[Bug] Virtual memory changes - addressing remaining issues on NetBSD

Changes related to VirtMem
  * Moved memory mapping code to mapMemory() and unmapMemory() helper functions
  * Added MemoryFlags::kMapShared to optionally allow MAP_SHARED when necessary
  * Clarified that MAP_SHARED is used by dual mapping by default
  * Extends MemoryFlags::kMMapMax... to use PROT_MPROTECT on NetBSD
  * Changed NetBSD dual mapping code to use MAP_SHARED to avoid COW

Changes related to JitAllocator
  * Propagate error from VirtMem (not just OOM) when VirtMem allocation failed
  * Added more tests to verify that RW + RX regions share the same content

src/asmjit/core/jitallocator.cpp

@@ -506,7 +506,7 @@ ASMJIT_FAVOR_SPEED static void JitAllocatorImpl_fillPattern(void* mem, uint32_t
 //
 // NOTE: The block doesn't have `kFlagEmpty` flag set, because the new block
 // is only allocated when it's actually needed, so it would be cleared anyway.
-static JitAllocatorBlock* JitAllocatorImpl_newBlock(JitAllocatorPrivateImpl* impl, JitAllocatorPool* pool, size_t blockSize) noexcept {
+static Error JitAllocatorImpl_newBlock(JitAllocatorPrivateImpl* impl, JitAllocatorBlock** dst, JitAllocatorPool* pool, size_t blockSize) noexcept {
   using Support::BitWord;
   using Support::kBitWordSizeInBits;
 
@@ -541,7 +541,10 @@ static JitAllocatorBlock* JitAllocatorImpl_newBlock(JitAllocatorPrivateImpl* imp
     if (block)
       ::free(block);
 
-    return nullptr;
+    if (err)
+      return err;
+    else
+      return kErrorOutOfMemory;
   }
 
   // Fill the memory if the secure mode is enabled.
@@ -551,7 +554,8 @@ static JitAllocatorBlock* JitAllocatorImpl_newBlock(JitAllocatorPrivateImpl* imp
   }
 
   memset(bitWords, 0, size_t(numBitWords) * 2 * sizeof(BitWord));
-  return new(block) JitAllocatorBlock(pool, virtMem, blockSize, blockFlags, bitWords, bitWords + numBitWords, areaSize);
+  *dst = new(block) JitAllocatorBlock(pool, virtMem, blockSize, blockFlags, bitWords, bitWords + numBitWords, areaSize);
+  return kErrorOk;
 }
 
 static void JitAllocatorImpl_deleteBlock(JitAllocatorPrivateImpl* impl, JitAllocatorBlock* block) noexcept {
@@ -798,12 +802,9 @@ Error JitAllocator::alloc(void** rxPtrOut, void** rwPtrOut, size_t size) noexcep
     if (ASMJIT_UNLIKELY(!blockSize))
       return DebugUtils::errored(kErrorOutOfMemory);
 
-    block = JitAllocatorImpl_newBlock(impl, pool, blockSize);
+    ASMJIT_PROPAGATE(JitAllocatorImpl_newBlock(impl, &block, pool, blockSize));
     areaIndex = 0;
 
-    if (ASMJIT_UNLIKELY(!block))
-      return DebugUtils::errored(kErrorOutOfMemory);
-
     JitAllocatorImpl_insertBlock(impl, block);
     block->_searchStart = areaSize;
     block->_largestUnusedArea = block->areaSize() - areaSize;
@@ -1018,6 +1019,34 @@ public:
   uint64_t _state[2];
 };
 
