linux-toradex.git/kernel/kcsan, branch v5.9-rc6 Linux kernel for Apalis and Colibri modules Merge branch 'kcsan' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into locking/core 2020-08-01T07:26:27+00:00 Ingo Molnar mingo@kernel.org 2020-08-01T07:25:21+00:00 63722bbca662b19eb39fe709c11a5fa3994b4c3f Pull v5.9 KCSAN bits from Paul E. McKenney. Perhaps the most important change is that GCC 11 now has all fixes in place to support KCSAN, so GCC support can be enabled again. Signed-off-by: Ingo Molnar <mingo@kernel.org> 
Pull v5.9 KCSAN bits from Paul E. McKenney.

Perhaps the most important change is that GCC 11 now has all fixes in place
to support KCSAN, so GCC support can be enabled again.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
kcsan: Improve IRQ state trace reporting 2020-07-31T10:12:03+00:00 Marco Elver elver@google.com 2020-07-29T11:09:16+00:00 92c209ac6d3d35783c16c8a717547183e6e11162 To improve the general usefulness of the IRQ state trace events with KCSAN enabled, save and restore the trace information when entering and exiting the KCSAN runtime as well as when generating a KCSAN report. Without this, reporting the IRQ trace events (whether via a KCSAN report or outside of KCSAN via a lockdep report) is rather useless due to continuously being touched by KCSAN. This is because if KCSAN is enabled, every instrumented memory access causes changes to IRQ trace events (either by KCSAN disabling/enabling interrupts or taking report_lock when generating a report). Before "lockdep: Prepare for NMI IRQ state tracking", KCSAN avoided touching the IRQ trace events via raw_local_irq_save/restore() and lockdep_off/on(). Fixes: 248591f5d257 ("kcsan: Make KCSAN compatible with new IRQ state tracking") Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20200729110916.3920464-2-elver@google.com Signed-off-by: Ingo Molnar <mingo@kernel.org> 
To improve the general usefulness of the IRQ state trace events with
KCSAN enabled, save and restore the trace information when entering and
exiting the KCSAN runtime as well as when generating a KCSAN report.

Without this, reporting the IRQ trace events (whether via a KCSAN report
or outside of KCSAN via a lockdep report) is rather useless due to
continuously being touched by KCSAN. This is because if KCSAN is
enabled, every instrumented memory access causes changes to IRQ trace
events (either by KCSAN disabling/enabling interrupts or taking
report_lock when generating a report).

Before "lockdep: Prepare for NMI IRQ state tracking", KCSAN avoided
touching the IRQ trace events via raw_local_irq_save/restore() and
lockdep_off/on().

Fixes: 248591f5d257 ("kcsan: Make KCSAN compatible with new IRQ state tracking")
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200729110916.3920464-2-elver@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
kcsan: Make KCSAN compatible with new IRQ state tracking 2020-07-10T10:00:00+00:00 Marco Elver elver@google.com 2020-06-24T11:32:46+00:00 248591f5d257a19c1cba9ab9da3536bfbc2f0149 The new IRQ state tracking code does not honor lockdep_off(), and as such we should again permit tracing by using non-raw functions in core.c. Update the lockdep_off() comment in report.c, to reflect the fact there is still a potential risk of deadlock due to using printk() from scheduler code. Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Ingo Molnar <mingo@kernel.org> Link: https://lkml.kernel.org/r/20200624113246.GA170324@elver.google.com 
The new IRQ state tracking code does not honor lockdep_off(), and as
such we should again permit tracing by using non-raw functions in
core.c. Update the lockdep_off() comment in report.c, to reflect the
fact there is still a potential risk of deadlock due to using printk()
from scheduler code.

Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200624113246.GA170324@elver.google.com
kcsan: Disable branch tracing in core runtime 2020-06-29T19:04:48+00:00 Marco Elver elver@google.com 2020-06-18T09:31:18+00:00 61d56d7aa5eca3b909bce51ba8125b0fa44d7e17 Disable branch tracing in core KCSAN runtime if branches are being traced (TRACE_BRANCH_PROFILING). This it to avoid its performance impact, but also avoid recursion in case KCSAN is enabled for the branch tracing runtime. The latter had already been a problem for KASAN: https://lore.kernel.org/lkml/CANpmjNOeXmD5E3O50Z3MjkiuCYaYOPyi+1rq=GZvEKwBvLR0Ug@mail.gmail.com/ Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
Disable branch tracing in core KCSAN runtime if branches are being
traced (TRACE_BRANCH_PROFILING). This it to avoid its performance
impact, but also avoid recursion in case KCSAN is enabled for the branch
tracing runtime.

