fix: plug memory map leak, save sp_el0, dynamic UART, kill loop

- Bootloader: reallocate memory map buffer when ExitBootServices fails,
  so GetMemoryMap doesn't scribble past the old allocation on retry.
- vectors.S: actually store sp_el0 into the exception frame. Previously
  it was read into x24 and then… vanished. EL0 tasks would wake up with
  a corrupted stack pointer. Not great.
- Serial: split hardcoded 0x09000000 into a fallback default; add
  SerialUpdate() so the DTB-parsed UART address actually gets used.
- DTB: add bounds check on reserved[] with PMM's 3 extra slots accounted
  for, so malformed/overstuffed DTBs don't silently corrupt memory.
- PMM.h: bump kVMMaxReservedRegions 128→256, define kPMMReservedRegionCount.
- Types.h: remove `#define loop while(1)`. while(true) is fine.
- Rename IOSerial* → Serial* — the IO prefix was redundant, Serial.c
  already lives under IO/.

Bootloader/Source/main.c

@@ -192,6 +192,7 @@ static efi_status_t populate_memory_map(Bootinfo* boot_info) {
     while (1) {
         status = gBS->GetMemoryMap(&map_size, map, &map_key, &descriptor_size, &descriptor_version);
         if (EFI_ERROR(status)) {
+            gBS->FreePool(map);
             return status;
         }
 
@@ -206,7 +207,12 @@ static efi_status_t populate_memory_map(Bootinfo* boot_info) {
             return EFI_SUCCESS;
         }
 
+        gBS->FreePool(map);
         map_size += 2 * descriptor_size;
+        status = gBS->AllocatePool(EfiLoaderData, map_size, (void**)&map);
+        if (EFI_ERROR(status)) {
+            return status;
+        }
     }
 }
 

Kernel/Include/IO/Serial.h

@@ -2,8 +2,9 @@
 #include <Types.h>
 
 enum {
-    kUARTBaseAddress = 0x09000000, // TODO: make it dynamic by parsing DTB
+    kUARTBaseAddress = 0x09000000,
 };
 
-Int32 IOSerialPutCharacter(ASCII character);
+void SerialUpdate(UInt64 address);
-Int32 IOSerialPutString(const ASCII* string);
+Int32 SerialPutCharacter(ASCII character);
+Int32 SerialPutString(const ASCII* string);

Kernel/Include/Types.h

@@ -31,4 +31,3 @@ typedef UInt64 Size;
 typedef char ASCII;
 
 typedef _Bool Boolean;
-#define loop while (1)

Kernel/Include/VM/PMM.h

@@ -4,7 +4,8 @@
 enum {
     kVMPageSize = 4096,
     kVMBlocksPerByte = 8,
-    kVMMaxReservedRegions = 128,
+    kVMMaxReservedRegions = 256,
+    kPMMReservedRegionCount = 3,
 };
 
 typedef struct {

Kernel/Source/Arch/DTB.c

@@ -28,6 +28,9 @@ void DTBParse(Pointer dtb, VMBootMemoryMap* bootMap) {
     Boolean inReservedMemory = false;
 
     while (true) {
+        if (bootMap->reservedCount + kPMMReservedRegionCount >= kVMMaxReservedRegions) {
+            OSPanic("Too many reserved memory regions!"); // should never occur but jic
+        }
         UInt32 token = BytesSwap32(*(UInt32*)structs);
         structs += 4;
 

Kernel/Source/Arch/vectors.S

@@ -54,6 +54,7 @@ ExceptionsTrapEntry:
 
     stp x30, x21, [sp, #16 * 15]
     stp x22, x23, [sp, #16 * 16]
+    stp x24, xzr, [sp, #16 * 17]
 
     mov x0, sp
     bl ExceptionsHandler

Kernel/Source/IO/Serial.c

@@ -2,22 +2,28 @@
 #include <Arch/IO.h>
 #include <Arch/CPU.h>
 
-Int32 IOSerialPutCharacter(ASCII character) {
+static UInt64 sUARTAddress = kUARTBaseAddress;
+
+void SerialUpdate(UInt64 address) {
+    sUARTAddress = address;
+}
+
+Int32 SerialPutCharacter(ASCII character) {
     // TXFF -- TRansmit FIFO Full for PL011 is 5 bit of FR reg (0x18)
-    UInt64 uartFR = kUARTBaseAddress + 0x18;
+    UInt64 uartFR = sUARTAddress + 0x18;
 
     while ((IOAddressRead32(uartFR) & (1 << 5)) != 0)  {
         CPUYield();
     }
 
-    IOAddressWrite32(kUARTBaseAddress, character);
+    IOAddressWrite32(sUARTAddress, character);
     return character;
 }
 
-Int32 IOSerialPutString(const ASCII* string) {
+Int32 SerialPutString(const ASCII* string) {
     Int i = 0;
     while (string[i] != '\0') {
-        IOSerialPutCharacter(string[i]);
+        SerialPutCharacter(string[i]);
         i++;
     }
 

Kernel/Source/KernelMain.c

@@ -3,6 +3,7 @@
 #include <Arch/Timer.h>
 #include <Arch/CPU.h>
 #include <Arch/GIC.h>
+#include <IO/Serial.h>
 #include <VM/PMM.h>
 #include <VM/VMM.h>
 #include <VM/Heap.h>
@@ -20,6 +21,7 @@ void KernelMain(Bootinfo* bootinfo) {
 
     bootMap.reservedCount = 0;
     DTBParse(bootinfo->dtb, &bootMap);
+    SerialUpdate(bootMap.UART.base);
 
     PMMInitialize(&bootMap);
     VMMInitialize(&bootMap, bootinfo);

Kernel/Source/OS/Log.c

@@ -11,5 +11,5 @@ void OSLog(const ASCII* format, ...) {
     StringFormatVariadic(buffer, kOSLogBufferSize, format, args);
     va_end(args);
 
-    IOSerialPutString(buffer);
+    SerialPutString(buffer);
 }

Kernel/Source/OS/Panic.c

@@ -40,7 +40,7 @@ static const ASCII* sFunMessages[] = {
 };
 
 __attribute__((noreturn)) static void Halt() {
-    loop {
+    while (true) {
         CPUDisableInterrupts();
         CPUWaitForInterrupt();
     }

Kernel/Source/OS/Scheduler.c

@@ -89,7 +89,7 @@ Address SchedulerNext(Address stackPointer) {
     if (gOSSchedulerCurrentTask->sleepTicks > 0) gOSSchedulerCurrentTask->sleepTicks--;
 
     OSTask* nextTask = gOSSchedulerCurrentTask->next;
-    loop {
+    while (true) {
         if (nextTask->state == OSTaskStateDead) {
             nextTask = nextTask->next;
             if (nextTask == gOSSchedulerCurrentTask) OSPanic("No running tasks");