+namespace JitAllocatorUtils {
+  static void fillPattern64(void* p_, uint64_t pattern, size_t sizeInBytes) noexcept {
+    uint64_t* p = static_cast<uint64_t*>(p_);
+    size_t n = sizeInBytes / 8u;
+
+    for (size_t i = 0; i < n; i++)
+      p[i] = pattern;
+  }
+
+  static bool verifyPattern64(const void* p_, uint64_t pattern, size_t sizeInBytes) noexcept {
+    const uint64_t* p = static_cast<const uint64_t*>(p_);
+    size_t n = sizeInBytes / 8u;
+
+    for (size_t i = 0; i < n; i++) {
+      if (p[i] != pattern) {
+        INFO("Pattern verification failed at 0x%p [%zu * 8]: value(0x%016llX) != expected(0x%016llX)",
+          p,
+          i,
+          (unsigned long long)p[i],
+          (unsigned long long)pattern);
+        return false;
+      }
+    }
+
+    return true;
+  }
+}
+
 // Helper class to verify that JitAllocator doesn't return addresses that overlap.
 class JitAllocatorWrapper {
 public:
@@ -1035,9 +1064,19 @@ public:
   class Record : public ZoneTreeNodeT<Record>,
                  public Range {
   public:
-    inline Record(uint8_t* addr, size_t size)
+    //! Read/write address, in case this is a dual mapping.
+    void* _rw;
+    //! Describes a pattern used to fill the allocated memory.
+    uint64_t pattern;
+
+    inline Record(void* rx, void* rw, size_t size, uint64_t pattern)
       : ZoneTreeNodeT<Record>(),
-        Range(addr, size) {}
+        Range(static_cast<uint8_t*>(rx), size),
+        _rw(rw),
+        pattern(pattern) {}
+
+    inline void* rx() const noexcept { return addr; }
+    inline void* rw() const noexcept { return _rw; }
 
     inline bool operator<(const Record& other) const noexcept { return addr < other.addr; }
     inline bool operator>(const Record& other) const noexcept { return addr > other.addr; }
@@ -1050,14 +1089,16 @@ public:
   ZoneAllocator _heap;
   ZoneTree<Record> _records;
   JitAllocator _allocator;
+  Random _rng;
 
   explicit JitAllocatorWrapper(const JitAllocator::CreateParams* params) noexcept
     : _zone(1024 * 1024),
       _heap(&_zone),
-      _allocator(params) {}
+      _allocator(params),
+      _rng(0x123456789u) {}
 
-  void _insert(void* p_, size_t size) noexcept {
+  void _insert(void* pRX, void* pRW, size_t size) noexcept {
-    uint8_t* p = static_cast<uint8_t*>(p_);
+    uint8_t* p = static_cast<uint8_t*>(pRX);
     uint8_t* pEnd = p + size - 1;
 
     Record* record;
@@ -1070,9 +1111,18 @@ public:
     if (record)
       EXPECT(record == nullptr, "Address [%p:%p] collides with a newly allocated [%p:%p]\n", record->addr, record->addr + record->size, p, p + size);
 
-    record = _heap.newT<Record>(p, size);
+    uint64_t pattern = _rng.nextUInt64();
+    record = _heap.newT<Record>(pRX, pRW, size, pattern);
     EXPECT(record != nullptr, "Out of memory, cannot allocate 'Record'");
 
+    {
+      VirtMem::ProtectJitReadWriteScope scope(pRW, size);
+      JitAllocatorUtils::fillPattern64(pRW, pattern, size);
+    }
+
+    VirtMem::flushInstructionCache(pRX, size);
+    EXPECT(JitAllocatorUtils::verifyPattern64(pRX, pattern, size) == true);
+
     _records.insert(record);
   }
 
@@ -1080,6 +1130,9 @@ public:
     Record* record = _records.get(static_cast<uint8_t*>(p));
     EXPECT(record != nullptr, "Address [%p] doesn't exist\n", p);
 
+    EXPECT(JitAllocatorUtils::verifyPattern64(record->rx(), record->pattern, record->size) == true);
+    EXPECT(JitAllocatorUtils::verifyPattern64(record->rw(), record->pattern, record->size) == true);
+
     _records.remove(record);
     _heap.release(record, sizeof(Record));
   }
@@ -1091,7 +1144,7 @@ public:
     Error err = _allocator.alloc(&rxPtr, &rwPtr, size);
     EXPECT(err == kErrorOk, "JitAllocator failed to allocate %zu bytes\n", size);
 
