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Move kernel to higher half.

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Return to having the bootloader re-map the kernel into the higher
half before jumping into the kernel entrypoint, so we don't have
to juggle pointers inside the kernel.
This commit is contained in:
Justin C. Miller
2018-04-19 01:34:30 -07:00
parent a27b8d6a3a
commit 3b560c063a
7 changed files with 134 additions and 9 deletions
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94
src/boot/memory.c
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@@ -8,6 +8,10 @@
#define INCREMENT_DESC(p, b) (EFI_MEMORY_DESCRIPTOR*)(((uint8_t*)(p))+(b))
size_t fixup_pointer_index = 0;
void **fixup_pointers[64];
uint64_t *new_pml4 = 0;
const CHAR16 *memory_type_names[] = {
L"EfiReservedMemoryType",
L"EfiLoaderCode",
@@ -37,6 +41,49 @@ memory_type_name(UINT32 value)
return memory_type_names[value];
}
void EFIAPI
memory_update_marked_addresses(EFI_EVENT UNUSED *event, void *context)
{
EFI_RUNTIME_SERVICES *runsvc = (EFI_RUNTIME_SERVICES*)context;
for (size_t i = 0; i < fixup_pointer_index; ++i) {
if (fixup_pointers[i])
runsvc->ConvertPointer(0, fixup_pointers[i]);
}
}
EFI_STATUS
memory_init_pointer_fixup(EFI_BOOT_SERVICES *bootsvc, EFI_RUNTIME_SERVICES *runsvc)
{
EFI_STATUS status;
EFI_EVENT event;
status = bootsvc->CreateEvent(
EVT_SIGNAL_VIRTUAL_ADDRESS_CHANGE,
TPL_CALLBACK,
(EFI_EVENT_NOTIFY)&memory_update_marked_addresses,
runsvc,
&event);
CHECK_EFI_STATUS_OR_RETURN(status, "Failed to initialize pointer update event.");
// Reserve a page for our replacement PML4
EFI_PHYSICAL_ADDRESS addr = 0;
status = bootsvc->AllocatePages(AllocateAnyPages, EfiLoaderData, 1, &addr);
CHECK_EFI_STATUS_OR_RETURN(status, "Failed to allocate PML4 page.");
new_pml4 = (uint64_t *)addr;
}
void
memory_mark_pointer_fixup(void **p)
{
if (fixup_pointer_index == 0) {
const size_t count = sizeof(fixup_pointers) / sizeof(void*);
for (size_t i = 0; i < count; ++i) fixup_pointers[i] = 0;
}
fixup_pointers[fixup_pointer_index++] = p;
}
void
copy_desc(EFI_MEMORY_DESCRIPTOR *src, EFI_MEMORY_DESCRIPTOR *dst, size_t len)
{
@@ -111,3 +158,50 @@ memory_dump_map(struct memory_map *map)
return EFI_SUCCESS;
}
void
memory_virtualize(EFI_RUNTIME_SERVICES *runsvc, struct memory_map *map)
{
memory_mark_pointer_fixup((void **)&runsvc);
memory_mark_pointer_fixup((void **)&map);
// Get the pointer to the start of PML4
uint64_t* cr3 = 0;
__asm__ __volatile__ ( "mov %%cr3, %0" : "=r" (cr3) );
// PML4 is indexed with bits 39:47 of the virtual address
uint64_t offset = (KERNEL_VIRT_ADDRESS >> 39) & 0x1ff;
// Double map the lower half pages that are present into the higher half
for (unsigned i = 0; i < offset; ++i) {
if (cr3[i] & 0x1)
new_pml4[i] = new_pml4[offset+i] = cr3[i];
else
new_pml4[i] = new_pml4[offset+i] = 0;
}
// Write our new PML4 pointer back to CR3
__asm__ __volatile__ ( "mov %0, %%cr3" :: "r" (new_pml4) );
EFI_MEMORY_DESCRIPTOR *end = INCREMENT_DESC(map->entries, map->length);
EFI_MEMORY_DESCRIPTOR *d = map->entries;
while (d < end) {
switch (d->Type) {
case KERNEL_MEMTYPE:
case KERNEL_FONT_MEMTYPE:
case KERNEL_DATA_MEMTYPE:
case KERNEL_LOG_MEMTYPE:
d->Attribute |= EFI_MEMORY_RUNTIME;
d->VirtualStart = d->PhysicalStart + KERNEL_VIRT_ADDRESS;
break;
default:
if (d->Attribute & EFI_MEMORY_RUNTIME) {
d->VirtualStart = d->PhysicalStart;
}
}
d = INCREMENT_DESC(d, map->size);
}
runsvc->SetVirtualAddressMap(map->length, map->size, map->version, map->entries);
}