feat: add kernel ACPI support for querying battery percentage, add battery indicator to desktop, move log state to 0:/state directory

kernel/src/Memory/Paging.cpp

@@ -5,6 +5,14 @@
 #include <CppLib/Spinlock.hpp>
 
 namespace Memory::VMM {
+
+    // Top of the contiguous HHDM mapping, published by Init() for callers that
+    // must validate a firmware-supplied physical address before dereferencing
+    // it through the HHDM.
+    static std::uint64_t g_hhdmLimit = 0;
+
+    std::uint64_t Paging::HhdmLimit() { return g_hhdmLimit; }
+
     Paging* g_paging = nullptr;
 
     static constexpr uint64_t LeafAddressMask = 0x000FFFFFFFFFF000ULL;
@@ -88,6 +96,7 @@ namespace Memory::VMM {
             if (entryEnd > maxPhysAddr) maxPhysAddr = entryEnd;
         }
         maxPhysAddr = (maxPhysAddr + 0xFFF) & ~0xFFFULL;
+        g_hhdmLimit = maxPhysAddr;
 
         for (uint64_t pageAddr = 0; pageAddr < maxPhysAddr; pageAddr += 0x1000) {
             Map(pageAddr, HHDM(pageAddr));

kernel/src/Memory/Paging.hpp

@@ -90,6 +90,14 @@ public:
         Paging();
         void Init(std::uint64_t kernelBaseVirt, std::uint64_t kernelSize, const montauk::boot::MemoryMap& memMap,
                   const montauk::boot::Framebuffer& framebuffer);
+        // Top of the contiguous HHDM mapping built by Init(). A physical
+        // address at or above this is NOT reachable at phys+hhdmBase, and
+        // dereferencing it there faults (non-canonical addresses raise #GP
+        // rather than #PF). Anything that turns firmware-supplied numbers into
+        // HHDM pointers -- the AML interpreter's SystemMemory regions above all
+        // -- must check against this first.
+        static std::uint64_t HhdmLimit();
+
         void Map(std::uint64_t physicalAddress, std::uint64_t virtualAddress);
         void MapMMIO(std::uint64_t physicalAddress, std::uint64_t virtualAddress);
         void MapWC(std::uint64_t physicalAddress, std::uint64_t virtualAddress);