This patch makes /proc/net per network namespace.  It modifies the global
variables proc_net and proc_net_stat to be per network namespace.
The proc_net file helpers are modified to take a network namespace argument,
and all of their callers are fixed to pass &init_net for that argument.
This ensures that all of the /proc/net files are only visible and
usable in the initial network namespace until the code behind them
has been updated to be handle multiple network namespaces.

Making /proc/net per namespace is necessary as at least some files
in /proc/net depend upon the set of network devices which is per
network namespace, and even more files in /proc/net have contents
that are relevant to a single network namespace.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Without attached patch against current -git I get following with
!PROC_SYSCTL (with EMBEDDED and PROC_FS set):

    CC      init/version.o
    LD      init/built-in.o
    LD      vmlinux
  fs/built-in.o: In function `do_proc_sys_lookup':
  proc_sysctl.c:(.text+0x26583): undefined reference to `sysctl_head_next'
  fs/built-in.o: In function `proc_sys_revalidate':
  proc_sysctl.c:(.text+0x265bb): undefined reference to `sysctl_head_finish'
  fs/built-in.o: In function `proc_sys_readdir':
  proc_sysctl.c:(.text+0x26720): undefined reference to `sysctl_head_next'
  proc_sysctl.c:(.text+0x267d8): undefined reference to `sysctl_head_finish'
  proc_sysctl.c:(.text+0x268e7): undefined reference to `sysctl_head_next'
  proc_sysctl.c:(.text+0x26910): undefined reference to `sysctl_head_finish'
  fs/built-in.o: In function `proc_sys_write':
  proc_sysctl.c:(.text+0x2695d): undefined reference to `sysctl_perm'
  proc_sysctl.c:(.text+0x2699c): undefined reference to `sysctl_head_finish'
  fs/built-in.o: In function `proc_sys_read':
  proc_sysctl.c:(.text+0x269e9): undefined reference to `sysctl_perm'
  proc_sysctl.c:(.text+0x26a25): undefined reference to `sysctl_head_finish'
  fs/built-in.o: In function `proc_sys_permission':
  proc_sysctl.c:(.text+0x26ad1): undefined reference to `sysctl_perm'
  proc_sysctl.c:(.text+0x26adb): undefined reference to `sysctl_head_finish'
  fs/built-in.o: In function `proc_sys_lookup':
  proc_sysctl.c:(.text+0x26b39): undefined reference to `sysctl_head_finish'
  make: *** [vmlinux] Virhe 1

All those functions are in fs/proc/proc_sysctl.c, which has no CONFIG_
#define's in it, so the patch makes the compilation of that file to depend
on CONFIG_PROC_SYSCTL (the simplest choice).

Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

With this change the sysctl inodes can be cached and nothing needs to be done
when removing a sysctl table.

For a cost of 2K code we will save about 4K of static tables (when we remove
de from ctl_table) and 70K in proc_dir_entries that we will not allocate, or
about half that on a 32bit arch.

The speed feels about the same, even though we can now cache the sysctl
dentries :(

We get the core advantage that we don't need to have a 1 to 1 mapping between
ctl table entries and proc files.  Making it possible to have /proc/sys vary
depending on the namespace you are in.  The currently merged namespaces don't
have an issue here but the network namespace under /proc/sys/net needs to have
different directories depending on which network adapters are visible.  By
simply being a cache different directories being visible depending on who you
are is trivial to implement.

[akpm@osdl.org: fix uninitialised var]
[akpm@osdl.org: fix ARM build]
[bunk@stusta.de: make things static]
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Attempts to read() from the non-existent dmesg buffer will return zero and
userspace tends to get stuck in a busyloop.

So just remove /dev/kmsg altogether if CONFIG_PRINTK=n.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

From: "Vivek Goyal" <vgoyal@in.ibm.com>

o Support for /proc/vmcore interface. This interface exports elf core image
  either in ELF32 or ELF64 format, depending on the format in which elf headers
  have been stored by crashed kernel.
o Added support for CONFIG_VMCORE config option.
o Removed the dependency on /proc/kcore.

From: "Eric W. Biederman" <ebiederm@xmission.com>

This patch has been refactored to more closely match the prevailing style in
the affected files.  And to clearly indicate the dependency between
/proc/kcore and proc/vmcore.c

From: Hariprasad Nellitheertha <hari@in.ibm.com>

This patch contains the code that provides an ELF format interface to the
previous kernel's memory post kexec reboot.

Signed off by Hariprasad Nellitheertha <hari@in.ibm.com>
Signed-off-by: Eric Biederman <ebiederm@xmission.com>
Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!