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#include "compiler.h"
#include "config.h"
#include "sbi.h"
// Implemented in head.S. Here we need the symbol in order to pass the address
// of the function when starting secondary harts.
extern void _start(void);
/*
* Similar to the Linux kernel and what I did in https://git.mssola.com/os/fbos,
* harts will enter in a lottery when starting. See the README.md file for more
* details on this.
*/
atomic_t hart_lottery __attribute__((__section__(".sdata")));
atomic_t hart_failed_lottery __attribute__((__section__(".sdata")));
// Fake a delay so it's easier on the eyes.
#define SLEEP() \
for (int i = 0; i < 1000000000; i++) { \
}
/*
* Printing utilities.
*/
void printk(const char *const message);
void write(const char *const message, size_t n)
{
struct sbi_ret ret = sbi_ecall2(DBCN_EXT, DBCN_WRITE, n, (unsigned long)message);
if (ret.error != SBI_SUCCESS) {
for (;;) {
;
}
}
}
size_t strlen(const char *const message)
{
size_t i = 0;
for (; message[i] != '\0'; i++)
;
return i;
}
__attribute__((__noreturn__)) void die(const char *const message)
{
if (message) {
printk(message);
}
for (;;)
;
}
void print_digit(uint64_t digit)
{
char buffer[2];
if (digit > 9) {
die("We cannot print numbers with two or more digits :D\n");
}
buffer[0] = '0' + digit;
buffer[1] = '\0';
write(buffer, 2);
}
void printk(const char *const message)
{
size_t len = strlen(message);
if (!len) {
return;
}
write(message, len);
}
/*
* Printing/asserting the stats of the lottery.
*/
void assert_lottery(uint64_t participated, uint64_t failed)
{
if (hart_lottery.value != participated) {
die("Bad number for participating harts\n");
}
if (hart_failed_lottery.value != failed) {
die("Bad number for failed harts\n");
}
}
void print_lottery(void)
{
printk("How many harts have _participated_ in the lottery? ");
print_digit(hart_lottery.value);
write("\n", 1);
printk("How many harts have _failed_ in the lottery? ");
print_digit(hart_failed_lottery.value);
write("\n", 1);
}
// Called at the very end of the program. It will shutdown the machine.
void end(void)
{
printk("\nTHE END\n");
// SBI call to the SRST extension to gracefully shutdown the machine.
sbi_ecall2(SRST_EXT, SRST_RESET, SRST_SHUTDOWN, SRST_NO_REASON);
}
void start_kernel(uint64_t hart_id, uintptr_t opaque)
{
printk("Hello, world!\n");
/*
* Figure out the harts that are meant to be stopped for now.
*/
unsigned int other_harts[NR_CPUS - 1];
struct sbi_ret ret;
printk("Hart that won the lottery: ");
print_digit(hart_id);
write("\n", 1);
printk("Hart still asleep: ");
for (unsigned int i = 0, j = 0; i < NR_CPUS; i++) {
if (i != hart_id) {
print_digit(i);
if (j + 1 < NR_CPUS - 1) {
write(", ", 2);
}
other_harts[j++] = i;
}
}
write("\n", 1);
/*
* ASSERT: all harts in 'other_harts' are marked as stopped by HSM.
*/
for (unsigned int i = 0; i < NR_CPUS - 1; i++) {
ret = sbi_ecall1(HSM_EXT, HSM_HART_GET_STATUS, other_harts[i]);
if (ret.error != SBI_SUCCESS) {
die("HSM_HART_GET_STATUS: unexpected error from SBI\n");
}
if (ret.value != HSM_HART_STOPPED) {
die("HSM_HART_GET_STATUS: hart that was supposed to be stopped is not!\n");
}
}
// Initial state of the lottery.
print_lottery();
assert_lottery(1, 0);
write("\n", 1);
/*
* Wake up the first hart.
*/
printk("Waking up first secondary hart\n");
ret = sbi_ecall3(HSM_EXT, HSM_HART_START, other_harts[0], (uintptr_t)&_start, opaque);
if (ret.error != SBI_SUCCESS) {
die("HSM_HART_START: unexpected error from SBI\n");
}
SLEEP();
ret = sbi_ecall1(HSM_EXT, HSM_HART_GET_STATUS, other_harts[0]);
if (ret.error != SBI_SUCCESS) {
die("HSM_HART_GET_STATUS: unexpected error from SBI\n");
}
if (ret.value != HSM_HART_STARTED) {
die("HSM_HART_GET_STATUS: hart that was supposed to be started is not!\n");
}
// Another hart should have entered the lottery and failed.
print_lottery();
assert_lottery(2, 1);
write("\n", 1);
/*
* Now wake up the rest.
*/
printk("Waking up the rest\n");
for (unsigned int i = 1; i < NR_CPUS - 1; i++) {
ret = sbi_ecall3(HSM_EXT, HSM_HART_START, other_harts[i], (uintptr_t)&_start, opaque);
if (ret.error != SBI_SUCCESS) {
die("HSM_HART_START: unexpected error from SBI\n");
}
}
SLEEP();
// All awake, only one good.
print_lottery();
assert_lottery(NR_CPUS, NR_CPUS - 1);
write("\n", 1);
/*
* Kernels usually don't quit, but let's do it for the heck of it; head.S
* will handle it.
*/
printk("Goodbye, cruel world!\n");
SLEEP();
}
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