tree 69b47689272566a1962ddf4d2f6f4e3afc9cf26e
parent 29a6b75e3306e587f1fea2d860583b19c6bd5f13
author Gabe Black <gabe.black@gmail.com> 1638268101 -0800
committer Gabe Black <gabe.black@gmail.com> 1638314963 +0000

cpu: In SimpleIndirectPredictor, avoid an accidental nullptr deref.

The default value of IPredEntry::tag is 0, and if we just blindly
compare the tag we're looking for against this value, we might run into
cases where we match against an uninitialized IPredEntry. In that case,
IPredEntry::target has not been initialized, and if we try to use it in
lookup(...) we'll dereference nullptr and segfault.

To avoid that, we can just add one additional check that makes sure that
not only does the tag of the IPredEntry match, but also that the value
of target is not null, and so the IPredEntry *actually* has tag 0 and
isn't just uninitialized.

Change-Id: I892d0df7c00a0a4cd3ca215fe3a7586ddbca9395
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/53403
Maintainer: Gabe Black <gabe.black@gmail.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>