hulk inclusion
category: feature
bugzilla: 5507
CVE: NA

----------------------------------------

support livepatch without ftrace for x86_64

supported now:
        livepatch relocation when init_patch after load_module;
        instruction patched when enable;
	activeness function check;
	enforcing the patch stacking principle;

x86_64 use variable length instruction, so there's no need to consider
extra implementation for long jumps.
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>
Signed-off-by: NLi Bin <huawei.libin@huawei.com>
Tested-by: NYang ZuoTing <yangzuoting@huawei.com>
Tested-by: NCheng Jian <cj.chengjian@huawei.com>
Reviewed-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Nzhangyi (F) <yi.zhang@huawei.com>
Reviewed-By: NXie XiuQi <xiexiuqi@huawei.com>
Reviewed-By: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

[ Upstream commit 4ff96fb52c6964ad42e0a878be8f86a2e8052ddd ]

klp_module_coming() is called for every module appearing in the system.
It sets obj->mod to a patched module for klp_object obj. Unfortunately
it leaves it set even if an error happens later in the function and the
patched module is not allowed to be loaded.

klp_is_object_loaded() uses obj->mod variable and could currently give a
wrong return value. The bug is probably harmless as of now.
Signed-off-by: NMiroslav Benes <mbenes@suse.cz>
Reviewed-by: NPetr Mladek <pmladek@suse.com>
Acked-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: NPetr Mladek <pmladek@suse.com>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

[ Upstream commit 9f255b632bf12c4dd7fc31caee89aa991ef75176 ]

It's possible for livepatch and ftrace to be toggling a module's text
permissions at the same time, resulting in the following panic:

  BUG: unable to handle page fault for address: ffffffffc005b1d9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0003) - permissions violation
  PGD 3ea0c067 P4D 3ea0c067 PUD 3ea0e067 PMD 3cc13067 PTE 3b8a1061
  Oops: 0003 [#1] PREEMPT SMP PTI
  CPU: 1 PID: 453 Comm: insmod Tainted: G           O  K   5.2.0-rc1-a188339ca5 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-20181126_142135-anatol 04/01/2014
  RIP: 0010:apply_relocate_add+0xbe/0x14c
  Code: fa 0b 74 21 48 83 fa 18 74 38 48 83 fa 0a 75 40 eb 08 48 83 38 00 74 33 eb 53 83 38 00 75 4e 89 08 89 c8 eb 0a 83 38 00 75 43 <89> 08 48 63 c1 48 39 c8 74 2e eb 48 83 38 00 75 32 48 29 c1 89 08
  RSP: 0018:ffffb223c00dbb10 EFLAGS: 00010246
  RAX: ffffffffc005b1d9 RBX: 0000000000000000 RCX: ffffffff8b200060
  RDX: 000000000000000b RSI: 0000004b0000000b RDI: ffff96bdfcd33000
  RBP: ffffb223c00dbb38 R08: ffffffffc005d040 R09: ffffffffc005c1f0
  R10: ffff96bdfcd33c40 R11: ffff96bdfcd33b80 R12: 0000000000000018
  R13: ffffffffc005c1f0 R14: ffffffffc005e708 R15: ffffffff8b2fbc74
  FS:  00007f5f447beba8(0000) GS:ffff96bdff900000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: ffffffffc005b1d9 CR3: 000000003cedc002 CR4: 0000000000360ea0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  Call Trace:
   klp_init_object_loaded+0x10f/0x219
   ? preempt_latency_start+0x21/0x57
   klp_enable_patch+0x662/0x809
   ? virt_to_head_page+0x3a/0x3c
   ? kfree+0x8c/0x126
   patch_init+0x2ed/0x1000 [livepatch_test02]
   ? 0xffffffffc0060000
   do_one_initcall+0x9f/0x1c5
   ? kmem_cache_alloc_trace+0xc4/0xd4
   ? do_init_module+0x27/0x210
   do_init_module+0x5f/0x210
   load_module+0x1c41/0x2290
   ? fsnotify_path+0x3b/0x42
   ? strstarts+0x2b/0x2b
   ? kernel_read+0x58/0x65
   __do_sys_finit_module+0x9f/0xc3
   ? __do_sys_finit_module+0x9f/0xc3
   __x64_sys_finit_module+0x1a/0x1c
   do_syscall_64+0x52/0x61
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

The above panic occurs when loading two modules at the same time with
ftrace enabled, where at least one of the modules is a livepatch module:

CPU0					CPU1
klp_enable_patch()
  klp_init_object_loaded()
    module_disable_ro()
    					ftrace_module_enable()
					  ftrace_arch_code_modify_post_process()
				    	    set_all_modules_text_ro()
      klp_write_object_relocations()
        apply_relocate_add()
	  *patches read-only code* - BOOM

A similar race exists when toggling ftrace while loading a livepatch
module.

