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Kernel/aarch64: Change base address of the kernel to 0x2000000000

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This is the same address that the x86_64 kernel runs at, and allows us
to run the kernel at a high virtual memory address. Since we now run
completely in high virtual memory, we can also unmap the identity
mapping. Additionally some changes in MMU.cpp are required to
successfully boot.
This commit is contained in:
Timon Kruiper 2023-01-07 15:01:51 +01:00 committed by Linus Groh
parent 3bc122fcef
commit c4a3af12fc
Notes: sideshowbarker 2024-07-17 10:08:28 +09:00 
Author: https://github.com/FireFox317
Commit: https://github.com/SerenityOS/serenity/commit/c4a3af12fc
Pull-request: https://github.com/SerenityOS/serenity/pull/16884
Reviewed-by: https://github.com/48cf
Reviewed-by: https://github.com/ADKaster
Reviewed-by: https://github.com/mrkct
Reviewed-by: https://github.com/nico ✅
4 changed files with 29 additions and 16 deletions
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25
Kernel/Arch/aarch64/MMU.cpp
View file

@ -32,6 +32,11 @@ namespace Kernel {
constexpr u32 START_OF_NORMAL_MEMORY = 0x00000000;
constexpr u32 END_OF_NORMAL_MEMORY = 0x3EFFFFFF;
// TODO: We should change the RPi drivers to use the MemoryManager to map physical memory,
// instead of mapping the complete MMIO region beforehand.
constexpr u32 START_OF_MMIO_MEMORY = 0x3F000000;
constexpr u32 END_OF_MMIO_MEMORY = 0x3F000000 + 0x00FFFFFF;
ALWAYS_INLINE static u64* descriptor_to_pointer(FlatPtr descriptor)
{
return (u64*)(descriptor & DESCRIPTOR_MASK);
@ -90,7 +95,7 @@ private:
template<typename T>
inline T* adjust_by_mapping_base(T* ptr)
{
return (T*)((FlatPtr)ptr);
return (T*)((FlatPtr)ptr - KERNEL_MAPPING_BASE);
}
static u64* insert_page_table(PageBumpAllocator& allocator, u64* page_table, VirtualAddress virtual_addr)
@ -144,7 +149,10 @@ static void setup_quickmap_page_table(PageBumpAllocator& allocator, u64* root_ta
{
// FIXME: Rename boot_pd_kernel_pt1023 to quickmap_page_table
// FIXME: Rename KERNEL_PT1024_BASE to quickmap_page_table_address
*adjust_by_mapping_base(&boot_pd_kernel_pt1023) = (PageTableEntry*)insert_page_table(allocator, root_table, VirtualAddress { KERNEL_PT1024_BASE });
auto kernel_pt1024_base = VirtualAddress(*adjust_by_mapping_base(&kernel_mapping_base) + KERNEL_PT1024_OFFSET);
auto quickmap_page_table = PhysicalAddress((PhysicalPtr)insert_page_table(allocator, root_table, kernel_pt1024_base));
*adjust_by_mapping_base(&boot_pd_kernel_pt1023) = (PageTableEntry*)quickmap_page_table.offset(KERNEL_MAPPING_BASE).get();
}
static void build_mappings(PageBumpAllocator& allocator, u64* root_table)
@ -153,10 +161,10 @@ static void build_mappings(PageBumpAllocator& allocator, u64* root_table)
u64 device_memory_flags = ACCESS_FLAG | PAGE_DESCRIPTOR | OUTER_SHAREABLE | DEVICE_MEMORY;
// Align the identity mapping of the kernel image to 2 MiB, the rest of the memory is initially not mapped.
auto start_of_kernel_range = VirtualAddress(((FlatPtr)start_of_kernel_image + KERNEL_MAPPING_BASE) & ~(FlatPtr)0x1fffff);
auto end_of_kernel_range = VirtualAddress((((FlatPtr)end_of_kernel_image + KERNEL_MAPPING_BASE) & ~(FlatPtr)0x1fffff) + 0x200000 - 1);
auto start_of_mmio_range = VirtualAddress(RPi::MMIO::the().peripheral_base_address().offset(KERNEL_MAPPING_BASE).get());
auto end_of_mmio_range = VirtualAddress(RPi::MMIO::the().peripheral_end_address().offset(KERNEL_MAPPING_BASE).get());
auto start_of_kernel_range = VirtualAddress((FlatPtr)start_of_kernel_image & ~(FlatPtr)0x1fffff);
auto end_of_kernel_range = VirtualAddress(((FlatPtr)end_of_kernel_image & ~(FlatPtr)0x1fffff) + 0x200000 - 1);
auto start_of_mmio_range = VirtualAddress(START_OF_MMIO_MEMORY + KERNEL_MAPPING_BASE);
auto end_of_mmio_range = VirtualAddress(END_OF_MMIO_MEMORY + KERNEL_MAPPING_BASE);
auto start_of_physical_kernel_range = PhysicalAddress(start_of_kernel_range.get()).offset(-KERNEL_MAPPING_BASE);
auto start_of_physical_mmio_range = PhysicalAddress(start_of_mmio_range.get()).offset(-KERNEL_MAPPING_BASE);
@ -242,9 +250,8 @@ static void setup_kernel_page_directory(u64* root_table)
void init_page_tables()
{
// We currently identity map the physical memory, so the offset is 0.
*adjust_by_mapping_base(&physical_to_virtual_offset) = 0;
*adjust_by_mapping_base(&kernel_mapping_base) = 0;
*adjust_by_mapping_base(&physical_to_virtual_offset) = KERNEL_MAPPING_BASE;
*adjust_by_mapping_base(&kernel_mapping_base) = KERNEL_MAPPING_BASE;
PageBumpAllocator allocator(adjust_by_mapping_base((u64*)page_tables_phys_start), adjust_by_mapping_base((u64*)page_tables_phys_end));
auto root_table = allocator.take_page();

