Just curious whether it is possible to specify a name for the non file-backed mmap region? Some thing like the [New VMA area] in the following example:
$ cat /proc/12345/maps ... 7fc062ef2000-7fc062f84000 r-xp 00000000 08:01 22688328 /usr/local/musl/lib/libc.so 7fc062f85000-7fc062f86000 r--p 00092000 08:01 22688328 /usr/local/musl/lib/libc.so 7fc062f86000-7fc062f87000 rw-p 00093000 08:01 22688328 /usr/local/musl/lib/libc.so 7fc062f87000-7fc062f8a000 rw-p 00000000 00:00 0 [New VMA area] 7fff6c384000-7fff6c3a5000 rw-p 00000000 00:00 0 [stack] 7fff6c3bd000-7fff6c3c0000 r--p 00000000 00:00 0 [vvar]
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Answer
The content of maps comes from the show_map_vma function in fs/proc/task_mmu.c. Looking at it, if you want a custom name for a non-file-backed mapping, it’d need to come from either vma->vm_ops->name or arch_vma_name. arch_vm_name is architecture-specific (as you’d expect from the name) and serves only to add a few hardcoded names for certain regions, so it’s not useful to you. That leaves vma->vm_ops->name as your only possibility, but when you call mmap with MAP_ANONYMOUS, vma_set_anonymous sets vma->vm_ops to NULL. Thus, strictly what you asked for is impossible without custom kernel code.
However, it may still be possible to do what you want. If you actually just want the memory to not be backed by disk, you can create an FD with the memfd_create syscall or a file in a non-disk-backed filesystem such as a tmpfs (e.g., /dev/shm, like shm_open uses). Either of these approaches will give you control over the filename that is used (e.g., /memfd:some_name (deleted) or /dev/shm/some_name).