Fix it by ensuring that the livepatch and ftrace code patching
operations -- and their respective permissions changes -- are protected
by the text_mutex.

Link: http://lkml.kernel.org/r/ab43d56ab909469ac5d2520c5d944ad6d4abd476.1560474114.git.jpoimboe@redhat.comReported-by: NJohannes Erdfelt <johannes@erdfelt.com>
Fixes: 444d13ff ("modules: add ro_after_init support")
Acked-by: NJessica Yu <jeyu@kernel.org>
Reviewed-by: NPetr Mladek <pmladek@suse.com>
Reviewed-by: NMiroslav Benes <mbenes@suse.cz>
Signed-off-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: NSteven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

euler inclusion
category: bugfix
Bugzilla: 9287/5507
CVE: N/A

----------------------------------------

module_get/put should protected by STOP_MACHINE_CONSISTENCY

fix commit 49e30bb60ea ("livepatch/core: split livepatch consistency")
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>
Reviewed-by: NZhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

euler inclusion
category: bugfix
bugzilla: 8810
CVE: NA

-------------------------------------------------

In klp_try_disable_patch, the argument enable of klp_check_calltrace
s hould be 0, fix it.

Fixes: 2a9167a2 ("livepatch/core: fix cache consistency when disable
patch")
Signed-off-by: NLi Bin <huawei.libin@huawei.com>
Reviewed-by: NHanjun Guo <guohanjun@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

euler inclusion
category: feature
Bugzilla: 5507
CVE: N/A

----------------------------------------

In the previous version we forced the association between
livepatch wo_ftrace and stop_machine. This is unwise and
obviously confusing.

commit d83a7cb3 ("livepatch: change to a per-task
consistency model") introduce a PER-TASK consistency model.
It's a hybrid of kGraft and kpatch: it uses kGraft's per-task
consistency and syscall barrier switching combined with
kpatch's stack trace switching. There are also a number of
fallback options which make it quite flexible.

So we split livepatch consistency for without ftrace to two model:
[1] PER-TASK consistency model.
per-task consistency and syscall barrier switching combined with
kpatch's stack trace switching.

[2] STOP-MACHINE consistency model.
stop-machine consistency and kpatch's stack trace switching.
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>
Reviewed-by: NLi Bin <huawei.libin@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

euler inclusion
category: feature
Bugzilla: 5507
CVE: N/A

----------------------------------------

livepatch wo_ftrace and kprobe are in conflict, because kprobe
may modify the instructions anywhere in the function.

So it's dangerous to patched/unpatched an function when there are
some kprobes registed on it. Restrict these situation.

we should hold kprobe_mutex in klp_check_patch_kprobed, but it's
static and can't export, so protect klp_check_patch_probe in
stop_machine to avoid registing kprobes when patching.

we do nothing for (un)register kprobes on the (old) function
which has been patched. because there are sone engineers need this.
certainly, it will not lead to hangs, but not recommended.
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>
Reviewed-by: NLi Bin <huawei.libin@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

euler inclusion
category: bugfix
bugzilla: 5507
CVE: NA

-------------------------------------------------

Independent instruction cache and data cache are used on
the aarch64 cpu chip. so we must flush the instruction
cache when enable/disable patch.

we miss it when disable patch, so just fix it.
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>
Reviewed-by: NLi Bin <huawei.libin@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

euler inclusion
category: feature
Bugzilla: 5507
CVE: N/A

----------------------------------------

front-tools kpatch-build support load and unload hooks, but the
kernel does not fit this feature. just implement it.
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>
Reviewed-by: NLi Bin <huawei.libin@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

euler inclusion
category: feature
Bugzilla: 5507
CVE: N/A

----------------------------------------

we need to modify the first 4 instructions of a livepatch function to
complete the long jump if offset out of short-range. So it's important
that this function must have more than 4 instructions, so we checked it
when the livepatch module insmod.

In fact, this corner case is highly unlikely tooccur on arm64, but it's
still an effective and meaningful check to avoid crash by doing this.
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>
Reviewed-by: NLi Bin <huawei.libin@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

euler inclusion
category: feature
Bugzilla: 5507
CVE: N/A

----------------------------------------

support livepatch without ftrace for ARM64

supported now:
        livepatch relocation when init_patch after load_module;
        instruction patched when enable;
        activeness function check;
        enforcing the patch stacking principle;
        long jump (both livepatch relocation and insn patched)
        module plts request by livepatch-relocation
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>
Reviewed-by: NLi Bin <huawei.libin@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

euler inclusion
category: feature
Bugzilla: 5507
CVE: N/A

----------------------------------------

support for livepatch without ftrace mode

new config for WO_FTRACE
	CONFIG_LIVEPATCH_WO_FTRACE=y
	CONFIG_LIVEPATCH_STACK=y

Implements livepatch without ftrace by direct jump, we
directly modify the first few instructions(usually one,
but four for long jumps under ARM64) of the old function
as jump instructions by stop_machine, so it will jump to
the first address of the new function when livepatch enable

KERNEL/MODULE
call/bl A---------------old_A------------
                        | jump new_A----+--------|
                        |               |        |
                        |               |        |
                        -----------------        |
                                                 |
                                                 |
                                                 |
livepatch_module-------------                    |
|                           |                    |
|new_A <--------------------+--------------------|
|                           |
|                           |
|---------------------------|
| .plt                      |
| ......PLTS for livepatch  |
-----------------------------

something we need to consider under different architectures:

1. jump instruction
2. partial relocation in new function requires for livepatch.
3. long jumps may be required if the jump address exceeds the
   offset. both for livepatch relocation and livepatch enable.
Signed-off-by: NCheng Jian <cj.chengjian@huawei.com>
Reviewed-by: NLi Bin <huawei.libin@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

livepatch module author can pass module name/old function name with more
than the defined character limit. With obj->name length greater than
MODULE_NAME_LEN, the livepatch module gets loaded but waits forever on
the module specified by obj->name to be loaded. It also populates a /sys
directory with an untruncated object name.

In the case of funcs->old_name length greater then KSYM_NAME_LEN, it
would not match against any of the symbol table entries. Instead loop
through the symbol table comparing them against a nonexisting function,
which can be avoided.

The same issues apply, to misspelled/incorrect names. At least gatekeep
the modules with over the limit string length, by checking for their
length during livepatch module registration.

Cc: stable@vger.kernel.org
Signed-off-by: NKamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Acked-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

klp_send_signals() and klp_force_transition() do not acquire klp_mutex,
because it seemed to be superfluous. A potential race in
klp_send_signals() was harmless and there was nothing in
klp_force_transition() which needed to be synchronized. That changed
with the addition of klp_forced variable during the review process.

There is a small window now, when klp_complete_transition() does not see
klp_forced set to true while all tasks have been already transitioned to
the target state. module_put() is called and the module can be removed.

Acquire klp_mutex in sysfs callback to prevent it. Do the same for the
signal sending just to be sure. There is no real downside to that.

Fixes: c99a2be7 ("livepatch: force transition to finish")
Fixes: 43347d56 ("livepatch: send a fake signal to all blocking tasks")
Reported-by: NJason Baron <jbaron@akamai.com>
Signed-off-by: NMiroslav Benes <mbenes@suse.cz>
Reviewed-by: NPetr Mladek <pmladek@suse.com>
Acked-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

Immediate flag has been used to disable per-task consistency and patch
all tasks immediately. It could be useful if the patch doesn't change any
function or data semantics.

However, it causes problems on its own. The consistency problem is
currently broken with respect to immediate patches.

func            a
patches         1i
                2i
                3

When the patch 3 is applied, only 2i function is checked (by stack
checking facility). There might be a task sleeping in 1i though. Such
task is migrated to 3, because we do not check 1i in
klp_check_stack_func() at all.

Coming atomic replace feature would be easier to implement and more
reliable without immediate.

Thus, remove immediate feature completely and save us from the problems.

Note that force feature has the similar problem. However it is
considered as a last resort. If used, administrator should not apply any
new live patches and should plan for reboot into an updated kernel.

