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authorMarco Elver <elver@google.com>2020-07-24 09:00:01 +0200
committerPaul E. McKenney <paulmck@kernel.org>2020-08-24 15:09:32 -0700
commit14e2ac8de0f91f12122a49f09897b0cd05256460 (patch)
tree938e24729e65eb3eed3403e7f084fbcfa8dbbcdc /kernel/kcsan/report.c
parentf9ea63193135473ed6b6ff06f016eb6248100041 (diff)
downloadlinux-14e2ac8de0f91f12122a49f09897b0cd05256460.tar.bz2
kcsan: Support compounded read-write instrumentation
Add support for compounded read-write instrumentation if supported by the compiler. Adds the necessary instrumentation functions, and a new type which is used to generate a more descriptive report. Furthermore, such compounded memory access instrumentation is excluded from the "assume aligned writes up to word size are atomic" rule, because we cannot assume that the compiler emits code that is atomic for compound ops. LLVM/Clang added support for the feature in: https://github.com/llvm/llvm-project/commit/785d41a261d136b64ab6c15c5d35f2adc5ad53e3 The new instrumentation is emitted for sets of memory accesses in the same basic block to the same address with at least one read appearing before a write. These typically result from compound operations such as ++, --, +=, -=, |=, &=, etc. but also equivalent forms such as "var = var + 1". Where the compiler determines that it is equivalent to emit a call to a single __tsan_read_write instead of separate __tsan_read and __tsan_write, we can then benefit from improved performance and better reporting for such access patterns. The new reports now show that the ops are both reads and writes, for example: read-write to 0xffffffff90548a38 of 8 bytes by task 143 on cpu 3: test_kernel_rmw_array+0x45/0xa0 access_thread+0x71/0xb0 kthread+0x21e/0x240 ret_from_fork+0x22/0x30 read-write to 0xffffffff90548a38 of 8 bytes by task 144 on cpu 2: test_kernel_rmw_array+0x45/0xa0 access_thread+0x71/0xb0 kthread+0x21e/0x240 ret_from_fork+0x22/0x30 Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/kcsan/report.c')
-rw-r--r--kernel/kcsan/report.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/kernel/kcsan/report.c b/kernel/kcsan/report.c
index 9d07e175de0f..3e83a69239fa 100644
--- a/kernel/kcsan/report.c
+++ b/kernel/kcsan/report.c
@@ -228,6 +228,10 @@ static const char *get_access_type(int type)
return "write";
case KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC:
return "write (marked)";
+ case KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE:
+ return "read-write";
+ case KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC:
+ return "read-write (marked)";
case KCSAN_ACCESS_SCOPED:
return "read (scoped)";
case KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_ATOMIC: