rpi firmware load time

gistfile1.txt

root@raspberrypi:~# gcc uptime.c -o uptime && ./uptime
uptime.c: In function ‘main’:
uptime.c:11:11: warning: comparison between pointer and integer
  if (addr == -1) {
           ^~
305.825899
4593.07 14749.79
root@raspberrypi:~# cat uptime.c

uptime.c

#include <stdint.h>
#include <sys/mman.h>
#include <stdio.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

int main(int argc, char **argv) {
        int fd = open("/dev/mem", O_RDONLY);
        void *addr = mmap(NULL, 16 * 1024 * 1024, PROT_READ, MAP_SHARED, fd, 0xfe000000);
        if (addr == -1) {
                perror("unable to mmap");
                return 1;
        }
        volatile uint32_t *st_clo = (volatile uint32_t*)(addr + 0x3004);
        uint32_t snapshot = *st_clo;
        printf("%3ld.%06ld\n", snapshot / 1000000, snapshot % 1000000);
        munmap(addr, 16 * 1024 * 1024);
        close(fd);
        fd = open("/proc/uptime", O_RDONLY);
        char buffer[1024];
        int size = read(fd, buffer, 1024);
        write(0, buffer, size);
        close(fd);
        return 0;
}

moved to https://github.com/librerpi/rpi-tools/blob/97c895e9977ae767538bf1c877fe32ec90df05c6/boottime.c

can this program be adapted for rpi3?

just change the peripheral base addr from 0xfe to 0x3f