The architectures would now need to provide HAVE_RELIABLE_STACKTRACE to
fully support livepatch.
Signed-off-by: NMiroslav Benes <mbenes@suse.cz>
Acked-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

If a task sleeps in a set of patched functions uninterruptedly, it could
block the whole transition indefinitely.  Thus it may be useful to clear
its TIF_PATCH_PENDING to allow the process to finish.

Admin can do that now by writing to force sysfs attribute in livepatch
sysfs directory. TIF_PATCH_PENDING is then cleared for all tasks and the
transition can finish successfully.

Important note! Administrator should not use this feature without a
clearance from a patch distributor. It must be checked that by doing so
the consistency model guarantees are not violated. Removal (rmmod) of
patch modules is permanently disabled when the feature is used. It
cannot be guaranteed there is no task sleeping in such module.
Signed-off-by: NMiroslav Benes <mbenes@suse.cz>
Acked-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: NPetr Mladek <pmladek@suse.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

Live patching consistency model is of LEAVE_PATCHED_SET and
SWITCH_THREAD. This means that all tasks in the system have to be marked
one by one as safe to call a new patched function. Safe means when a
task is not (sleeping) in a set of patched functions. That is, no
patched function is on the task's stack. Another clearly safe place is
the boundary between kernel and userspace. The patching waits for all
tasks to get outside of the patched set or to cross the boundary. The
transition is completed afterwards.

The problem is that a task can block the transition for quite a long
time, if not forever. It could sleep in a set of patched functions, for
example.  Luckily we can force the task to leave the set by sending it a
fake signal, that is a signal with no data in signal pending structures
(no handler, no sign of proper signal delivered). Suspend/freezer use
this to freeze the tasks as well. The task gets TIF_SIGPENDING set and
is woken up (if it has been sleeping in the kernel before) or kicked by
rescheduling IPI (if it was running on other CPU). This causes the task
to go to kernel/userspace boundary where the signal would be handled and
the task would be marked as safe in terms of live patching.

There are tasks which are not affected by this technique though. The
fake signal is not sent to kthreads. They should be handled differently.
They can be woken up so they leave the patched set and their
TIF_PATCH_PENDING can be cleared thanks to stack checking.

For the sake of completeness, if the task is in TASK_RUNNING state but
not currently running on some CPU it doesn't get the IPI, but it would
eventually handle the signal anyway. Second, if the task runs in the
kernel (in TASK_RUNNING state) it gets the IPI, but the signal is not
handled on return from the interrupt. It would be handled on return to
the userspace in the future when the fake signal is sent again. Stack
checking deals with these cases in a better way.

If the task was sleeping in a syscall it would be woken by our fake
signal, it would check if TIF_SIGPENDING is set (by calling
signal_pending() predicate) and return ERESTART* or EINTR. Syscalls with
ERESTART* return values are restarted in case of the fake signal (see
do_signal()). EINTR is propagated back to the userspace program. This
could disturb the program, but...

* each process dealing with signals should react accordingly to EINTR
  return values.
* syscalls returning EINTR happen to be quite common situation in the
  system even if no fake signal is sent.
* freezer sends the fake signal and does not deal with EINTR anyhow.
  Thus EINTR values are returned when the system is resumed.

The very safe marking is done in architectures' "entry" on syscall and
interrupt/exception exit paths, and in a stack checking functions of
livepatch.  TIF_PATCH_PENDING is cleared and the next
recalc_sigpending() drops TIF_SIGPENDING. In connection with this, also
call klp_update_patch_state() before do_signal(), so that
recalc_sigpending() in dequeue_signal() can clear TIF_PATCH_PENDING
immediately and thus prevent a double call of do_signal().

Note that the fake signal is not sent to stopped/traced tasks. Such task
prevents the patching to finish till it continues again (is not traced
anymore).

Last, sending the fake signal is not automatic. It is done only when
admin requests it by writing 1 to signal sysfs attribute in livepatch
sysfs directory.
Signed-off-by: NMiroslav Benes <mbenes@suse.cz>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: x86@kernel.org
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

__klp_disable_patch() should never be called when the patch is not
enabled. Let's add the same warning that we have in __klp_enable_patch().

This allows to remove the check when calling klp_pre_unpatch_callback().
It was strange anyway because it repeatedly checked per-patch flag
for each patched object.
Signed-off-by: NPetr Mladek <pmladek@suse.com>
Acked-by: NJoe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

The post_unpatch_enabled flag in struct klp_callbacks is set when a
pre-patch callback successfully executes, indicating that we need to
call a corresponding post-unpatch callback when the patch is reverted.
This is true for ordinary patch disable as well as the error paths of
klp_patch_object() callers.

