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Some questions about gdb's remote protocol and reverse debugging
- From: Julian Smith <jsmith at undo-software dot com>
- To: gdb at sources dot redhat dot com
- Date: Tue, 11 Aug 2009 22:44:01 +0100
- Subject: Some questions about gdb's remote protocol and reverse debugging
I've been trying out gdb-cvs's remote protocol, specifically the
commands for reverse debugging, and i have a couple of questions that i
was hoping someone might be able to help me with. I'm using Linux on
x86-32 and x86-64.
First, if i'm understanding things correctly, gdb appears to default to
software breakpoints, using the 'Z0' and 'z0' commands and, if these
aren't supported by the remote target, it then tries to use 'M' and 'm'
to write breakpoints directly into the inferior's memory.
Is there any way to tell gdb to try to use hardware breakpoints (with
the 'Z1' and 'z1' commands) before resorting to 'M' and 'm' ? [In the
environment i'm working in, UndoDB, hardware breakpoints are more
convenient because they don't require any patching up of %pc, and
poking breakpoints directly into memory is not supported.]
Second, am i right in thinking that gdb does things like reverse-step
and reverse-next by effectively doing many reverse-stepi's (with 'bs'),
interleaved with 'g' commands to get the registers? If so, are there
any plans to try to avoid the overhead of this somehow ?