIN32
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#include <windows.h>
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#else
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#include <sys/types.h>
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#include <fcntl.h>
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#include <signal.h>
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#include <unistd.h>
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#include <sys/stat.h>
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#include <sys/wait.h>
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#include <sys/mman.h>
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#ifndef MAP_ANON
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#ifdef MAP_ANONYMOUS
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#define MAP_ANON MAP_ANONYMOUS
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#else
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#error "Don't know how to get anonymous memory"
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#endif
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#endif
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#endif
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#define SIZxPTR ((int)(sizeof(uintptr_t)*2))
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/* This program assumes that a whole number of return instructions fit into
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* 32 bits, and that 32-bit alignment is sufficient for a branch destination.
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* For architectures where this is not true, fiddling with RETURN_INSTR_TYPE
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* can be enough.
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*/
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#if defined __i386__ || defined __x86_64__ || \
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defined __i386 || defined __x86_64 || \
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defined _M_IX86 || defined _M_AMD64
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#define RETURN_INSTR 0xC3C3C3C3 /* ret; ret; ret; ret */
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#elif defined __arm__ || defined _M_ARM
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#define RETURN_INSTR 0xE12FFF1E /* bx lr */
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// PPC has its own style of CPU-id #defines. There is no Windows for
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// PPC as far as I know, so no _M_ variant.
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#elif defined _ARCH_PPC || defined _ARCH_PWR || defined _ARCH_PWR2
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#define RETURN_INSTR 0x4E800020 /* blr */
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#elif defined __sparc || defined __sparcv9
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#define RETURN_INSTR 0x81c3e008 /* retl */
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#elif defined __alpha
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#define RETURN_INSTR 0x6bfa8001 /* ret */
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#elif defined __hppa
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#define RETURN_INSTR 0xe840c002 /* bv,n r0(rp) */
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#elif defined __mips
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#define RETURN_INSTR 0x03e00008 /* jr ra */
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#ifdef __MIPSEL
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/* On mipsel, jr ra needs to be followed by a nop.
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0x03e00008 as a 64 bits integer just does that */
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#define RETURN_INSTR_TYPE uint64_t
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#endif
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#elif defined __s390__
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#define RETURN_INSTR 0x07fe0000 /* br %r14 */
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#elif defined __aarch64__
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#define RETURN_INSTR 0xd65f03c0 /* ret */
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#elif defined __ia64
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struct ia64_instr { uint32_t mI[4]; };
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static const ia64_instr _return_instr =
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{{ 0x00000011, 0x00000001, 0x80000200, 0x00840008 }}; /* br.ret.sptk.many b0 */
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#define RETURN_INSTR _return_instr
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#define RETURN_INSTR_TYPE ia64_instr
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#else
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#error "Need return instruction for this architecture"
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#endif
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#ifndef RETURN_INSTR_TYPE
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#define RETURN_INSTR_TYPE uint32_t
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#endif
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// Miscellaneous Windows/Unix portability gumph
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#ifdef _WIN32
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// Uses of this function deliberately leak the string.
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static LPSTR
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StrW32Error(DWORD aErrcode)
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{
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LPSTR errmsg;
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FormatMessageA(FORMAT_MESSAGE_ALLOCATE_BUFFER |
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FORMAT_MESSAGE_FROM_SYSTEM |
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FORMAT_MESSAGE_IGNORE_INSERTS,
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nullptr, aErrcode, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
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(LPSTR)&errmsg, 0, nullptr);
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// FormatMessage puts an unwanted newline at the end of the string
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size_t n = strlen(errmsg)-1;
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while (errmsg[n] == '\r' || errmsg[n] == '\n') {
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n--;
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}
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errmsg[n+1] = '\0';
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return errmsg;
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}
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#define LastErrMsg() (StrW32Error(GetLastError()))
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// Because we use VirtualAlloc in MEM_RESERVE mode, the "page size" we want
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// is the allocation granularity.
