diff options
Diffstat (limited to 'arch/x86_64/src/context_switching')
6 files changed, 88 insertions, 38 deletions
diff --git a/arch/x86_64/src/context_switching/main.cpp b/arch/x86_64/src/context_switching/main.cpp index 7db9583..5901998 100644 --- a/arch/x86_64/src/context_switching/main.cpp +++ b/arch/x86_64/src/context_switching/main.cpp @@ -29,7 +29,19 @@ namespace teachos::arch::context_switching 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_global_descriptor_table_register() -> void { kernel::cpu::call(KERNEL_CODE_POINTER); } + auto reload_gdtr() -> void + { + // asm volatile("pushq $0x8\n\t" // Push new CS + // "lea 1f(%%rip), %%rax\n\t" // Get address of label 1 into RAX + // "pushq %%rax\n\t" // Push return address + // "lretq\n" // Far return (loads CS:RIP) + // "1:\n\t" // Label to return to + // : + // : + // : "rax", "memory"); + + kernel::cpu::call(KERNEL_CODE_POINTER); + } auto user_mode_main() -> void { @@ -83,9 +95,7 @@ namespace teachos::arch::context_switching kernel::cpu::write_msr(IA32_FMASK_ADDRESS, 0U); uint64_t kernel_cs = KERNEL_CODE_SEGMENT_SELECTOR; - // We want to provide the user code segment, but the instruction calculates + 0x10 to fill the - // cs register (See https://www.felixcloutier.com/x86/sysret). - uint64_t user_cs = USER_CODE_SEGMENT_SELECTOR - 0x10; + uint64_t user_cs = KERNEL_CODE_SEGMENT_SELECTOR; uint64_t star_value = (kernel_cs << 32) | (user_cs << 48); kernel::cpu::write_msr(IA32_STAR_ADDRESS, star_value); @@ -102,17 +112,17 @@ namespace teachos::arch::context_switching { kernel::cpu::clear_interrupt_flag(); - segment_descriptor_table::update_global_descriptor_table_register(); + segment_descriptor_table::update_gdtr(); interrupt_descriptor_table::update_interrupt_descriptor_table_register(); - reload_global_descriptor_table_register(); + reload_gdtr(); segment_descriptor_table::update_task_state_segment_register(); kernel::cpu::set_interrupt_flag(); initalized = true; } - descriptor_tables tables = {segment_descriptor_table::get_or_create_global_descriptor_table(), + descriptor_tables tables = {segment_descriptor_table::get_or_create_gdt(), interrupt_descriptor_table::get_or_create_interrupt_descriptor_table()}; return tables; } diff --git a/arch/x86_64/src/context_switching/segment_descriptor_table/global_descriptor_table.cpp b/arch/x86_64/src/context_switching/segment_descriptor_table/global_descriptor_table.cpp index a497632..dd22603 100644 --- a/arch/x86_64/src/context_switching/segment_descriptor_table/global_descriptor_table.cpp +++ b/arch/x86_64/src/context_switching/segment_descriptor_table/global_descriptor_table.cpp @@ -1,11 +1,11 @@ #include "arch/context_switching/segment_descriptor_table/global_descriptor_table.hpp" -#include "arch/context_switching/segment_descriptor_table/segment_descriptor.hpp" +#include "arch/context_switching/segment_descriptor_table/segment_descriptor_base.hpp" +#include "arch/context_switching/segment_descriptor_table/segment_descriptor_extension.hpp" #include "arch/context_switching/segment_descriptor_table/task_state_segment.hpp" #include "arch/exception_handling/assert.hpp" #include "arch/kernel/cpu/gdtr.hpp" #include "arch/kernel/cpu/tr.hpp" -#include "arch/stl/vector.hpp" namespace teachos::arch::context_switching::segment_descriptor_table { @@ -26,7 +26,6 @@ namespace teachos::arch::context_switching::segment_descriptor_table } else if (segment_descriptor_type == segment_descriptor_type::DATA_SEGMENT) { - flags |= gdt_flags::UPPER_BOUND; access_level |= access_byte::WRITABLE; } @@ -34,7 +33,7 @@ namespace teachos::arch::context_switching::segment_descriptor_table return segment_descriptor; } - auto create_task_state_segment_descriptor(task_state_segment * tss) -> segment_descriptor + auto create_tss_descriptor(task_state_segment * tss) -> segment_descriptor { constexpr uint64_t TSS_LIMIT = sizeof(task_state_segment) - 1; access_byte const tss_access_byte{access_byte::PRESENT | access_byte::DESCRIPTOR_LEVEL_KERNEL | @@ -45,43 +44,51 @@ namespace teachos::arch::context_switching::segment_descriptor_table return tss_descriptor; } - auto create_global_descriptor_table() -> global_descriptor_table + auto create_gdt() -> global_descriptor_table * { - segment_descriptor const null_segment{0}; - segment_descriptor const kernel_code_segment = - create_segment_descriptor(segment_descriptor_type::CODE_SEGMENT, access_byte::DESCRIPTOR_LEVEL_KERNEL); - segment_descriptor const kernel_data_segment = - create_segment_descriptor(segment_descriptor_type::DATA_SEGMENT, access_byte::DESCRIPTOR_LEVEL_KERNEL); - segment_descriptor const user_code_segment = - create_segment_descriptor(segment_descriptor_type::CODE_SEGMENT, access_byte::DESCRIPTOR_LEVEL_USER); - segment_descriptor const user_data_segment = - create_segment_descriptor(segment_descriptor_type::DATA_SEGMENT, access_byte::DESCRIPTOR_LEVEL_USER); + segment_descriptor_base const null_segment{segment_descriptor{0}}; + segment_descriptor_base const kernel_code_segment{ + create_segment_descriptor(segment_descriptor_type::CODE_SEGMENT, access_byte::DESCRIPTOR_LEVEL_KERNEL)}; + segment_descriptor_base const kernel_data_segment{ + create_segment_descriptor(segment_descriptor_type::DATA_SEGMENT, access_byte::DESCRIPTOR_LEVEL_KERNEL)}; + segment_descriptor_base const user_code_segment{ + create_segment_descriptor(segment_descriptor_type::CODE_SEGMENT, access_byte::DESCRIPTOR_LEVEL_USER)}; + segment_descriptor_base const user_data_segment{ + create_segment_descriptor(segment_descriptor_type::DATA_SEGMENT, access_byte::DESCRIPTOR_LEVEL_USER)}; // Task State Segment needs to be kept alive static auto tss = new task_state_segment(); - segment_descriptor const tss_descriptor = create_task_state_segment_descriptor(tss); - - global_descriptor_table global_descriptor_table{null_segment, kernel_code_segment, kernel_data_segment, - user_code_segment, user_data_segment, tss_descriptor}; - return global_descriptor_table; - } + segment_descriptor const tss_descriptor = create_tss_descriptor(tss); + segment_descriptor_base const tss_descriptor_base{tss_descriptor}; + segment_descriptor_extension const tss_descriptor_extension{tss_descriptor}; + + decltype(auto) gdt = new global_descriptor_table{}; + gdt->null = null_segment; + gdt->kernel_code = kernel_code_segment; + gdt->kernel_data = kernel_data_segment; + gdt->user_code = user_code_segment; + gdt->user_data = user_data_segment; + gdt->tss_low = tss_descriptor_base; + gdt->tss_high = tss_descriptor_extension; + + return gdt; + }; } // namespace - auto get_or_create_global_descriptor_table() -> global_descriptor_table & + auto get_or_create_gdt() -> global_descriptor_table & { // Global Descriptor Table needs to be kept alive - static global_descriptor_table gdt = create_global_descriptor_table(); - return gdt; + static global_descriptor_table * gdt = create_gdt(); + return *gdt; } - auto update_global_descriptor_table_register() -> void + auto update_gdtr() -> void { - decltype(auto) gdt = get_or_create_global_descriptor_table(); + decltype(auto) gdt = get_or_create_gdt(); // Calculate the size of the gdt in bytes - 1. This subtraction occurs because the maximum value of Size is 65535, // while the GDT can be up to 65536 bytes in length (8192 entries). Further, no GDT can have a size of 0 bytes. - global_descriptor_table_pointer gdt_pointer{static_cast<uint16_t>((gdt.size() * sizeof(segment_descriptor)) - 1), - gdt.data()}; + global_descriptor_table_pointer gdt_pointer{static_cast<uint16_t>((7 * sizeof(seg_desc)) - 1), &gdt.null}; kernel::cpu::load_global_descriptor_table(gdt_pointer); auto const stored_gdt_pointer = kernel::cpu::store_global_descriptor_table(); @@ -92,11 +99,11 @@ namespace teachos::arch::context_switching::segment_descriptor_table auto update_task_state_segment_register() -> void { - decltype(auto) gdt = get_or_create_global_descriptor_table(); + get_or_create_gdt(); // Load task state segment descriptor from the last element in