Atmosphere/mesosphere/kernel_ldr/source/kern_init_loader.cpp

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/*
* Copyright (c) 2018-2020 Atmosphère-NX
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <mesosphere.hpp>
#include "kern_init_loader_asm.hpp"
/* Necessary for calculating kernelldr size/base for initial identity mapping */
extern "C" {
extern const u8 __start__[];
extern const u8 __end__[];
}
namespace ams::kern::init::loader {
namespace {
static_assert(InitialProcessBinarySizeMax <= KernelResourceSize);
constexpr size_t InitialPageTableRegionSizeMax = 2_MB;
static_assert(InitialPageTableRegionSizeMax < KernelPageTableHeapSize + KernelInitialPageHeapSize);
/* Global Allocator. */
KInitialPageAllocator g_initial_page_allocator;
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KInitialPageAllocator::State g_final_page_allocator_state;
void RelocateKernelPhysically(uintptr_t &base_address, KernelLayout *&layout) {
KPhysicalAddress correct_base = KSystemControl::Init::GetKernelPhysicalBaseAddress(base_address);
if (correct_base != base_address) {
const uintptr_t diff = GetInteger(correct_base) - base_address;
const size_t size = layout->rw_end_offset;
/* 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;
layout = reinterpret_cast<KernelLayout *>(reinterpret_cast<uintptr_t>(layout) + diff);
}
}
void EnsureEntireDataCacheFlushed() {
/* Flush shared cache. */
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cpu::FlushEntireDataCacheSharedForInit();
cpu::DataSynchronizationBarrier();
/* Flush local cache. */
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cpu::FlushEntireDataCacheLocalForInit();
cpu::DataSynchronizationBarrier();
/* Flush shared cache. */
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cpu::FlushEntireDataCacheSharedForInit();
cpu::DataSynchronizationBarrier();
/* Invalidate entire instruction cache. */
cpu::InvalidateEntireInstructionCacheForInit();
/* Invalidate entire TLB. */
cpu::InvalidateEntireTlb();
}
#ifdef ATMOSPHERE_BOARD_NINTENDO_NX
ALWAYS_INLINE bool ShouldPerformCpuSpecificSetup() {
/* Perform cpu-specific setup only on < 10.0.0. */
return kern::GetTargetFirmware() < ams::TargetFirmware_10_0_0;
}
#else
consteval ALWAYS_INLINE bool ShouldPerformCpuSpecificSetup() {
/* Always perform cpu-specific setup. */
return true;
}
#endif
void SetupInitialIdentityMapping(KInitialPageTable &ttbr1_table, uintptr_t base_address, uintptr_t kernel_size, uintptr_t page_table_region, size_t page_table_region_size, KInitialPageTable::IPageAllocator &allocator) {
/* Make a new page table for TTBR0_EL1. */
KInitialPageTable ttbr0_table(allocator.Allocate());
/* Map in an RWX identity mapping for the kernel. */
constexpr PageTableEntry KernelRWXIdentityAttribute(PageTableEntry::Permission_KernelRWX, PageTableEntry::PageAttribute_NormalMemory, PageTableEntry::Shareable_InnerShareable, PageTableEntry::MappingFlag_Mapped);
ttbr0_table.Map(base_address, kernel_size, base_address, KernelRWXIdentityAttribute, allocator);
/* Map in an RWX identity mapping for ourselves. */
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>(__start__), PageSize);
const uintptr_t kernel_ldr_size = util::AlignUp(reinterpret_cast<uintptr_t>(__end__), PageSize) - kernel_ldr_base;
ttbr0_table.Map(kernel_ldr_base, kernel_ldr_size, kernel_ldr_base, KernelRWXIdentityAttribute, allocator);
/* 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);
ttbr0_table.Map(page_table_region, page_table_region_size, page_table_region, KernelRWXIdentityAttribute, allocator);
/* Place the L1 table addresses in the relevant system registers. */
cpu::SetTtbr0El1(ttbr0_table.GetL1TableAddress());
cpu::SetTtbr1El1(ttbr1_table.GetL1TableAddress());
/* Setup MAIR_EL1, TCR_EL1. */
