Add zone dump to /proc/mm.

Sweet, now we can look at all the zones (physical memory) currently in play.

Building the procfs files with ksprintf and rickety buffer presizing feels
pretty shoddy but I'll fix it up eventually.

Kernel/MemoryManager.h

@@ -16,6 +16,7 @@ enum class PageFaultResponse {
 };
 
 struct Zone : public Retainable<Zone> {
+    friend ByteBuffer procfs$mm();
 public:
     ~Zone();
     size_t size() const { return m_pages.size() * PAGE_SIZE; }

Kernel/ProcFileSystem.cpp

@@ -121,10 +121,19 @@ void ProcFileSystem::removeProcess(Task& task)
 ByteBuffer procfs$mm()
 {
     InterruptDisabler disabler;
-    auto buffer = ByteBuffer::createUninitialized(1024);
+    size_t zonePageCount = 0;
+    for (auto* zone : MM.m_zones)
+        zonePageCount += zone->m_pages.size();
+    auto buffer = ByteBuffer::createUninitialized(1024 + 80 * MM.m_zones.size() + zonePageCount * 10);
     char* ptr = (char*)buffer.pointer();
     ptr += ksprintf(ptr, "Zone count: %u\n", MM.m_zones.size());
     ptr += ksprintf(ptr, "Free physical pages: %u\n", MM.m_freePages.size());
+    for (auto* zone : MM.m_zones) {
+        ptr += ksprintf(ptr, "Zone %p size: %u\n  ", zone, zone->size());
+        for (auto page : zone->m_pages)
+            ptr += ksprintf(ptr, "%x ", page);
+        ptr += ksprintf(ptr, "\n");
+    }
     buffer.trim(ptr - (char*)buffer.pointer());
     return buffer;
 }