linux-toradex.git/kernel/context_tracking.c, branch v5.10-rc3

context_tracking: Ensure that the critical path cannot be instrumented

2020-06-11T13:14:36+00:00

context tracking lacks a few protection mechanisms against instrumentation:

 - While the core functions are marked NOKPROBE they lack protection
   against function tracing which is required as the function entry/exit
   points can be utilized by BPF.

 - static functions invoked from the protected functions need to be marked
   as well as they can be instrumented otherwise.

 - using plain inline allows the compiler to emit traceable and probable
   functions.

Fix this by marking the functions noinstr and converting the plain inlines
to __always_inline.

The NOKPROBE_SYMBOL() annotations are removed as the .noinstr.text section
is already excluded from being probed.

Cures the following objtool warnings:

 vmlinux.o: warning: objtool: enter_from_user_mode()+0x34: call to __context_tracking_exit() leaves .noinstr.text section
 vmlinux.o: warning: objtool: prepare_exit_to_usermode()+0x29: call to __context_tracking_enter() leaves .noinstr.text section
 vmlinux.o: warning: objtool: syscall_return_slowpath()+0x29: call to __context_tracking_enter() leaves .noinstr.text section
 vmlinux.o: warning: objtool: do_syscall_64()+0x7f: call to __context_tracking_enter() leaves .noinstr.text section
 vmlinux.o: warning: objtool: do_int80_syscall_32()+0x3d: call to __context_tracking_enter() leaves .noinstr.text section
 vmlinux.o: warning: objtool: do_fast_syscall_32()+0x9c: call to __context_tracking_enter() leaves .noinstr.text section

and generates new ones...

Signed-off-by: Thomas Gleixner 
Reviewed-by: Masami Hiramatsu 
Reviewed-by: Alexandre Chartre 
Acked-by: Peter Zijlstra 
Link: https://lkml.kernel.org/r/20200505134340.811520478@linutronix.de

context-tracking: Introduce CONFIG_HAVE_TIF_NOHZ

2020-02-14T15:05:04+00:00

A few archs (x86, arm, arm64) don't rely anymore on TIF_NOHZ to call
into context tracking on user entry/exit but instead use static keys
(or not) to optimize those calls. Ideally every arch should migrate to
that behaviour in the long run.

Settle a config option to let those archs remove their TIF_NOHZ
definitions.

Signed-off-by: Frederic Weisbecker 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Borislav Petkov 
Cc: Andy Lutomirski 
Cc: Russell King 
Cc: Catalin Marinas 
Cc: Will Deacon 
Cc: Ralf Baechle 
Cc: Paul Burton 
Cc: Benjamin Herrenschmidt 
Cc: Paul Mackerras 
Cc: Michael Ellerman 
Cc: David S. Miller

context_tracking: Rename context_tracking_is_enabled() => context_tracking_enabled()

2019-10-29T09:01:12+00:00

Remove the superfluous "is" in the middle of the name. We want to
standardize the naming so that it can be expanded through suffixes:

	context_tracking_enabled()
	context_tracking_enabled_cpu()
	context_tracking_enabled_this_cpu()

Signed-off-by: Frederic Weisbecker 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Jacek Anaszewski 
Cc: Linus Torvalds 
Cc: Pavel Machek 
Cc: Peter Zijlstra 
Cc: Rafael J . Wysocki 
Cc: Rik van Riel 
Cc: Thomas Gleixner 
Cc: Viresh Kumar 
Cc: Wanpeng Li 
Cc: Yauheni Kaliuta 
Link: https://lkml.kernel.org/r/20191016025700.31277-6-frederic@kernel.org
Signed-off-by: Ingo Molnar

treewide: Add SPDX license identifier for missed files

2019-05-21T08:50:45+00:00

Add SPDX license identifiers to all files which:

 - Have no license information of any form

 - Have EXPORT_.*_SYMBOL_GPL inside which was used in the
   initial scan/conversion to ignore the file

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

  GPL-2.0-only

Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

context_tracking: Switch to new static_branch API

2015-11-24T08:56:43+00:00

This is much less error-prone than the old code.

