diff options
Diffstat (limited to 'arch/x86_64/src/context_switching')
| -rw-r--r-- | arch/x86_64/src/context_switching/descriptor_table/global_descriptor_table.cpp | 27 |
1 files changed, 12 insertions, 15 deletions
diff --git a/arch/x86_64/src/context_switching/descriptor_table/global_descriptor_table.cpp b/arch/x86_64/src/context_switching/descriptor_table/global_descriptor_table.cpp index 77bd3e9..21a76e8 100644 --- a/arch/x86_64/src/context_switching/descriptor_table/global_descriptor_table.cpp +++ b/arch/x86_64/src/context_switching/descriptor_table/global_descriptor_table.cpp @@ -54,9 +54,12 @@ namespace teachos::arch::context_switching::descriptor_table create_segment_descriptor(segment_descriptor_type::CODE_SEGMENT, access_level::USER); segment_descriptor user_data_segment = create_segment_descriptor(segment_descriptor_type::DATA_SEGMENT, access_level::USER); + // Task State Segment needs to be kept alive + static auto tss = new task_state_segment(); + segment_descriptor 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}; + 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; } @@ -67,20 +70,15 @@ namespace teachos::arch::context_switching::descriptor_table access_byte::TASK_STATE_SEGMENT_AVAILABLE}; gdt_flags tss_gdt_flags{0U, limit}; uint64_t tss_address = reinterpret_cast<uint64_t>(tss); - constexpr uint64_t tss_limit = sizeof(task_state_segment) - 1; - segment_descriptor tss_descriptor{tss_access_byte, tss_gdt_flags, tss_address, tss_limit}; - + constexpr uint64_t TSS_LIMIT = sizeof(task_state_segment) - 1; + segment_descriptor tss_descriptor{tss_access_byte, tss_gdt_flags, tss_address, TSS_LIMIT}; return tss_descriptor; } - auto initialize_global_descriptor_table() -> global_descriptor_table + auto initialize_global_descriptor_table() -> global_descriptor_table & { - auto gdt = create_global_descriptor_table(); - - // Add TSS segment descriptor to GDT - auto tss = new task_state_segment(); - auto tss_descriptor = create_task_state_segment_descriptor(tss); - gdt.push_back(tss_descriptor); + // Global Descriptor Table needs to be kept alive + static auto gdt = create_global_descriptor_table(); // Load GDT into GDTR global_descriptor_table_pointer gdt_pointer{static_cast<uint16_t>(gdt.size() - 1), &gdt}; @@ -91,14 +89,13 @@ namespace teachos::arch::context_switching::descriptor_table gdt_pointer == stored_gdt_pointer, "[Global Descriptor Table] Loaded GDTR value is not the same as the stored value."); - // Load Task Register (LTR) using the index of TSS descriptor - uint16_t tss_selector = (gdt.size() - 1) * sizeof(segment_descriptor); + // Calculate the offset of the gdt in bytes to the TSS descriptor + uint16_t const tss_selector = (gdt.size() - 1) * sizeof(segment_descriptor); kernel::cpu::load_task_register(tss_selector); auto stored_task_register = kernel::cpu::store_task_register(); arch::exception_handling::assert(tss_selector == stored_task_register, "[Global Descriptor Table] Loaded TR value is not the same as the stored value."); - return gdt; } } // namespace teachos::arch::context_switching::descriptor_table |