-    _insert(rxPtr, size);
+    _insert(rxPtr, rwPtr, size);
     return rxPtr;
   }
 
@@ -1156,7 +1209,7 @@ static void BitVectorRangeIterator_testRandom(Random& rnd, size_t count) noexcep
 }
 
 static void test_jit_allocator_alloc_release() noexcept {
-  size_t kCount = BrokenAPI::hasArg("--quick") ? 1000 : 100000;
+  size_t kCount = BrokenAPI::hasArg("--quick") ? 20000 : 100000;
 
   struct TestParams {
     const char* name;
@@ -1316,8 +1369,8 @@ UNIT(jit_allocator) {
   test_jit_allocator_alloc_release();
   test_jit_allocator_query();
 }
-#endif
+#endif // ASMJIT_TEST
 
 ASMJIT_END_NAMESPACE
 
-#endif
+#endif // !ASMJIT_NO_JIT

src/asmjit/core/osutils.cpp

@@ -76,7 +76,7 @@ uint32_t OSUtils::getTickCount() noexcept {
   uint64_t t = (uint64_t(ts.tv_sec ) * 1000u) + (uint64_t(ts.tv_nsec) / 1000000u);
   return uint32_t(t & 0xFFFFFFFFu);
 #else
-  #pragma message("asmjit::OSUtils::getTickCount() doesn't have implementation for the target OS.")
+  #pragma message("[asmjit] OSUtils::getTickCount() doesn't have implementation for the target OS.")
   return 0;
 #endif
 }

src/asmjit/core/virtmem.cpp

@@ -43,7 +43,7 @@
     #define MAP_ANONYMOUS MAP_ANON
   #endif
 
-  #define ASMJIT_DUAL_MAPPING_ANON_FD
+  #define ASMJIT_ANONYMOUS_MEMORY_USE_FD
 
   #if defined(__APPLE__) || defined(__BIONIC__)
     #define ASMJIT_VM_SHM_DETECT 0
@@ -61,8 +61,8 @@
   #endif
 
   #if defined(__NetBSD__) && defined(MAP_REMAPDUP) && defined(PROT_MPROTECT)
-    #undef ASMJIT_DUAL_MAPPING_ANON_FD
+    #undef ASMJIT_ANONYMOUS_MEMORY_USE_FD
-    #define ASMJIT_DUAL_MAPPING_REMAPDUP
+    #define ASMJIT_ANONYMOUS_MEMORY_USE_REMAPDUP
   #endif
 #endif
 
@@ -73,6 +73,7 @@ ASMJIT_BEGIN_SUB_NAMESPACE(VirtMem)
 // Virtual Memory Utilities
 // ========================
 
+ASMJIT_MAYBE_UNUSED
 static const constexpr MemoryFlags dualMappingFilter[2] = {
   MemoryFlags::kAccessWrite | MemoryFlags::kMMapMaxAccessWrite,
   MemoryFlags::kAccessExecute | MemoryFlags::kMMapMaxAccessExecute
@@ -286,13 +287,13 @@ static int mmProtFromMemoryFlags(MemoryFlags memoryFlags) noexcept {
 // Virtual Memory [Posix] - Anonymus Memory
 // ========================================
 
-#if defined(ASMJIT_DUAL_MAPPING_ANON_FD)
+#if defined(ASMJIT_ANONYMOUS_MEMORY_USE_FD)
 
