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gecko-dev/mfbt/tests/TestPoisonArea.cpp

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