The latter had already been a problem for KASAN:
https://lore.kernel.org/lkml/CANpmjNOeXmD5E3O50Z3MjkiuCYaYOPyi+1rq=GZvEKwBvLR0Ug@mail.gmail.com/

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
kcsan: Simplify compiler flags 2020-06-29T19:04:48+00:00 Marco Elver elver@google.com 2020-06-18T09:31:17+00:00 2839a232071f588d334543fb86f5689b43353842 Simplify the set of compiler flags for the runtime by removing cc-option from -fno-stack-protector, because all supported compilers support it. This saves us one compiler invocation during build. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
Simplify the set of compiler flags for the runtime by removing cc-option
from -fno-stack-protector, because all supported compilers support it.
This saves us one compiler invocation during build.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
kcsan: Add jiffies test to test suite 2020-06-29T19:04:48+00:00 Marco Elver elver@google.com 2020-06-16T12:36:25+00:00 56b031f0abf55254d47a329010574733fa9a27b8 Add a test that KCSAN nor the compiler gets confused about accesses to jiffies on different architectures. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
Add a test that KCSAN nor the compiler gets confused about accesses to
jiffies on different architectures.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
kcsan: Remove existing special atomic rules 2020-06-29T19:04:48+00:00 Marco Elver elver@google.com 2020-06-16T12:36:24+00:00 7e766560e6e2c1cf2782f00e63c31564e4c9f0fe Remove existing special atomic rules from kcsan_is_atomic_special() because they are no longer needed. Since we rely on the compiler emitting instrumentation distinguishing volatile accesses, the rules have become redundant. Let's keep kcsan_is_atomic_special() around, so that we have an obvious place to add special rules should the need arise in future. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
Remove existing special atomic rules from kcsan_is_atomic_special()
because they are no longer needed. Since we rely on the compiler
emitting instrumentation distinguishing volatile accesses, the rules
have become redundant.

Let's keep kcsan_is_atomic_special() around, so that we have an obvious
place to add special rules should the need arise in future.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
kcsan: Rename test.c to selftest.c 2020-06-29T19:04:48+00:00 Marco Elver elver@google.com 2020-06-16T12:36:23+00:00 acfa087ccf2d2eff46186477f53e4c3ffbdb033d Rename 'test.c' to 'selftest.c' to better reflect its purpose (Kconfig variable and code inside already match this). This is to avoid confusion with the test suite module in 'kcsan-test.c'. No functional change. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
Rename 'test.c' to 'selftest.c' to better reflect its purpose (Kconfig
variable and code inside already match this). This is to avoid confusion
with the test suite module in 'kcsan-test.c'.

No functional change.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
kcsan: Silence -Wmissing-prototypes warning with W=1 2020-06-29T19:04:48+00:00 Marco Elver elver@google.com 2020-06-16T12:36:22+00:00 9dd979bae4cf76558ff816abe83283308fb1ae8c The functions here should not be forward declared for explicit use elsewhere in the kernel, as they should only be emitted by the compiler due to sanitizer instrumentation. Add forward declarations a line above their definition to shut up warnings in W=1 builds. Link: https://lkml.kernel.org/r/202006060103.jSCpnV1g%lkp@intel.com Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
The functions here should not be forward declared for explicit use
elsewhere in the kernel, as they should only be emitted by the compiler
due to sanitizer instrumentation.  Add forward declarations a line above
their definition to shut up warnings in W=1 builds.

Link: https://lkml.kernel.org/r/202006060103.jSCpnV1g%lkp@intel.com
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
kcsan: Prefer '__no_kcsan inline' in test 2020-06-29T19:04:48+00:00 Marco Elver elver@google.com 2020-06-02T14:36:33+00:00 2888557f68db334a3839dcc262264a4c436f576b Instead of __no_kcsan_or_inline, prefer '__no_kcsan inline' in test -- this is in case we decide to remove __no_kcsan_or_inline. Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> 
Instead of __no_kcsan_or_inline, prefer '__no_kcsan inline' in test --
this is in case we decide to remove __no_kcsan_or_inline.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>