Add README.md for third_party/processor-trace.
Change-Id: I30df39245a591e7672a9afd6ec9e0e6afe817e7d
diff --git a/README.md b/README.md
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+# processor-trace
+
+This is the processor trace (PT) support from Intel.
+This repo was originally cloned from https://github.com/01org/processor-trace,
+with its master branch at commit afbae2983b1978f1f1fe267bfc3fd24a7e41673a.
+
+To see differences with upstream, assuming master is up to date
+with origin/master:
+
+bash$ git remote add github https://github.com/01org/processor-trace
+bash$ git fetch github
+bash$ git checkout master
+bash$ git cherry -v github/master
+
+Commits that begin with "-" are ones upstream has and we do not.
+Commits that begin with "+" are ones we have and upstream does not.