As currently coded, we inadvertently execute the post-patch callback
twice in klp_module_coming() when klp_patch_object() fails:

  - We explicitly call klp_post_unpatch_callback() for the failed object
  - We call it again for the same object (and all the others) via
    klp_cleanup_module_patches_limited()

We should clear the flag in klp_post_unpatch_callback() to make
sure that the callback is not called twice. It makes the API
more safe.

(We could have removed the callback from the former error path as it
would be covered by the latter call, but I think that is is cleaner to
clear the post_unpatch_enabled after its invoked. For example, someone
might later decide to call the callback only when obj->patched flag is
set.)

There is another mistake in the error path of klp_coming_module() in
which it skips the post-unpatch callback for the klp_transition_patch.
However, the pre-patch callback was called even for this patch, so be
sure to make the corresponding callbacks for all patches.

Finally, I used this opportunity to make klp_pre_patch_callback() more
readable.

[jkosina@suse.cz: incorporate changelog wording changes proposed by Joe Lawrence]
Signed-off-by: NPetr Mladek <pmladek@suse.com>
Acked-by: NJoe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

Provide livepatch modules a klp_object (un)patching notification
mechanism.  Pre and post-(un)patch callbacks allow livepatch modules to
setup or synchronize changes that would be difficult to support in only
patched-or-unpatched code contexts.

Callbacks can be registered for target module or vmlinux klp_objects,
but each implementation is klp_object specific.

  - Pre-(un)patch callbacks run before any (un)patching transition
    starts.

  - Post-(un)patch callbacks run once an object has been (un)patched and
    the klp_patch fully transitioned to its target state.

Example use cases include modification of global data and registration
of newly available services/handlers.

See Documentation/livepatch/callbacks.txt for details and
samples/livepatch/ for examples.
Signed-off-by: NJoe Lawrence <joe.lawrence@redhat.com>
Acked-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Acked-by: NMiroslav Benes <mbenes@suse.cz>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

When an incoming module is considered for livepatching by
klp_module_coming(), it iterates over multiple patches and multiple
kernel objects in this order:

	list_for_each_entry(patch, &klp_patches, list) {
		klp_for_each_object(patch, obj) {

which means that if one of the kernel objects fails to patch,
klp_module_coming()'s error path needs to unpatch and cleanup any kernel
objects that were already patched by a previous patch.
Reported-by: NMiroslav Benes <mbenes@suse.cz>
Suggested-by: NPetr Mladek <pmladek@suse.com>
Signed-off-by: NJoe Lawrence <joe.lawrence@redhat.com>
Acked-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: NPetr Mladek <pmladek@suse.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

Add missing newlines to some pr_err() strings.
Signed-off-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Acked-by: NMiroslav Benes <mbenes@suse.cz>
Acked-by: NJessica Yu <jeyu@redhat.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

It's reported that the time of insmoding a klp.ko for one of our
out-tree modules is too long.

~ time sudo insmod klp.ko
real	0m23.799s
user	0m0.036s
sys	0m21.256s

Then we found the reason: our out-tree module used a lot of static local
variables, so klp.ko has a lot of relocation records which reference the
module. Then for each such entry klp_find_object_symbol() is called to
resolve it, but this function uses the interface kallsyms_on_each_symbol()
even for finding module symbols, so will waste a lot of time on walking
through vmlinux kallsyms table many times.

This patch changes it to use module_kallsyms_on_each_symbol() for modules
symbols. After we apply this patch, the sys time reduced dramatically.

~ time sudo insmod klp.ko
real	0m1.007s
user	0m0.032s
sys	0m0.924s
Signed-off-by: NZhou Chengming <zhouchengming1@huawei.com>
Acked-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Acked-by: NJessica Yu <jeyu@redhat.com>
Acked-by: NMiroslav Benes <mbenes@suse.cz>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

klp_mutex is shared between core.c and transition.c, and as such would
rather be properly located in a header so that we don't have to play
'extern' games from .c sources.

This also silences sparse warning (wrongly) suggesting that klp_mutex
should be defined static.
Acked-by: NMiroslav Benes <mbenes@suse.cz>
Acked-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

Currently we do not allow patch module to unload since there is no
method to determine if a task is still running in the patched code.

