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<p class="MsoNormal">Hello,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">We have found that certain invalid encodings were erroneously decoded as NEON/Crypto instructions.<o:p></o:p></p>
<p class="MsoNormal">ThumbDisassembler::getInstruction didn’t validate that an instruction’s bits 26:27 are 11, before resetting them to 00 to match an ARM NEON encoding.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">As an example:<o:p></o:p></p>
<p class="MsoNormal">==========<o:p></o:p></p>
<p class="MsoNormal">$ echo 0x00 0xfc 0x40 0x0c | llvm-mc -disassemble -triple thumbv8 -show-encoding<o:p></o:p></p>
<p class="MsoNormal"> .text<o:p></o:p></p>
<p class="MsoNormal"> sha256h.32 q0, q0, q0 @ encoding: [0x00,0xff,0x40,0x0c]<o:p></o:p></p>
<p class="MsoNormal">==========<o:p></o:p></p>
<p class="MsoNormal">Here, [0x00 0xfc 0x40 0x0c] has been decoded into an MCInst whose encoding is [0x00,0xff,0x40,0x0c].<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">OK to commit this fix?<o:p></o:p></p>
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