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#include <errno.h>
#include <fcntl.h>
// #include <linux/fb.h>
#include <stdarg.h>
#include <string.h>
#include <stdio.h>
#include <sys/uio.h>
#include <unistd.h>
static const char* tmp_fmt(const char* fmt, ...)
{
static char msg[1024] = { 0 };
va_list va; va_start(va, fmt);
vsnprintf(msg, sizeof(msg), fmt, va);
va_end(va);
return msg;
}
static void spew(const char* message)
{
// Kernel log is available after init
int kmfd = open("/dev/kmsg", O_WRONLY | O_CLOEXEC);
struct iovec msgvec[] = {
#define STRVEC(str) { .iov_base = (void*)(str), .iov_len = __builtin_strlen(str) }
STRVEC("rlwsd: "),
STRVEC(message),
STRVEC("\n")
#undef STRVEC
};
writev(kmfd, msgvec, sizeof(msgvec) / sizeof(*msgvec));
close(kmfd);
}
static void panic(const char* message)
{
spew(message);
_exit(1); // Triggers a kernel panic since we're PID 1
}
int main(void)
{
int fd = open("/dev/fb0", O_RDWR | O_CLOEXEC);
if (fd < 0) {
panic(tmp_fmt("Failed to open /dev/fb0: %s", strerror(errno)));
}
const char* msg = "[rlwsd] HELLO!\n";
write(1, msg, __builtin_strlen(msg));
for (;;)
{
pause();
}
}
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