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Kernel: Move kernel above the 3GB virtual address mark

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The kernel and its static data structures are no longer identity-mapped
in the bottom 8MB of the address space, but instead move above 3GB.

The first 8MB above 3GB are pseudo-identity-mapped to the bottom 8MB of
the physical address space. But things don't have to stay this way!

Thanks to Jesse who made an earlier attempt at this, it was really easy
to get device drivers working once the page tables were in place! :^)

Fixes #734.
This commit is contained in:
Andreas Kling 2020-01-17 19:59:20 +01:00
parent cee597a728
commit e362b56b4f
17 changed files with 325 additions and 125 deletions
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135
Kernel/VM/MemoryManager.cpp
View file

@ -21,13 +21,9 @@ MemoryManager& MM
return *s_the;
}
MemoryManager::MemoryManager(u32 physical_address_for_kernel_page_tables)
MemoryManager::MemoryManager()
{
m_kernel_page_directory = PageDirectory::create_at_fixed_address(PhysicalAddress(physical_address_for_kernel_page_tables));
for (size_t i = 0; i < 4; ++i) {
m_low_page_tables[i] = (PageTableEntry*)(physical_address_for_kernel_page_tables + PAGE_SIZE * (5 + i));
memset(m_low_page_tables[i], 0, PAGE_SIZE);
}
m_kernel_page_directory = PageDirectory::create_kernel_page_directory();
initialize_paging();
@ -49,32 +45,11 @@ void MemoryManager::initialize_paging()
dbgprintf("MM: Kernel page directory @ %p\n", kernel_page_directory().cr3());
#endif
#ifdef MM_DEBUG
dbgprintf("MM: Protect against null dereferences\n");
#endif
// Make null dereferences crash.
map_protected(VirtualAddress(0), PAGE_SIZE);
#ifdef MM_DEBUG
dbgprintf("MM: Identity map bottom 8MB\n");
#endif
// The bottom 8 MB (except for the null page) are identity mapped & supervisor only.
// Every process shares these mappings.
create_identity_mapping(kernel_page_directory(), VirtualAddress(PAGE_SIZE), (8 * MB) - PAGE_SIZE);
// Disable execution from 0MB through 1MB (BIOS data, legacy things, ...)
if (g_cpu_supports_nx) {
for (size_t i = 0; i < (1 * MB); i += PAGE_SIZE) {
auto& pte = ensure_pte(kernel_page_directory(), VirtualAddress(i));
pte.set_execute_disabled(true);
}
// Disable execution from 2MB through 8MB (kmalloc, kmalloc_eternal, slabs, page tables, ...)
for (size_t i = 1; i < 4; ++i) {
auto& pte = kernel_page_directory().table().directory(0)[i];
pte.set_execute_disabled(true);
}
}
// Disable execution from 0MB through 2MB (BIOS data, legacy things, ...)
if (g_cpu_supports_nx)
quickmap_pd(kernel_page_directory(), 0)[0].set_execute_disabled(true);
#if 0
// Disable writing to the kernel text and rodata segments.
extern u32 start_of_kernel_text;
extern u32 start_of_kernel_data;
@ -91,17 +66,7 @@ void MemoryManager::initialize_paging()
pte.set_execute_disabled(true);
}
}
// FIXME: We should move everything kernel-related above the 0xc0000000 virtual mark.
// Basic physical memory map:
// 0 -> 1 MB We're just leaving this alone for now.
// 1 -> 2 MB Kernel image.
// (last page before 2MB) Used by quickmap_page().
// 2 MB -> 4 MB kmalloc_eternal() space.
// 4 MB -> 7 MB kmalloc() space.
// 7 MB -> 8 MB Supervisor physical pages (available for allocation!)
// 8 MB -> MAX Userspace physical pages (available for allocation!)
#endif
// Basic virtual memory map:
// 0 -> 4 KB Null page (so nullptr dereferences crash!)
@ -109,15 +74,16 @@ void MemoryManager::initialize_paging()
// 8 MB -> 3 GB Available to userspace.
// 3GB -> 4 GB Kernel-only virtual address space (>0xc0000000)
m_quickmap_addr = VirtualAddress(0xffe00000);
#ifdef MM_DEBUG
dbgprintf("MM: Quickmap will use %p\n", m_quickmap_addr.get());
#endif
m_quickmap_addr = VirtualAddress((2 * MB) - PAGE_SIZE);
RefPtr<PhysicalRegion> region;
bool region_is_super = false;
for (auto* mmap = (multiboot_memory_map_t*)multiboot_info_ptr->mmap_addr; (unsigned long)mmap < multiboot_info_ptr->mmap_addr + multiboot_info_ptr->mmap_length; mmap = (multiboot_memory_map_t*)((unsigned long)mmap + mmap->size + sizeof(mmap->size))) {
auto* mmap = (multiboot_memory_map_t*)(0xc0000000 + multiboot_info_ptr->mmap_addr);
for (; (unsigned long)mmap < (0xc0000000 + multiboot_info_ptr->mmap_addr) + (multiboot_info_ptr->mmap_length); mmap = (multiboot_memory_map_t*)((unsigned long)mmap + mmap->size + sizeof(mmap->size))) {
kprintf("MM: Multiboot mmap: base_addr = 0x%x%08x, length = 0x%x%08x, type = 0x%x\n",
(u32)(mmap->addr >> 32),
(u32)(mmap->addr & 0xffffffff),
@ -221,6 +187,7 @@ void MemoryManager::initialize_paging()
if (g_cpu_supports_smap) {
// Turn on CR4.SMAP
kprintf("x86: Enabling SMAP\n");
asm volatile(
"mov %cr4, %eax\n"
"orl $0x200000, %eax\n"
@ -261,18 +228,14 @@ PageTableEntry& MemoryManager::ensure_pte(PageDirectory& page_directory, Virtual
u32 page_directory_index = (vaddr.get() >> 21) & 0x1ff;
u32 page_table_index = (vaddr.get() >> 12) & 0x1ff;
PageDirectoryEntry& pde = page_directory.table().directory(page_directory_table_index)[page_directory_index];
auto* pd = quickmap_pd(page_directory, page_directory_table_index);
PageDirectoryEntry& pde = pd[page_directory_index];
if (!pde.is_present()) {
#ifdef MM_DEBUG
dbgprintf("MM: PDE %u not present (requested for V%p), allocating\n", page_directory_index, vaddr.get());
#endif
if (page_directory_table_index == 0 && page_directory_index < 4) {
ASSERT(&page_directory == m_kernel_page_directory);
pde.set_page_table_base((u32)m_low_page_tables[page_directory_index]);
pde.set_user_allowed(false);
pde.set_present(true);
pde.set_writable(true);
pde.set_global(true);
if (page_directory_table_index == 3 && page_directory_index < 4) {
ASSERT_NOT_REACHED();
} else {
auto page_table = allocate_supervisor_physical_page();
#ifdef MM_DEBUG
@ -292,7 +255,13 @@ PageTableEntry& MemoryManager::ensure_pte(PageDirectory& page_directory, Virtual
page_directory.m_physical_pages.set(page_directory_index, move(page_table));
}
}
return pde.page_table_base()[page_table_index];
//if (&page_directory != &kernel_page_directory() && page_directory_table_index != 3) {
return quickmap_pt(PhysicalAddress((u32)pde.page_table_base()))[page_table_index];
//}
auto* phys_ptr = &pde.page_table_base()[page_table_index];
return *(PageTableEntry*)((u8*)phys_ptr + 0xc0000000);
