[ECOS] how does GDB set breakpoint to MPC860.

[Jonathan Larmour]

Tony Ko wrote:
> 
> hi.
> I'm curious about HOW GDB sets breakpoint to MPC860 when source-level-
> debugging.

For eCos it just uses software breakpoints. I don't know off-hand whether
there's a special breakpoint instruction, or if it is an illegal
instruction; but in either case the instruction at the breakpoint address
is replaced with the breakpoint instruction, which causes a trap which
causes the stub to be entered. The original contents of the insn at the
breakpoint address are restored when continuing from the breakpoint.

> ( I mean what registers are used and something like that)
> and more, what's mean by single-step trace?

I don't think I've heard of the specific term "single-step trace", although
single-stepping is obvious. What's the context?

Jifl
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