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Currently, for data moving, we generate an msanread of the source, followed by an msanwrite of the destination. msanread checks the source is initialized. This has a problem: if the source is an aggregate type containing alignment paddings, the padding bytes may not be thought as initialized by MSAN. If we copy the aggregate type by value, if it counts as a read, MSAN reports using uninitialized data. This CL changes it to use __msan_memmove for data copying, which tells MSAN to propagate initialized-ness but not check for it. Caveat: technically __msan_memmove is not a public API of MSAN, although the C compiler does generate direct calls to it. Also, when instrumenting a load of a struct, split the instrumentation to fields, instead of generating an msanread for the whole struct. This skips padding bytes, which may not be considered initialized in MSAN. Fixes #42820. Change-Id: Id861c8bbfd94cfcccefcc58eaf9e4eb43b4d85c6 Reviewed-on: https://go-review.googlesource.com/c/go/+/270859 Trust: Cherry Zhang <cherryyz@google.com> Run-TryBot: Cherry Zhang <cherryyz@google.com> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Austin Clements <austin@google.com> |
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