linux-toradex.git/kernel/sys.c, branch v2.6.27-rc1

kexec jump

2008-07-26T19:00:04+00:00

This patch provides an enhancement to kexec/kdump.  It implements the
following features:

- Backup/restore memory used by the original kernel before/after
  kexec.

- Save/restore CPU state before/after kexec.

The features of this patch can be used as a general method to call program in
physical mode (paging turning off).  This can be used to call BIOS code under
Linux.

kexec-tools needs to be patched to support kexec jump. The patches and
the precompiled kexec can be download from the following URL:

       source: http://khibernation.sourceforge.net/download/release_v10/kexec-tools/kexec-tools-src_git_kh10.tar.bz2
       patches: http://khibernation.sourceforge.net/download/release_v10/kexec-tools/kexec-tools-patches_git_kh10.tar.bz2
       binary: http://khibernation.sourceforge.net/download/release_v10/kexec-tools/kexec_git_kh10

Usage example of calling some physical mode code and return:

1. Compile and install patched kernel with following options selected:

CONFIG_X86_32=y
CONFIG_KEXEC=y
CONFIG_PM=y
CONFIG_KEXEC_JUMP=y

2. Build patched kexec-tool or download the pre-built one.

3. Build some physical mode executable named such as "phy_mode"

4. Boot kernel compiled in step 1.

5. Load physical mode executable with /sbin/kexec. The shell command
   line can be as follow:

   /sbin/kexec --load-preserve-context --args-none phy_mode

6. Call physical mode executable with following shell command line:

   /sbin/kexec -e

Implementation point:

To support jumping without reserving memory.  One shadow backup page (source
page) is allocated for each page used by kexeced code image (destination
page).  When do kexec_load, the image of kexeced code is loaded into source
pages, and before executing, the destination pages and the source pages are
swapped, so the contents of destination pages are backupped.  Before jumping
to the kexeced code image and after jumping back to the original kernel, the
destination pages and the source pages are swapped too.

C ABI (calling convention) is used as communication protocol between
kernel and called code.

A flag named KEXEC_PRESERVE_CONTEXT for sys_kexec_load is added to
indicate that the loaded kernel image is used for jumping back.

Now, only the i386 architecture is supported.

Signed-off-by: Huang Ying 
Acked-by: Vivek Goyal 
Cc: "Eric W. Biederman" 
Cc: Pavel Machek 
Cc: Nigel Cunningham 
Cc: "Rafael J. Wysocki" 
Cc: Ingo Molnar 
Cc: Thomas Gleixner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

unexport uts_sem

2008-07-25T17:53:45+00:00

With the removal of the Solaris binary emulation the export of
uts_sem became unused.

Signed-off-by: Adrian Bunk 
Acked-by: David S. Miller 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

call_usermodehelper(): increase reliability

2008-07-25T17:53:28+00:00

Presently call_usermodehelper_setup() uses GFP_ATOMIC.  but it can return
NULL _very_ easily.

GFP_ATOMIC is needed only when we can't sleep.  and, GFP_KERNEL is robust
and better.

thus, I add gfp_mask argument to call_usermodehelper_setup().

So, its callers pass the gfp_t as below:

call_usermodehelper() and call_usermodehelper_keys():
	depend on 'wait' argument.
call_usermodehelper_pipe():
	always GFP_KERNEL because always run under process context.
orderly_poweroff():
	pass to GFP_ATOMIC because may run under interrupt context.

Signed-off-by: KOSAKI Motohiro 
Cc: "Paul Menage" 
Reviewed-by: Li Zefan 
Acked-by: Jeremy Fitzhardinge 
Cc: Rusty Russell 
Cc: Andi Kleen 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

sys_prctl(): fix return of uninitialized value

2008-05-24T16:56:13+00:00

If none of the switch cases match, the PR_SET_PDEATHSIG and
PR_SET_DUMPABLE cases of the switch statement will never write to local
variable `error'.

Signed-off-by: Shi Weihua 
Cc: Andrew G. Morgan 
Acked-by: "Serge E. Hallyn" 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pids: sys_getpgid: fix unsafe *pid usage, s/tasklist/rcu/

2008-04-30T15:29:49+00:00

1. sys_getpgid() needs rcu_read_lock() to derive the pgrp _nr, even if
   the task is current, otherwise we can race with another thread which
   does sys_setpgid().

