minimal cpu exception handling

applications/init/main.cpp

@@ -9,6 +9,7 @@ uint32_t fb_height;
 uint32_t fb_pitch;
 
 int main(int, char **) {
+
   mercury::syscall::get_framebuffer(fb, fb_width, fb_height, fb_pitch);
   for (uint32_t y = 0; y < fb_height; ++y)
     for (uint32_t x = 0; x < fb_width; ++x) {
@@ -20,5 +21,6 @@ int main(int, char **) {
       fb[y * fb_pitch + x] = mercury::syscall::encode_color(c);
     }
   mercury::syscall::draw_framebuffer();
-  return 0;
+
+  return 1 / 0;
 }

kernel/entry.cpp

@@ -184,15 +184,6 @@ extern "C" [[noreturn]] void entry() {
 
 }
 
-static void print_mem() {
-  uint64_t used_vram_mib = (paging::get_used_vram_page_count() + 128) / 256;
-  uint64_t free_pram_mib = (paging::get_free_pram_page_count() + 128) / 256;
-  terminal::put_int_decimal(used_vram_mib);
-  terminal::put_string_sz(" MiB kernel memory mapped.\n");
-  terminal::put_int_decimal(free_pram_mib);
-  terminal::put_string_sz(" MiB physical memory free.\n");
-}
-
 [[noreturn]] static void print_and_halt(const char *msg) {
   terminal::put_string_sz(msg);
   while (1)
@@ -230,25 +221,11 @@ extern "C" [[noreturn]] void start_user_mode(
   if (!init_file)
     print_and_halt("/bin/init.elf does not exist.");
 
-  terminal::put_string_sz("/bin/init.elf is ");
-  terminal::put_int_decimal(init_file->dir_entry.length);
-  terminal::put_string_sz(" bytes long.\n");
-
   application::app_instance *init;
   if (application::create_app(*init_file, init) !=
       application::create_app_result::success)
     print_and_halt("failed to parse /bin/init.elf.");
 
-  terminal::put_string_sz("/bin/init.elf loaded:\n  instruction pointer 0x");
-  terminal::put_int_hex(init->saved_regs.rip, 8);
-  terminal::put_string_sz("\n  stack pointer 0x");
-  terminal::put_int_hex(init->saved_regs.rsp, 8);
-  terminal::put_string_sz("\n  ");
-  terminal::put_int_decimal(init->count_mapped_vram_pages() * 2);
-  terminal::put_string_sz(" MiB userspace memory used\n");
-
-  print_mem();
-  terminal::put_string_sz("switching to /bin/init.elf.\n");
   application::running_app = init;
   start_user_mode(init->saved_regs.rip, init->saved_regs.rsp, init->p4_paddr);
 

