diff options
Diffstat (limited to 'arch/x86_64/pre/src/memory')
16 files changed, 1296 insertions, 0 deletions
diff --git a/arch/x86_64/pre/src/memory/allocator/area_frame_allocator.cpp b/arch/x86_64/pre/src/memory/allocator/area_frame_allocator.cpp new file mode 100644 index 0000000..a5a1b49 --- /dev/null +++ b/arch/x86_64/pre/src/memory/allocator/area_frame_allocator.cpp @@ -0,0 +1,85 @@ +#include "arch/memory/allocator/area_frame_allocator.hpp" + +#include "arch/exception_handling/assert.hpp" + +#include <algorithm> +#include <array> +#include <ranges> + +namespace teachos::arch::memory::allocator +{ + area_frame_allocator::area_frame_allocator(multiboot::memory_information const & mem_info) + : next_free_frame() + , current_area(std::nullopt) + , memory_areas(mem_info.areas) + , kernel_start(physical_frame::containing_address(mem_info.kernel_start)) + , kernel_end(physical_frame::containing_address(mem_info.kernel_end)) + , multiboot_start(physical_frame::containing_address(mem_info.multiboot_start)) + , multiboot_end(physical_frame::containing_address(mem_info.multiboot_end)) + { + choose_next_area(); + } + + auto area_frame_allocator::choose_next_area() -> void + { + current_area = std::nullopt; + auto next_area_with_free_frames = memory_areas | std::views::filter([this](auto const & area) { + auto address = area.base_address + area.area_length - 1; + return physical_frame::containing_address(address) >= next_free_frame; + }); + + auto const lowest_area_with_free_frames = std::ranges::min_element( + next_area_with_free_frames, [](auto const & a, auto const & b) { return a.base_address < b.base_address; }); + + if (lowest_area_with_free_frames != next_area_with_free_frames.end()) + { + current_area = *lowest_area_with_free_frames; + // Update the `next_free_frame` according to the new memory area + auto const start_frame = physical_frame::containing_address(current_area.value().base_address); + if (next_free_frame < start_frame) + { + next_free_frame = start_frame; + } + } + } + + auto area_frame_allocator::allocate_frame() -> std::optional<physical_frame> + { + // Only try to allocate memory if current_area is not null, because + // the current_area is null if there is no more available memory. + if (!current_area.has_value()) + { + return std::nullopt; + } + + auto const address = current_area.value().base_address + current_area.value().area_length - 1; + physical_frame current_area_last_frame = physical_frame::containing_address(address); + + if (next_free_frame > current_area_last_frame) + { + // All frames of current area are used, switch to next area. + choose_next_area(); + } + else if (next_free_frame >= kernel_start && next_free_frame <= kernel_end) + { + // `physical_frame` is used by the kernel or multiboot information structure. + next_free_frame = allocator::physical_frame{kernel_end.frame_number + 1}; + } + else if (next_free_frame >= multiboot_start && next_free_frame <= multiboot_end) + { + // `physical_frame` is used by the kernel or multiboot information structure. + next_free_frame = allocator::physical_frame{multiboot_end.frame_number + 1}; + } + else + { + // Frame is unused, increment `next_free_frame` and return it. + next_free_frame.frame_number += 1; + return next_free_frame; + } + + // `physical_frame` was not valid, try it again with the updated `next_free_frame`. + return allocate_frame(); + } + + auto area_frame_allocator::deallocate_frame(physical_frame const & physical_frame) -> void { (void)physical_frame; } +} // namespace teachos::arch::memory::allocator diff --git a/arch/x86_64/pre/src/memory/allocator/tiny_frame_allocator.cpp b/arch/x86_64/pre/src/memory/allocator/tiny_frame_allocator.cpp new file mode 100644 index 0000000..3cdf9c7 --- /dev/null +++ b/arch/x86_64/pre/src/memory/allocator/tiny_frame_allocator.cpp @@ -0,0 +1,34 @@ +#include "arch/memory/allocator/tiny_frame_allocator.hpp" + +#include "arch/exception_handling/panic.hpp" + +namespace teachos::arch::memory::allocator +{ + auto tiny_frame_allocator::allocate_frame() -> std::optional<physical_frame> + { + for (auto & frame_option : frames) + { + if (frame_option.has_value()) + { + auto value = frame_option; + frame_option.reset(); + return value; + } + } + return std::nullopt; + } + + auto tiny_frame_allocator::deallocate_frame(physical_frame const & physical_frame) -> void + { + for (auto & frame_option : frames) + { + if (!frame_option.has_value()) + { + frame_option.emplace(physical_frame); + return; + } + } + exception_handling::panic( + "[Tiny Frame Allocator] Attempted to deallocate more than the 3 frames, that can be held"); + } +} // namespace teachos::arch::memory::allocator diff --git a/arch/x86_64/pre/src/memory/heap/bump_allocator.cpp b/arch/x86_64/pre/src/memory/heap/bump_allocator.cpp new file mode 100644 index 0000000..525f45c --- /dev/null +++ b/arch/x86_64/pre/src/memory/heap/bump_allocator.cpp @@ -0,0 +1,54 @@ +#include "arch/memory/heap/bump_allocator.hpp" + +#include "arch/exception_handling/assert.hpp" + +#include <limits> +#include <type_traits> + +namespace teachos::arch::memory::heap +{ + namespace + { + template<typename T> + auto saturating_add(T x, T y) -> T + requires std::is_unsigned_v<T> + { + if (x > std::numeric_limits<T>::max() - y) + { + return std::numeric_limits<T>::max(); + } + T result = x + y; + return result; + } + } // namespace + + auto bump_allocator::allocate(std::size_t size) -> void * + { + // Reading the value only has to be done once, because compare_exchange_weak updates the value as well if the + // exchange failed, becuase the value was not the expected one. + auto alloc_start = next.load(std::memory_order::relaxed); + // Repeat allocation until it succeeds, has to be done, because another allocator could overtake it at any time + // causing the value to differ and the calculation to have to be redone. + for (;;) + { + auto const alloc_end = saturating_add(alloc_start, size); + arch::exception_handling::assert(alloc_end <= heap_end, "[Heap Allocator] Out of memory"); + // Check if the atomic value is still the one initally loaded, if it isn't we have been overtaken by another + // thread and need to redo the calculation. Spurious failure by weak can be ignored, because the whole allocation + // is wrapped in an infinite for loop so a failure that wasn't actually one will simply be retried until it works. + auto const updated = next.compare_exchange_weak(alloc_start, alloc_end, std::memory_order::relaxed); + if (updated) + { + return reinterpret_cast<void *>(alloc_start); + } + } + } + + auto bump_allocator::deallocate(void * pointer) noexcept -> void + { + if (pointer) + { + } + } + +} // namespace teachos::arch::memory::heap diff --git a/arch/x86_64/pre/src/memory/heap/global_heap_allocator.cpp b/arch/x86_64/pre/src/memory/heap/global_heap_allocator.cpp new file mode 100644 index 0000000..35cd623 --- /dev/null +++ b/arch/x86_64/pre/src/memory/heap/global_heap_allocator.cpp @@ -0,0 +1,135 @@ +#include "arch/memory/heap/global_heap_allocator.hpp" + +#include "arch/context_switching/syscall/main.hpp" +#include "arch/exception_handling/assert.hpp" +#include "arch/kernel/cpu/segment_register.hpp" +#include "arch/memory/heap/bump_allocator.hpp" +#include "arch/memory/heap/linked_list_allocator.hpp" +#include "arch/memory/heap/user_heap_allocator.hpp" + +namespace teachos::arch::memory::heap +{ + namespace + { + constexpr char NOT_REGISTRED_ERROR_MESSAGE[] = + "Attempted to allocate or deallocate using the global_heap_allocator before " + "register_heap_allocation_type was called."; + constexpr uint16_t KERNEL_CODE_INDEX = 1U; + + [[gnu::section(".user_text")]] + auto os_in_kernel_mode() -> bool + { + auto const cs = teachos::arch::kernel::cpu::read_code_segment_register(); + return cs.get_index() == KERNEL_CODE_INDEX; + } + } // namespace + + heap_allocator * global_heap_allocator::kernel_allocator_instance = nullptr; + user_heap_allocator * global_heap_allocator::user_allocator_instance = nullptr; + + auto global_heap_allocator::kmalloc(std::size_t size) -> void * { return kernel().allocate(size); } + + auto global_heap_allocator::kfree(void * pointer) noexcept -> void { kernel().deallocate(pointer); } + + auto global_heap_allocator::malloc(std::size_t size) -> void * { return user().allocate(size); } + + auto global_heap_allocator::free(void * pointer) noexcept -> void { user().deallocate(pointer); } + + auto global_heap_allocator::register_heap_allocator(heap_allocator_type new_type) -> void + { + exception_handling::assert(kernel_allocator_instance == nullptr, + "Calling register_heap_allocator_type can only be done once."); + + switch (new_type) + { + case heap_allocator_type::NONE: + // Nothing to do + break; + case heap_allocator_type::BUMP: { + static bump_allocator kernel_allocator{KERNEL_HEAP_START, KERNEL_HEAP_START + KERNEL_HEAP_SIZE}; + kernel_allocator_instance = &kernel_allocator; + break; + } + case heap_allocator_type::LINKED_LIST: { + static linked_list_allocator kernel_allocator{KERNEL_HEAP_START, KERNEL_HEAP_START + KERNEL_HEAP_SIZE}; + kernel_allocator_instance = &kernel_allocator; + break; + } + } + + [[gnu::section(".user_data")]] + static user_heap_allocator user_allocator{}; + user_allocator_instance = &user_allocator; + } + + auto global_heap_allocator::kernel() -> heap_allocator & + { + exception_handling::assert(kernel_allocator_instance != nullptr, NOT_REGISTRED_ERROR_MESSAGE); + + return *kernel_allocator_instance; + } + + auto global_heap_allocator::user() -> user_heap_allocator & + { + context_switching::syscall::syscall( + context_switching::syscall::type::ASSERT, + {user_allocator_instance != nullptr, reinterpret_cast<uint64_t>(&NOT_REGISTRED_ERROR_MESSAGE)}); + return *user_allocator_instance; + } +} // namespace teachos::arch::memory::heap + +auto operator new(std::size_t size) -> void * +{ + if (teachos::arch::memory::heap::os_in_kernel_mode()) + { + return teachos::arch::memory::heap::global_heap_allocator::kmalloc(size); + } + return teachos::arch::memory::heap::global_heap_allocator::malloc(size); +} + +auto operator delete(void * pointer) noexcept -> void +{ + if (teachos::arch::memory::heap::os_in_kernel_mode()) + { + teachos::arch::memory::heap::global_heap_allocator::kfree(pointer); + } + teachos::arch::memory::heap::global_heap_allocator::free(pointer); +} + +auto operator delete(void * pointer, std::size_t size) noexcept -> void +{ + (void)size; + if (teachos::arch::memory::heap::os_in_kernel_mode()) + { + teachos::arch::memory::heap::global_heap_allocator::kfree(pointer); + } + teachos::arch::memory::heap::global_heap_allocator::free(pointer); +} + +auto operator new[](std::size_t size) -> void * +{ + if (teachos::arch::memory::heap::os_in_kernel_mode()) + { + return teachos::arch::memory::heap::global_heap_allocator::kmalloc(size); + } + return teachos::arch::memory::heap::global_heap_allocator::malloc(size); +} + +auto operator delete[](void * pointer) noexcept -> void +{ + if (teachos::arch::memory::heap::os_in_kernel_mode()) + { + teachos::arch::memory::heap::global_heap_allocator::kfree(pointer); + } + teachos::arch::memory::heap::global_heap_allocator::free(pointer); +} + +auto operator delete[](void * pointer, std::size_t size) noexcept -> void +{ + (void)size; + if (teachos::arch::memory::heap::os_in_kernel_mode()) + { + teachos::arch::memory::heap::global_heap_allocator::kfree(pointer); + } + teachos::arch::memory::heap::global_heap_allocator::free(pointer); +} diff --git a/arch/x86_64/pre/src/memory/heap/linked_list_allocator.cpp b/arch/x86_64/pre/src/memory/heap/linked_list_allocator.cpp new file mode 100644 index 0000000..00ca366 --- /dev/null +++ b/arch/x86_64/pre/src/memory/heap/linked_list_allocator.cpp @@ -0,0 +1,177 @@ +#include "arch/memory/heap/linked_list_allocator.hpp" + +#include "arch/exception_handling/assert.hpp" +#include "arch/exception_handling/panic.hpp" + +#include <algorithm> + +namespace teachos::arch::memory::heap +{ + linked_list_allocator::linked_list_allocator(std::size_t heap_start, std::size_t heap_end) + : first(nullptr) + , mutex{kstd::mutex{}} + { + auto const heap_size = heap_end - heap_start; + exception_handling::assert( + heap_size > min_allocatable_size(), + "[Linked List Allocator] Total heap size can not be smaller than minimum of 16 bytes to hold " + "atleast one memory hole entry"); + first = new (reinterpret_cast<void *>(heap_start)) memory_block(heap_size, nullptr); + } + + auto linked_list_allocator::allocate(std::size_t size) -> void * + { + // Add size of size_t to the total allocated size, because we add a header that includes the size of the allocated + // block, to allow for deallocation without the need to call with the corresponding size + auto const total_size = size + sizeof(std::size_t); + mutex.lock(); + + memory_block * previous = nullptr; + auto current = first; + + while (current != nullptr) + { + if (current->size == total_size) + { + auto const memory_address = remove_free_memory_block(previous, current); + new (memory_address) std::size_t(total_size); + mutex.unlock(); + return