Linux – ls -l /proc/self | increamental PID

First, you can not convert the addresses to have just 8 digits. Memory addresses can and will have much larger values than could be represented with just 8 digits.

The reason why memory addresses are represented in /proc/pid/maps as they are is on the line 283 in fs/proc/task_mmu.c (or task_nommu.c) in a recent kernel source tree:

283         seq_printf(m, "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu ",
284                         start,
285                         end,
286                         flags & VM_READ ? 'r' : '-',
287                         flags & VM_WRITE ? 'w' : '-',
288                         flags & VM_EXEC ? 'x' : '-',
289                         flags & VM_MAYSHARE ? 's' : 'p',
290                         pgoff,
291                         MAJOR(dev), MINOR(dev), ino);

What this boils down to is that in any memory address which has a hex string representation shorter than 8 digits, will get padded with leading zeros. Any value larger than that will be represented as it is, not truncated to 8 digits. That's just the way how printk()'s printf-style formatting works.

Now what to make out of all this? Probably you should take a minute to think about why would you want to truncate memory addresses to 8 digits. What do you think is the benefit of doing so?

Check the kernel documentation for information about files in /proc.

There is one such file per process because not all processes see the same mount points. Chroot is a traditional Unix feature that makes it possible to restrict processes to a subtree of the filesystem tree. A chrooted process would not see mount points outside its root. Linux takes this further with namespaces: a process can compose its own view of the filesystem by grafting subtrees around.

For more information on mount namespaces, see per process private file system mount points and Michael Kerrisk's articles on namespaces on LWN.