adds patterns to recognize certain x86 endbr as function starts (#1531)

Not an exhaustive list but it will be easy to add more, once they are
discovered.

Author: ivg

oasis/x86

@@ -74,7 +74,8 @@ Library x86_plugin
                    X86_legacy_fp_lifter,
                    X86_legacy_bil_register,
                    X86_legacy_operands
- DataFiles:        semantics/*.lisp ($datadir/bap/primus/semantics)
+ DataFiles:        semantics/*.lisp ($datadir/bap/primus/semantics),
+                   patterns/*.xml ($datadir/bap/signatures/x86)
  XMETAExtraLines:  tags="disassembler, lifter, x86, abi"
 
 Library x86_test

plugins/x86/patterns/cet.xml

@@ -0,0 +1,16 @@
+<patternlist>
+  <pattern>
+    <data>0xf30f1efa 0x55</data>     <!--endbr64; push rbp-->
+    <funcstart/>
+  </pattern>
+
+  <pattern>
+    <data>0xf30f1efa 0x53</data>     <!--endbr64; push rbx-->
+    <funcstart/>
+  </pattern>
+
+  <pattern>
+    <data>0xf30f1efa 0x415.</data>     <!--endbr64; push rbx-->
+    <funcstart/>
+  </pattern>
+</patternlist>

plugins/x86/patterns/patternconstraints.xml

@@ -0,0 +1,5 @@
+<patternconstraints>
+  <language id="x86_64">
+    <patternfile>cet.xml</patternfile>
+  </language>
+</patternconstraints>