 // Some operating systems don't allow /dev/shm to be executable. On Linux this happens when /dev/shm is mounted with
 // 'noexec', which is enforced by systemd. Other operating systems like MacOS also restrict executable permissions
 // regarding /dev/shm, so we use a runtime detection before attempting to allocate executable memory. Sometimes we
-// don't need the detection as we know it would always result in `AnonymousMemStrategy::kTmpDir`.
+// don't need the detection as we know it would always result in `AnonymousMemoryStrategy::kTmpDir`.
-enum class AnonymousMemStrategy : uint32_t {
+enum class AnonymousMemoryStrategy : uint32_t {
   kUnknown = 0,
   kDevShm = 1,
   kTmpDir = 2
@@ -333,9 +334,13 @@ public:
 #if defined(__linux__) && defined(__NR_memfd_create)
     // Linux specific 'memfd_create' - if the syscall returns `ENOSYS` it means
     // it's not available and we will never call it again (would be pointless).
+    //
+    // NOTE: There is also memfd_create() libc function in FreeBSD, but it internally
+    // uses `shm_open(SHM_ANON, ...)` so it's not needed to add support for it (it's
+    // not a syscall as in Linux).
 
     // Zero initialized, if ever changed to '1' that would mean the syscall is not
-    // available and we must use `shm_open()` and `shm_unlink()`.
+    // available and we must use `shm_open()` and `shm_unlink()` (or regular `open()`).
     static volatile uint32_t memfd_create_not_supported;
 
     if (!memfd_create_not_supported) {
@@ -440,7 +445,7 @@ public:
 };
 
 #if ASMJIT_VM_SHM_DETECT
-static Error detectAnonMemStrategy(AnonymousMemStrategy* strategyOut) noexcept {
+static Error detectAnonymousMemoryStrategy(AnonymousMemoryStrategy* strategyOut) noexcept {
   AnonymousMemory anonMem;
   Info vmInfo = info();
 
@@ -451,39 +456,39 @@ static Error detectAnonMemStrategy(AnonymousMemStrategy* strategyOut) noexcept {
   if (ptr == MAP_FAILED) {
     int e = errno;
     if (e == EINVAL) {
-      *strategyOut = AnonymousMemStrategy::kTmpDir;
+      *strategyOut = AnonymousMemoryStrategy::kTmpDir;
       return kErrorOk;
     }
     return DebugUtils::errored(asmjitErrorFromErrno(e));
   }
   else {
     munmap(ptr, vmInfo.pageSize);
-    *strategyOut = AnonymousMemStrategy::kDevShm;
+    *strategyOut = AnonymousMemoryStrategy::kDevShm;
     return kErrorOk;
   }
 }
 #endif
 
-static Error getAnonMemStrategy(AnonymousMemStrategy* strategyOut) noexcept {
+static Error getAnonymousMemoryStrategy(AnonymousMemoryStrategy* strategyOut) noexcept {
 #if ASMJIT_VM_SHM_DETECT
   // Initially don't assume anything. It has to be tested whether '/dev/shm' was mounted with 'noexec' flag or not.
-  static std::atomic<uint32_t> globalShmStrategy;
+  static std::atomic<uint32_t> globalStrategy;
 
-  AnonymousMemStrategy strategy = static_cast<AnonymousMemStrategy>(globalShmStrategy.load());
+  AnonymousMemoryStrategy strategy = static_cast<AnonymousMemoryStrategy>(globalStrategy.load());
-  if (strategy == AnonymousMemStrategy::kUnknown) {
+  if (strategy == AnonymousMemoryStrategy::kUnknown) {
-    ASMJIT_PROPAGATE(detectAnonMemStrategy(&strategy));
+    ASMJIT_PROPAGATE(detectAnonymousMemoryStrategy(&strategy));
-    globalShmStrategy.store(static_cast<uint32_t>(strategy));
+    globalStrategy.store(static_cast<uint32_t>(strategy));
   }
 
   *strategyOut = strategy;
   return kErrorOk;
 #else
-  *strategyOut = AnonymousMemStrategy::kTmpDir;
+  *strategyOut = AnonymousMemoryStrategy::kTmpDir;
   return kErrorOk;
 #endif
 }
 
