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'Super-secret' debugger discovered in AMD CPUs
From: InfoSec News <alerts () infosecnews org>
Date: Tue, 16 Nov 2010 00:13:25 -0600 (CST)
http://www.theregister.co.uk/2010/11/15/amd_secret_debugger/ By Dan Goodin in San Francisco The Register 15th November 2010 A hardware hacker has discovered a secret debugging feature hidden in all AMD chips made in the past decade. The password-protected debugger came as a shock to reverse-engineers who have hungered for an on-chip mechanism for performing conditional and direct-hardware breakpoint operations. Although AMD has built the firmware-controlled feature into all chips since the Athlon XP, the company kept it a closely guarded secret that was only disclosed late last week by a hacker who goes by the name Czernobyl. “AMD processors (Athlon XP and better) have included firmware-based debugging features that expand greatly over standard, architecturally defined capabilities of x86,” the hacker wrote. “For some reason, though, AMD has been tightly secretive about these features; hint of their existence was gained by glancing at CBID's page.” To put a chip into developer mode, a user must first enter what amounts to a password -- 9C5A203A -- into the CPU's EDI register. Czernobyl was able to deduce the secret setting by brute forcing the key. [...]
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