feat: overhaul userspace heap and virtual memory

kernel/src/Api/UserMemory.hpp

@@ -5,6 +5,7 @@
 
 #include <Sched/Scheduler.hpp>
 #include <Memory/Paging.hpp>
+#include <Api/Heap.hpp>
 
 namespace montauk::abi::UserMemory {
 
@@ -32,6 +33,21 @@ namespace montauk::abi::UserMemory {
         uint64_t pml4Phys = CurrentPml4();
         if (pml4Phys == 0) return false;
 
+        if (Memory::VMM::Paging::IsUserRangeAccessible(pml4Phys, addr, size, requireWrite))
+            return true;
+
+        // Anonymous VMAs are demand-committed. Validation precedes the actual
+        // kernel copy, so materialize missing pages here with the same access
+        // type that the copy will perform.
+        uint64_t page = addr & ~0xFFFULL;
+        uint64_t last = (addr + size - 1) & ~0xFFFULL;
+        for (;;) {
+            if (!Memory::VMM::Paging::IsUserRangeAccessible(pml4Phys, page, 1, requireWrite) &&
+                !TryHandleAnonymousPageFault(page, requireWrite ? 2ULL : 0ULL))
+                return false;
+            if (page == last) break;
+            page += 0x1000ULL;
+        }
         return Memory::VMM::Paging::IsUserRangeAccessible(pml4Phys, addr, size, requireWrite);
     }
 
@@ -58,7 +74,7 @@ namespace montauk::abi::UserMemory {
         const char* str = (const char*)addr;
         for (uint64_t i = 0; i < maxLen; i++) {
             if (!Memory::VMM::Paging::IsUserRangeAccessible(pml4Phys, addr + i, 1, false)) {
-                return false;
+                if (!TryHandleAnonymousPageFault(addr + i, 0)) return false;
             }
             if (str[i] == '\0') return true;
         }