-#endif // ASMJIT_DUAL_MAPPING_ANON_FD
+#endif // ASMJIT_ANONYMOUS_MEMORY_USE_FD
 
 // Virtual Memory [Posix] - Hardened Runtime & MAP_JIT
 // ===================================================
@@ -554,19 +559,37 @@ static inline int mmMapJitFromMemoryFlags(MemoryFlags memoryFlags) noexcept {
 #endif
 }
 
-// Returns BSD-specific `PROT_MAX()` flags.
+ASMJIT_MAYBE_UNUSED
-static inline int mmMaxProtFromMemoryFlags(MemoryFlags memoryFlags) noexcept {
+static MemoryFlags maxAccessFlagsToRegularAccessFlags(MemoryFlags memoryFlags) noexcept {
-#if defined(PROT_MAX)
   static constexpr uint32_t kMaxProtShift = Support::ConstCTZ<uint32_t(MemoryFlags::kMMapMaxAccessRead)>::value;
+  return MemoryFlags(uint32_t(memoryFlags & MemoryFlags::kMMapMaxAccessRWX) >> kMaxProtShift);
+}
 
-  if (Support::test(memoryFlags, MemoryFlags::kMMapMaxAccessReadWrite | MemoryFlags::kMMapMaxAccessExecute))
+ASMJIT_MAYBE_UNUSED
-    return PROT_MAX(mmProtFromMemoryFlags((MemoryFlags)(uint32_t(memoryFlags) >> kMaxProtShift)));
+static MemoryFlags regularAccessFlagsToMaxAccessFlags(MemoryFlags memoryFlags) noexcept {
-  else
+  static constexpr uint32_t kMaxProtShift = Support::ConstCTZ<uint32_t(MemoryFlags::kMMapMaxAccessRead)>::value;
-    return 0;
+  return MemoryFlags(uint32_t(memoryFlags & MemoryFlags::kAccessRWX) << kMaxProtShift);
+}
+
+// Returns maximum protection flags from `memoryFlags`.
+//
+// Uses:
+//   - `PROT_MPROTECT()` on NetBSD.
+//   - `PROT_MAX()` when available(BSD).
+ASMJIT_MAYBE_UNUSED
+static inline int mmMaxProtFromMemoryFlags(MemoryFlags memoryFlags) noexcept {
+  MemoryFlags acc = maxAccessFlagsToRegularAccessFlags(memoryFlags);
+  if (acc != MemoryFlags::kNone) {
+#if defined(__NetBSD__) && defined(PROT_MPROTECT)
+    return PROT_MPROTECT(mmProtFromMemoryFlags(acc));
+#elif defined(PROT_MAX)
+    return PROT_MAX(mmProtFromMemoryFlags(acc));
 #else
-  DebugUtils::unused(memoryFlags);
+    return 0;
-  return 0;
 #endif
+  }
+
+  return 0;
 }
 
 static HardenedRuntimeFlags getHardenedRuntimeFlags() noexcept {
@@ -581,75 +604,89 @@ static HardenedRuntimeFlags getHardenedRuntimeFlags() noexcept {
   return flags;
 }
 
-Error alloc(void** p, size_t size, MemoryFlags memoryFlags) noexcept {
+static Error mapMemory(void** p, size_t size, MemoryFlags memoryFlags, int fd = -1, off_t offset = 0) noexcept {
   *p = nullptr;
   if (size == 0)
     return DebugUtils::errored(kErrorInvalidArgument);
 
   int protection = mmProtFromMemoryFlags(memoryFlags) | mmMaxProtFromMemoryFlags(memoryFlags);
-  int mmFlags = MAP_PRIVATE | MAP_ANONYMOUS | mmMapJitFromMemoryFlags(memoryFlags);
+  int mmFlags = mmMapJitFromMemoryFlags(memoryFlags);
 