The consistency model gives us the way because when the unpatching
finishes we know that all tasks were marked as safe to call an original
function. Thus every new call to the function calls the original code
and at the same time no task can be somewhere in the patched code,
because it had to leave that code to be marked as safe.

We can safely let the patch module go after that.

Completion is used for synchronization between module removal and sysfs
infrastructure in a similar way to commit 942e4431 ("module: Fix
mod->mkobj.kobj potentially freed too early").

Note that we still do not allow the removal for immediate model, that is
no consistency model. The module refcount may increase in this case if
somebody disables and enables the patch several times. This should not
cause any harm.

With this change a call to try_module_get() is moved to
__klp_enable_patch from klp_register_patch to make module reference
counting symmetric (module_put() is in a patch disable path) and to
allow to take a new reference to a disabled module when being enabled.

Finally, we need to be very careful about possible races between
klp_unregister_patch(), kobject_put() functions and operations
on the related sysfs files.

kobject_put(&patch->kobj) must be called without klp_mutex. Otherwise,
it might be blocked by enabled_store() that needs the mutex as well.
In addition, enabled_store() must check if the patch was not
unregisted in the meantime.

There is no need to do the same for other kobject_put() callsites
at the moment. Their sysfs operations neither take the lock nor
they access any data that might be freed in the meantime.

There was an attempt to use kobjects the right way and prevent these
races by design. But it made the patch definition more complicated
and opened another can of worms. See
https://lkml.kernel.org/r/1464018848-4303-1-git-send-email-pmladek@suse.com

[Thanks to Petr Mladek for improving the commit message.]
Signed-off-by: NMiroslav Benes <mbenes@suse.cz>
Signed-off-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: NPetr Mladek <pmladek@suse.com>
Acked-by: NMiroslav Benes <mbenes@suse.cz>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

Change livepatch to use a basic per-task consistency model.  This is the
foundation which will eventually enable us to patch those ~10% of
security patches which change function or data semantics.  This is the
biggest remaining piece needed to make livepatch more generally useful.

This code stems from the design proposal made by Vojtech [1] in November
2014.  It's a hybrid of kGraft and kpatch: it uses kGraft's per-task
consistency and syscall barrier switching combined with kpatch's stack
trace switching.  There are also a number of fallback options which make
it quite flexible.

Patches are applied on a per-task basis, when the task is deemed safe to
switch over.  When a patch is enabled, livepatch enters into a
transition state where tasks are converging to the patched state.
Usually this transition state can complete in a few seconds.  The same
sequence occurs when a patch is disabled, except the tasks converge from
the patched state to the unpatched state.

An interrupt handler inherits the patched state of the task it
interrupts.  The same is true for forked tasks: the child inherits the
patched state of the parent.

Livepatch uses several complementary approaches to determine when it's
safe to patch tasks:

1. The first and most effective approach is stack checking of sleeping
   tasks.  If no affected functions are on the stack of a given task,
   the task is patched.  In most cases this will patch most or all of
   the tasks on the first try.  Otherwise it'll keep trying
   periodically.  This option is only available if the architecture has
   reliable stacks (HAVE_RELIABLE_STACKTRACE).

2. The second approach, if needed, is kernel exit switching.  A
   task is switched when it returns to user space from a system call, a
   user space IRQ, or a signal.  It's useful in the following cases:

   a) Patching I/O-bound user tasks which are sleeping on an affected
      function.  In this case you have to send SIGSTOP and SIGCONT to
      force it to exit the kernel and be patched.
   b) Patching CPU-bound user tasks.  If the task is highly CPU-bound
      then it will get patched the next time it gets interrupted by an
      IRQ.
   c) In the future it could be useful for applying patches for
      architectures which don't yet have HAVE_RELIABLE_STACKTRACE.  In
      this case you would have to signal most of the tasks on the
      system.  However this isn't supported yet because there's
      currently no way to patch kthreads without
      HAVE_RELIABLE_STACKTRACE.

3. For idle "swapper" tasks, since they don't ever exit the kernel, they
   instead have a klp_update_patch_state() call in the idle loop which
   allows them to be patched before the CPU enters the idle state.

   (Note there's not yet such an approach for kthreads.)