}
void MemoryManager::map_protected(VirtualAddress vaddr, size_t length)
@ -325,9 +294,9 @@ void MemoryManager::create_identity_mapping(PageDirectory& page_directory, Virtu
}
}
void MemoryManager::initialize(u32 physical_address_for_kernel_page_tables)
void MemoryManager::initialize()
{
s_the = new MemoryManager(physical_address_for_kernel_page_tables);
s_the = new MemoryManager;
}
Region* MemoryManager::kernel_region_from_vaddr(VirtualAddress vaddr)
@ -349,6 +318,29 @@ Region* MemoryManager::user_region_from_vaddr(Process& process, VirtualAddress v
return &region;
}
dbg() << process << " Couldn't find user region for " << vaddr;
if (auto* kreg = kernel_region_from_vaddr(vaddr)) {
dbg() << process << " OTOH, there is a kernel region: " << kreg->range() << ": " << kreg->name();
} else {
dbg() << process << " AND no kernel region either";
}
process.dump_regions();
kprintf("Kernel regions:\n");
kprintf("BEGIN END SIZE ACCESS NAME\n");
for (auto& region : MM.m_kernel_regions) {
kprintf("%08x -- %08x %08x %c%c%c%c%c%c %s\n",
region.vaddr().get(),
region.vaddr().offset(region.size() - 1).get(),
region.size(),
region.is_readable() ? 'R' : ' ',
region.is_writable() ? 'W' : ' ',
region.is_executable() ? 'X' : ' ',
region.is_shared() ? 'S' : ' ',
region.is_stack() ? 'T' : ' ',
region.vmobject().is_purgeable() ? 'P' : ' ',
region.name().characters());
}
return nullptr;
}
@ -567,7 +559,7 @@ RefPtr<PhysicalPage> MemoryManager::allocate_supervisor_physical_page()
dbgprintf("MM: allocate_supervisor_physical_page vending P%p\n", page->paddr().get());
#endif
fast_u32_fill((u32*)page->paddr().as_ptr(), 0, PAGE_SIZE / sizeof(u32));
fast_u32_fill((u32*)page->paddr().offset(0xc0000000).as_ptr(), 0, PAGE_SIZE / sizeof(u32));
++m_super_physical_pages_used;
return page;
}
@ -601,6 +593,37 @@ void MemoryManager::flush_tlb(VirtualAddress vaddr)
: "memory");
}
extern "C" PageTableEntry boot_pd3_pde1023_pt[1024];
PageDirectoryEntry* MemoryManager::quickmap_pd(PageDirectory& directory, size_t pdpt_index)
{
auto& pte = boot_pd3_pde1023_pt[4];
auto pd_paddr = directory.m_directory_pages[pdpt_index]->paddr();
if (pte.physical_page_base() != pd_paddr.as_ptr()) {
//dbgprintf("quickmap_pd: Mapping P%p at 0xffe04000 in pte @ %p\n", directory.m_directory_pages[pdpt_index]->paddr().as_ptr(), &pte);
pte.set_physical_page_base(pd_paddr.get());
pte.set_present(true);
pte.set_writable(true);
pte.set_user_allowed(false);
flush_tlb(VirtualAddress(0xffe04000));
}
return (PageDirectoryEntry*)0xffe04000;
}
PageTableEntry* MemoryManager::quickmap_pt(PhysicalAddress pt_paddr)
{
auto& pte = boot_pd3_pde1023_pt[8];
if (pte.physical_page_base() != pt_paddr.as_ptr()) {
//dbgprintf("quickmap_pt: Mapping P%p at 0xffe08000 in pte @ %p\n", pt_paddr.as_ptr(), &pte);
pte.set_physical_page_base(pt_paddr.get());
pte.set_present(true);
pte.set_writable(true);
pte.set_user_allowed(false);
flush_tlb(VirtualAddress(0xffe08000));
}
return (PageTableEntry*)0xffe08000;
}
void MemoryManager::map_for_kernel(VirtualAddress vaddr, PhysicalAddress paddr, bool cache_disabled)
{
auto& pte = ensure_pte(kernel_page_directory(), vaddr);