-  void* ptr = mmap(nullptr, size, protection, mmFlags, -1, 0);
+  mmFlags |= Support::test(memoryFlags, MemoryFlags::kMapShared) ? MAP_SHARED : MAP_PRIVATE;
+  if (fd == -1)
+    mmFlags |= MAP_ANONYMOUS;
+
+  void* ptr = mmap(nullptr, size, protection, mmFlags, fd, offset);
   if (ptr == MAP_FAILED)
-    return DebugUtils::errored(kErrorOutOfMemory);
+    return DebugUtils::errored(asmjitErrorFromErrno(errno));
 
   *p = ptr;
   return kErrorOk;
 }
 
-Error release(void* p, size_t size) noexcept {
+static Error unmapMemory(void* p, size_t size) noexcept {
   if (ASMJIT_UNLIKELY(munmap(p, size) != 0))
-    return DebugUtils::errored(kErrorInvalidArgument);
+    return DebugUtils::errored(asmjitErrorFromErrno(errno));
 
   return kErrorOk;
 }
 
+Error alloc(void** p, size_t size, MemoryFlags memoryFlags) noexcept {
+  return mapMemory(p, size, memoryFlags);
+}
+
+Error release(void* p, size_t size) noexcept {
+  return unmapMemory(p, size);
+}
 
 Error protect(void* p, size_t size, MemoryFlags memoryFlags) noexcept {
   int protection = mmProtFromMemoryFlags(memoryFlags);
   if (mprotect(p, size, protection) == 0)
     return kErrorOk;
 
-  return DebugUtils::errored(kErrorInvalidArgument);
+  return DebugUtils::errored(asmjitErrorFromErrno(errno));
 }
 
 // Virtual Memory [Posix] - Dual Mapping
 // =====================================
 
-#if defined(ASMJIT_DUAL_MAPPING_REMAPDUP)
+static Error unmapDualMapping(DualMapping* dm, size_t size) noexcept {
-static void unmapDualMapping(DualMapping* dm, size_t size) noexcept {
+  Error err1 = unmapMemory(dm->rx, size);
-  if (dm->rw)
+  Error err2 = kErrorOk;
-    munmap(dm->rw, size);
 
-  if (dm->rx)
+  if (dm->rx != dm->rw)
-    munmap(dm->rx, size);
+    err2 = unmapMemory(dm->rw, size);
+
+  // We can report only one error, so report the first...
+  if (err1 || err2)
+    return DebugUtils::errored(err1 ? err1 : err2);
+
+  dm->rx = nullptr;
+  dm->rw = nullptr;
+  return kErrorOk;
 }
 
+#if defined(ASMJIT_ANONYMOUS_MEMORY_USE_REMAPDUP)
 static Error allocDualMappingUsingRemapdup(DualMapping* dmOut, size_t size, MemoryFlags memoryFlags) noexcept {
+  MemoryFlags maxAccessFlags = regularAccessFlagsToMaxAccessFlags(memoryFlags);
+  MemoryFlags finalFlags = memoryFlags | maxAccessFlags | MemoryFlags::kMapShared;
+
+  MemoryFlags rxFlags = finalFlags & ~(MemoryFlags::kAccessWrite | MemoryFlags::kMMapMaxAccessWrite);
+  MemoryFlags rwFlags = finalFlags & ~(MemoryFlags::kAccessExecute);
+
+  // Allocate RW mapping.
   DualMapping dm {};
+  ASMJIT_PROPAGATE(mapMemory(&dm.rw, size, rwFlags));
 
-  dm.rw = mmap(NULL, size, PROT_MPROTECT(mmProtFromMemoryFlags(memoryFlags)), MAP_ANONYMOUS, -1, 0);
+  // Allocate RX mapping.
-  if (dm.rw == MAP_FAILED) {
+  dm.rx = mremap(dm.rw, size, nullptr, size, MAP_REMAPDUP);
-    return DebugUtils::errored(asmjitErrorFromErrno(errno));
-  }
-
-  dm.rx = mremap(dm.rw, size, NULL, size, MAP_REMAPDUP);
   if (dm.rx == MAP_FAILED) {
     int e = errno;
-    unmapDualMapping(&dm, size);
+    munmap(dm.rw, size);
     return DebugUtils::errored(asmjitErrorFromErrno(e));
   }
 
