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Merge branch 'interrupts'

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Simponic 2021-03-08 23:31:08 -07:00
commit fe3d7ad832
5 changed files with 46 additions and 105 deletions
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34
include/idt.h
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@ -2,6 +2,7 @@
#define IDT_H
#include "types.h"
#include "isr.h"
struct IDT {
uint32_t base;
@ -20,37 +21,4 @@ struct IDT createIDT(uint32_t base, uint16_t selector, uint8_t flags);
void encodeIDT(uint8_t* idtEntry, struct IDT source);
void initializeIDT();
extern void isr0 ();
extern void isr1 ();
extern void isr2 ();
extern void isr3 ();
extern void isr4 ();
extern void isr5 ();
extern void isr6 ();
extern void isr7 ();
extern void isr8 ();
extern void isr9 ();
extern void isr10();
extern void isr11();
extern void isr12();
extern void isr13();
extern void isr14();
extern void isr15();
extern void isr16();
extern void isr17();
extern void isr18();
extern void isr19();
extern void isr20();
extern void isr21();
extern void isr22();
extern void isr23();
extern void isr24();
extern void isr25();
extern void isr26();
extern void isr27();
extern void isr28();
extern void isr29();
extern void isr30();
extern void isr31();
#endif // IDT_H

36
include/isr.h
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@ -10,4 +10,40 @@ struct registers{
uint32_t eip, cs, eflags, useresp, ss;
} __attribute__((packed));
extern void isr_common_stub();
extern void isr_handler(struct registers regs);
extern void isr0 ();
extern void isr1 ();
extern void isr2 ();
extern void isr3 ();
extern void isr4 ();
extern void isr5 ();
extern void isr6 ();
extern void isr7 ();
extern void isr8 ();
extern void isr9 ();
extern void isr10();
extern void isr11();
extern void isr12();
extern void isr13();
extern void isr14();
extern void isr15();
extern void isr16();
extern void isr17();
extern void isr18();
extern void isr19();
extern void isr20();
extern void isr21();
extern void isr22();
extern void isr23();
extern void isr24();
extern void isr25();
extern void isr26();
extern void isr27();
extern void isr28();
extern void isr29();
extern void isr30();
extern void isr31();
#endif // ISR_H