reinterpret_cast<void *>(reinterpret_cast<std::size_t>(memory_address) + sizeof(std::size_t)); + } + else if (current->size >= total_size + min_allocatable_size()) + { + // Ensure that the allocated size block is atleast 16 bytes (required because if we free the hole afterwards + // there needs to be enough space for a memory block). Therefore we allocate more than is actually required if + // the total size was less and simply deallocate it as well + auto const max_size = std::max(total_size, min_allocatable_size()); + auto const memory_address = split_free_memory_block(previous, current, max_size); + new (memory_address) std::size_t(max_size); + mutex.unlock(); + return reinterpret_cast<void *>(reinterpret_cast<std::size_t>(memory_address) + sizeof(std::size_t)); + } + + previous = current; + current = current->next; + } + + exception_handling::panic("[Linked List Allocator] Out of memory"); + } + + auto linked_list_allocator::deallocate(void * pointer) noexcept -> void + { + mutex.lock(); + + // Read configured header size of the complete allocated block + auto const header_pointer = reinterpret_cast<void *>(reinterpret_cast<std::size_t>(pointer) - sizeof(std::size_t)); + auto const total_size = *reinterpret_cast<std::size_t *>(header_pointer); + + auto const start_address = reinterpret_cast<std::size_t>(header_pointer); + auto const end_address = start_address + total_size; + + memory_block * previous = nullptr; + auto current = first; + + while (current != nullptr) + { + // Current address of the free memory block now points to an address that is after our block to deallocate in heap + // memory space. + if (reinterpret_cast<std::size_t>(current) >= end_address) + { + break; + } + + previous = current; + current = current->next; + } + + coalesce_free_memory_block(previous, current, header_pointer, total_size); + mutex.unlock(); + } + + auto linked_list_allocator::remove_free_memory_block(memory_block * previous_block, memory_block * current_block) + -> void * + { + return replace_free_memory_block(previous_block, current_block, current_block->next); + } + + auto linked_list_allocator::split_free_memory_block(memory_block * previous_block, memory_block * current_block, + std::size_t size) -> void * + { + auto const end_address = reinterpret_cast<std::size_t>(current_block) + size; + auto const new_block = + new (reinterpret_cast<void *>(end_address)) memory_block(current_block->size - size, current_block->next); + return replace_free_memory_block(previous_block, current_block, new_block); + } + + auto linked_list_allocator::replace_free_memory_block(memory_block * previous_block, memory_block * current_block, + memory_block * new_block) -> void * + { + auto const start_address = reinterpret_cast<std::size_t>(current_block); + // If we want to allocate into the first block that is before any other free block, then there exists no previous + // free block (nullptr). Therefore we have to overwrite the first block instead of overwriting its next value. + if (previous_block == nullptr) + { + first = new_block; + } + else + { + previous_block->next = new_block; + } + current_block->~memory_block(); + return reinterpret_cast<void *>(start_address); + } + + auto linked_list_allocator::coalesce_free_memory_block(memory_block * previous_block, memory_block * current_block, + void * pointer, std::size_t size) -> void + { + auto const start_address = reinterpret_cast<std::size_t>(pointer); + auto const end_address = start_address + size; + + // Inital values if there are no adjacent blocks either before or after, meaning we have to simply create a free + // memory block that is placed in between the previous and next block. + auto block_size = size; + auto next_block = current_block; + + // If the block we want to deallocate is before another free block and we can therefore combine both into one. + // This is done by deleting the current free block and creating a new block at the start address of the block to + // deallocate with both the size of the block to deallcoate and the free block next to it. + if (end_address == reinterpret_cast<std::size_t>(current_block)) + { + block_size += current_block->size; + next_block = current_block->next; + current_block->~memory_block(); + } + + // If the block we want to deallocate is behind another free block and we can therefore combine both