massive overhaul to my exception system

Makefile

@@ -3,7 +3,7 @@
 
 CC = i686-elf-gcc
 
-DEBUG_FLAGS = -D__TESTING__ -g -Wno-div-by-zero
+DEBUG_FLAGS = -D__TESTING__ -g 
 
 CFLAGS = -m32 -ffreestanding -Wall -Wextra -Werror -Wpedantic --sysroot=$(PWD)/sysroot -isystem=/usr/include -Iinclude -MD $(DEBUG_FLAGS)
 
@@ -39,7 +39,7 @@ all: kernel.elf
 env: install-headers install-libs # TODO: change this to a file specific target, so it doesnt recompile everytime, and so we can move as a prereq on kernel.elf
 	util/./gen-clangd.sh
 
-kernel.elf: install-headers install-libs $(c_kern_objects) $(asm_kern_objects)
+kernel.elf: install-headers install-libs env $(c_kern_objects) $(asm_kern_objects)
 	$(CC) $(CFLAGS) -T $(shell find . -name "link.ld") -o $@ $(c_kern_objects) $(asm_kern_objects) -nostdlib -lk -lgcc 
 
 os.iso: kernel.elf

TODO.md

@@ -1,7 +1,6 @@
 ## What do I need to do?
 
-Exception handling is a must for next part, we need to be able to dianogse issues better
+### Features I want
 
-    - Want the address of the fault
+- A kernel bus
-    - Proper handling of the issue
+    - some kind of driver where I can send messages that can eventually be accessed globally by other drives / applications
-    - Maybe dump registers?

kernel/arch/idt/idt.c

@@ -1,10 +1,9 @@
+#include <stdatomic.h>
 #include <stdbool.h>
 #include <stdint.h>
-
-#ifdef __TESTING__
-#include <kernel/_kernel.h>
 #include <stdio.h>
-#endif
+
+#include <kernel/_kernel.h>
 #include <kernel/x86/idt.h>
 #include <kernel/x86/pic.h>
 #include <kernel/x86/io.h>
@@ -19,21 +18,218 @@ static bool vectors[IDT_MAX_DESCRIPTORS];
 
 extern struct keyboard_state keyb_state;
 
-void exception_handler(struct cpu_state __attribute__((unused)) cpu, uint32_t interrupt, struct stack_state stack)
+
+#define EXTERNAL_BIT (0x1)
+
+#define TBL_GDT (0x0)
+#define TBL_LDT (0x2)
+#define TBL_IDT (0x1)
+#define TBL_IDT_TWO (0x3)
+
+static void examine_selector(uint32_t selector)
 {
-	printf("%1 %2\n", interrupt, stack.eflags);
+	printf("The interrupt arised %s.\n", (selector & EXTERNAL_BIT) == EXTERNAL_BIT ? "externally" : "internally");
-	if (interrupt <= 31) { // TODO: implement proper handling for each exception, also implement the proper gates & error code checking
+
-#ifdef __TESTING__
+
-		kerror("EXCEPTION");
+	printf("The descriptor 0x%x, is located in the ", selector, (selector & 0x0000FFFF) >> 3);
-		printf("Exeption: %2\n", interrupt);
+	if ((((selector >> 1) & TBL_IDT) == TBL_IDT)
-#endif
+			|| ((selector >> 1) & TBL_IDT_TWO) == TBL_IDT_TWO) {
-		//__asm__ volatile ("cli; hlt"); // hangs the computer
+		puts("IDT.");
+
+	} else if (((selector >> 1) & TBL_LDT) == TBL_LDT) {
+		puts("LDT.");
+	} else 	{
+		puts("GDT.");
 	}
 	
