Merge "bpf: Ringbuf: Ensure we acquire load the length for the ring buf entry" into main am: 3d2a3c5eb4
Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/3327114
Change-Id: I8641af2182f92d2d6c868743545bcca81770deba
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
diff --git a/bpf/headers/include/bpf/BpfRingbuf.h b/bpf/headers/include/bpf/BpfRingbuf.h
index 4bcd259..5fe4ef7 100644
--- a/bpf/headers/include/bpf/BpfRingbuf.h
+++ b/bpf/headers/include/bpf/BpfRingbuf.h
@@ -99,6 +99,7 @@
// 32-bit kernel will just ignore the high-order bits.
std::atomic_uint64_t* mConsumerPos = nullptr;
std::atomic_uint32_t* mProducerPos = nullptr;
+ std::atomic_uint32_t* mLength = nullptr;
// In order to guarantee atomic access in a 32 bit userspace environment, atomic_uint64_t is used
// in addition to std::atomic<T>::is_always_lock_free that guarantees that read / write operations
@@ -247,7 +248,8 @@
// u32 len;
// u32 pg_off;
// };
- uint32_t length = *reinterpret_cast<volatile uint32_t*>(start_ptr);
+ mLength = reinterpret_cast<decltype(mLength)>(start_ptr);
+ uint32_t length = mLength->load(std::memory_order_acquire);
// If the sample isn't committed, we're caught up with the producer.
if (length & BPF_RINGBUF_BUSY_BIT) return count;