add some comments

source/loader/layers/sanitizer/asan_interceptor.cpp

@@ -84,6 +84,13 @@ ur_program_handle_t getProgram(ur_kernel_handle_t Kernel) {
 
 } // namespace
 
+/// The memory chunk allocated from the underlying allocator looks like this:
+/// L L L L L L U U U U U U R R
+/// L -- left redzone words (0 or more bytes)
+/// U -- user memory.
+/// R -- right redzone (0 or more bytes)
+///
+/// ref: "compiler-rt/lib/asan/asan_allocator.cpp" Allocator::Allocate
 ur_result_t SanitizerInterceptor::allocateMemory(
  ur_context_handle_t Context, ur_device_handle_t Device,
  const ur_usm_desc_t *Properties, ur_usm_pool_handle_t Pool, size_t Size,
@@ -232,12 +239,11 @@ void SanitizerInterceptor::postLaunchKernel(ur_kernel_handle_t Kernel,
  DeviceSanitizerFormat(AH->ErrorType),
  DeviceSanitizerFormat(AH->MemoryType));
  context.logger.always(
- stderr,
  "%s of size %u at kernel <%s> LID(%lu, %lu, %lu) GID(%lu, "
  "%lu, %lu)\n",
  AH->IsWrite ? "WRITE" : "READ", AH->AccessSize, Func, AH->LID0,
  AH->LID1, AH->LID2, AH->GID0, AH->GID1, AH->GID2);
- context.logger.always(stderr, " #0 %s %s:%d\n", Func, File, AH->Line);
+ context.logger.always(" #0 %s %s:%d\n", Func, File, AH->Line);
  if (!AH->IsRecover) {
  abort();
  }
@@ -377,6 +383,13 @@ ur_result_t SanitizerInterceptor::enqueueMemSetShadow(
  return UR_RESULT_SUCCESS;
 }
 
+/// Each 8 bytes of application memory are mapped into one byte of shadow memory
+/// The meaning of that byte:
+/// - Negative: All bytes are not accessible (poisoned)
+/// - 0: All bytes are accessible
+/// - 1 <= k <= 7: Only the first k bytes is accessible
+///
+/// ref: https://github.com/google/sanitizers/wiki/AddressSanitizerAlgorithm#mapping
 ur_result_t SanitizerInterceptor::enqueueAllocInfo(
  ur_context_handle_t Context, ur_device_handle_t Device,
  ur_queue_handle_t Queue, std::shared_ptr<USMAllocInfo> &AllocInfo,