kernel/interrupts.asm

@@ -0,0 +1,254 @@
+bits 64
+
+global load_gdt_and_idt
+
+section .rodata
+
+;0x28 picked to align with limine choice
+
+;0x18 - tss
+;0x28 - kernel code
+;0x30 - kernel data
+;0x38 - user data
+;0x40 - user code
+
+tss:
+  times 9 dd 0
+  dq 0xffffffffffeff000
+  times 15 dd 0
+
+gdtr:
+  dw 0x47
+  dq gdt
+
+idtr:
+  dw 4095
+  dq idt
+
+section .bss
+
+idt:
+  resq 512
+
+global exception_info
+exception_info:
+.rax:
+  resq 1
+.rbx:
+  resq 1
+.rcx:
+  resq 1
+.rdx:
+  resq 1
+.rdi:
+  resq 1
+.rsi:
+  resq 1
+.rbp:
+  resq 1
+.rsp:
+  resq 1
+.r8:
+  resq 1
+.r9:
+  resq 1
+.r10:
+  resq 1
+.r11:
+  resq 1
+.r12:
+  resq 1
+.r13:
+  resq 1
+.r14:
+  resq 1
+.r15:
+  resq 1
+.cr3:
+  resq 1
+.rip:
+  resq 1
+.rflags:
+  resq 1
+.error:
+  resq 1
+.has_error:
+  resb 1
+.exception_number:
+  resb 1
+
+section .rodata
+
+has_error_code:
+  db 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1, 1, 1, 1, 0
+
+exception_isrs:
+  dq exception_00, exception_01, exception_02, exception_03
+  dq exception_04, exception_05, exception_06, exception_07
+  dq exception_08, exception_09, exception_0a, exception_0b
+  dq exception_0c, exception_0d, exception_0e, exception_0f
+
+section .text
+
+extern print_exception
+
+exception_00:
+  mov byte [exception_info.exception_number], 0x00
+  jmp exception_common
+exception_01:
+  mov byte [exception_info.exception_number], 0x01
+  jmp exception_common
+exception_02:
+  mov byte [exception_info.exception_number], 0x02
+  jmp exception_common
+exception_03:
+  mov byte [exception_info.exception_number], 0x03
+  jmp exception_common
+exception_04:
+  mov byte [exception_info.exception_number], 0x04
+  jmp exception_common
+exception_05:
+  mov byte [exception_info.exception_number], 0x05
+  jmp exception_common
+exception_06:
+  mov byte [exception_info.exception_number], 0x06
+  jmp exception_common
+exception_07:
+  mov byte [exception_info.exception_number], 0x07
+  jmp exception_common
+exception_08:
+  mov byte [exception_info.exception_number], 0x08
+  jmp exception_common
+exception_09:
+  mov byte [exception_info.exception_number], 0x09
+  jmp exception_common
+exception_0a:
+  mov byte [exception_info.exception_number], 0x0a
+  jmp exception_common
+exception_0b:
+  mov byte [exception_info.exception_number], 0x0b
+  jmp exception_common
+exception_0c:
+  mov byte [exception_info.exception_number], 0x0c
+  jmp exception_common
+exception_0d:
+  mov byte [exception_info.exception_number], 0x0d
+  jmp exception_common
+exception_0e:
+  mov byte [exception_info.exception_number], 0x0e
+  jmp exception_common
+exception_0f:
+  mov byte [exception_info.exception_number], 0x0f
+  jmp exception_common
+
+exception_common:
+  mov qword [exception_info.rax], rax
+
+  movzx rax, byte [exception_info.exception_number]
+  mov al, byte [has_error_code + rax]
+  test al, al
+  jz .no_error_code
+
+  mov byte [exception_info.has_error], 1
+  pop rax
+  mov qword [exception_info.error], rax
+  jmp .post_error_code
+
+.no_error_code:
+  mov byte [exception_info.has_error], 0
+
+.post_error_code:
+  mov qword [exception_info.rbx], rbx
+  mov qword [exception_info.rcx], rcx
+  mov qword [exception_info.rdx], rdx
+  mov qword [exception_info.rdi], rdi
+  mov qword [exception_info.rsi], rsi
+  mov qword [exception_info.rbp], rbp
+  mov qword [exception_info.r8], r8
+  mov qword [exception_info.r9], r9
+  mov qword [exception_info.r10], r10
+  mov qword [exception_info.r11], r11
+  mov qword [exception_info.r12], r12
+  mov qword [exception_info.r13], r13
+  mov qword [exception_info.r14], r14
+  mov qword [exception_info.r15], r15
+
+  pop rax
+  mov qword [exception_info.rip], rax
+  pop rax
+  pop rax
+  mov qword [exception_info.rflags], rax
+  pop rax
+  mov qword [exception_info.rsp], rax
+
+  mov rax, cr3
+  mov qword [exception_info.cr3], rax
+
+  jmp print_exception
+
+set_isr:
+;rdi - index
+;sil - 1 if this is a trap, 0 if it is an interrupt
+;rdx - isr pointer
+
+  shl rdi, 4
+  add rdi, idt
+
+  mov word [rdi], dx
+  shr rdx, 16
+  mov word [rdi + 6], dx
+  shr rdx, 16
+  mov dword [rdi + 8], edx
+
+  or sil, 0xef
+  mov byte [rdi + 5], sil
+  mov word [rdi + 2], 0x28
+  mov byte [rdi + 4], 1
+
+  ret
+
+section .data
+
+gdt:
+  dq 0
+  dq 0
+  dq 0
+.tss:
+  dq 0x0000e90000000067
+  dq 0;tss is 2 qwords wide
+  dq 0x00209b0000000000
+  dq 0x00009b0000000000
+  dq 0x0000fb0000000000
+  dq 0x0020fb0000000000
+
+section .text
+
+load_gdt_and_idt:
+
+  mov rcx, 8
+
+.loop:
+
+  mov rdi, rcx
+  dec rdi
+  mov sil, 1
+  mov rdx, qword [exception_isrs + rdi * 8]
+  call set_isr
+
+  loop .loop
+
+  mov rax, tss
+
+  mov word [gdt.tss + 2], ax
+  shr rax, 16
+  mov byte [gdt.tss + 4], al
+  mov byte [gdt.tss + 7], ah
+  shr rax, 16
+  mov dword [gdt.tss + 8], eax
+
+  lgdt [gdtr]
+  lidt [idtr]
+  mov ax, 0x18
+  ltr ax
+
+  ret