-	if (interrupt == PIC_KEYB) {
+	return;	
-		unsigned char in = inb(0x60);
+}
-		do_keypress(decode_scancode(in));
+
-		PIC_sendEOI(1);
+#undef TBL_GDT
+#undef TBL_LDT
+#undef TBL_IDT
+#undef TBL_IDT_TWO
+
+#define PF_P (1 << 0)
+#define PF_W (1 << 1)
+#define PF_U (1 << 2)
+#define PF_R (1 << 3)
+#define PF_I (1 << 4)
+#define PF_PK (1 << 5)
+#define PF_SS (1 << 6)
+#define PF_SGX (1 << 15)
+static void examine_page_fault(uint32_t error_code)
+{
+	puts("Page fault:");
+	if (error_code & PF_P) {
+		puts("Page-protection violation.");
+	} else {
+		puts("Not present page.");
+	}
+
+	if (error_code & PF_W) {
+		puts("Write access.");
+	} else {
+		puts("Read access.");
+	}
+
+	if (error_code & PF_U) {
+		puts("In CPL 3.");
+	} 
+
+	if (error_code & PF_R) { // Only applies if PSE or PAE are set in CR4
+		puts("One or more page directory entires contain reserved bits which are set to 1.");
+	} 
+
+	if (error_code & PF_I) { // Only applicable when the No-Execute bit is supported and enabled
+		puts("Instruction fetch.");
+	} 
+
+	if (error_code & PF_PK) {
+		puts("Protection-key violation"); //TODO PRKU (user mode access) or PRKS MSR (supervisor mode access) specifies the key rights
+	} 
+
+	if (error_code & PF_SS) {
+		puts("Shadow stack access.");
+	} 
+
+	if (error_code & PF_SGX) { // Unrelated to ordinary paging
+		puts("SGX vioilation");
+	}
+
+	// TODO, also sets CR2 reg to the virtual address which caused the page fault
+}
+#undef PF_P
+#undef PF_W
+#undef PF_U
+#undef PF_R
+#undef PF_I
+#undef PF_PK
+#undef PF_SS
+#undef PF_SGX
+
+#define EXCEPTION_LOCATION() printf("Exception occurred at 0x%2\n", stack.eip)
+
+void exception_handler(struct cpu_state __attribute__((unused)) cpu, uint32_t interrupt, struct stack_state stack)
+{
+	uint32_t inbyte;
+	switch (interrupt) {
+		/** EXCEPTIONS BEGIN **/
+		case EXCEPT_DIV_ERR:
+			kerror("EXCEPTION: DIV BY ZERO");
+			EXCEPTION_LOCATION();
+			break;
+		case EXCEPT_DEBUG:
+			kinfo("EXCEPTION: DEBUG"); // TODO: this one has more specific requirements
+			break;
+		case EXCEPT_NMI:
+			kinfo("EXCEPTION: NON-MASKABLE INTERRUPT"); // TODO
+			break;
+		case EXCEPT_BREAKPOINT:
+			kinfo("EXCEPTION: BREAKPOINT");
+			// TODO
+			break;
+		case EXCEPT_OVERFLOW:
+			kerror("EXCEPTION: OVERFLOW");
+			break;
+		case EXCEPT_BOUND_RANGE_EXCEEDED:
+			kerror("EXCEPTION: BOUND RANGE EXCEEDED");
+			EXCEPTION_LOCATION();
+			break;
+		case EXCEPT_INVALID_OPCODE:
+			kerror("EXCEPTION: INVALID OPCODE");
+			EXCEPTION_LOCATION();
+			break;
+		case EXCEPT_DEVICE_NOT_AVAILABLE:
+			kerror("EXCEPTION: DEVICE NOT AVAILABLE");
+			printf("Instructions expecting an FPU were used, but no FPU was found. Is it disabled in CR0? Do you have an FPU?\n");
+			EXCEPTION_LOCATION();
+			break;
+		case EXCEPT_DOUBLE_FAULT:
+			kerror("EXCEPTION: DOUBLE FAULT");
+			__asm__ volatile ("cli; hlt"); // boned
+			break;
+		case EXCEPT_INVALID_TSS:
+			kerror("EXCEPTION: INVALID TSS");
+			examine_selector(stack.error_code);
+			// TODO: when i implement the TSS, the EIP will be one of two things
+			// if this occurs before loading segmenet selectors from the TSS, EIP will be the instruction that caused the instruction
+			// otherwise its the first instruction in the new task
+			break;
+		case EXCEPT_SEG_NOT_PRESENT:
+			kerror("EXCEPTION: SEGMENT NOT PRESENT");
+			EXCEPTION_LOCATION();
+			examine_selector(stack.error_code);
+			break;
+		case EXCEPT_STACK_SEG_FAULT:
+			kerror("EXCEPTION: STACK-SEGMENT FAULT");
+			if (stack.error_code == 0) {
+				EXCEPTION_LOCATION();
+			} else {
+				printf("Tried loading non-present stack segment during hardware task switch.\n");
+				examine_selector(stack.error_code);
+			}
+			break;
+		case EXCEPT_GENERAL_PROTECTION:
+			kerror("EXCEPTION: GENERAL PROTECTION FAULT");
+			EXCEPTION_LOCATION();
+			if (stack.error_code != 0)
+				examine_selector(stack.error_code);
+			break;
+		case EXCEPT_PAGE_FAULT:
+			kerror("EXCEPTION: PAGE FAULT");
+			EXCEPTION_LOCATION();
+			examine_page_fault(stack.error_code);
+			break;
+		case EXCEPT_FLOATING_POINT_ERR_FPU:
+			kerror("EXCEPTION: FLOATING POINT ERROR FPU");
+			// TODO: this requires a custom handler, it needs another register
+			break;
+		case EXCEPT_ALIGNMENT_CHECK:
+			kerror("EXCEPTION: ALIGNMENT CHECK");
+
+			// TODO: only in CPL3
+			break;
+		case EXCEPT_MACHINE_CHECK:
+			kerror("EXCEPTION: MACHINE CHECK");
+			// TODO disabled by default
+			break;
+		case EXCEPT_FLOATING_POINT_ERR_SIMD:
+			kerror("EXCEPTION: FLOATING POINT ERROR SIMD");
+			// TODO disabled by default
+			break;
+		case EXCEPT_VIRT:
+			kerror("EXCEPTION: VIRTUALIZATION");
+			break;
+		case EXCEPT_CTRL_PROT:
+			kerror("EXCEPTION: CONTROL PROTECTION");
+			printf("Error code: 0x%2\n", stack.error_code);
+			break;
+		case EXCEPT_HYPERVISOR_INJECTION:
+			kerror("EXCEPTION: HYPERVISOR INJECTION");
+			break;
+		case EXCEPT_VMM_COMMUNICATION:
+			kerror("EXCEPTION: VMM COMMUNICATION");
+			printf("Error code: 0x%2\n", stack.error_code);
+			break;
+		case EXCEPT_SECURITY_EXCEPTION:
+			kerror("EXCEPTION: SECURITY");
+			printf("Error code: 0x%2\n", stack.error_code);
+			break;
+		/** EXCEPTIONS END **/
+
+		/** PIC BEGIN **/
+		case PIC_KEYB:
+			inbyte = inb(0x60);
+			do_keypress(decode_scancode(inbyte));
+			PIC_sendEOI(1);
+			break;
+
+		/** PIC END **/
+		default:
+			kerror("EXCEPTION: UNHANDLED EXCEPTION OR INTERRUPT");
+			printf("Error code: 0x%2\n", stack.error_code);
+			break;
 	}
 }
 

