[ISN] 'Super-secret' debugger discovered in AMD CPUs

From: InfoSec News <alerts_at_private>
Date: Tue, 16 Nov 2010 00:13:25 -0600 (CST)

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.


Tegatai Managed Colocation: Four Provider Blended
Tier-1 Bandwidth, Fortinet Universal Threat Management,
Natural Disaster Avoidance, Always-On Power Delivery 
Network, Cisco Switches, SAS 70 Type II Datacenter. 
Find peace of mind, Defend your Critical Infrastructure.
Received on Mon Nov 15 2010 - 22:13:25 PST

This archive was generated by hypermail 2.2.0 : Mon Nov 15 2010 - 22:21:56 PST