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kern: update KernelLdr for 19.0.0 (new checks, dummy function call).

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Also, fix a few very embarassing mistakes in kernel ldr:
* We have been mapping the page table region RWX for a few years now, accidentally.
* My attempt at making initial page tables not use bit 58 was broken in multiple ways.
This commit is contained in:
Michael Scire 2025-04-07 16:46:58 -07:00
parent 4e99a5e08d
commit 85fd13f724
4 changed files with 27 additions and 18 deletions
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17
mesosphere/kernel_ldr/source/kern_init_loader.cpp
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@ -49,7 +49,7 @@ namespace ams::kern::init::loader {
constinit void *g_final_state[2];
void RelocateKernelPhysically(uintptr_t &base_address, KernelLayout *&layout) {
void RelocateKernelPhysically(uintptr_t &base_address, KernelLayout *&layout, const uintptr_t &ini_base_address) {
/* Adjust layout to be correct. */
{
const ptrdiff_t layout_offset = reinterpret_cast<uintptr_t>(layout) - base_address;
@ -74,6 +74,12 @@ namespace ams::kern::init::loader {
const uintptr_t diff = GetInteger(correct_base) - base_address;
const size_t size = layout->rw_end_offset;
/* Check that the new kernel doesn't overlap with us. */
MESOSPHERE_INIT_ABORT_UNLESS((GetInteger(correct_base) >= reinterpret_cast<uintptr_t>(__bin_end__)) || (GetInteger(correct_base) + size <= reinterpret_cast<uintptr_t>(__bin_start__)));
/* Check that the new kernel doesn't overlap with the initial process binary. */
MESOSPHERE_INIT_ABORT_UNLESS((ini_base_address + InitialProcessBinarySizeMax <= GetInteger(correct_base)) || (GetInteger(correct_base) + size <= ini_base_address));
/* Conversion from KPhysicalAddress to void * is safe here, because MMU is not set up yet. */
std::memmove(reinterpret_cast<void *>(GetInteger(correct_base)), reinterpret_cast<void *>(base_address), size);
base_address += diff;
@ -90,11 +96,11 @@ namespace ams::kern::init::loader {
constexpr PageTableEntry KernelLdrRWXIdentityAttribute(PageTableEntry::Permission_KernelRWX, PageTableEntry::PageAttribute_NormalMemory, PageTableEntry::Shareable_InnerShareable, PageTableEntry::MappingFlag_Mapped);
const uintptr_t kernel_ldr_base = util::AlignDown(reinterpret_cast<uintptr_t>(__bin_start__), PageSize);
const uintptr_t kernel_ldr_size = util::AlignUp(reinterpret_cast<uintptr_t>(__bin_end__), PageSize) - kernel_ldr_base;
init_pt.Map(kernel_ldr_base, kernel_ldr_size, kernel_ldr_base, KernelRWXIdentityAttribute, allocator, 0);
init_pt.Map(kernel_ldr_base, kernel_ldr_size, kernel_ldr_base, KernelLdrRWXIdentityAttribute, allocator, 0);
/* Map in the page table region as RW- for ourselves. */
constexpr PageTableEntry PageTableRegionRWAttribute(PageTableEntry::Permission_KernelRW, PageTableEntry::PageAttribute_NormalMemory, PageTableEntry::Shareable_InnerShareable, PageTableEntry::MappingFlag_Mapped);
init_pt.Map(page_table_region, page_table_region_size, page_table_region, KernelRWXIdentityAttribute, allocator, 0);
init_pt.Map(page_table_region, page_table_region_size, page_table_region, PageTableRegionRWAttribute, allocator, 0);
/* Place the L1 table addresses in the relevant system registers. */
cpu::SetTtbr0El1(init_pt.GetTtbr0L1TableAddress());
@ -165,7 +171,7 @@ namespace ams::kern::init::loader {
uintptr_t Main(uintptr_t base_address, KernelLayout *layout, uintptr_t ini_base_address) {
/* Relocate the kernel to the correct physical base address. */
/* Base address and layout are passed by reference and modified. */
RelocateKernelPhysically(base_address, layout);
RelocateKernelPhysically(base_address, layout, ini_base_address);
/* Validate kernel layout. */
const uintptr_t rx_offset = layout->rx_offset;
@ -229,6 +235,9 @@ namespace ams::kern::init::loader {
/* Setup initial identity mapping. TTBR1 table passed by reference. */
SetupInitialIdentityMapping(init_pt, base_address, bss_end_offset, resource_end_address, InitialPageTableRegionSizeMax, g_initial_page_allocator, reinterpret_cast<KernelSystemRegisters *>(base_address + sysreg_offset));
/* NOTE: On 19.0.0+, Nintendo calls an unknown function here on init_pt and g_initial_page_allocator. */
/* This is stubbed in prod KernelLdr. */
/* Generate a random slide for the kernel's base address. */
const KVirtualAddress virtual_base_address = GetRandomKernelBaseAddress(init_pt, base_address, bss_end_offset);