Given the following test program:

#include <sys/auxv.h>
#include <stdio.h>

int main() {
    unsigned long *x = (void*)getauxval(AT_RANDOM);
    printf("*getauxval(AT_RANDOM) %lx\n", *x);
}

shadow currently produces non-deterministic results:

$ shadow-exec ./a.out 
*getauxval(AT_RANDOM) 280741edbe5ef200
$ shadow-exec ./a.out 
*getauxval(AT_RANDOM) f2cf2d8a17f3400c

i.e. this is initialized with some random value before shadow gets control. Maybe by the dynamic linker/loader? Or maybe even by the linux kernel itself?

I'm not aware of any real-world programs that use this value, though it would be a subtle source of nondeterminism to detect if and when we do bump into it. (I was hoping maybe it was the source of nondeterminism in #2693 , but it doesn't appear to be)