2. Use rcu_read_lock() instead of tasklist_lock when pid != 0, make sure
   that we don't use the NULL pid if the task exits right after successful
   find_task_by_vpid().

Signed-off-by: Oleg Nesterov 
Cc: Roland McGrath 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pids: sys_getsid: fix unsafe *pid usage, fix possible 0 instead of -ESRCH

2008-04-30T15:29:49+00:00

1. sys_getsid() needs rcu_read_lock() to derive the session _nr, even if
   the task is current, otherwise we can race with another thread which
   does sys_setsid().

2. The task can exit between find_task_by_vpid() and task_session_vnr(),
   in that unlikely case sys_getsid() returns 0 instead of -ESRCH.

Signed-off-by: Oleg Nesterov 
Cc: Roland McGrath 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

pids: sys_setpgid: use change_pid() helper

2008-04-30T15:29:49+00:00

Use change_pid() instead of detach_pid() + attach_pid() in sys_setpgid().

This way task_pgrp() is not NULL in between.

Signed-off-by: Oleg Nesterov 
Cc:  "Eric W. Biederman" 
Cc: Pavel Emelyanov 
Cc: Roland McGrath 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

k_getrusage: don't take rcu_read_lock()

2008-04-30T15:29:34+00:00

Just a trivial example, more to come.

k_getrusage() holds rcu_read_lock() because it was previously required by
lock_task_sighand().  Unneeded now.

Signed-off-by: Oleg Nesterov 
Cc: "Eric W. Biederman" 
Cc: "Paul E. McKenney" 
Cc: Roland McGrath 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

add RUSAGE_THREAD

2008-04-29T15:05:59+00:00

Add the RUSAGE_THREAD option for the getrusage system call.  This is
essentially Roland's patch from http://lkml.org/lkml/2008/1/18/589, but the
line about RUSAGE_LWP line has been removed, as suggested by Ulrich and
Christoph.

Signed-off-by: Roland McGrath 
Signed-off-by: Sripathi Kodi 
Cc: Ingo Molnar 
Cc: Michael Kerrisk 
Cc: Ulrich Drepper 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

capabilities: implement per-process securebits

2008-04-28T15:58:26+00:00

Filesystem capability support makes it possible to do away with (set)uid-0
based privilege and use capabilities instead.  That is, with filesystem
support for capabilities but without this present patch, it is (conceptually)
possible to manage a system with capabilities alone and never need to obtain
privilege via (set)uid-0.

Of course, conceptually isn't quite the same as currently possible since few
user applications, certainly not enough to run a viable system, are currently
prepared to leverage capabilities to exercise privilege.  Further, many
applications exist that may never get upgraded in this way, and the kernel
will continue to want to support their setuid-0 base privilege needs.

Where pure-capability applications evolve and replace setuid-0 binaries, it is
desirable that there be a mechanisms by which they can contain their
privilege.  In addition to leveraging the per-process bounding and inheritable
sets, this should include suppressing the privilege of the uid-0 superuser
from the process' tree of children.

The feature added by this patch can be leveraged to suppress the privilege
associated with (set)uid-0.  This suppression requires CAP_SETPCAP to
initiate, and only immediately affects the 'current' process (it is inherited
through fork()/exec()).  This reimplementation differs significantly from the
historical support for securebits which was system-wide, unwieldy and which
has ultimately withered to a dead relic in the source of the modern kernel.

With this patch applied a process, that is capable(CAP_SETPCAP), can now drop
all legacy privilege (through uid=0) for itself and all subsequently
fork()'d/exec()'d children with:

  prctl(PR_SET_SECUREBITS, 0x2f);

This patch represents a no-op unless CONFIG_SECURITY_FILE_CAPABILITIES is
enabled at configure time.

[akpm@linux-foundation.org: fix uninitialised var warning]
[serue@us.ibm.com: capabilities: use cap_task_prctl when !CONFIG_SECURITY]
Signed-off-by: Andrew G. Morgan 
Acked-by: Serge Hallyn 
Reviewed-by: James Morris 
Cc: Stephen Smalley 
Cc: Paul Moore 
Signed-off-by: Serge E. Hallyn 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds