This is the mail archive of the
mailing list for the Archer project.
Re: ugdb && breakpoints
Oleg> Now, to continue the tracee, gdb does not restore the
Oleg> original instruction. Instead, it
Oleg> - writes this insn into _start code
Oleg> - changes regs->ip to point to this insn
Oleg> - does single-step to execute this insn
Oleg> - changes regs->ip again
This is what is done for non-stop.
I believe it is called "displaced stepping" in gdb.
I think eventually we would like it if uprobes did this work, instead of
gdb doing it. Presumably that would yield better performance. E.g., if
we have a thread-specific breakpoint, then other threads hitting that
breakpoint could simply do the displaced stepping via uprobes, and not
report a breakpoint hit to gdb at all.
For all-stop, breakpoints are handled differently, though I don't
remember how offhand.