Signed-off-by: Andy Lutomirski 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Denys Vlasenko 
Cc: Frederic Weisbecker 
Cc: H. Peter Anvin 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/812df7e64f120c5c7c08481f36a8caa9f53b2199.1447361906.git.luto@kernel.org
Signed-off-by: Ingo Molnar

context_tracking: avoid irq_save/irq_restore on guest entry and exit

2015-11-10T11:06:23+00:00

guest_enter and guest_exit must be called with interrupts disabled,
since they take the vtime_seqlock with write_seq{lock,unlock}.
Therefore, it is not necessary to check for exceptions, nor to
save/restore the IRQ state, when context tracking functions are
called by guest_enter and guest_exit.

Split the body of context_tracking_entry and context_tracking_exit
out to __-prefixed functions, and use them from KVM.

Rik van Riel has measured this to speed up a tight vmentry/vmexit
loop by about 2%.

Cc: Andy Lutomirski 
Cc: Frederic Weisbecker 
Cc: Paul McKenney 
Reviewed-by: Rik van Riel 
Tested-by: Rik van Riel 
Signed-off-by: Paolo Bonzini

context_tracking: remove duplicate enabled check

2015-11-10T11:06:22+00:00

All calls to context_tracking_enter and context_tracking_exit
are already checking context_tracking_is_enabled, except the
context_tracking_user_enter and context_tracking_user_exit
functions left in for the benefit of assembly calls.

Pull the check up to those functions, by making them simple
wrappers around the user_enter and user_exit inline functions.

Cc: Frederic Weisbecker 
Cc: Paul McKenney 
Reviewed-by: Rik van Riel 
Tested-by: Rik van Riel 
Acked-by: Andy Lutomirski 
Signed-off-by: Paolo Bonzini

context_tracking: Inherit TIF_NOHZ through forks instead of context switches

2015-05-07T10:02:51+00:00

TIF_NOHZ is used by context_tracking to force syscall slow-path
on every task in order to track userspace roundtrips. As such,
it must be set on all running tasks.

It's currently explicitly inherited through context switches.
There is no need to do it in this fast-path though. The flag
could simply be set once for all on all tasks, whether they are
running or not.

Lets do this by setting the flag for the init task on early boot,
and let it propagate through fork inheritance.

While at it, mark context_tracking_cpu_set() as init code, we
only need it at early boot time.

Suggested-by: Oleg Nesterov 
Signed-off-by: Frederic Weisbecker 
Reviewed-by: Rik van Riel 
Cc: Borislav Petkov 
Cc: Chris Metcalf 
Cc: Dave Jones 
Cc: H. Peter Anvin 
Cc: Martin Schwidefsky 
Cc: Mike Galbraith 
Cc: Paul E . McKenney 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Rafael J . Wysocki 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1430928266-24888-3-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar

context_tracking: Protect against recursion

2015-05-07T10:02:50+00:00

Context tracking recursion can happen when an exception triggers
in the middle of a call to a context tracking probe.

This special case can be caused by vmalloc faults. If an access
to a memory area allocated by vmalloc happens in the middle of
context_tracking_enter(), we may run into an endless fault loop
because the exception in turn calls context_tracking_enter()
which faults on the same vmalloc'ed memory, triggering an
exception again, etc...

Some rare crashes have been reported so lets protect against
this with a recursion counter.

Reported-by: Dave Jones 
Signed-off-by: Frederic Weisbecker 
Reviewed-by: Rik van Riel 
Acked-by: Peter Zijlstra (Intel) 
Cc: Borislav Petkov 
Cc: Chris Metcalf 
Cc: H. Peter Anvin 
Cc: Martin Schwidefsky 
Cc: Mike Galbraith 
Cc: Oleg Nesterov 
Cc: Paul E. McKenney 
Cc: Rafael J . Wysocki 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1430928266-24888-2-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar

context_tracking: Export context_tracking_user_enter/exit

2015-03-09T14:43:00+00:00

Export context_tracking_user_enter/exit so it can be used by KVM.

Reviewed-by: Paul E. McKenney 
Signed-off-by: Rik van Riel 
Cc: Paul E. McKenney 
Cc: Andy Lutomirski 
Cc: Will deacon 
Cc: Marcelo Tosatti 
Cc: Christian Borntraeger 
Cc: Luiz Capitulino 
Cc: Paolo Bonzini 
Signed-off-by: Frederic Weisbecker