linux/arch/mn10300
Pavel Emelyanov a8fc927780 sk-filter: Add ability to get socket filter program (v2)
The SO_ATTACH_FILTER option is set only. I propose to add the get
ability by using SO_ATTACH_FILTER in getsockopt. To be less
irritating to eyes the SO_GET_FILTER alias to it is declared. This
ability is required by checkpoint-restore project to be able to
save full state of a socket.

There are two issues with getting filter back.

First, kernel modifies the sock_filter->code on filter load, thus in
order to return the filter element back to user we have to decode it
into user-visible constants. Fortunately the modification in question
is interconvertible.

Second, the BPF_S_ALU_DIV_K code modifies the command argument k to
speed up the run-time division by doing kernel_k = reciprocal(user_k).
Bad news is that different user_k may result in same kernel_k, so we
can't get the original user_k back. Good news is that we don't have
to do it. What we need to is calculate a user2_k so, that

  reciprocal(user2_k) == reciprocal(user_k) == kernel_k

i.e. if it's re-loaded back the compiled again value will be exactly
the same as it was. That said, the user2_k can be calculated like this

  user2_k = reciprocal(kernel_k)

with an exception, that if kernel_k == 0, then user2_k == 1.

The optlen argument is treated like this -- when zero, kernel returns
the amount of sock_fprog elements in filter, otherwise it should be
large enough for the sock_fprog array.

changes since v1:
* Declared SO_GET_FILTER in all arch headers
* Added decode of vlan-tag codes

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2012-11-01 11:17:15 -04:00
..
boot MN10300: And Panasonic AM34 subarch and implement SMP 2010-10-27 17:28:55 +01:00
configs cgroup: remove the ns_cgroup 2011-05-26 17:12:34 -07:00
include sk-filter: Add ability to get socket filter program (v2) 2012-11-01 11:17:15 -04:00
kernel Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal 2012-10-12 10:49:08 +09:00
lib Disintegrate asm/system.h for MN10300 2012-03-28 18:30:02 +01:00
mm mn10300: mm/dma-alloc.c needs <linux/export.h> 2012-07-11 16:04:42 -07:00
oprofile MN10300: Kill MN10300's own profiling Kconfig 2009-04-09 10:53:16 -07:00
proc-mn2ws0050 Disintegrate asm/system.h for MN10300 2012-03-28 18:30:02 +01:00
proc-mn103e010 MN10300: Create general kernel debugger cache flushing 2011-03-18 16:54:30 +00:00
unit-asb2303 mn10300: move setup_jiffies_interrupt() to cevt-mn10300.c 2012-07-11 16:04:41 -07:00
unit-asb2305 mn10300: move setup_jiffies_interrupt() to cevt-mn10300.c 2012-07-11 16:04:41 -07:00
unit-asb2364 mn10300: move setup_jiffies_interrupt() to cevt-mn10300.c 2012-07-11 16:04:41 -07:00
Kconfig Merge branch 'modules-next' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux 2012-10-14 13:39:34 -07:00
Kconfig.debug MN10300: Deprecate gdbstub 2011-03-18 16:54:32 +00:00
Makefile mn10300: only add -mmem-funcs to KBUILD_CFLAGS if gcc supports it 2012-10-06 03:04:36 +09:00