From 533b7c9e7151afeba86c4751129eb037961d987c Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Sat, 8 Oct 2022 15:00:42 +0200
Subject: [PATCH] Refactor ACPI::get_rsdt_or_xsdt()

Much better now.

Also, remove a FIXME in PMM.cpp, since we do map the page bitmap to virtual memory now.
---
 kernel/src/acpi/RSDT.cpp  | 30 ++++++++++++++++--------------
 kernel/src/memory/PMM.cpp |  3 +--
 2 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/kernel/src/acpi/RSDT.cpp b/kernel/src/acpi/RSDT.cpp
index 5a9ee145..52ffaec7 100644
--- a/kernel/src/acpi/RSDT.cpp
+++ b/kernel/src/acpi/RSDT.cpp
@@ -9,26 +9,28 @@
 
 extern BOOTBOOT bootboot;
 
-ACPI::SDTHeader* ACPI::get_rsdt_or_xsdt() // FIXME: Refactor this ugly code.
+ACPI::SDTHeader* ACPI::get_rsdt_or_xsdt()
 {
-    static void* cache = nullptr;
-    if (cache) return (SDTHeader*)cache;
+    static SDTHeader* cache = nullptr;
+    if (cache) return cache;
+
     kdbgln("First time accessing the RSDT/XSDT, mapping it into memory");
     void* physical = (void*)bootboot.arch.x86_64.acpi_ptr;
-    uint64_t offset = (uint64_t)physical % PAGE_SIZE;
     kdbgln("RSDT/XSDT physical address: %lx", (uint64_t)physical);
-    cache = MemoryManager::get_unaligned_mapping(physical);
-    uint64_t numPages = 1;
-    while ((offset + ((SDTHeader*)cache)->Length) > (numPages * PAGE_SIZE))
+
+    cache = (SDTHeader*)MemoryManager::get_unaligned_mapping(physical);
+
+    uint64_t offset = (uint64_t)physical % PAGE_SIZE;
+    uint64_t rsdt_pages = (offset + cache->Length) / PAGE_SIZE;
+
+    if (rsdt_pages > 1)
     {
-        kwarnln("RSDT/XSDT extends beyond the mapped page, mapping one more page");
-        MemoryManager::release_unaligned_mappings(cache, numPages);
-        numPages++;
-        cache = MemoryManager::get_unaligned_mappings(cache, numPages);
+        MemoryManager::release_unaligned_mapping(cache);
+        cache = (SDTHeader*)MemoryManager::get_unaligned_mappings(cache, rsdt_pages);
     }
-    kdbgln("Mapped RSDT/XSDT to virtual address %lx, uses %ld pages", (uint64_t)cache, numPages);
-    SDTHeader* result = (SDTHeader*)cache;
-    return result;
+
+    kdbgln("Mapped RSDT/XSDT to virtual address %lx, uses %ld pages", (uint64_t)cache, rsdt_pages);
+    return cache;
 }
 
 bool ACPI::validate_rsdt_or_xsdt(ACPI::SDTHeader* root_sdt)
diff --git a/kernel/src/memory/PMM.cpp b/kernel/src/memory/PMM.cpp
index b8ab8ea1..94f35373 100644
--- a/kernel/src/memory/PMM.cpp
+++ b/kernel/src/memory/PMM.cpp
@@ -48,8 +48,7 @@ void PMM::init()
     }
 
     bitmap_addr = (char*)biggest_chunk;
-    virtual_bitmap_addr =
-        bitmap_addr; // FIXME: map this to a virtual address (ideally in the kernel heap between -128M and -64M)
+    virtual_bitmap_addr = bitmap_addr;
     ASSERT((total_mem / PAGE_SIZE / 8) < biggest_chunk_size);
     bitmap_size = total_mem / PAGE_SIZE / 8 + 1;
     memset(bitmap_addr, 0xFF, bitmap_size);