73
src/boot.s
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@ -5,45 +5,24 @@ FLAGS equ MBALIGN | MEMINFO ; this is the Multiboot 'flag' field
MAGIC equ 0x1BADB002 ; 'magic number' lets bootloader find the header
CHECKSUM equ -(MAGIC + FLAGS) ; checksum of above, to prove we are multiboot
; Declare a multiboot header that marks the program as a kernel. These are magic
; values that are documented in the multiboot standard. The bootloader will
; search for this signature in the first 8 KiB of the kernel file, aligned at a
; 32-bit boundary. The signature is in its own section so the header can be
; forced to be within the first 8 KiB of the kernel file.
section .multiboot
align 4
dd MAGIC
dd FLAGS
dd CHECKSUM
; The multiboot standard does not define the value of the stack pointer register
; (esp) and it is up to the kernel to provide a stack. This allocates room for a
; small stack by creating a symbol at the bottom of it, then allocating 16384
; bytes for it, and finally creating a symbol at the top. The stack grows
; downwards on x86. The stack is in its own section so it can be marked nobits,
; which means the kernel file is smaller because it does not contain an
; uninitialized stack. The stack on x86 must be 16-byte aligned according to the
; System V ABI standard and de-facto extensions. The compiler will assume the
; stack is properly aligned and failure to align the stack will result in
; undefined behavior.
section .bss
align 16
stack_bottom:
resb 16384 ; 16 KiB
stack_top:
; The linker script specifies _start as the entry point to the kernel and the
; bootloader will jump to this position once the kernel has been loaded. It
; doesn't make sense to return from this function as the bootloader is gone.
; Declare _start as a function symbol with the given symbol size.
section .text
global reloadSegments ; Flush GDT
reloadSegments:
; Reload CS register containing code selector:
JMP 0x08:reload_CS ; 0x08 points at the new code selector
reload_CS:
; Reload data segment registers:
MOV AX, 0x10 ; 0x10 points at the new data selector
MOV DS, AX
MOV ES, AX
@ -56,7 +35,7 @@ reload_CS:
[GLOBAL isr%1] ; %1 accesses the first parameter.
isr%1:
cli
push byte 0
push byte %1
push byte %1
jmp isr_common_stub
%endmacro
@ -102,12 +81,8 @@ ISR_NOERRCODE 29
ISR_NOERRCODE 30
ISR_NOERRCODE 31
[EXTERN isr_handler]
; This is our common ISR stub. It saves the processor state, sets
; up for kernel mode segments, calls the C-level fault handler,
; and finally restores the stack frame.
isr_common_stub:
pusha ; Pushes edi,esi,ebp,esp,ebx,edx,ecx,eax
@ -133,54 +108,12 @@ isr_common_stub:
sti
iret ; pops 5 things at once: CS, EIP, EFLAGS, SS, and ESP
global _start:function (_start.end - _start)
_start:
; The bootloader has loaded us into 32-bit protected mode on a x86
; machine. Interrupts are disabled. Paging is disabled. The processor
; state is as defined in the multiboot standard. The kernel has full
; control of the CPU. The kernel can only make use of hardware features
; and any code it provides as part of itself. There's no printf
; function, unless the kernel provides its own <stdio.h> header and a
; printf implementation. There are no security restrictions, no
; safeguards, no debugging mechanisms, only what the kernel provides
; itself. It has absolute and complete power over the
; machine.
; To set up a stack, we set the esp register to point to the top of our
; stack (as it grows downwards on x86 systems). This is necessarily done
; in assembly as languages such as C cannot function without a stack.
mov esp, stack_top
; This is a good place to initialize crucial processor state before the
; high-level kernel is entered. It's best to minimize the early
; environment where crucial features are offline. Note that the
; processor is not fully initialized yet: Features such as floating
; point instructions and instruction set extensions are not initialized
; yet. The GDT should be loaded here. Paging should be enabled here.
; C++ features such as global constructors and exceptions will require
; runtime support to work as well.
; Enter the high-level kernel. The ABI requires the stack is 16-byte
; aligned at the time of the call instruction (which afterwards pushes
; the return pointer of size 4 bytes). The stack was originally 16-byte
; aligned above and we've since pushed a multiple of 16 bytes to the
; stack since (pushed 0 bytes so far) and the alignment is thus
; preserved and the call is well defined.
; note, that if you are building on Windows, C functions may have "_" prefix in assembly: _kernel_main
extern kernel_main
extern kernel_main
call kernel_main
; If the system has nothing more to do, put the computer into an
; infinite loop. To do that:
; 1) Disable interrupts with cli (clear interrupt enable in eflags).
; They are already disabled by the bootloader, so this is not needed.
; Mind that you might later enable interrupts and return from
; kernel_main (which is sort of nonsensical to do).
; 2) Wait for the next interrupt to arrive with hlt (halt instruction).
; Since they are disabled, this will lock up the computer.
; 3) Jump to the hlt instruction if it ever wakes up due to a
; non-maskable interrupt occurring or due to system management mode.
cli
.hang: hlt

5
src/gdt.c
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@ -1,4 +1,5 @@
#include "gdt.h"
#include "print.h"
extern void reloadSegments();
@ -11,6 +12,10 @@ void encodeGDT(uint8_t* gdtEntry, struct GDT source) {
// Size: 1 (32 bit protected mode)
gdtEntry[6] = 0xC0;
}
else if (source.limit == 0) {
// Don't set any granularity for null entry
gdtEntry[6] = 0;
}
else {
// Granularity: 0 (1 byte segments)
// Size: 1

3
src/kernel.c
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@ -15,7 +15,6 @@ void kernel_main(void) {
initializeIDT();
printToMonitor("Hello\n");
printIntToMonitor(10, 10);
asm ("int $0x3");
asm ("int $0x4");
asm("int $0x01");
}