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static SYSTEM_INFO sInfo_;
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static inline uint32_t
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PageSize()
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{
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return sInfo_.dwAllocationGranularity;
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}
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static void*
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ReserveRegion(uintptr_t aRequest, bool aAccessible)
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{
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return VirtualAlloc((void*)aRequest, PageSize(),
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aAccessible ? MEM_RESERVE|MEM_COMMIT : MEM_RESERVE,
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aAccessible ? PAGE_EXECUTE_READWRITE : PAGE_NOACCESS);
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}
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static void
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ReleaseRegion(void* aPage)
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{
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VirtualFree(aPage, PageSize(), MEM_RELEASE);
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}
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static bool
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ProbeRegion(uintptr_t aPage)
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{
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return aPage >= (uintptr_t)sInfo_.lpMaximumApplicationAddress &&
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aPage + PageSize() >= (uintptr_t)sInfo_.lpMaximumApplicationAddress;
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}
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static bool
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MakeRegionExecutable(void*)
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{
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return false;
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}
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#undef MAP_FAILED
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#define MAP_FAILED 0
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#else // Unix
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#define LastErrMsg() (strerror(errno))
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static unsigned long gUnixPageSize;
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static inline unsigned long
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PageSize()
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{
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return gUnixPageSize;
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}
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static void*
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ReserveRegion(uintptr_t aRequest, bool aAccessible)
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{
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return mmap(reinterpret_cast<void*>(aRequest), PageSize(),
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aAccessible ? PROT_READ|PROT_WRITE : PROT_NONE,
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MAP_PRIVATE|MAP_ANON, -1, 0);
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}
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static void
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ReleaseRegion(void* aPage)
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{
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munmap(aPage, PageSize());
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}
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static bool
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ProbeRegion(uintptr_t aPage)
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{
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return !!madvise(reinterpret_cast<void*>(aPage), PageSize(), MADV_NORMAL);
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}
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static int
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MakeRegionExecutable(void* aPage)
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{
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return mprotect((caddr_t)aPage, PageSize(), PROT_READ|PROT_WRITE|PROT_EXEC);
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}
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#endif
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static uintptr_t
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ReservePoisonArea()
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{
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if (sizeof(uintptr_t) == 8) {
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// Use the hardware-inaccessible region.
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// We have to avoid 64-bit constants and shifts by 32 bits, since this
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// code is compiled in 32-bit mode, although it is never executed there.
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uintptr_t result = (((uintptr_t(0x7FFFFFFFu) << 31) << 1 |
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uintptr_t(0xF0DEAFFFu)) &
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~uintptr_t(PageSize()-1));
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printf("INFO | poison area assumed at 0x%.*" PRIxPTR "\n", SIZxPTR, result);
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return result;
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}
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// First see if we can allocate the preferred poison address from the OS.
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uintptr_t candidate = (0xF0DEAFFF & ~(PageSize() - 1));
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void* result = ReserveRegion(candidate, false);
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if (result == reinterpret_cast<void*>(candidate)) {
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// success - inaccessible page allocated
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printf("INFO | poison area allocated at 0x%.*" PRIxPTR
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" (preferred addr)\n", SIZxPTR, reinterpret_cast<uintptr_t>(result));
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return candidate;
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}
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// That didn't work, so see if the preferred address is within a range
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// of permanently inacessible memory.
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if (ProbeRegion(candidate)) {
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// success - selected page cannot be usable memory
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if (result != MAP_FAILED) {
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ReleaseRegion(result);
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}
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printf("INFO | poison area assumed at 0x%.*" PRIxPTR
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" (preferred addr)\n", SIZxPTR, candidate);
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return candidate;
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}
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// The preferred address is already in use. Did the OS give us a
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// consolation prize?
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if (result != MAP_FAILED) {
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uintptr_t ures = reinterpret_cast<uintptr_t>(result);
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printf("INFO | poison area allocated at 0x%.*" PRIxPTR
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" (consolation prize)\n", SIZxPTR, ures);
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return ures;
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}
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// It didn't, so try to allocate again, without any constraint on
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// the address.
