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#include <string.h>
#include <paging.h>
#include <dev/v86.h>
#define EFLAGS_VM 0x20000
#define V86_VALID_FLAGS 0xDFF
// ---- Ugly big static data
STATIC_MUTEX(v86_mutex);
v86_regs_t v86_regs;
bool v86_if;
pagedir_t *v86_pagedir = 0;
void* v86_alloc_addr;
bool v86_retval;
thread_t *v86_caller_thread = 0;
thread_t *v86_thread = 0;
uint32_t v86_int_no;
pagedir_t *v86_prev_pagedir = 0;
// ---- Setup code
void v86_thread_main(void*);
void v86_ex_handler(registers_t *regs);
void v86_pf_handler(void*, registers_t *regs, void* addr);
void v86_asm_enter_v86(v86_regs_t*);
bool v86_begin_session() {
mutex_lock(&v86_mutex);
if (v86_pagedir == 0) {
v86_pagedir = create_pagedir(v86_pf_handler, 0);
if (v86_pagedir == 0) return false;
v86_prev_pagedir = get_current_pagedir();
switch_pagedir(v86_pagedir);
for (void* addr = (void*)V86_ALLOC_ADDR; addr < (void*)V86_STACK_TOP; addr += PAGE_SIZE) {
pd_map_page(addr, (uint32_t)addr / PAGE_SIZE, true);
}
for (void* addr = (void*)V86_BIOS_BEGIN; addr < (void*)V86_BIOS_END; addr += PAGE_SIZE) {
pd_map_page(addr, (uint32_t)addr / PAGE_SIZE, true);
}
pd_map_page(0, 0, true);
} else {
v86_prev_pagedir = get_current_pagedir();
switch_pagedir(v86_pagedir);
}
if (v86_thread == 0) {
v86_thread = new_thread(v86_thread_main, (void*)1);
if (v86_thread == 0) return false;
v86_thread->user_ex_handler = v86_ex_handler;
v86_retval = false;
start_thread(v86_thread);
while (!v86_retval) yield();
}
v86_alloc_addr = (void*)V86_ALLOC_ADDR;
memset(&v86_regs, 0, sizeof(v86_regs));
return true;
}
void v86_end_session() {
switch_pagedir(v86_prev_pagedir);
v86_prev_pagedir = 0;
v86_caller_thread = 0;
mutex_unlock(&v86_mutex);
}
void* v86_alloc(size_t size) {
void* addr = v86_alloc_addr;
v86_alloc_addr += size;
return addr;
}
bool v86_bios_int(uint8_t int_no) {
v86_caller_thread = current_thread;
v86_int_no = int_no;
int st = enter_critical(CL_NOSWITCH);
resume_on(v86_thread);
wait_on(current_thread);
exit_critical(st);
return v86_retval;
}
void v86_run_bios_int(uint32_t int_no) {
switch_pagedir(v86_pagedir);
uint16_t *ivt = (uint16_t*)0;
v86_regs.cs = ivt[2 * int_no + 1];
v86_regs.ip = ivt[2 * int_no];
v86_regs.ss = ((V86_STACK_TOP - 0x10000) >> 4);
v86_regs.sp = 0;
v86_if = true;
v86_asm_enter_v86(&v86_regs);
}
void v86_thread_main(void* z) {
enter_critical(CL_NOSWITCH);
if (z) v86_retval = true;
wait_on(current_thread);
v86_run_bios_int(v86_int_no);
}
void v86_exit_thread(bool status) {
v86_retval = status;
resume_on(v86_caller_thread);
v86_thread_main(0);
}
bool v86_gpf_handler(registers_t *regs) {
uint8_t* ip = (uint8_t*)V86_LIN_OF_SEG_OFF(regs->cs, regs->eip);
uint16_t *stack = (uint16_t*)V86_LIN_OF_SEG_OFF(regs->ss, (regs->esp & 0xFFFF));
uint32_t *stack32 = (uint32_t*)stack;
bool is_operand32 = false; // bool is_address32 = false;
while (true) {
switch (ip[0]) {
case 0x66: // O32
is_operand32 = true;
ip++; regs->eip = (uint16_t)(regs->eip + 1);
break;
case 0x67: // A32
// is_address32 = true;
ip++; regs->eip = (uint16_t)(regs->eip + 1);
break;
case 0x9C: // PUSHF
if (is_operand32) {
regs->esp = ((regs->esp & 0xFFFF) - 4) & 0xFFFF;
stack32--;
*stack32 = regs->eflags & V86_VALID_FLAGS;
if (v86_if)
*stack32 |= EFLAGS_IF;
else
*stack32 &= ~EFLAGS_IF;
} else {
regs->esp = ((regs->esp & 0xFFFF) - 2) & 0xFFFF;
stack--;
*stack = regs->eflags;
if (v86_if)
*stack |= EFLAGS_IF;
else
*stack &= ~EFLAGS_IF;
}
regs->eip = (uint16_t)(regs->eip + 1);
return true;
case 0x9D: // POPF
if (is_operand32) {
regs->eflags = EFLAGS_IF | EFLAGS_VM | (stack32[0] & V86_VALID_FLAGS);
v86_if = (stack32[0] & EFLAGS_IF) != 0;
regs->esp = ((regs->esp & 0xFFFF) + 4) & 0xFFFF;
} else {
regs->eflags = EFLAGS_IF | EFLAGS_VM | stack[0];
v86_if = (stack[0] & EFLAGS_IF) != 0;
regs->esp = ((regs->esp & 0xFFFF) + 2) & 0xFFFF;
}
regs->eip = (uint16_t)(regs->eip + 1);
return true;
case 0xCF: // IRET
v86_regs.ax = (uint16_t)regs->eax;
v86_regs.bx = (uint16_t)regs->ebx;
v86_regs.cx = (uint16_t)regs->ecx;
v86_regs.dx = (uint16_t)regs->edx;
v86_regs.di = (uint16_t)regs->edi;
v86_regs.si = (uint16_t)regs->esi;
v86_exit_thread(true);
case 0xFA: // CLI
v86_if = false;
regs->eip = (uint16_t)(regs->eip + 1);
return true;
case 0xFB: // STI
v86_if = true;
regs->eip = (uint16_t)(regs->eip + 1);
return true;
default:
return false;
}
}
}
void v86_ex_handler(registers_t *regs) {
if (regs->int_no == EX_GENERAL_PROTECTION) {
if (!v86_gpf_handler(regs)) v86_exit_thread(false);
} else {
v86_exit_thread(false);
}
}
void v86_pf_handler(void* zero, registers_t *regs, void* addr) {
dbg_printf("Unexpected V86 PF at 0x%p\n", addr);
if (current_thread == v86_thread) {
v86_exit_thread(false);
} else {
PANIC("V86 memory access exception.");
}
}
/* vim: set ts=4 sw=4 tw=0 noet :*/
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