/* TODO: Define these bits properly elsewhere, document exactly what each bit set is doing .*/
constexpr u64 MairValue = 0x0000000044FF0400ul;
constexpr u64 TcrValue = 0x00000011B5193519ul;
cpu::MemoryAccessIndirectionRegisterAccessor(MairValue).Store();
cpu::TranslationControlRegisterAccessor(TcrValue).Store();
/* Perform cpu-specific setup if needed. */
if (ShouldPerformCpuSpecificSetup()) {
SavedRegisterState saved_registers;
SaveRegistersToTpidrEl1(&saved_registers);
ON_SCOPE_EXIT { VerifyAndClearTpidrEl1(&saved_registers); };
/* Main ID specific setup. */
cpu::MainIdRegisterAccessor midr_el1;
if (midr_el1.GetImplementer() == cpu::MainIdRegisterAccessor::Implementer::ArmLimited) {
/* ARM limited specific setup. */
const auto cpu_primary_part = midr_el1.GetPrimaryPartNumber();
const auto cpu_variant = midr_el1.GetVariant();
const auto cpu_revision = midr_el1.GetRevision();
if (cpu_primary_part == cpu::MainIdRegisterAccessor::PrimaryPartNumber::CortexA57) {
/* Cortex-A57 specific setup. */
/* Non-cacheable load forwarding enabled. */
u64 cpuactlr_value = 0x1000000;
/* Enable the processor to receive instruction cache and TLB maintenance */
/* operations broadcast from other processors in the cluster; */
/* set the L2 load/store data prefetch distance to 8 requests; */
/* set the L2 instruction fetch prefetch distance to 3 requests. */
u64 cpuectlr_value = 0x1B00000040;
/* Disable load-pass DMB on certain hardware variants. */
if (cpu_variant == 0 || (cpu_variant == 1 && cpu_revision <= 1)) {
cpuactlr_value |= 0x800000000000000;
}
/* Set actlr and ectlr. */
if (cpu::GetCpuActlrEl1() != cpuactlr_value) {
cpu::SetCpuActlrEl1(cpuactlr_value);
}
if (cpu::GetCpuEctlrEl1() != cpuectlr_value) {
cpu::SetCpuEctlrEl1(cpuectlr_value);
}
} else if (cpu_primary_part == cpu::MainIdRegisterAccessor::PrimaryPartNumber::CortexA53) {
/* Cortex-A53 specific setup. */
/* Set L1 data prefetch control to allow 5 outstanding prefetches; */
/* enable device split throttle; */
/* set the number of independent data prefetch streams to 2; */
/* disable transient and no-read-allocate hints for loads; */
/* set write streaming no-allocate threshold so the 128th consecutive streaming */
/* cache line does not allocate in the L1 or L2 cache. */
u64 cpuactlr_value = 0x90CA000;
/* Enable hardware management of data coherency with other cores in the cluster. */
u64 cpuectlr_value = 0x40;
/* If supported, enable data cache clean as data cache clean/invalidate. */
if (cpu_variant != 0 || (cpu_variant == 0 && cpu_revision > 2)) {
cpuactlr_value |= 0x100000000000;
}
/* Set actlr and ectlr. */
if (cpu::GetCpuActlrEl1() != cpuactlr_value) {
cpu::SetCpuActlrEl1(cpuactlr_value);
}
if (cpu::GetCpuEctlrEl1() != cpuectlr_value) {
cpu::SetCpuEctlrEl1(cpuectlr_value);
}
}
}
}
/* Ensure that the entire cache is flushed. */
EnsureEntireDataCacheFlushed();
/* Setup SCTLR_EL1. */
/* TODO: Define these bits properly elsewhere, document exactly what each bit set is doing .*/
constexpr u64 SctlrValue = 0x0000000034D5D925ul;
cpu::SetSctlrEl1(SctlrValue);
cpu::EnsureInstructionConsistency();
}
KVirtualAddress GetRandomKernelBaseAddress(KInitialPageTable &page_table, KPhysicalAddress phys_base_address, size_t kernel_size) {
/* Define useful values for random generation. */
constexpr uintptr_t KernelBaseAlignment = 0x200000;
constexpr uintptr_t KernelBaseRangeMin = 0xFFFFFF8000000000;
constexpr uintptr_t KernelBaseRangeMax = 0xFFFFFFFFFFE00000;
constexpr uintptr_t KernelBaseRangeEnd = KernelBaseRangeMax - 1;
static_assert(util::IsAligned(KernelBaseRangeMin, KernelBaseAlignment));
static_assert(util::IsAligned(KernelBaseRangeMax, KernelBaseAlignment));
static_assert(KernelBaseRangeMin <= KernelBaseRangeEnd);
