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V86 returns to caller

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This commit is contained in:
Lucia Ceionia 2022-09-17 16:31:41 -05:00
parent 8bfcd4fd19
commit 1545a9a790
5 changed files with 8 additions and 6 deletions
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1
Makefile
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@ -9,7 +9,6 @@ CFLAGS = -target "i686-elf" -m32 -ffreestanding -march=pentium-m -fno-stack-prot
all: $(objects)
nasm boot.nasm -o boot.bin
# not sure why but if interrupt.c has any optimization everything just breaks immediately
gcc -Tlink.ld -m32 -ffreestanding -nostartfiles -nostdlib -o kernel.bin\
$(objects)
dd bs=256 count=1 conv=notrunc if=boot.bin of=virtdisk.bin

5
handler.nasm
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@ -20,9 +20,8 @@ and eax, 1 << 17 ; VM flag
test eax, eax
pop eax
jnz gpf_handler_v86
mov word [0xb8000], 0x0f00 | 'G'
mov word [0xb8002], 0x0f00 | 'P'
mov word [0xb8004], 0x0f00 | 'F'
mov dword [0xb8000], 0x0f000f00 | 'G' | 'P' << 16
mov dword [0xb8004], 0x0f000f00 | 'F' | '!' << 16
.hlt:
hlt
jmp .hlt

3
interrupt.c
View File

@ -128,6 +128,7 @@ void gpf_handler_v86(struct interrupt_frame *frame, unsigned long error_code) {
// vga += (sizeof(uint8_t)*2)*2;
//}
vga = (char*)0xb8000 + (160*3);
uint32_t *tss_esp0 = (uint32_t*)0x20004;
for(;;) {
switch (ip[0]) {
case 0x66: // O32
@ -176,7 +177,7 @@ void gpf_handler_v86(struct interrupt_frame *frame, unsigned long error_code) {
vga[0] = 'I'; vga[2]++; if (vga[2] < '0') vga[2] = '0';
switch (ip[1]) {
case 0x30:
asm ("jmp jmp_usermode_test");
asm ("mov %%eax, %%esp\nret"::"a"(*tss_esp0));
for(;;);
case 0x3:
kbd_wait();

4
kernel.c
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@ -52,8 +52,10 @@ void print_cr4() {
printDword(reg, 0xB8000 + (160*5) + 50 + 8*4 + 4);
}
__attribute((__no_caller_saved_registers__))
extern void enter_v86(uint32_t ss, uint32_t esp, uint32_t cs, uint32_t eip);
extern void v86Code();
__attribute((__no_caller_saved_registers__))
extern void jmp_usermode_test();
/*
@ -107,6 +109,6 @@ void start() {
print_cr4();
FARPTR v86_entry = i386LinearToFp(v86Code);
enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry));
//jmp_usermode_test();
jmp_usermode_test();
}

1
v86.nasm
View File

@ -71,6 +71,7 @@ jmp $
global enter_v86
enter_v86:
mov ebp, esp ; save stack pointer
mov dword [0x20004], ebp ; tss ESP0
push dword [ebp+4] ; ss
push dword [ebp+8] ; esp
pushfd ; eflags