14
Kernel/Arch/aarch64/linker.ld
View file

@ -1,5 +1,7 @@
ENTRY(start)
KERNEL_MAPPING_BASE = 0x2000000000;
/* TODO: Add FLAGS to the program headers */
PHDRS
{
@ -11,17 +13,17 @@ PHDRS
SECTIONS
{
. = 0x00080000;
. = KERNEL_MAPPING_BASE + 0x80000;
start_of_kernel_image = .;
.text ALIGN(4K) : AT (ADDR(.text))
.text ALIGN(4K) : AT (ADDR(.text) - KERNEL_MAPPING_BASE)
{
*(.text.first)
*(.text*)
} :text
.rodata ALIGN(4K) : AT (ADDR(.rodata))
.rodata ALIGN(4K) : AT (ADDR(.rodata) - KERNEL_MAPPING_BASE)
{
start_heap_ctors = .;
*libkernel_heap.a:*(.init_array)
@ -34,19 +36,19 @@ SECTIONS
*(.rodata*)
} :data
.data ALIGN(4K) : AT (ADDR(.data))
.data ALIGN(4K) : AT (ADDR(.data) - KERNEL_MAPPING_BASE)
{
*(.data*)
} :data
.ksyms ALIGN(4K) : AT (ADDR(.ksyms))
.ksyms ALIGN(4K) : AT (ADDR(.ksyms) - KERNEL_MAPPING_BASE)
{
start_of_kernel_ksyms = .;
*(.kernel_symbols)
end_of_kernel_ksyms = .;
} :ksyms
.bss ALIGN(4K) (NOLOAD) : AT (ADDR(.bss))
.bss ALIGN(4K) (NOLOAD) : AT (ADDR(.bss) - KERNEL_MAPPING_BASE)
{
start_of_bss = .;
*(.bss)

3
Kernel/Arch/aarch64/pre_init.cpp
View file

@ -48,6 +48,9 @@ extern "C" [[noreturn]] void pre_init()
"add sp, sp, x0 \n" ::[base] "r"(kernel_mapping_base)
: "x0");
// We can now unmap the identity map as everything is running in high virtual memory at this point.
unmap_identity_map();
// Clear the frame pointer (x29) and link register (x30) to make sure the kernel cannot backtrace
// into this code, and jump to actual init function in the kernel.
asm volatile(

3
Kernel/Sections.h
View file

@ -18,7 +18,8 @@
#define KERNEL_MAPPING_BASE 0x2000000000
#define KERNEL_PD_END (kernel_mapping_base + KERNEL_PD_SIZE)
#define KERNEL_PT1024_BASE (kernel_mapping_base + 0x3FE00000)
#define KERNEL_PT1024_OFFSET 0x3FE00000
#define KERNEL_PT1024_BASE (kernel_mapping_base + KERNEL_PT1024_OFFSET)
#define KERNEL_MAX_CPU_COUNT 64
#define KERNEL_QUICKMAP_PT_PER_CPU_BASE (KERNEL_PT1024_BASE + (1 * KERNEL_MAX_CPU_COUNT * PAGE_SIZE))