-  MemoryFlags rxAccessFlags = memoryFlags & ~dualMappingFilter[0];
+  if (mprotect(dm.rx, size, mmProtFromMemoryFlags(rxFlags)) != 0) {
-  MemoryFlags rwAccessFlags = memoryFlags & ~dualMappingFilter[1];
-
-  if (mprotect(dm.rw, size, mmProtFromMemoryFlags(rwAccessFlags)) != 0) {
-    int e = errno;
-    unmapDualMapping(&dm, size);
-    return DebugUtils::errored(asmjitErrorFromErrno(e));
-  }
-
-  if (mprotect(dm.rx, size, mmProtFromMemoryFlags(rxAccessFlags)) != 0) {
     int e = errno;
     unmapDualMapping(&dm, size);
     return DebugUtils::errored(asmjitErrorFromErrno(e));
@@ -667,14 +704,14 @@ Error allocDualMapping(DualMapping* dm, size_t size, MemoryFlags memoryFlags) no
   if (off_t(size) <= 0)
     return DebugUtils::errored(size == 0 ? kErrorInvalidArgument : kErrorTooLarge);
 
-#if defined(ASMJIT_DUAL_MAPPING_REMAPDUP)
+#if defined(ASMJIT_ANONYMOUS_MEMORY_USE_REMAPDUP)
   return allocDualMappingUsingRemapdup(dm, size, memoryFlags);
-#elif defined(ASMJIT_DUAL_MAPPING_ANON_FD)
+#elif defined(ASMJIT_ANONYMOUS_MEMORY_USE_FD)
   bool preferTmpOverDevShm = Support::test(memoryFlags, MemoryFlags::kMappingPreferTmp);
   if (!preferTmpOverDevShm) {
-    AnonymousMemStrategy strategy;
+    AnonymousMemoryStrategy strategy;
-    ASMJIT_PROPAGATE(getAnonMemStrategy(&strategy));
+    ASMJIT_PROPAGATE(getAnonymousMemoryStrategy(&strategy));
-    preferTmpOverDevShm = (strategy == AnonymousMemStrategy::kTmpDir);
+    preferTmpOverDevShm = (strategy == AnonymousMemoryStrategy::kTmpDir);
   }
 
   AnonymousMemory anonMem;
@@ -683,16 +720,12 @@ Error allocDualMapping(DualMapping* dm, size_t size, MemoryFlags memoryFlags) no
 
   void* ptr[2];
   for (uint32_t i = 0; i < 2; i++) {
-    MemoryFlags accessFlags = memoryFlags & ~dualMappingFilter[i];
+    MemoryFlags restrictedMemoryFlags = memoryFlags & ~dualMappingFilter[i];
-    int protection = mmProtFromMemoryFlags(accessFlags) | mmMaxProtFromMemoryFlags(accessFlags);
+    Error err = mapMemory(&ptr[i], size, restrictedMemoryFlags | MemoryFlags::kMapShared, anonMem.fd(), 0);
-
+    if (err != kErrorOk) {
-    ptr[i] = mmap(nullptr, size, protection, MAP_SHARED, anonMem.fd(), 0);
-    if (ptr[i] == MAP_FAILED) {
-      // Get the error now before `munmap()` has a chance to clobber it.
-      int e = errno;
       if (i == 1)
-        munmap(ptr[0], size);
+        unmapMemory(ptr[0], size);
-      return DebugUtils::errored(asmjitErrorFromErrno(e));
+      return err;
     }
   }
 
@@ -705,16 +738,7 @@ Error allocDualMapping(DualMapping* dm, size_t size, MemoryFlags memoryFlags) no
 }
 