into one. + // This is done by simply changin the size of the previous block to include the size of the block to deallocate. + // This is done, because the previous block might still be referencered by the next field of other memory blocks. + if (previous_block != nullptr && + start_address == (reinterpret_cast<std::size_t>(previous_block) + previous_block->size)) + { + block_size += previous_block->size; + + previous_block->size = block_size; + previous_block->next = next_block; + return; + } + + // Check if the block we want to deallocate is contained in the previous block, because if it is it can only mean + // that the block has already been deallocated and we therefore attempted a double free. + exception_handling::assert(previous_block == nullptr || + start_address >= + (reinterpret_cast<std::size_t>(previous_block) + previous_block->size), + "[Linked List Allocator] Attempted double free detected"); + + auto const new_block = new (pointer) memory_block(block_size, next_block); + // If we want to deallocate the first block that is before any other free block, then there exists no previous free + // block (nullptr). Therefore we have to overwrite the first block instead of overwriting its + // next value. + if (previous_block == nullptr) + { + first = new_block; + return; + } + previous_block->next = new_block; + } + +} // namespace teachos::arch::memory::heap diff --git a/arch/x86_64/pre/src/memory/heap/memory_block.cpp b/arch/x86_64/pre/src/memory/heap/memory_block.cpp new file mode 100644 index 0000000..bc97bd6 --- /dev/null +++ b/arch/x86_64/pre/src/memory/heap/memory_block.cpp @@ -0,0 +1,15 @@ +#include "arch/memory/heap/memory_block.hpp" + +#include <string.h> + +namespace teachos::arch::memory::heap +{ + memory_block::memory_block(std::size_t size, memory_block * next) + { + memset(static_cast<void *>(this), 0U, size); + this->size = size; + this->next = next; + } + + memory_block::~memory_block() { memset(static_cast<void *>(this), 0U, sizeof(memory_block)); } +} // namespace teachos::arch::memory::heap diff --git a/arch/x86_64/pre/src/memory/heap/user_heap_allocator.cpp b/arch/x86_64/pre/src/memory/heap/user_heap_allocator.cpp new file mode 100644 index 0000000..427a68a --- /dev/null +++ b/arch/x86_64/pre/src/memory/heap/user_heap_allocator.cpp @@ -0,0 +1,200 @@ +#include "arch/memory/heap/user_heap_allocator.hpp" + +#include "arch/context_switching/syscall/main.hpp" + +#include <algorithm> + +namespace teachos::arch::memory::heap +{ + auto user_heap_allocator::allocate(std::size_t size) -> void * + { + // Add size of size_t to the total allocated size, because we add a header that includes the size of the allocated + // block, to allow for deallocation without the need to call with the corresponding size + auto const total_size = size + sizeof(std::size_t); + mutex.lock(); + + memory_block * previous = nullptr; + auto current = first; + + while (current != nullptr) + { + auto memory = allocate_into_memory_block_if_big_enough(current, previous, total_size); + if (memory.has_value()) + { + return memory.value(); + } + + previous = current; + current = current->next; + } + + current = expand_heap_if_full(); + + if (current != nullptr) + { + auto memory = allocate_into_memory_block_if_big_enough(current, previous, total_size); + if (memory.has_value()) + { + return memory.value(); + } + } + + char constexpr OUT_OF_MEMORY_ERROR_MESSAGE[] = "[Linked List Allocator] Out of memory"; + context_switching::syscall::syscall(context_switching::syscall::type::ASSERT, + {false, reinterpret_cast<uint64_t>(&OUT_OF_MEMORY_ERROR_MESSAGE)}); + return nullptr; + } + + auto user_heap_allocator::deallocate(void * pointer) noexcept -> void + { + mutex.lock(); + + // Read configured header size of the complete allocated block + auto const header_pointer = reinterpret_cast<void *>(reinterpret_cast<std::size_t>(pointer) - sizeof(std::size_t)); + auto const total_size = *reinterpret_cast<std::size_t *>(header_pointer); + + auto const start_address = reinterpret_cast<std::size_t>(header_pointer); + auto const end_address = start_address + total_size; + + memory_block * previous = nullptr; + auto current = first; + + while (current != nullptr) + { + // Current address of the free memory block now points to an address that is after our block to deallocate in heap + // memory space. + if (reinterpret_cast<std::size_t>(current) >= end_address) + { + break; + } + + previous = current; + current = current->next; + } + + coalesce_free_memory_block(previous, current, header_pointer, total_size); + mutex.unlock(); + } + + auto user_heap_allocator::allocate_into_memory_block_if_big_enough(memory_block * current, memory_block * previous, + std::size_t total_size) -> std::optional<void *> + { + if (current->size == total_size) + { + auto const memory_address = remove_free_memory_block(previous, current); + new (memory_address) std::size_t(total_size); + mutex.unlock(); + return reinterpret_cast<void *>(reinterpret_cast<std::size_t>(memory_address) + sizeof(std::size_t)); + } + else if (current->size >= total_size + min_allocatable_size()) + { + // Ensure that the allocated size block is atleast 16 bytes (required because if we free the hole afterwards + // there needs to be enough space for a memory block). Therefore we allocate more than is actually required if + // the total size was less and simply deallocate it as well + auto const max_size = std::max(total_size, min_allocatable_size()); + auto const memory_address = split_free_memory_block(previous, current, max_size); + new (memory_address) std::size_t(max_size); + mutex.unlock(); + return reinterpret_cast<void *>(reinterpret_cast<std::size_t>(memory_address) + sizeof(std::size_t)); + } + return std::nullopt; + } + + auto user_heap_allocator::expand_heap_if_full() -> memory_block * + { + auto const result = context_switching::syscall::syscall(context_switching::syscall::type::EXPAND_HEAP); + + uint64_t const heap_start = result.values.arg_0; + uint64_t const heap_size = result.values.arg_1; + return !result.error_code ? new (reinterpret_cast<void *>(heap_start)) memory_block(heap_size, nullptr) : nullptr; + } + + auto user_heap_allocator::remove_free_memory_block(memory_block * previous_block, memory_block * current_block) + -> void * + { + return replace_free_memory_block(previous_block, current_block, current_block->next); + } + + auto user_heap_allocator::split_free_memory_block(memory_block * previous_block, memory_block * current_block, + std::size_t size) -> void * + { + auto const end_address = reinterpret_cast<std::size_t>(current_block) + size; + auto const new_block = + new (reinterpret_cast<void *>(end_address)) memory_block(current_block->size - size, current_block->next); + return replace_free_memory_block(previous_block, current_block, new_block); + } + + auto user_heap_allocator::replace_free_memory_block(memory_block * previous_block, memory_block * current_block, + memory_block * new_block) -> void * + { + auto const start_address = reinterpret_cast<std::size_t>(current_block); + // If we want to allocate into the first block that is before any other free block, then there exists no previous + // free block (nullptr). Therefore we have to overwrite the first block instead of overwriting its next value. + if (previous_block == nullptr) + { + first = new_block; + } + else + { + previous_block->next = new_block; + } + current_block->~memory_block(); + return reinterpret_cast<void *>(start_address); + } + + auto user_heap_allocator::coalesce_free_memory_block(memory_block * previous_block, memory_block * current_block, + void * pointer, std::size_t size) -> void + { + auto const start_address = reinterpret_cast<std::size_t>(pointer); + auto const end_address = start_address + size; + + // Inital values if there are no adjacent blocks either before or after, meaning we have to simply create a free + // memory block that is placed in between the previous and next block. + auto block_size = size; + auto next_block = current_block; + + // If the block we want to deallocate is before another free block and we can therefore combine both into one. + // This is done by deleting the current free block and creating a new block at the start address of the block to + // deallocate with both the size of the block to deallcoate and the free block next to it. + if (end_address == reinterpret_cast<std::size_t>(current_block)) + { + block_size += current_block->size; + next_block = current_block->next; + current_block->~memory_block(); + } + + // If the block we want to deallocate is behind another free block and we can therefore combine both into one. + // This is done by simply changin the size of the previous block to include