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result = ReserveRegion(0, false);
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if (result != MAP_FAILED) {
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uintptr_t ures = reinterpret_cast<uintptr_t>(result);
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printf("INFO | poison area allocated at 0x%.*" PRIxPTR
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" (fallback)\n", SIZxPTR, ures);
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return ures;
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}
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printf("ERROR | no usable poison area found\n");
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return 0;
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}
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/* The "positive control" area confirms that we can allocate a page with the
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* proper characteristics.
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*/
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static uintptr_t
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ReservePositiveControl()
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{
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void* result = ReserveRegion(0, false);
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if (result == MAP_FAILED) {
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printf("ERROR | allocating positive control | %s\n", LastErrMsg());
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return 0;
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}
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printf("INFO | positive control allocated at 0x%.*" PRIxPTR "\n",
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SIZxPTR, (uintptr_t)result);
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return (uintptr_t)result;
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}
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/* The "negative control" area confirms that our probe logic does detect a
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* page that is readable, writable, or executable.
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*/
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static uintptr_t
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ReserveNegativeControl()
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{
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void* result = ReserveRegion(0, true);
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if (result == MAP_FAILED) {
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printf("ERROR | allocating negative control | %s\n", LastErrMsg());
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return 0;
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}
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// Fill the page with return instructions.
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RETURN_INSTR_TYPE* p = reinterpret_cast<RETURN_INSTR_TYPE*>(result);
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RETURN_INSTR_TYPE* limit =
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reinterpret_cast<RETURN_INSTR_TYPE*>(
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reinterpret_cast<char*>(result) + PageSize());
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while (p < limit) {
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*p++ = RETURN_INSTR;
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}
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// Now mark it executable as well as readable and writable.
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// (mmap(PROT_EXEC) may fail when applied to anonymous memory.)
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if (MakeRegionExecutable(result)) {
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printf("ERROR | making negative control executable | %s\n", LastErrMsg());
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return 0;
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}
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printf("INFO | negative control allocated at 0x%.*" PRIxPTR "\n",
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SIZxPTR, (uintptr_t)result);
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return (uintptr_t)result;
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}
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static void
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JumpTo(uintptr_t aOpaddr)
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{
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#ifdef __ia64
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struct func_call
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{
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uintptr_t mFunc;
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uintptr_t mGp;
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} call = { aOpaddr, };
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((void (*)())&call)();
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#else
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((void (*)())aOpaddr)();
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#endif
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}
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#ifdef _WIN32
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static BOOL
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IsBadExecPtr(uintptr_t aPtr)
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{
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BOOL ret = false;
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#if defined(_MSC_VER) && !defined(__clang__)
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__try {
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JumpTo(aPtr);
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} __except (EXCEPTION_EXECUTE_HANDLER) {
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ret = true;
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}
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#else
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printf("INFO | exec test not supported on MinGW or clang-cl builds\n");
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// We do our best
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ret = IsBadReadPtr((const void*)aPtr, 1);
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#endif
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return ret;
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}
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#endif
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/* Test each page. */
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static bool
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TestPage(const char* aPageLabel, uintptr_t aPageAddr, int aShouldSucceed)
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{
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const char* oplabel;
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uintptr_t opaddr;
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bool failed = false;
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for (unsigned int test = 0; test < 3; test++) {
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switch (test) {
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// The execute test must be done before the write test, because the
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// write test will clobber memory at the target address.
