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#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/uio.h>
#include <sys/wait.h>
#include <stdbool.h>
#include <stdio.h>
// ref: https://git.suckless.org/sinit/file/sinit.c.html
static void panic(const char* message)
{
// Attempt to spew to kernel log
int kmfd = open("/dev/kmsg", O_WRONLY | O_CLOEXEC);
int fd = (kmfd >= 0) ? kmfd : 2;
struct iovec msgvec[] = {
#define STRVEC(str) { .iov_base = (void*)(str), .iov_len = __builtin_strlen(str) }
STRVEC("rlinit: "),
STRVEC(message),
STRVEC("\n")
#undef STRVEC
};
writev(fd, msgvec, sizeof(msgvec) / sizeof(*msgvec));
if (kmfd >= 0) {
close(kmfd);
}
_exit(1); // Triggers a kernel panic since we're PID 1
}
static bool mkdir_if_missing(const char* path, mode_t mode)
{
return mkdir(path, mode) == 0 || errno == EEXIST;
}
int main(void)
{
if (getpid() != 1) {
panic("PID is not 1. Aborting.");
}
// Set up filesystem in descending priority
//
// @@ include errno in error messages
if (!mkdir_if_missing("/dev", 0755)) {
panic("Failed to create /dev");
}
if (mount("devtmpfs", "/dev", "devtmpfs", MS_NOSUID, 0) < 0) {
panic("Failed to mount /dev");
}
if (!mkdir_if_missing("/proc", 0555)) {
panic("Failed to create /proc");
}
if (mount("proc", "/proc", "proc", MS_NOSUID | MS_NOEXEC | MS_NODEV, 0) < 0) {
panic("Failed to mount /proc");
}
if (!mkdir_if_missing("/sys", 0555)) {
panic("Failed to create /sys");
}
if (mount("sysfs", "/sys", "sysfs", MS_NOSUID | MS_NOEXEC | MS_NODEV, 0) < 0) {
panic("Failed to mount /sys");
}
if (!mkdir_if_missing("/tmp", 0777)) {
panic("Failed to create /tmp");
}
chmod("/tmp", 01777);
// Test write to kernel log
{
int kmfd = open("/dev/kmsg", O_WRONLY | O_CLOEXEC);
if (kmfd >= 0) {
const char* hello = "<6>Rushmore Linux - Nothing is beyond our reach.\n";
write(kmfd, hello, __builtin_strlen(hello));
close(kmfd);
}
}
pid_t child = fork();
switch(child) {
case 0: {
char* const argv[] = { "/rltest", 0 };
execv(argv[0], argv);
panic("execvp failed");
} break;
case -1: {
panic("Failed to fork()");
} break;
}
// @@ reap child processes
for (;;) pause();
}
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