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#include "arch/context_switching/main.hpp"
#include "arch/boot/pointers.hpp"
#include "arch/context_switching/syscall/syscall_enable.hpp"
#include "arch/kernel/cpu/call.hpp"
#include "arch/kernel/cpu/if.hpp"
#include "arch/kernel/cpu/segment_register.hpp"
#include "arch/kernel/cpu/tr.hpp"
#include "arch/user/main.hpp"
namespace teachos::arch::context_switching
{
namespace
{
constexpr interrupt_descriptor_table::segment_selector KERNEL_CODE_SEGMENT_SELECTOR{
1U, interrupt_descriptor_table::segment_selector::REQUEST_LEVEL_KERNEL};
constexpr kernel::cpu::far_pointer KERNEL_CODE_POINTER{&kernel::cpu::reload_data_segment_registers,
KERNEL_CODE_SEGMENT_SELECTOR};
constexpr context_switching::interrupt_descriptor_table::segment_selector USER_CODE_SEGMENT_SELECTOR{
3U, context_switching::interrupt_descriptor_table::segment_selector::REQUEST_LEVEL_USER};
constexpr context_switching::interrupt_descriptor_table::segment_selector USER_DATA_SEGMENT_SELECTOR{
4U, context_switching::interrupt_descriptor_table::segment_selector::REQUEST_LEVEL_USER};
auto reload_gdtr() -> void { kernel::cpu::call(KERNEL_CODE_POINTER); }
} // namespace
auto initialize_descriptor_tables() -> descriptor_tables
{
static bool initalized = false;
if (!initalized)
{
kernel::cpu::clear_interrupt_flag();
segment_descriptor_table::update_gdtr();
interrupt_descriptor_table::update_interrupt_descriptor_table_register();
reload_gdtr();
segment_descriptor_table::update_tss_register();
kernel::cpu::set_interrupt_flag();
initalized = true;
}
descriptor_tables tables = {segment_descriptor_table::get_or_create_gdt(),
interrupt_descriptor_table::get_or_create_interrupt_descriptor_table()};
return tables;
}
auto switch_to_user_mode() -> void
{
syscall::enable_syscall();
switch_context(USER_DATA_SEGMENT_SELECTOR, USER_CODE_SEGMENT_SELECTOR, user::main);
}
auto switch_context(interrupt_descriptor_table::segment_selector data_segment,
interrupt_descriptor_table::segment_selector code_segment, void (*return_function)()) -> void
{
(void)initialize_descriptor_tables();
kernel::cpu::set_data_segment_registers(data_segment);
kernel::cpu::set_code_segment_register(data_segment, code_segment, reinterpret_cast<uint64_t>(return_function));
}
} // namespace teachos::arch::context_switching
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