 Error releaseDualMapping(DualMapping* dm, size_t size) noexcept {
-  Error err = release(dm->rx, size);
+  return unmapDualMapping(dm, size);
-  if (dm->rx != dm->rw)
-    err |= release(dm->rw, size);
-
-  if (err)
-    return DebugUtils::errored(kErrorInvalidArgument);
-
-  dm->rx = nullptr;
-  dm->rw = nullptr;
-  return kErrorOk;
 }
 #endif
 
@@ -735,7 +759,7 @@ void flushInstructionCache(void* p, size_t size) noexcept {
   char* end = start + size;
   __builtin___clear_cache(start, end);
 #else
-  #pragma message("asmjit::VirtMem::flushInstructionCache() doesn't have implementation for the target OS and compiler")
+  #pragma message("[asmjit] VirtMem::flushInstructionCache() doesn't have implementation for the target OS and compiler")
   DebugUtils::unused(p, size);
 #endif
 }
@@ -770,7 +794,7 @@ HardenedRuntimeInfo hardenedRuntimeInfo() noexcept {
 
 void protectJitMemory(ProtectJitAccess access) noexcept {
 #if defined(ASMJIT_HAS_PTHREAD_JIT_WRITE_PROTECT_NP)
-  pthread_jit_write_protect_np(static_cast<uint32_t>(access));
+  pthread_jit_write_protect_np(static_cast<int>(access));
 #else
   DebugUtils::unused(access);
 #endif
@@ -778,4 +802,29 @@ void protectJitMemory(ProtectJitAccess access) noexcept {
 
 ASMJIT_END_SUB_NAMESPACE
 
-#endif
+// JitAllocator - Tests
+// ====================
+
+#if defined(ASMJIT_TEST)
+ASMJIT_BEGIN_NAMESPACE
+
+UNIT(virt_mem) {
+  VirtMem::Info vmInfo = VirtMem::info();
+
+  INFO("VirtMem::info():");
+  INFO("  pageSize: %zu", size_t(vmInfo.pageSize));
+  INFO("  pageGranularity: %zu", size_t(vmInfo.pageGranularity));
+
+  VirtMem::HardenedRuntimeInfo hardenedRtInfo = VirtMem::hardenedRuntimeInfo();
+  VirtMem::HardenedRuntimeFlags hardenedFlags = hardenedRtInfo.flags;
+
+  INFO("VirtMem::hardenedRuntimeInfo():");
+  INFO("  flags:");
+  INFO("    kEnabled: %s", Support::test(hardenedFlags, VirtMem::HardenedRuntimeFlags::kEnabled) ? "true" : "false");
+  INFO("    kMapJit: %s", Support::test(hardenedFlags, VirtMem::HardenedRuntimeFlags::kMapJit) ? "true" : "false");
+}
+
+ASMJIT_END_NAMESPACE
+#endif // ASMJIT_TEST
+
+#endif // !ASMJIT_NO_JIT

src/asmjit/core/virtmem.h

@@ -96,6 +96,13 @@ enum class MemoryFlags : uint32_t {
   //! MemoryFlags::kMMapMaxAccessExecute.
   kMMapMaxAccessRWX = kMMapMaxAccessRead | kMMapMaxAccessWrite | kMMapMaxAccessExecute,
 
+  //! Use `MAP_SHARED` when calling mmap().
+  //!
+  //! \note In some cases `MAP_SHARED` may be set automatically. For example when using dual mapping it's important to
+  //! to use `MAP_SHARED` instead of `MAP_PRIVATE` to ensure that the OS would not copy pages on write (that would mean
+  //! updating only the RW mapped region and not RX mapped one).
+  kMapShared = 0x00000100u,
+
   //! Not an access flag, only used by `allocDualMapping()` to override the default allocation strategy to always use
   //! a 'tmp' directory instead of "/dev/shm" (on POSIX platforms). Please note that this flag will be ignored if the
   //! operating system allows to allocate an executable memory by a different API than `open()` or `shm_open()`. For