The Debug Registers

Starting with the 386, all IA32 processors provide hardware breakpoint detection. This is implemented using the processor's debug registers. These registers are illustrated in Figure 16-1 on page 377. Other processor functions associated with debug include:

  • The debug exception (Exception 1). This exception is generated when the processor encounters a breakpoint match on a condition specified in the debug registers.

  • The breakpoint instruction exception (Exception 3). This exception is generated when the processor executes the breakpoint (INT3) instruction.

  • The Trap bit in a task's TSS. Causes a debug exception when a task switch occurs to a task with this bit (the T bit) set to one.

  • The EFlags[RF]. When set to one by the debugger, ...

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