the global descriptor table, done by calculating // offset in bytes to the start of the segment descriptor (5 * 16) = 80 - uint16_t const tss_selector = (gdt.size() - 1) * sizeof(segment_descriptor_table::segment_descriptor); + uint16_t const tss_selector = (7 - 1) * sizeof(segment_descriptor_table::segment_descriptor); kernel::cpu::load_task_register(tss_selector); auto const stored_task_register = kernel::cpu::store_task_register(); diff --git a/arch/x86_64/src/context_switching/segment_descriptor_table/global_descriptor_table_pointer.cpp b/arch/x86_64/src/context_switching/segment_descriptor_table/global_descriptor_table_pointer.cpp index a4a5de8..b7d2da4 100644 --- a/arch/x86_64/src/context_switching/segment_descriptor_table/global_descriptor_table_pointer.cpp +++ b/arch/x86_64/src/context_switching/segment_descriptor_table/global_descriptor_table_pointer.cpp @@ -2,8 +2,7 @@ namespace teachos::arch::context_switching::segment_descriptor_table { - global_descriptor_table_pointer::global_descriptor_table_pointer(uint16_t table_length, - segment_descriptor * address) + global_descriptor_table_pointer::global_descriptor_table_pointer(uint16_t table_length, seg_desc * address) : table_length(table_length) , address(address) { diff --git a/arch/x86_64/src/context_switching/segment_descriptor_table/segment_descriptor.cpp b/arch/x86_64/src/context_switching/segment_descriptor_table/segment_descriptor.cpp index 74f93b2..e74156b 100644 --- a/arch/x86_64/src/context_switching/segment_descriptor_table/segment_descriptor.cpp +++ b/arch/x86_64/src/context_switching/segment_descriptor_table/segment_descriptor.cpp @@ -32,4 +32,15 @@ namespace teachos::arch::context_switching::segment_descriptor_table return _access.contains_flags(access_byte::CODE_SEGMENT) ? segment_descriptor_type::CODE_SEGMENT : segment_descriptor_type::DATA_SEGMENT; } + + auto segment_descriptor::get_limit_1() -> uint16_t { return _limit_1; } + + auto segment_descriptor::get_base_1() -> uint32_t { return _base_1; } + + auto segment_descriptor::get_access() -> access_byte { return _access; } + + auto segment_descriptor::get_flag() -> gdt_flags { return _flag; } + + auto segment_descriptor::get_base_2() -> uint64_t { return _base_2; } + } // namespace teachos::arch::context_switching::segment_descriptor_table diff --git a/arch/x86_64/src/context_switching/segment_descriptor_table/segment_descriptor_base.cpp b/arch/x86_64/src/context_switching/segment_descriptor_table/segment_descriptor_base.cpp new file mode 100644 index 0000000..f82dbb9 --- /dev/null +++ b/arch/x86_64/src/context_switching/segment_descriptor_table/segment_descriptor_base.cpp @@ -0,0 +1,13 @@ +#include "arch/context_switching/segment_descriptor_table/segment_descriptor_base.hpp" + +namespace teachos::arch::context_switching::segment_descriptor_table +{ + segment_descriptor_base::segment_descriptor_base(segment_descriptor segment_descriptor) + : _limit_1(segment_descriptor.get_limit_1()) + , _base_1(segment_descriptor.get_base_1()) + , _access(segment_descriptor.get_access()) + , _flag(segment_descriptor.get_flag()) + { + // Nothing to do + } +} // namespace teachos::arch::context_switching::segment_descriptor_table diff --git a/arch/x86_64/src/context_switching/segment_descriptor_table/segment_descriptor_extension.cpp b/arch/x86_64/src/context_switching/segment_descriptor_table/segment_descriptor_extension.cpp new file mode 100644 index 0000000..b2649d0 --- /dev/null +++ b/arch/x86_64/src/context_switching/segment_descriptor_table/segment_descriptor_extension.cpp @@ -0,0 +1,10 @@ +#include "arch/context_switching/segment_descriptor_table/segment_descriptor_extension.hpp" + +namespace teachos::arch::context_switching::segment_descriptor_table +{ + segment_descriptor_extension::segment_descriptor_extension(segment_descriptor segment_descriptor) + : _base_2(segment_descriptor.get_base_2()) + { + // Nothing to do + } +} // namespace teachos::arch::context_switching::segment_descriptor_table |