kernel/interrupts.cpp

@@ -0,0 +1,119 @@
+#include <mercury/kernel/terminal.hpp>
+
+using namespace mercury::kernel;
+
+struct [[gnu::packed]] exception_info_t {
+
+  uint64_t rax;
+  uint64_t rbx;
+  uint64_t rcx;
+  uint64_t rdx;
+  uint64_t rdi;
+  uint64_t rsi;
+  uint64_t rbp;
+  uint64_t rsp;
+  uint64_t r8;
+  uint64_t r9;
+  uint64_t r10;
+  uint64_t r11;
+  uint64_t r12;
+  uint64_t r13;
+  uint64_t r14;
+  uint64_t r15;
+
+  uint64_t cr3;
+  uint64_t rip;
+  uint64_t rflags;
+
+  uint64_t error;
+  uint8_t has_error;//0 or 1
+  uint8_t exception_number;
+
+};
+
+extern exception_info_t exception_info;
+
+const char *exception_types[] = {
+  "division error",
+  "",
+  "non-maskable interrupt",
+  "",
+  "",
+  "",
+  "invalid opcode",
+  "",
+  "double fault (uh oh)",
+  "",
+  "",
+  "",
+  "stack fault",
+  "general protection fault",
+  "page fault",
+  ""
+};
+
+const char *flag_names[] = {
+  " cf",
+  "",
+  " pf",
+  "",
+  " af",
+  "",
+  " zf",
+  " sf",
+  " tf",
+  " if",
+  " df",
+  " of",
+  "",
+  "",
+  " nt",
+  " md"
+};
+
+void print_line(const char *r1, const char *r2, uint64_t r1v, uint64_t r2v) {
+  terminal::put_string_sz("\n  ");
+  terminal::put_string_sz(r1);
+  terminal::put_string_sz(": 0x");
+  terminal::put_int_hex(r1v, 16);
+  terminal::put_string_sz("  ");
+  terminal::put_string_sz(r2);
+  terminal::put_string_sz(": 0x");
+  terminal::put_int_hex(r2v, 16);
+}
+
+extern "C" [[noreturn]] void print_exception() {
+
+  terminal::put_string_sz("exception handler:\n  type: ");
+  terminal::put_string_sz(exception_types[exception_info.exception_number]);
+  terminal::put_string_sz(" (0x");
+  terminal::put_int_hex(exception_info.exception_number, 2);
+  terminal::put_char(')');
+
+  if (exception_info.has_error == 1) {
+    terminal::put_string_sz("\n  error code: 0x");
+    terminal::put_int_hex(exception_info.error, 16);
+  }
+
+  terminal::put_string_sz("\n  flags:");
+  if (exception_info.rflags == 0)
+    terminal::put_string_sz(" [none]");
+  else
+    for (int i = 0; i < 16; ++i)
+      if (((exception_info.rflags >> i) & 1) == 1)
+        terminal::put_string_sz(flag_names[i]);
+
+  print_line("rip", "cr3", exception_info.rip, exception_info.cr3);
+  print_line("rax", "rbx", exception_info.rax, exception_info.rbx);
+  print_line("rcx", "rdx", exception_info.rcx, exception_info.rdx);
+  print_line("rdi", "rsi", exception_info.rdi, exception_info.rsi);
+  print_line("rbp", "rsp", exception_info.rbp, exception_info.rsp);
+  print_line("r8 ", "r9 ", exception_info.r8 , exception_info.r9 );
+  print_line("r10", "r11", exception_info.r10, exception_info.r11);
+  print_line("r12", "r13", exception_info.r12, exception_info.r13);
+  print_line("r14", "r15", exception_info.r14, exception_info.r15);
+
+  while (1)
+    asm ("hlt");
+
+}

kernel/syscall.asm

@@ -1,45 +1,9 @@
 bits 64
 
-global load_gdt_and_idt
 global start_user_mode
 
-section .rodata
-
-;0x28 picked to align with limine choice
-;0x28 - kernel code
-;0x30 - kernel data
-;0x38 - user data
-;0x40 - user code
-
-gdtr:
-  dw 0x47
-  dq gdt
-
-gdt:
-  dq 0
-  dq 0
-  dq 0
-  dq 0
-  dq 0
-  dq 0x00209b0000000000
-  dq 0x00009b0000000000
-  dq 0x0000fb0000000000
-  dq 0x0020fb0000000000
-
-idtr:
-  dw 4095
-  dq idt
-
-idt:
-  times 256 - ($ - idt) / 16 dq 0
-
 section .text
 
-load_gdt_and_idt:
-  lgdt [gdtr]
-  lidt [idtr]
-  ret
-
 extern syscall_encode_color
 
 encode_color_syscall:

makefile

@@ -41,7 +41,8 @@ obj/kernel/%.asm.o: kernel/%.asm
 
 KERNEL_OBJECTS = allocator.cpp application.cpp entry.cpp framebuffer.cpp \
   paging.asm paging.cpp storage.cpp storage/bd/memory.cpp terminal.cpp \
-	storage/fs/tarfs.cpp utility.cpp vfile.cpp syscall.asm syscall.cpp
+  storage/fs/tarfs.cpp utility.cpp vfile.cpp syscall.asm syscall.cpp \
+  interrupts.asm interrupts.cpp
 obj/kernel.elf: ${KERNEL_OBJECTS:%=obj/kernel/%.o}
 	ld ${KLD_ARGS} $^ -o $@