All the above approaches may be skipped by setting the 'immediate' flag
in the 'klp_patch' struct, which will disable per-task consistency and
patch all tasks immediately.  This can be useful if the patch doesn't
change any function or data semantics.  Note that, even with this flag
set, it's possible that some tasks may still be running with an old
version of the function, until that function returns.

There's also an 'immediate' flag in the 'klp_func' struct which allows
you to specify that certain functions in the patch can be applied
without per-task consistency.  This might be useful if you want to patch
a common function like schedule(), and the function change doesn't need
consistency but the rest of the patch does.

For architectures which don't have HAVE_RELIABLE_STACKTRACE, the user
must set patch->immediate which causes all tasks to be patched
immediately.  This option should be used with care, only when the patch
doesn't change any function or data semantics.

In the future, architectures which don't have HAVE_RELIABLE_STACKTRACE
may be allowed to use per-task consistency if we can come up with
another way to patch kthreads.

The /sys/kernel/livepatch/<patch>/transition file shows whether a patch
is in transition.  Only a single patch (the topmost patch on the stack)
can be in transition at a given time.  A patch can remain in transition
indefinitely, if any of the tasks are stuck in the initial patch state.

A transition can be reversed and effectively canceled by writing the
opposite value to the /sys/kernel/livepatch/<patch>/enabled file while
the transition is in progress.  Then all the tasks will attempt to
converge back to the original patch state.

[1] https://lkml.kernel.org/r/20141107140458.GA21774@suse.czSigned-off-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Acked-by: NMiroslav Benes <mbenes@suse.cz>
Acked-by: Ingo Molnar <mingo@kernel.org>        # for the scheduler changes
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

For the consistency model we'll need to know the sizes of the old and
new functions to determine if they're on the stacks of any tasks.
Signed-off-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Acked-by: NMiroslav Benes <mbenes@suse.cz>
Reviewed-by: NPetr Mladek <pmladek@suse.com>
Reviewed-by: NKamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

The sysfs enabled value is a boolean, so kstrtobool() is a better fit
for parsing the input string since it does the range checking for us.
Suggested-by: NPetr Mladek <pmladek@suse.com>
Signed-off-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Acked-by: NMiroslav Benes <mbenes@suse.cz>
Reviewed-by: NPetr Mladek <pmladek@suse.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

Move functions related to the actual patching of functions and objects
into a new patch.c file.
Signed-off-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Acked-by: NMiroslav Benes <mbenes@suse.cz>
Reviewed-by: NPetr Mladek <pmladek@suse.com>
Reviewed-by: NKamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

klp_patch_object()'s callers already ensure that the object is loaded,
so its call to klp_is_object_loaded() is unnecessary.

This will also make it possible to move the patching code into a
separate file.
Signed-off-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Acked-by: NMiroslav Benes <mbenes@suse.cz>
Reviewed-by: NPetr Mladek <pmladek@suse.com>
Reviewed-by: NKamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

Once we have a consistency model, patches and their objects will be
enabled and disabled at different times.  For example, when a patch is
disabled, its loaded objects' funcs can remain registered with ftrace
indefinitely until the unpatching operation is complete and they're no
longer in use.

It's less confusing if we give them different names: patches can be
enabled or disabled; objects (and their funcs) can be patched or
unpatched:

- Enabled means that a patch is logically enabled (but not necessarily
  fully applied).

- Patched means that an object's funcs are registered with ftrace and
  added to the klp_ops func stack.

Also, since these states are binary, represent them with booleans
instead of ints.
Signed-off-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Acked-by: NMiroslav Benes <mbenes@suse.cz>
Reviewed-by: NPetr Mladek <pmladek@suse.com>
Reviewed-by: NKamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

Create temporary stubs for klp_update_patch_state() so we can add
TIF_PATCH_PENDING to different architectures in separate patches without
breaking build bisectability.
Signed-off-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: NPetr Mladek <pmladek@suse.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

There's no reliable way to determine which module tainted the kernel
with TAINT_LIVEPATCH.  For example, /sys/module/<klp module>/taint
doesn't report it.  Neither does the "mod -t" command in the crash tool.

Make it crystal clear who the guilty party is by associating
TAINT_LIVEPATCH with any module which sets the "livepatch" modinfo
attribute.  The flag will still get set in the kernel like before, but
now it also sets the same flag in mod->taint.

Note that now the taint flag gets set when the module is loaded rather
than when it's enabled.

