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Fixed & Improved Makefile, Made V86 GPF handler not directly dereference

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a null pointer - due to optimization breaking.
This commit is contained in:
Lucia Ceionia 2022-09-16 15:50:58 -05:00
parent 880118e7b4
commit 192d4f04ed
7 changed files with 40 additions and 33 deletions
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23
Makefile
View File

@ -1,17 +1,20 @@
#TODO make the makefile use targets instead of this mess
all:
objects = entry.o kernel.o handler.o interrupt.o v86.o print.o
CFLAGS = -target "i686-elf" -m32 -ffreestanding -march=pentium-m -fno-stack-protector -nostdlib -c
%.o: %.nasm
nasm -f elf32 -o $@ $<
%.o: %.c
clang $(CFLAGS) -O2 $<
all: $(objects)
nasm boot.nasm -o boot.bin
nasm -f elf32 -o entry.o entry.nasm
nasm -f elf32 -o handler.o handler.nasm
nasm -f elf32 -o v86.o v86.nasm
clang -target "i686-elf" -ffreestanding -m32 -O2 -march=pentium-m -fno-stack-protector -nostdlib -c kernel.c
clang -target "i686-elf" -ffreestanding -m32 -O2 -mgeneral-regs-only -march=pentium-m -fno-stack-protector -nostdlib -c print.c
# not sure why but if interrupt.c has any optimization everything just breaks immediately
clang -target "i686-elf" -ffreestanding -m32 -mgeneral-regs-only -march=pentium-m -fno-stack-protector -nostdlib -c interrupt.c
#clang -target "i686-elf" -ffreestanding -m32 -mgeneral-regs-only -march=i386 -fno-stack-protector -nostdlib -c -o kernel.o kernel.c
gcc -Tlink.ld -m32 -ffreestanding -nostartfiles -nostdlib -o kernel.bin entry.o v86.o handler.o kernel.o print.o interrupt.o
gcc -Tlink.ld -m32 -ffreestanding -nostartfiles -nostdlib -o kernel.bin\
$(objects)
dd bs=256 count=1 conv=notrunc if=boot.bin of=virtdisk.bin
dd bs=512 seek=1 conv=notrunc if=kernel.bin of=virtdisk.bin
virtdisk:
dd bs=1M count=32 if=/dev/zero of=virtdisk.bin
echo -n -e '\x55\xaa' | dd bs=1 seek=510 conv=notrunc of=virtdisk.bin

3
entry.nasm
View File

@ -93,6 +93,9 @@ ret
extern tss_data
global ivt
ivt: dd 0x00000000
gdt_desc:
dw gdt_end - gdt
dd gdt

38
interrupt.c
View File

@ -66,18 +66,20 @@ void IRQ_clear_mask(char IRQline) {
}
char v86_if = 0;
extern uint16_t *ivt;
extern void real_test();
__attribute((__no_caller_saved_registers__))
extern void kbd_wait();
extern void jmp_usermode_test();
#define VALID_FLAGS 0xDFF
__attribute__ ((interrupt))
void gpf_handler_v86(struct interrupt_frame *frame, unsigned long error_code) {
asm volatile("mov %%ax,%%ds"::"a"(0x10));
uint8_t *ip;
uint16_t *stack, *ivt;
uint16_t *stack;
uint32_t *stack32;
char is_operand32 = 0, is_address32 = 0;
ip = (size_t)(((frame->cs << 4) + frame->eip) & 0xFFFFF);
ivt = (uint16_t*)0x0000;
ip = (uint8_t*)(size_t)(((frame->cs << 4) + frame->eip) & 0xFFFFF);
stack = FP_TO_LINEAR(frame->ss, frame->esp);
stack32 = (uint32_t*)stack;
@ -156,37 +158,28 @@ void gpf_handler_v86(struct interrupt_frame *frame, unsigned long error_code) {
goto done;
case 0xCD: // INT n
vga[0] = 'I'; vga[2]++; if (vga[2] < '0') vga[2] = '0';
asm volatile("nop\nnop");
switch (ip[1]) {
case 0x30: // Exit V86 Mode?
asm volatile("nop\nnop");
asm volatile("jmp jmp_usermode_test");
//__builtin_unreachable();
break;
//case 0x20: // ???
//case 0x21: // ???
case 0x3: // Debugger trap
case 0x30:
asm("jmp jmp_usermode_test");
for(;;);
case 0x3:
kbd_wait();
asm volatile("nop");
default:
stack -= 3;
stack = &stack[-3];
frame->esp = ((frame->esp & 0xffff) - 6) & 0xffff;
stack[0] = (uint16_t) (frame->eip + 2);
stack[1] = frame->cs;
stack[2] = (uint16_t) frame->eflags;
if (v86_if)
stack[2] |= EFLAG_IF;
else
stack[2] &= ~EFLAG_IF;
//if (v86_if)
// stack[2] |= EFLAG_IF;
//else
// stack[2] &= ~EFLAG_IF;
frame->cs = ivt[ip[1] * 2 + 1];
frame->eip = ivt[ip[1] * 2];
asm volatile("nop");
//frame->cs = 0;
//frame->eip = real_test;
goto done;
break;
}
goto done;
case 0xCF: // IRET
@ -206,7 +199,6 @@ void gpf_handler_v86(struct interrupt_frame *frame, unsigned long error_code) {
goto done;
default:
for(;;);
goto done;
}
}
done:

1
kernel.c
View File

@ -98,6 +98,7 @@ void start() {
if (!sse) return;
enable_sse();
// edit
setup_interrupts();
setup_tss();
print_flags();

4
print.c
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@ -1,20 +1,24 @@
#include "print.h"
__attribute((__always_inline__))
__attribute((__no_caller_saved_registers__))
char nibbleToHex(uint8_t n) {
return n > 9 ? (n - 10) + 'A' : n + '0';
}
__attribute((__always_inline__))
__attribute((__no_caller_saved_registers__))
void printByte(uint8_t v, uint16_t *buff) {
*(char *)&buff[0] = nibbleToHex((v >> 4) & 0xF);
*(char *)&buff[1] = nibbleToHex(v & 0xF);
}
__attribute((__always_inline__))
__attribute((__no_caller_saved_registers__))
void printWord(uint16_t v, uint16_t *buff) {
printByte(v >> 8, buff);
printByte(v, &buff[2]);
}
__attribute((__always_inline__))
__attribute((__no_caller_saved_registers__))
void printDword(uint32_t v, uint16_t *buff) {
printWord(v >> 16, buff);
printWord(v, &buff[4]);

3
print.h
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@ -1,6 +1,9 @@
#pragma once
#include <stdint.h>
__attribute((__no_caller_saved_registers__))
void printByte(uint8_t v, uint16_t *buff);
__attribute((__no_caller_saved_registers__))
void printWord(uint16_t v, uint16_t *buff);
__attribute((__no_caller_saved_registers__))
void printDword(uint32_t v, uint16_t *buff);

1
v86.nasm
View File

@ -54,6 +54,7 @@ inc byte [0]
;mov ax, 0x6666
;mov sp, ax
int 3
int 3
;jmp .loop
mov ax, 0x13
int 0x10