From 6bf0a5cb5034a7e684dcc3500e841785237ce2dd Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 19:32:43 +0200 Subject: Adding upstream version 1:115.7.0. Signed-off-by: Daniel Baumann --- mfbt/Poison.cpp | 206 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 206 insertions(+) create mode 100644 mfbt/Poison.cpp (limited to 'mfbt/Poison.cpp') diff --git a/mfbt/Poison.cpp b/mfbt/Poison.cpp new file mode 100644 index 0000000000..db523b928a --- /dev/null +++ b/mfbt/Poison.cpp @@ -0,0 +1,206 @@ +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* vim: set ts=8 sts=2 et sw=2 tw=80: */ +/* 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/. */ + +/* + * A poison value that can be used to fill a memory space with + * an address that leads to a safe crash when dereferenced. + */ + +#include "mozilla/Poison.h" + +#include "mozilla/Assertions.h" +#ifdef _WIN32 +# include +#elif !defined(__OS2__) +# include +# ifndef __wasi__ +# include +# ifndef MAP_ANON +# ifdef MAP_ANONYMOUS +# define MAP_ANON MAP_ANONYMOUS +# else +# error "Don't know how to get anonymous memory" +# endif +# endif +# endif +#endif + +// Freed memory is filled with a poison value, which we arrange to +// form a pointer either to an always-unmapped region of the address +// space, or to a page that has been reserved and rendered +// inaccessible via OS primitives. See tests/TestPoisonArea.cpp for +// extensive discussion of the requirements for this page. The code +// from here to 'class FreeList' needs to be kept in sync with that +// file. + +#ifdef _WIN32 +static void* ReserveRegion(uintptr_t aRegion, uintptr_t aSize) { + return VirtualAlloc((void*)aRegion, aSize, MEM_RESERVE, PAGE_NOACCESS); +} + +static void ReleaseRegion(void* aRegion, uintptr_t aSize) { + VirtualFree(aRegion, aSize, MEM_RELEASE); +} + +static bool ProbeRegion(uintptr_t aRegion, uintptr_t aSize) { + SYSTEM_INFO sinfo; + GetSystemInfo(&sinfo); + if (aRegion >= (uintptr_t)sinfo.lpMaximumApplicationAddress && + aRegion + aSize >= (uintptr_t)sinfo.lpMaximumApplicationAddress) { + return true; + } else { + return false; + } +} + +static uintptr_t GetDesiredRegionSize() { + SYSTEM_INFO sinfo; + GetSystemInfo(&sinfo); + return sinfo.dwAllocationGranularity; +} + +# define RESERVE_FAILED 0 + +#elif defined(__OS2__) +static void* ReserveRegion(uintptr_t aRegion, uintptr_t aSize) { + // OS/2 doesn't support allocation at an arbitrary address, + // so return an address that is known to be invalid. + return (void*)0xFFFD0000; +} + +static void ReleaseRegion(void* aRegion, uintptr_t aSize) { return; } + +static bool ProbeRegion(uintptr_t aRegion, uintptr_t aSize) { + // There's no reliable way to probe an address in the system + // arena other than by touching it and seeing if a trap occurs. + return false; +} + +static uintptr_t GetDesiredRegionSize() { + // Page size is fixed at 4k. + return 0x1000; +} + +# define RESERVE_FAILED 0 + +#elif defined(__wasi__) + +# define RESERVE_FAILED 0 + +static void* ReserveRegion(uintptr_t aRegion, uintptr_t aSize) { + return RESERVE_FAILED; +} + +static void ReleaseRegion(void* aRegion, uintptr_t aSize) { return; } + +static bool ProbeRegion(uintptr_t aRegion, uintptr_t aSize) { + const auto pageSize = 1 << 16; + MOZ_ASSERT(pageSize == sysconf(_SC_PAGESIZE)); + auto heapSize = __builtin_wasm_memory_size(0) * pageSize; + return aRegion + aSize < heapSize; +} + +static uintptr_t GetDesiredRegionSize() { return 0; } + +#else // __wasi__ + +# include "mozilla/TaggedAnonymousMemory.h" + +static void* ReserveRegion(uintptr_t aRegion, uintptr_t aSize) { + return MozTaggedAnonymousMmap(reinterpret_cast(aRegion), aSize, + PROT_NONE, MAP_PRIVATE | MAP_ANON, -1, 0, + "poison"); +} + +static void ReleaseRegion(void* aRegion, uintptr_t aSize) { + munmap(aRegion, aSize); +} + +static bool ProbeRegion(uintptr_t aRegion, uintptr_t aSize) { +# ifdef XP_SOLARIS + if (posix_madvise(reinterpret_cast(aRegion), aSize, + POSIX_MADV_NORMAL)) { +# else + if (madvise(reinterpret_cast(aRegion), aSize, MADV_NORMAL)) { +# endif + return true; + } else { + return false; + } +} + +static uintptr_t GetDesiredRegionSize() { return sysconf(_SC_PAGESIZE); } + +# define RESERVE_FAILED MAP_FAILED + +#endif // system dependencies + +static_assert((sizeof(uintptr_t) == 4 || sizeof(uintptr_t) == 8) && + (sizeof(uintptr_t) == sizeof(void*))); + +static uintptr_t ReservePoisonArea(uintptr_t rgnsize) { + 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. + return (((uintptr_t(0x7FFFFFFFu) << 31) << 1 | uintptr_t(0xF0DEAFFFu)) & + ~(rgnsize - 1)); + } + + // First see if we can allocate the preferred poison address from the OS. + uintptr_t candidate = (0xF0DEAFFF & ~(rgnsize - 1)); + void* result = ReserveRegion(candidate, rgnsize); + if (result == (void*)candidate) { + // success - inaccessible page allocated + return candidate; + } + + // That didn't work, so see if the preferred address is within a range + // of permanently inacessible memory. + if (ProbeRegion(candidate, rgnsize)) { + // success - selected page cannot be usable memory + if (result != RESERVE_FAILED) { + ReleaseRegion(result, rgnsize); + } + return candidate; + } + + // The preferred address is already in use. Did the OS give us a + // consolation prize? + if (result != RESERVE_FAILED) { + return uintptr_t(result); + } + + // It didn't, so try to allocate again, without any constraint on + // the address. + result = ReserveRegion(0, rgnsize); + if (result != RESERVE_FAILED) { + return uintptr_t(result); + } + + MOZ_CRASH("no usable poison region identified"); +} + +static uintptr_t GetPoisonValue(uintptr_t aBase, uintptr_t aSize) { + if (aSize == 0) { // can't happen + return 0; + } + return aBase + aSize / 2 - 1; +} + +// Poison is used so pervasively throughout the codebase that we decided it was +// best to actually use ordered dynamic initialization of globals (AKA static +// constructors) for this. This way everything will have properly initialized +// poison -- except other dynamic initialization code in libmozglue, which there +// shouldn't be much of. (libmozglue is one of the first things loaded, and +// specifically comes before libxul, so nearly all gecko code runs strictly +// after this.) +extern "C" { +uintptr_t gMozillaPoisonSize = GetDesiredRegionSize(); +uintptr_t gMozillaPoisonBase = ReservePoisonArea(gMozillaPoisonSize); +uintptr_t gMozillaPoisonValue = + GetPoisonValue(gMozillaPoisonBase, gMozillaPoisonSize); +} -- cgit v1.2.3