I also renamed find_livepatch_modinfo() to check_modinfo_livepatch() to
better reflect its purpose: it's basically a livepatch-specific
sub-function of check_modinfo().
Reported-by: NChunyu Hu <chuhu@redhat.com>
Reviewed-by: NPetr Mladek <pmladek@suse.com>
Acked-by: NMiroslav Benes <mbenes@suse.cz>
Acked-by: NJessica Yu <jeyu@redhat.com>
Acked-by: NRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

Introduce arch_klp_init_object_loaded() to complete any additional
arch-specific tasks during patching. Architecture code may override this
function.
Signed-off-by: NJessica Yu <jeyu@redhat.com>
Reviewed-by: NPetr Mladek <pmladek@suse.com>
Acked-by: NMiroslav Benes <mbenes@suse.cz>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

Add ro_after_init support for modules by adding a new page-aligned section
in the module layout (after rodata) for ro_after_init data and enabling RO
protection for that section after module init runs.
Signed-off-by: NJessica Yu <jeyu@redhat.com>
Acked-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NRusty Russell <rusty@rustcorp.com.au>

Current object-walking helper checks the presence of obj->funcs to
determine the end of objs array in klp_object structure. This is
somewhat fragile because one can easily forget about funcs definition
during livepatch creation. In such a case the livepatch module is
successfully loaded and all objects after the incorrect one are omitted.
This is very confusing. Let's make the helper more robust and check also
for the other external member, name. Thus the helper correctly stops on
an empty item of the array. We need to have a check for obj->funcs in
klp_init_object() to make it work.

The same applies to a func-walking helper.

As a benefit we'll check for new_func member definition during the
livepatch initialization. There is no such check anywhere in the code
now.

[jkosina@suse.cz: fix shortlog]
Signed-off-by: NMiroslav Benes <mbenes@suse.cz>
Acked-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Acked-by: NJessica Yu <jeyu@redhat.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

When livepatch tries to patch a function it takes the function address
and asks ftrace to install the livepatch handler at that location.
ftrace will look for an mcount call site at that exact address.

On powerpc the mcount location is not the first instruction of the
function, and in fact it's not at a constant offset from the start of
the function. To accommodate this add a hook which arch code can
override to customise the behaviour.
Signed-off-by: NTorsten Duwe <duwe@suse.de>
Signed-off-by: NBalbir Singh <bsingharora@gmail.com>
Signed-off-by: NPetr Mladek <pmladek@suse.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

Commit 425595a7 ("livepatch: reuse module loader code to write
relocations") adds a possibility of dereferncing pointers supplied by the
consumer of the livepatch API before sanity (NULL) checking them (patch
and patch->mod).

Spotted by smatch tool.
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Acked-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Acked-by: NJessica Yu <jeyu@redhat.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

Reuse module loader code to write relocations, thereby eliminating the need
for architecture specific relocation code in livepatch. Specifically, reuse
the apply_relocate_add() function in the module loader to write relocations
instead of duplicating functionality in livepatch's arch-dependent
klp_write_module_reloc() function.

In order to accomplish this, livepatch modules manage their own relocation
sections (marked with the SHF_RELA_LIVEPATCH section flag) and
livepatch-specific symbols (marked with SHN_LIVEPATCH symbol section
index). To apply livepatch relocation sections, livepatch symbols
referenced by relocs are resolved and then apply_relocate_add() is called
to apply those relocations.

In addition, remove x86 livepatch relocation code and the s390
klp_write_module_reloc() function stub. They are no longer needed since
relocation work has been offloaded to module loader.

Lastly, mark the module as a livepatch module so that the module loader
canappropriately identify and initialize it.
Signed-off-by: NJessica Yu <jeyu@redhat.com>
Reviewed-by: NMiroslav Benes <mbenes@suse.cz>
Acked-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>   # for s390 changes
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

Remove the livepatch module notifier in favor of directly enabling and
disabling patches to modules in the module loader. Hard-coding the
function calls ensures that ftrace_module_enable() is run before
klp_module_coming() during module load, and that klp_module_going() is
run before ftrace_release_mod() during module unload. This way, ftrace
and livepatch code is run in the correct order during the module
load/unload sequence without dependence on the module notifier call chain.
Signed-off-by: NJessica Yu <jeyu@redhat.com>
Reviewed-by: NPetr Mladek <pmladek@suse.cz>
Acked-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Acked-by: NRusty Russell <rusty@rustcorp.com.au>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>