const uintptr_t kernel_offset = GetInteger(phys_base_address) % KernelBaseAlignment;
/* Repeatedly generate a random virtual address until we get one that's unmapped in the destination page table. */
while (true) {
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const uintptr_t random_kaslr_slide = KSystemControl::Init::GenerateRandomRange(KernelBaseRangeMin / KernelBaseAlignment, KernelBaseRangeEnd / KernelBaseAlignment);
const KVirtualAddress kernel_region_start = random_kaslr_slide * KernelBaseAlignment;
const KVirtualAddress kernel_region_end = kernel_region_start + util::AlignUp(kernel_offset + kernel_size, KernelBaseAlignment);
const size_t kernel_region_size = GetInteger(kernel_region_end) - GetInteger(kernel_region_start);
/* Make sure the region has not overflowed */
if (kernel_region_start >= kernel_region_end) {
continue;
}
/* Make sure that the region stays within our intended bounds. */
if (kernel_region_end > KernelBaseRangeMax) {
continue;
}
/* Validate we can map the range we've selected. */
if (!page_table.IsFree(kernel_region_start, kernel_region_size)) {
continue;
}
/* Our range is valid! */
return kernel_region_start + kernel_offset;
}
}
}
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);
/* Validate kernel layout. */
const uintptr_t rx_offset = layout->rx_offset;
const uintptr_t rx_end_offset = layout->rx_end_offset;
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const uintptr_t ro_offset = layout->ro_offset;
const uintptr_t ro_end_offset = layout->ro_end_offset;
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const uintptr_t rw_offset = layout->rw_offset;
/* UNUSED: const uintptr_t rw_end_offset = layout->rw_end_offset; */
const uintptr_t bss_end_offset = layout->bss_end_offset;
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MESOSPHERE_INIT_ABORT_UNLESS(util::IsAligned(rx_offset, PageSize));
MESOSPHERE_INIT_ABORT_UNLESS(util::IsAligned(rx_end_offset, PageSize));
MESOSPHERE_INIT_ABORT_UNLESS(util::IsAligned(ro_offset, PageSize));
MESOSPHERE_INIT_ABORT_UNLESS(util::IsAligned(ro_end_offset, PageSize));
MESOSPHERE_INIT_ABORT_UNLESS(util::IsAligned(rw_offset, PageSize));
MESOSPHERE_INIT_ABORT_UNLESS(util::IsAligned(bss_end_offset, PageSize));
const uintptr_t bss_offset = layout->bss_offset;
const uintptr_t ini_load_offset = layout->ini_load_offset;
const uintptr_t dynamic_offset = layout->dynamic_offset;
const uintptr_t init_array_offset = layout->init_array_offset;
const uintptr_t init_array_end_offset = layout->init_array_end_offset;
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/* Determine the size of the resource region. */
const size_t resource_region_size = KMemoryLayout::GetResourceRegionSizeForInit();
/* Setup the INI1 header in memory for the kernel. */
const uintptr_t ini_end_address = base_address + ini_load_offset + resource_region_size;
const uintptr_t ini_load_address = ini_end_address - InitialProcessBinarySizeMax;
if (ini_base_address != ini_load_address) {
/* The INI is not at the correct address, so we need to relocate it. */
const InitialProcessBinaryHeader *ini_header = reinterpret_cast<const InitialProcessBinaryHeader *>(ini_base_address);
if (ini_header->magic == InitialProcessBinaryMagic && ini_header->size <= InitialProcessBinarySizeMax) {
/* INI is valid, relocate it. */
std::memmove(reinterpret_cast<void *>(ini_load_address), ini_header, ini_header->size);
} else {
/* INI is invalid. Make the destination header invalid. */
std::memset(reinterpret_cast<void *>(ini_load_address), 0, sizeof(InitialProcessBinaryHeader));
}
}
/* We want to start allocating page tables at ini_end_address. */
g_initial_page_allocator.Initialize(ini_end_address);
/* Make a new page table for TTBR1_EL1. */
KInitialPageTable ttbr1_table(g_initial_page_allocator.Allocate());
