Do not use /proc/self/exe to allow running in chroot without /proc

[probonopd]

Running in a chroot, /proc may not be mounted:

Cannot open /proc/self/exe: No such file or directory
execv error: No such file or directory

An alternative on Linux to using either /proc/self/exe or argv[0] is using the information passed by the ELF interpreter, made available by glibc as such:

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

int main(int argc, char **argv)
{
    printf("%s\n", (char *)getauxval(AT_EXECFN));
    return(0);
}

Note that getauxval is a glibc extension, and to be robust you should check so that it doesn't return NULL (indicating that the ELF interpreter hasn't provided the AT_EXECFN parameter), but I don't think this is ever actually a problem on Linux.

Source: https://code.i-harness.com/en/q/f9d4a

[probonopd]

This returns a relative path, we need the absolute one. Can we combine it with readlink to get an absolute one?

[CherryDT]

Just ran into this one on a shared hosting. Would be great if it could work...