From aba154ad01fc0e1e1274f2582b1493e78daa2559 Mon Sep 17 00:00:00 2001 From: Fabian Imhof Date: Sat, 29 Mar 2025 14:47:04 +0000 Subject: fix gdt segments, improve idt and trial&error for triple fault --- .../interrupt_descriptor_table/gate_descriptor.cpp | 2 ++ .../interrupt_descriptor_table.cpp | 14 ++++++---- .../interrupt_descriptor_table_pointer.cpp | 2 +- arch/x86_64/src/context_switching/main.cpp | 30 +++++++++++++--------- .../global_descriptor_table.cpp | 5 +--- 5 files changed, 31 insertions(+), 22 deletions(-) (limited to 'arch/x86_64/src/context_switching') diff --git a/arch/x86_64/src/context_switching/interrupt_descriptor_table/gate_descriptor.cpp b/arch/x86_64/src/context_switching/interrupt_descriptor_table/gate_descriptor.cpp index 28f289c..d86c459 100644 --- a/arch/x86_64/src/context_switching/interrupt_descriptor_table/gate_descriptor.cpp +++ b/arch/x86_64/src/context_switching/interrupt_descriptor_table/gate_descriptor.cpp @@ -8,6 +8,7 @@ namespace teachos::arch::context_switching::interrupt_descriptor_table , _ist(flags >> 32U) , _flags(flags >> 40U) , _offset_2(flags >> 48U) + , _offset_3(flags >> 64U) { // Nothing to do. } @@ -18,6 +19,7 @@ namespace teachos::arch::context_switching::interrupt_descriptor_table , _ist(ist) , _flags(flags) , _offset_2(offset >> 16U) + , _offset_3(offset >> 48U) { // Nothing to do. } diff --git a/arch/x86_64/src/context_switching/interrupt_descriptor_table/interrupt_descriptor_table.cpp b/arch/x86_64/src/context_switching/interrupt_descriptor_table/interrupt_descriptor_table.cpp index ddc098e..1c1de68 100644 --- a/arch/x86_64/src/context_switching/interrupt_descriptor_table/interrupt_descriptor_table.cpp +++ b/arch/x86_64/src/context_switching/interrupt_descriptor_table/interrupt_descriptor_table.cpp @@ -1,20 +1,24 @@ #include "arch/context_switching/interrupt_descriptor_table/interrupt_descriptor_table.hpp" #include "arch/exception_handling/assert.hpp" +#include "arch/interrupt_handling/generic_interrupt_handler.hpp" #include "arch/kernel/cpu/idtr.hpp" namespace teachos::arch::context_switching::interrupt_descriptor_table { namespace { + auto create_interrupt_descriptor_table() -> interrupt_descriptor_table { - uint64_t offset = 0U; + // @MTO: This address resolution is most certainly wrong -> numbers in dbg seem off (offset_3 = 0) + uint64_t offset = reinterpret_cast(&interrupt_handling::generic_interrupt_handler); segment_selector selector{0U, segment_selector::REQUEST_LEVEL_KERNEL}; ist_offset ist{0U}; - idt_flags flags{idt_flags::DESCRIPTOR_LEVEL_KERNEL}; - gate_descriptor gate_descriptor{selector, ist, flags, offset}; - return interrupt_descriptor_table{gate_descriptor}; + idt_flags flags{idt_flags::DESCRIPTOR_LEVEL_KERNEL | idt_flags::PRESENT}; + gate_descriptor descriptor{selector, ist, flags, offset}; + + return interrupt_descriptor_table{descriptor}; } } // namespace @@ -24,7 +28,7 @@ namespace teachos::arch::context_switching::interrupt_descriptor_table static auto idt = create_interrupt_descriptor_table(); interrupt_descriptor_table_pointer idt_pointer{static_cast((idt.size() * sizeof(gate_descriptor)) - 1), - &idt}; + idt.data()}; kernel::cpu::load_interrupt_descriptor_table(idt_pointer); auto const stored_gdt_pointer = kernel::cpu::store_interrupt_descriptor_table(); diff --git a/arch/x86_64/src/context_switching/interrupt_descriptor_table/interrupt_descriptor_table_pointer.cpp b/arch/x86_64/src/context_switching/interrupt_descriptor_table/interrupt_descriptor_table_pointer.cpp index 981944d..7bcbae6 100644 --- a/arch/x86_64/src/context_switching/interrupt_descriptor_table/interrupt_descriptor_table_pointer.cpp +++ b/arch/x86_64/src/context_switching/interrupt_descriptor_table/interrupt_descriptor_table_pointer.cpp @@ -3,7 +3,7 @@ namespace teachos::arch::context_switching::interrupt_descriptor_table { interrupt_descriptor_table_pointer::interrupt_descriptor_table_pointer(uint16_t table_length, - interrupt_descriptor_table * address) + gate_descriptor * address) : table_length(table_length) , address(address) { diff --git a/arch/x86_64/src/context_switching/main.cpp b/arch/x86_64/src/context_switching/main.cpp index a5bd3fb..f449a3a 100644 --- a/arch/x86_64/src/context_switching/main.cpp +++ b/arch/x86_64/src/context_switching/main.cpp @@ -10,24 +10,30 @@ namespace teachos::arch::context_switching { auto initialize_descriptor_tables() -> descriptor_tables { + kernel::cpu::clear_interrupt_flag(); decltype(auto) global_descriptor_table = segment_descriptor_table::initialize_global_descriptor_table(); decltype(auto) interrupt_descriptor_table = interrupt_descriptor_table::initialize_interrupt_descriptor_table(); - kernel::cpu::far_pointer pointer{&boot::reload_segment_register, 1 * sizeof(segment_descriptor_table::segment_descriptor)}; - asm volatile("rex64 lcall *%[far_function_pointer]" : : [far_function_pointer] "m" (pointer)); + kernel::cpu::far_pointer pointer{&boot::reload_segment_register, + 1 * sizeof(segment_descriptor_table::segment_descriptor)}; + asm volatile("rex64 lcall *%[far_function_pointer]" : : [far_function_pointer] "m"(pointer)); - // // 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 = - // (global_descriptor_table.size() - 1) * sizeof(segment_descriptor_table::segment_descriptor); - // kernel::cpu::load_task_register(tss_selector); + // 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 = + (global_descriptor_table.size() - 1) * sizeof(segment_descriptor_table::segment_descriptor); + kernel::cpu::load_task_register(tss_selector); - // auto const 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."); + auto const 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."); - // FIXME: We currently cannot enable interrupts, since for some reason, we will later run into what looks like a GP. Maybe because no IDT is loaded? Maybe our boot code segment is not set up correctly? - // kernel::cpu::set_interrupt_flag(); + // FIXME: We currently cannot enable interrupts, since for some reason, we will later run into what looks like a GP + // and triple fault. + + // @MTO: SOMETIMES i get past a breakpoint here???? seems to happen when i actually pause before (f.e. inside the + // idt). NEVER happened when stepping through quickly. Can you reproduce this? + kernel::cpu::set_interrupt_flag(); descriptor_tables tables = {global_descriptor_table, 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 37ee778..d9ad91c 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 @@ -17,17 +17,14 @@ namespace teachos::arch::context_switching::segment_descriptor_table { uint8_t access_level_bits = access_byte::PRESENT | access_byte::CODE_OR_DATA_SEGMENT | *reinterpret_cast(&access_level); - uint8_t gdt_flags_bits = gdt_flags::GRANULARITY; + uint8_t gdt_flags_bits = gdt_flags::GRANULARITY | gdt_flags::LONG_MODE; if (segment_descriptor_type == segment_descriptor_type::CODE_SEGMENT) { - gdt_flags_bits |= gdt_flags::LONG_MODE; access_level_bits |= access_byte::CODE_SEGMENT | access_byte::READABLE; } else if (segment_descriptor_type == segment_descriptor_type::DATA_SEGMENT) { gdt_flags_bits |= 1 << 2; - // FIXME: Look at those bit flags, something seems off. - // gdt_flags_bits |= gdt_flags::UPPER_BOUND; access_level_bits |= access_byte::WRITABLE; } -- cgit v1.2.3