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Kernel: Introduce basic pre-kernel environment

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This implements a simple bootloader that is capable of loading ELF64
kernel images. It does this by using QEMU/GRUB to load the kernel image
from disk and pass it to our bootloader as a Multiboot module.

The bootloader then parses the ELF image and sets it up appropriately.
The kernel's entry point is a C++ function with architecture-native
code.

Co-authored-by: Liav A <liavalb@gmail.com>
This commit is contained in:
Gunnar Beutner 2021-07-18 14:47:32 +02:00 • committed by Andreas Kling
parent 357ddd393e
commit 7e94b090fe
30 changed files with 1207 additions and 181 deletions
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30
Kernel/VM/PageDirectory.cpp
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@ -6,12 +6,15 @@
#include <AK/Memory.h>
#include <AK/Singleton.h>
#include <Kernel/Prekernel/Prekernel.h>
#include <Kernel/Process.h>
#include <Kernel/Random.h>
#include <Kernel/Sections.h>
#include <Kernel/VM/MemoryManager.h>
#include <Kernel/VM/PageDirectory.h>
extern u8* end_of_kernel_image;
namespace Kernel {
static AK::Singleton<HashMap<FlatPtr, PageDirectory*>> s_cr3_map;
@ -28,16 +31,19 @@ RefPtr<PageDirectory> PageDirectory::find_by_cr3(FlatPtr cr3)
return cr3_map().get(cr3).value_or({});
}
extern "C" FlatPtr kernel_base;
#if ARCH(X86_64)
extern "C" PageDirectoryEntry boot_pml4t[1024];
extern "C" void* boot_pml4t;
#endif
extern "C" PageDirectoryEntry* boot_pdpt[4];
extern "C" PageDirectoryEntry boot_pd0[1024];
extern "C" PageDirectoryEntry boot_pd3[1024];
extern "C" void* boot_pdpt;
extern "C" void* boot_pd0;
extern "C" void* boot_pd_kernel;
UNMAP_AFTER_INIT PageDirectory::PageDirectory()
{
m_range_allocator.initialize_with_range(VirtualAddress(KERNEL_BASE + KERNEL_PD_OFFSET), KERNEL_PD_END - (KERNEL_BASE + KERNEL_PD_OFFSET));
// make sure this starts in a new page directory to make MemoryManager::initialize_physical_pages() happy
FlatPtr start_of_range = ((FlatPtr)&end_of_kernel_image & ~(FlatPtr)0x1fffff) + 0x200000;
m_range_allocator.initialize_with_range(VirtualAddress(start_of_range), KERNEL_PD_END - start_of_range);
m_identity_range_allocator.initialize_with_range(VirtualAddress(FlatPtr(0x00000000)), 0x00200000);
}
@ -51,13 +57,13 @@ UNMAP_AFTER_INIT void PageDirectory::allocate_kernel_directory()
#endif
PhysicalAddress boot_pdpt_paddr(virtual_to_low_physical((FlatPtr)boot_pdpt));
PhysicalAddress boot_pd0_paddr(virtual_to_low_physical((FlatPtr)boot_pd0));
PhysicalAddress boot_pd3_paddr(virtual_to_low_physical((FlatPtr)boot_pd3));
PhysicalAddress boot_pd_kernel_paddr(virtual_to_low_physical((FlatPtr)boot_pd_kernel));
dmesgln("MM: boot_pdpt @ {}", boot_pdpt_paddr);
dmesgln("MM: boot_pd0 @ {}", boot_pd0_paddr);
dmesgln("MM: boot_pd3 @ {}", boot_pd3_paddr);
dmesgln("MM: boot_pd_kernel @ {}", boot_pd_kernel_paddr);
m_directory_table = PhysicalPage::create(boot_pdpt_paddr, MayReturnToFreeList::No);
m_directory_pages[0] = PhysicalPage::create(boot_pd0_paddr, MayReturnToFreeList::No);
m_directory_pages[3] = PhysicalPage::create(boot_pd3_paddr, MayReturnToFreeList::No);
m_directory_pages[(kernel_base >> 30) & 0x1ff] = PhysicalPage::create(boot_pd_kernel_paddr, MayReturnToFreeList::No);
}
PageDirectory::PageDirectory(const RangeAllocator* parent_range_allocator)
@ -83,15 +89,13 @@ PageDirectory::PageDirectory(const RangeAllocator* parent_range_allocator)
m_directory_table = MM.allocate_user_physical_page();
if (!m_directory_table)
return;
auto kernel_pd_index = (KERNEL_BASE >> 30) & 0xffu;
for (size_t i = 0; i < 4; i++) {
if (i == kernel_pd_index)
continue;
auto kernel_pd_index = (kernel_base >> 30) & 0x1ffu;
for (size_t i = 0; i < kernel_pd_index; i++) {
m_directory_pages[i] = MM.allocate_user_physical_page();
if (!m_directory_pages[i])
return;
}
// Share the top 1 GiB of kernel-only mappings (>=3GiB or >=KERNEL_BASE)
// Share the top 1 GiB of kernel-only mappings (>=kernel_base)
m_directory_pages[kernel_pd_index] = MM.kernel_page_directory().m_directory_pages[kernel_pd_index];
#if ARCH(X86_64)