refactor syscall ABI and FAT32 driver to use request structs and string views natively, enforce handle access rights on object lookup, add scheduler statistics tracking, fix KiSchedule to prevent 50% idle throttling on CPU-bound threads, better document x64 initial user stack alignment, fix process teardown to properly signal exit events and manage thread counts, optimize doom file I/O with a custom handle struct to internally track position and size, add SubsystemData to TEB for generic thread-local state, apply PAGE_NX to non-executable PE sections in the loader, update native apps, tests, and shells to match new APIs, update kernel32 directory retrieval.

code/kernel/mm_virt.c

@@ -290,29 +290,6 @@ __declspec(dllexport) KSTATUS CopyToUser(void* userDst, const void* kernelSrc, s
     return STATUS_SUCCESS;
 }
 
-__declspec(dllexport) KSTATUS CopyStringFromUser(char* kernelDst,
-                                                 size_t kernelDstSize,
-                                                 const char* userSrc) {
-    if (!kernelDst || kernelDstSize == 0 || !userSrc)
-        return STATUS_INVALID_PARAMETER;
-
-    for (size_t i = 0; i < kernelDstSize; i++) {
-        KSTATUS s = MmProbeUserRead(userSrc + i, 1);
-        if (!KSUCCESS(s)) {
-            kernelDst[0] = '\0';
-            return s;
-        }
-
-        char ch = userSrc[i];
-        kernelDst[i] = ch;
-        if (ch == '\0')
-            return STATUS_SUCCESS;
-    }
-
-    kernelDst[kernelDstSize - 1] = '\0';
-    return STATUS_BUFFER_TOO_SMALL;
-}
-
 // ---------------------------------------------------------------------------
 // Boundary-tag allocator (used for both pool and user heap)
 // ---------------------------------------------------------------------------
@@ -595,6 +572,9 @@ static HEAP gPoolHeap;
 // User heap
 // ---------------------------------------------------------------------------
 static HEAP gUserHeap;
+__declspec(dllexport) void MmFreeUserImage(void* ptr, size_t size);
+static SPINLOCK gUserImageLock = SPINLOCK_INIT;
+static uintptr_t gUserImageNext = USER_LIMIT;
 
 // ---------------------------------------------------------------------------
 // Module init
@@ -621,8 +601,15 @@ void MmInitializeVirtual(PHYSICAL_ADDRESS bootPml4Phys, size_t poolSize) {
     gUserHeap.Start    = USER_BASE;
     gUserHeap.Brk      = USER_BASE;
     gUserHeap.Limit    = USER_LIMIT;
-    gUserHeap.MapFlags = PAGE_PRESENT | PAGE_WRITE | PAGE_USER;
+    gUserHeap.MapFlags = PAGE_PRESENT | PAGE_WRITE | PAGE_USER | PAGE_NX;
     gUserHeap.Lock     = (SPINLOCK)SPINLOCK_INIT;
+
+    // Executable image mappings grow downward from the top of user space.
+    // The regular user heap grows upward from USER_BASE.  Keeping them in
+    // separate page-aligned regions prevents W^X section protection from
+    // changing heap metadata or adjacent allocations.
+    gUserImageLock = (SPINLOCK)SPINLOCK_INIT;
+    gUserImageNext = USER_LIMIT;
 }
 
 void MmActivate(void) {
@@ -654,6 +641,60 @@ __declspec(dllexport) void* MmReallocateUserMemory(void* ptr, size_t newSize) {
     return KiHeapRealloc(&gUserHeap, ptr, newSize);
 }
 
+
+__declspec(dllexport) void* MmAllocateUserImage(size_t size) {
+    KeAssertIrql(PASSIVE_LEVEL);
+    if (!size) return (void*)0;
+
+    size_t pagesSize = (size + PAGE_SIZE - 1) & ~(PAGE_SIZE - 1);
+    if (pagesSize < size) return (void*)0;
+
+    uintptr_t flags = KeAcquireSpinlock(&gUserImageLock);
+
+    if (pagesSize > gUserImageNext || gUserImageNext - pagesSize < gUserHeap.Brk) {
+        KeReleaseSpinlock(&gUserImageLock, flags);
+        return (void*)0;
+    }
+
+    uintptr_t base = gUserImageNext - pagesSize;
+    gUserImageNext = base;
+    KeReleaseSpinlock(&gUserImageLock, flags);
+
+    for (uintptr_t va = base; va < base + pagesSize; va += PAGE_SIZE) {
+        PHYSICAL_ADDRESS frame = MmAllocateFrame();
+        if (!frame) {
+            MmFreeUserImage((void*)base, va - base);
+            return (void*)0;
+        }
+        KSTATUS s = MmMapPage(va, frame, PAGE_PRESENT | PAGE_WRITE | PAGE_USER | PAGE_NX);
+        if (!KSUCCESS(s)) {
+            MmFreeFrame(frame);
+            MmFreeUserImage((void*)base, va - base);
+            return (void*)0;
+        }
+    }
+
+    memset((void*)base, 0, pagesSize);
+    return (void*)base;
+}
+
+__declspec(dllexport) void MmFreeUserImage(void* ptr, size_t size) {
+    KeAssertIrql(PASSIVE_LEVEL);
+    if (!ptr || !size) return;
+
+    uintptr_t base = (uintptr_t)ptr & PAGE_MASK;
+    size_t pagesSize = (size + PAGE_SIZE - 1) & ~(PAGE_SIZE - 1);
+    if (pagesSize < size) return;
+
+    for (uintptr_t va = base; va < base + pagesSize; va += PAGE_SIZE) {
+        PHYSICAL_ADDRESS phys = MmGetPhysicalAddress(va);
+        if (!phys) continue;
+        if (KSUCCESS(MmUnmapPage(va))) {
+            MmFreeFrame(phys);
+        }
+    }
+}
+
 size_t MmGetKernelPoolUsage(void) {
     // Returns bytes committed to the kernel pool
     return (size_t)(gPoolHeap.Brk - gPoolHeap.Start);