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/* needs to stay the first line */
asm(".code16gcc\njmp $0, $main");
/* space for additional code */
char WRITE_CHARACTER_TTY = 0x0E;
// Syscall found here http://www.ctyme.com/intr/rb-0106.htm
void putc(char c) {
short command = WRITE_CHARACTER_TTY << 8 | c;
// volatile because there is no output, so the function might get optimized
// away
// clang-format off
asm volatile(
"int $0x10;"
::"a"(command)
);
// clang-format on
}
void print(char const *const str) {
for (int i = 0; str[i] != '\0'; ++i) {
putc(str[i]);
}
}
// Syscall found here http://www.ctyme.com/intr/rb-1754.htm
char getc() {
char ret;
asm volatile(
".no_key:"
"xor %%eax, %%eax;"
"mov $0x0100, %%ax;" // check for keystroke:
"int $0x16;" // http://www.ctyme.com/intr/rb-1755.htm
"jz .no_key;" // wait for a key
".done:"
"xor %%eax, %%eax;"
"mov $0x1000, %%ax;" // get keystroke: http://www.ctyme.com/intr/rb-1754.htm
"int $0x16;"
"mov %%al, %%bl;" // temp store char in bl
"mov $0400, %%ax;" // clear keyboard buffer:
"int $0x16;" // http://www.ctyme.com/intr/rb-1759.htm
: "=b"(ret)
:
: "eax");
return ret;
}
void sleep(short ms) {
long ys = ms * 1000;
short cx = ys >> 16;
short dx = ys;
// http://www.ctyme.com/intr/rb-1525.htm : Int 15/AH=86h bios wait
char ah = 0x86;
char al = 0x00;
short command = ah << 8 | al;
asm volatile("int $0x15;" : : "a"(command), "cx"(cx), "dx"(dx));
}
void main(void) {
print("Hello!\n\r");
while (1) {
char buf[9];
for (unsigned char i = 0; i < 8; i++) {
char c = getc();
if (c == '\r') {
if (i == 0) { // empty entry
print("Reboot!\n\r");
sleep(250); // too see the reboot print out, even if short
asm volatile(
"cli;" // disable interrupts
"mov $0x0FE, %%al;" // tell the keyboard controller to...
"out %%al, $0x64;" // ...activate the CPU reset line
".halt:"
"hlt;" // some motherboards require this
"jmp .halt;" :: // and again, just to be sure
: "al");
return;
} else {
break;
}
}
buf[i] = c;
buf[i + 1] = 0;
putc('*');
}
while (1) {
if (getc() == '\r')
break;
}
print("\n\r");
print(buf);
print("\n\r");
}
}
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