kernel/arch/idt/idt_src.s

@@ -3,14 +3,6 @@ extern exception_handler_err
 
 %macro isr_err_stub 1
 isr_stub_%+%1:
-	;pushad
-	;cld
-	;push dword %1
-	;call exception_handler_err
-	;pop eax ; pop the error
-	;pop eax ; make sure to pop off the dword!!
-	;popad
-	;iret
 	push dword %1 ; push the interrupt number
 	jmp common_interrupt_handler
 
@@ -18,13 +10,6 @@ isr_stub_%+%1:
 
 %macro isr_no_err_stub 1
 isr_stub_%+%1:
-	;pushad
-	;cld
-	;push dword %1
-	;call exception_handler
-	;pop eax
-	;popad
-	;iret
 	push dword 0 
 	push dword %1
 	jmp common_interrupt_handler
@@ -51,7 +36,8 @@ common_interrupt_handler:
 	pop ebx
 	pop eax
 	
-	; restore the esp
+	; lets move the stack before the error code and interrupt number
+	; since we don't want these to be popped anywhere
 	add esp, 8
 
 	iret

kernel/include/kernel/x86/idt.h

@@ -15,7 +15,6 @@
 #define EXCEPT_INVALID_OPCODE 6
 #define EXCEPT_DEVICE_NOT_AVAILABLE 7
 #define EXCEPT_DOUBLE_FAULT 8
-#define EXCEPT_SEG_OVERRUN 9
 #define EXCEPT_INVALID_TSS 10
 #define EXCEPT_SEG_NOT_PRESENT 11
 #define EXCEPT_STACK_SEG_FAULT 12
@@ -27,6 +26,9 @@
 #define EXCEPT_FLOATING_POINT_ERR_SIMD 19
 #define EXCEPT_VIRT 20
 #define EXCEPT_CTRL_PROT 21
+#define EXCEPT_HYPERVISOR_INJECTION 28
+#define EXCEPT_VMM_COMMUNICATION 29
+#define EXCEPT_SECURITY_EXCEPTION 30
 
 struct cpu_state {
 	uint32_t eax;