Kernel: Add better support for bootloaders loading the kernel

Before I assumed that bootloaders loaded the kernel at physical address
0, but this patch kinda allows loading to different addresses. This
still doesn't fully work as kernel bootstrap paging relies on kernel
being loaded at 0

bootloader/bios/boot.S

@@ -172,3 +172,5 @@ banan_boot_info:
 		.long framebuffer
 	boot_memory_map:
 		.long memory_map
+	boot_kernel_paddr:
+		.long 0

kernel/arch/i686/PageTable.cpp

@@ -1,3 +1,4 @@
+#include <kernel/BootInfo.h>
 #include <kernel/CPUID.h>
 #include <kernel/Lock/SpinLock.h>
 #include <kernel/Memory/kmalloc.h>
@@ -128,6 +129,18 @@ namespace Kernel
 		return (uint64_t*)page;
 	}
 
+	template<typename T>
+	static paddr_t V2P(const T vaddr)
+	{
+		return (vaddr_t)vaddr - KERNEL_OFFSET + g_boot_info.kernel_paddr;
+	}
+
+	template<typename T>
+	static vaddr_t P2V(const T paddr)
+	{
+		return (paddr_t)paddr - g_boot_info.kernel_paddr + KERNEL_OFFSET;
+	}
+
 	void PageTable::initialize_kernel()
 	{
 		ASSERT(s_global_pdpte == 0);

kernel/arch/x86_64/PageTable.cpp

@@ -1,6 +1,5 @@
-#include <kernel/Arch.h>
+#include <kernel/BootInfo.h>
 #include <kernel/CPUID.h>
-#include <kernel/InterruptController.h>
 #include <kernel/Lock/SpinLock.h>
 #include <kernel/Memory/kmalloc.h>
 #include <kernel/Memory/PageTable.h>
@@ -147,6 +146,18 @@ namespace Kernel
 		return (uint64_t*)page;
 	}
 
+	template<typename T>
+	static paddr_t V2P(const T vaddr)
+	{
+		return (vaddr_t)vaddr - KERNEL_OFFSET + g_boot_info.kernel_paddr;
+	}
+
+	template<typename T>
+	static vaddr_t P2V(const T paddr)
+	{
+		return (paddr_t)paddr - g_boot_info.kernel_paddr + KERNEL_OFFSET;
+	}
+
 	void PageTable::initialize_kernel()
 	{
 		ASSERT(s_global_pml4e == 0);

kernel/include/kernel/BananBootloader.h

@@ -33,4 +33,5 @@ struct BananBootloaderInfo
 	uint32_t command_line_addr;
 	uint32_t framebuffer_addr;
 	uint32_t memory_map_addr;
+	uint32_t kernel_paddr;
 } __attribute__((packed));

kernel/include/kernel/BootInfo.h

@@ -37,6 +37,7 @@ namespace Kernel
 		BAN::String					command_line;
 		FramebufferInfo				framebuffer			{};
 		RSDP						rsdp				{};
+		paddr_t                     kernel_paddr        {};
 		BAN::Vector<MemoryMapEntry>	memory_map_entries;
 	};
 

kernel/include/kernel/Memory/Types.h

@@ -10,9 +10,6 @@
 	#error
 #endif
 
-#define V2P(vaddr) (((vaddr_t)(vaddr)) - KERNEL_OFFSET)
-#define P2V(paddr) (((paddr_t)(paddr)) + KERNEL_OFFSET)
-
 #define PAGE_SIZE ((uintptr_t)4096)
 #define PAGE_SIZE_SHIFT 12
 #define PAGE_ADDR_MASK (~(uintptr_t)0xFFF)

kernel/kernel/ACPI/ACPI.cpp

@@ -254,7 +254,7 @@ acpi_release_global_lock:
 		return *s_instance;
 	}
 
-	static bool is_rsdp(uintptr_t rsdp_addr)
+	static bool is_rsdp(vaddr_t rsdp_addr)
 	{
 		const RSDP* rsdp = (const RSDP*)rsdp_addr;
 
@@ -287,7 +287,7 @@ acpi_release_global_lock:
 			return &g_boot_info.rsdp;
 
 		// Look in main BIOS area below 1 MB
-		for (uintptr_t addr = P2V(0x000E0000); addr < P2V(0x000FFFFF); addr += 16)
+		for (vaddr_t addr = 0x000E0000 + KERNEL_OFFSET; addr < 0x000FFFFF + KERNEL_OFFSET; addr += 16)
 			if (is_rsdp(addr))
 				return reinterpret_cast<const RSDP*>(addr);
 		return nullptr;

kernel/kernel/BootInfo.cpp

@@ -66,6 +66,8 @@ namespace Kernel
 				memcpy(&g_boot_info.rsdp, &rsdp, BAN::Math::min<uint32_t>(rsdp.length, sizeof(g_boot_info.rsdp)));
 			}
 		}
+
+		g_boot_info.kernel_paddr = 0;
 	}
 
 	static BAN::StringView get_early_boot_command_line_multiboot2(uint32_t info)
@@ -104,6 +106,8 @@ namespace Kernel
 			g_boot_info.memory_map_entries[i].length	= mmap_entry.length;
 			g_boot_info.memory_map_entries[i].type		= mmap_entry.type;
 		}
+
+		g_boot_info.kernel_paddr = banan_bootloader_info.kernel_paddr;
 	}
 
 	static BAN::StringView get_early_boot_command_line_banan_bootloader(uint32_t info)

kernel/kernel/Memory/Heap.cpp

@@ -40,8 +40,8 @@ namespace Kernel
 				continue;
 
 			paddr_t start = entry.address;
-			if (start < V2P(g_kernel_end))
-				start = V2P(g_kernel_end);
+			if (start < (vaddr_t)g_kernel_end - KERNEL_OFFSET + g_boot_info.kernel_paddr)
+				start = (vaddr_t)g_kernel_end - KERNEL_OFFSET + g_boot_info.kernel_paddr;
 			if (auto rem = start % PAGE_SIZE)
 				start += PAGE_SIZE - rem;
 

kernel/kernel/Memory/kmalloc.cpp

@@ -1,9 +1,8 @@
 #include <BAN/Errors.h>
 #include <kernel/kprint.h>
+#include <kernel/BootInfo.h>
 #include <kernel/Memory/kmalloc.h>
 
-#include <kernel/Thread.h>
-
 #define MB (1 << 20)
 
 extern uint8_t g_kernel_end[];
@@ -424,7 +423,7 @@ BAN::Optional<Kernel::paddr_t> kmalloc_paddr_of(Kernel::vaddr_t vaddr)
 	using namespace Kernel;
 
 	if ((vaddr_t)s_kmalloc_storage <= vaddr && vaddr < (vaddr_t)s_kmalloc_storage + sizeof(s_kmalloc_storage))
-		return V2P(vaddr);
+		return vaddr - KERNEL_OFFSET + g_boot_info.kernel_paddr;
 
 	return {};
 }