/proc/$PID/environ contains the environment as it was when the proc was started. To get the current environment, we need to inspect its memory to find out how it has changed. POSIX defines a char **__environ symbol that we will need to find. Unfortunately, inspecting the memory of another process is not typically permitted, even if the process is owned by the same user (see /etc/sysctl.d/10-ptrace.conf for details). So we might want to print the current environment if we can (e.g. with process_vm_readv or ptrace), and print a warning and the contents of /proc/$PID/environ if we can't. We should be able to do this for both live processes and core files.

Open question: If we can't find __environ, and we don't have access to /proc (e.g. a coredump without systemd-coredump metadata, should we try to find the environment from the initial stack layout, which places argc, then argv pointers, then envp pointers?