the size of the block to deallocate. + // This is done, because the previous block might still be referencered by the next field of other memory blocks. + if (previous_block != nullptr && + start_address == (reinterpret_cast<std::size_t>(previous_block) + previous_block->size)) + { + block_size += previous_block->size; + + previous_block->size = block_size; + previous_block->next = next_block; + return; + } + + // Check if the block we want to deallocate is contained in the previous block, because if it is it can only mean + // that the block has already been deallocated and we therefore attempted a double free. + char constexpr DOUBLE_FREE_ERROR_MESSAGE[] = "[Linked List Allocator] Attempted double free detected"; + context_switching::syscall::syscall( + context_switching::syscall::type::ASSERT, + {previous_block == nullptr || + start_address >= (reinterpret_cast<std::size_t>(previous_block) + previous_block->size), + reinterpret_cast<uint64_t>(&DOUBLE_FREE_ERROR_MESSAGE)}); + + auto const new_block = new (pointer) memory_block(block_size, next_block); + // If we want to deallocate the first block that is before any other free block, then there exists no previous free + // block (nullptr). Therefore we have to overwrite the first block instead of overwriting its + // next value. + if (previous_block == nullptr) + { + first = new_block; + return; + } + previous_block->next = new_block; + } + +} // namespace teachos::arch::memory::heap diff --git a/arch/x86_64/pre/src/memory/main.cpp b/arch/x86_64/pre/src/memory/main.cpp new file mode 100644 index 0000000..2746a71 --- /dev/null +++ b/arch/x86_64/pre/src/memory/main.cpp @@ -0,0 +1,77 @@ +#include "arch/memory/main.hpp" + +#include "arch/exception_handling/assert.hpp" +#include "arch/kernel/cpu/control_register.hpp" +#include "arch/kernel/cpu/msr.hpp" +#include "arch/memory/allocator/area_frame_allocator.hpp" +#include "arch/memory/allocator/concept.hpp" +#include "arch/memory/heap/global_heap_allocator.hpp" +#include "arch/memory/paging/active_page_table.hpp" +#include "arch/memory/paging/kernel_mapper.hpp" + +#include <optional> + +namespace teachos::arch::memory +{ + namespace + { + static std::optional<allocator::area_frame_allocator> frame_allocator; + + auto create_frame_allocator(multiboot::memory_information const & memory_information) + -> allocator::area_frame_allocator & + { + frame_allocator.emplace(memory_information); + return frame_allocator.value(); + } + + auto get_frame_allocator() -> allocator::area_frame_allocator & + { + exception_handling::assert(frame_allocator.has_value(), + "[Initialization] Frame allocator has not been created yet"); + return frame_allocator.value(); + } + } // namespace + + auto remap_heap(std::size_t heap_start, std::size_t heap_size, paging::entry::bitset additional_flags = {}) -> void + { + decltype(auto) allocator = get_frame_allocator(); + decltype(auto) active_table = paging::active_page_table::create_or_get(); + auto const start_page = paging::virtual_page::containing_address(heap_start); + auto const end_page = ++(paging::virtual_page::containing_address(heap_start + heap_size - 1)); + + paging::page_container::iterator const begin{start_page}; + paging::page_container::iterator const end{end_page}; + paging::page_container const pages{begin, end}; + + constexpr auto base_flags = paging::entry::WRITABLE; + auto const flags = base_flags | additional_flags; + + for (auto const & page : pages) + { + active_table.map_page_to_next_free_frame(allocator, page, flags); + } + } + + auto initialize_memory_management() -> void + { + static bool has_been_called = false; + arch::exception_handling::assert(!has_been_called, + "[Initialization] Memory management has already been initialized"); + has_been_called = true; + + auto const memory_information = multiboot::read_multiboot2(); + decltype(auto) allocator = create_frame_allocator(memory_information); + + kernel::cpu::set_cr0_bit(kernel::cpu::cr0_flags::WRITE_PROTECT); + kernel::cpu::set_efer_bit(kernel::cpu::efer_flags::NXE); + + paging::kernel_mapper kernel(allocator, memory_information); + kernel.remap_kernel(); + video::vga::text::write("Kernel remapping successful", video::vga::text::common_attributes::green_on_black); + video::vga::text::newline(); + + remap_heap(heap::KERNEL_HEAP_START, heap::KERNEL_HEAP_SIZE); + video::vga::text::write |