[wazari972]

I thought that these HW 'breakpoint' registers were (only) used to implement watchpoint, that is, read/write operations on data. Can they be used to implement 'instruction breakpoints'?

[pcwalton]

You can set the "break on" bitfield to "execute" (0) to have the debug register function as a normal breakpoint.

[jasonzemos]

On register %dr7 there are 4-bit switches for each of the 4 breakpoints. The first two bits can trap on Instruction (0b00), Write (0b01), and ReadWrite (0b11). The second two bits specify the alignment of Byte (0b00), Short (0b01), Long (0b10), and Int (0b11).

[burfog]

Sure, but normally you wouldn't waste them on that. You might use them for instruction breakpoints in ROM, or when you suspect that the program checksums itself.