/* Setup initial identity mapping. TTBR1 table passed by reference. */
SetupInitialIdentityMapping(ttbr1_table, base_address, bss_end_offset, ini_end_address, InitialPageTableRegionSizeMax, g_initial_page_allocator);
/* Generate a random slide for the kernel's base address. */
const KVirtualAddress virtual_base_address = GetRandomKernelBaseAddress(ttbr1_table, base_address, bss_end_offset);
/* Map kernel .text as R-X. */
constexpr PageTableEntry KernelTextAttribute(PageTableEntry::Permission_KernelRX, PageTableEntry::PageAttribute_NormalMemory, PageTableEntry::Shareable_InnerShareable, PageTableEntry::MappingFlag_Mapped);
ttbr1_table.Map(virtual_base_address + rx_offset, rx_end_offset - rx_offset, base_address + rx_offset, KernelTextAttribute, g_initial_page_allocator);
/* Map kernel .rodata and .rwdata as RW-. */
/* Note that we will later reprotect .rodata as R-- */
constexpr PageTableEntry KernelRoDataAttribute(PageTableEntry::Permission_KernelR, PageTableEntry::PageAttribute_NormalMemory, PageTableEntry::Shareable_InnerShareable, PageTableEntry::MappingFlag_Mapped);
constexpr PageTableEntry KernelRwDataAttribute(PageTableEntry::Permission_KernelRW, PageTableEntry::PageAttribute_NormalMemory, PageTableEntry::Shareable_InnerShareable, PageTableEntry::MappingFlag_Mapped);
ttbr1_table.Map(virtual_base_address + ro_offset, ro_end_offset - ro_offset, base_address + ro_offset, KernelRwDataAttribute, g_initial_page_allocator);
ttbr1_table.Map(virtual_base_address + rw_offset, bss_end_offset - rw_offset, base_address + rw_offset, KernelRwDataAttribute, g_initial_page_allocator);
/* On 10.0.0+, Physically randomize the kernel region. */
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if (kern::GetTargetFirmware() >= ams::TargetFirmware_10_0_0) {
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ttbr1_table.PhysicallyRandomize(virtual_base_address + rx_offset, bss_end_offset - rx_offset, true);
}
/* Clear kernel .bss. */
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std::memset(GetVoidPointer(virtual_base_address + bss_offset), 0, bss_end_offset - bss_offset);
/* Apply relocations to the kernel. */
const Elf::Dyn *kernel_dynamic = reinterpret_cast<const Elf::Dyn *>(GetInteger(virtual_base_address) + dynamic_offset);
Elf::ApplyRelocations(GetInteger(virtual_base_address), kernel_dynamic);
/* Call the kernel's init array functions. */
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/* NOTE: The kernel does this after reprotecting .rodata, but we do it before. */
/* This allows our global constructors to edit .rodata, which is valuable for editing the SVC tables to support older firmwares' ABIs. */
Elf::CallInitArrayFuncs(GetInteger(virtual_base_address) + init_array_offset, GetInteger(virtual_base_address) + init_array_end_offset);
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/* Reprotect .rodata as R-- */
ttbr1_table.Reprotect(virtual_base_address + ro_offset, ro_end_offset - ro_offset, KernelRwDataAttribute, KernelRoDataAttribute);
/* Return the difference between the random virtual base and the physical base. */
return GetInteger(virtual_base_address) - base_address;
}
KPhysicalAddress AllocateKernelInitStack() {
return g_initial_page_allocator.Allocate() + PageSize;
}
uintptr_t GetFinalPageAllocatorState() {
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g_initial_page_allocator.GetFinalState(std::addressof(g_final_page_allocator_state));
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if (kern::GetTargetFirmware() >= ams::TargetFirmware_10_0_0) {
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return reinterpret_cast<uintptr_t>(std::addressof(g_final_page_allocator_state));
} else {
return g_final_page_allocator_state.next_address;
}
}
}