Почему в ioports и iomem одни нули?

Question

[DVoropaev]

/proc$ cat /proc/ioports 
0000-0000 : PCI Bus 0000:00
  0000-0000 : dma1
  0000-0000 : pic1
  0000-0000 : timer0
  0000-0000 : timer1
  0000-0000 : keyboard
  0000-0000 : PNP0C09:00
    0000-0000 : EC data
  0000-0000 : keyboard
...
...
...
/proc$ cat /proc/iomem 
00000000-00000000 : reserved
00000000-00000000 : System RAM
00000000-00000000 : reserved
00000000-00000000 : PCI Bus 0000:00
00000000-00000000 : Video ROM
00000000-00000000 : Adapter ROM
00000000-00000000 : PCI Bus 0000:00
00000000-00000000 : PCI Bus 0000:00
00000000-00000000 : PCI Bus 0000:00
00000000-00000000 : PCI Bus 0000:00
00000000-00000000 : reserved
  00000000-00000000 : PCI Bus 0000:00
...
...
...

Answer 1

[jcmvbkbc]

Потому что вот такой код в kernel/resource.c занимается приготовлением этих значений:

if (file_ns_capable(m->file, &init_user_ns, CAP_SYS_ADMIN)) {
                start = r->start;
                end = r->end;
        } else {
                start = end = 0;
        }

Т.е. чтобы получить не нули нужно иметь CAP_SYS_ADMIN.
Это изменение появилось в ядре с версии 4.6:

commit 51d7b120418e99d6b3bf8df9eb3cc31e8171dee4
Author: Linus Torvalds <[e-mail]>
Date:   Thu Apr 14 12:05:37 2016 -0700

    /proc/iomem: only expose physical resource addresses to privileged users

    In commit c4004b02f8e5b ("x86: remove the kernel code/data/bss resources
    from /proc/iomem") I was hoping to remove the phyiscal kernel address
    data from /proc/iomem entirely, but that had to be reverted because some
    system programs actually use it.

    This limits all the detailed resource information to properly
    credentialed users instead.

    Signed-off-by: Linus Torvalds <[e-mail]>