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[-rcu/kcsan,20/23] mm, kcsan: Enable barrier instrumentation

Message ID 20211005105905.1994700-21-elver@google.com (mailing list archive)
State New
Headers show
Series kcsan: Support detecting a subset of missing memory barriers | expand

Commit Message

Marco Elver Oct. 5, 2021, 10:59 a.m. UTC 
Some memory management calls imply memory barriers that are required to
avoid false positives. For example, without the correct instrumentation,
we could observe data races of the following variant:

                   T0           |           T1
        ------------------------+------------------------
                                |
         *a = 42;    ---+       |
         kfree(a);      |       |
                        |       | b = kmalloc(..); // b == a
          <reordered> <-+       | *b = 42;         // not a data race!
                                |

Therefore, instrument memory barriers in all allocator code currently
not being instrumented in a default build.

Signed-off-by: Marco Elver <elver@google.com>
---
 mm/Makefile | 2 ++
 1 file changed, 2 insertions(+)
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Patch

diff --git a/mm/Makefile b/mm/Makefile
index fc60a40ce954..11e9fcd410be 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -15,6 +15,8 @@  KCSAN_SANITIZE_slab_common.o := n
 KCSAN_SANITIZE_slab.o := n
 KCSAN_SANITIZE_slub.o := n
 KCSAN_SANITIZE_page_alloc.o := n
+# But enable explicit instrumentation for memory barriers.
+KCSAN_INSTRUMENT_BARRIERS := y
 
 # These files are disabled because they produce non-interesting and/or
 # flaky coverage that is not a function of syscall inputs. E.g. slab is out of