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case 0: oplabel = "reading"; opaddr = aPageAddr + PageSize()/2 - 1; break;
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case 1: oplabel = "executing"; opaddr = aPageAddr + PageSize()/2; break;
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case 2: oplabel = "writing"; opaddr = aPageAddr + PageSize()/2 - 1; break;
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default: abort();
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}
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#ifdef _WIN32
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BOOL badptr;
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switch (test) {
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case 0: badptr = IsBadReadPtr((const void*)opaddr, 1); break;
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case 1: badptr = IsBadExecPtr(opaddr); break;
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case 2: badptr = IsBadWritePtr((void*)opaddr, 1); break;
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default: abort();
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}
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if (badptr) {
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if (aShouldSucceed) {
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printf("TEST-UNEXPECTED-FAIL | %s %s\n", oplabel, aPageLabel);
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failed = true;
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} else {
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printf("TEST-PASS | %s %s\n", oplabel, aPageLabel);
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}
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} else {
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// if control reaches this point the probe succeeded
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if (aShouldSucceed) {
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printf("TEST-PASS | %s %s\n", oplabel, aPageLabel);
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} else {
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printf("TEST-UNEXPECTED-FAIL | %s %s\n", oplabel, aPageLabel);
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failed = true;
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}
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}
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#else
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pid_t pid = fork();
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if (pid == -1) {
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printf("ERROR | %s %s | fork=%s\n", oplabel, aPageLabel,
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LastErrMsg());
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exit(2);
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} else if (pid == 0) {
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volatile unsigned char scratch;
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switch (test) {
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case 0: scratch = *(volatile unsigned char*)opaddr; break;
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case 1: JumpTo(opaddr); break;
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case 2: *(volatile unsigned char*)opaddr = 0; break;
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default: abort();
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}
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(void)scratch;
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_exit(0);
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} else {
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int status;
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if (waitpid(pid, &status, 0) != pid) {
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printf("ERROR | %s %s | wait=%s\n", oplabel, aPageLabel,
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LastErrMsg());
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exit(2);
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}
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if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {
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if (aShouldSucceed) {
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printf("TEST-PASS | %s %s\n", oplabel, aPageLabel);
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|
} else {
|
|
printf("TEST-UNEXPECTED-FAIL | %s %s | unexpected successful exit\n",
|
|
oplabel, aPageLabel);
|
|
failed = true;
|
|
}
|
|
} else if (WIFEXITED(status)) {
|
|
printf("ERROR | %s %s | unexpected exit code %d\n",
|
|
oplabel, aPageLabel, WEXITSTATUS(status));
|
|
exit(2);
|
|
} else if (WIFSIGNALED(status)) {
|
|
if (aShouldSucceed) {
|
|
printf("TEST-UNEXPECTED-FAIL | %s %s | unexpected signal %d\n",
|
|
oplabel, aPageLabel, WTERMSIG(status));
|
|
failed = true;
|
|
} else {
|
|
printf("TEST-PASS | %s %s | signal %d (as expected)\n",
|
|
oplabel, aPageLabel, WTERMSIG(status));
|
|
}
|
|
} else {
|
|
printf("ERROR | %s %s | unexpected exit status %d\n",
|
|
oplabel, aPageLabel, status);
|
|
exit(2);
|
|
}
|
|
}
|
|
#endif
|
|
}
|
|
return failed;
|
|
}
|
|
|
|
int
|
|
main()
|
|
{
|
|
#ifdef _WIN32
|
|
GetSystemInfo(&sInfo_);
|
|
#else
|
|
gUnixPageSize = sysconf(_SC_PAGESIZE);
|
|
#endif
|
|
|
|
uintptr_t ncontrol = ReserveNegativeControl();
|
|
uintptr_t pcontrol = ReservePositiveControl();
|
|
uintptr_t poison = ReservePoisonArea();
|
|
|
|
if (!ncontrol || !pcontrol || !poison) {
|
|
return 2;
|
|
}
|
|
|
|
bool failed = false;
|
|
failed |= TestPage("negative control", ncontrol, 1);
|
|
failed |= TestPage("positive control", pcontrol, 0);
|
|
failed |= TestPage("poison area", poison, 0);
|
|
|
|
return failed ? 1 : 0;
|
|
}
|