Re: PATCH: breakpoints for gdbserver

[Daniel Jacobowitz <drow at mvista dot com>]

On Tue, Apr 16, 2002 at 01:32:18AM -0400, Daniel Jacobowitz wrote:
> This gives gdbserver a framework for memory-shadowing breakpoints, invisible
> to GDB.  They won't behave gracefully if GDB tries to single-step over them
> or if the user puts breakpoints at the same places; I intend to control all
> the cases where gdbserver might insert them with command line options, so
> that if (say) you want to debug LinuxThreads, you can turn off gdbserver
> thread support.  That's the only way to get reasonable results, IMHO.
> 
> There's a little bit of ugliness here, in that some targets do not support
> PTRACE_SINGLESTEP.  If gdbserver does not know how to single-step a target,
> the backend for that target should supply a function to find a safe
> instruction that we know will be reached, to place a temporary breakpoint
> on.  It can be the next instruction, or it can be the function return
> address, since the only places these breakpoints will be used (so far, at
> least) are on empty marker functions in the dynamic linker or in
> LinuxThreads or in some similar event-based debugging technique.  Hurdles
> will be dealt with as they arise; I don't want to over-complicate this. 
> Both single-step and resume breakpoint methods have been tested.
> 
> The only target to actually support breakpoints right now is i386-*-linux-gnu. 
> I'll go through and add breakpoints for all the other gdbserver targets at a
> not-too-future date.
> 
> I'll commit this in a day or so unless someone sees a problem with it.  Next
> on my list is a per-inferior register cache, and then I'll knuckle down to
> the core of an actual threads package.  No documentation is needed with this
> patch, although when I have a little time I may write a small gdbserver
> internals document... on the off chance someone actually wants to resurrect
> this on a target I don't have, and all...

Committed.

> 2002-04-16  Daniel Jacobowitz  <drow@mvista.com>
> 
> 	* gdbserver/mem-break.c: New file.
> 	* gdbserver/mem-break.h: New file.
> 	* gdbserver/Makefile.in: Add mem-break.o rule; update server.h
> 	dependencies.
> 	* gdbserver/inferiors.c (struct inferior_info): Add target_data
> 	member.
> 	(clear_inferiors): Free target_data member if set.
> 	(inferior_target_data, set_inferior_target_data): New functions.
> 	* gdbserver/linux-i386-low.c (i386_breakpoint, i386_breakpoint_len)
> 	(i386_stop_pc, i386_set_pc): New.  Add to the_low_target.
> 	* gdbserver/linux-low.c (linux_bp_reinsert): New variable.
> 	(struct inferior_linux_data): New.
> 	(linux_create_inferior): Use set_inferior_target_data.
> 	(linux_attach): Likewise.  Call add_inferior.
> 	(linux_wait_for_one_inferior): New function.
> 	(linux_wait): Call it.
> 	(linux_write_memory): Add const.
> 	(initialize_low): Call set_breakpoint_data.
> 	* gdbserver/linux-low.h (struct linux_target_ops): Add breakpoint
> 	handling members.
> 	* gdbserver/server.c (attach_inferior): Remove extra add_inferior
> 	call.
> 	* gdbserver/server.h: Include mem-break.h.  Update inferior.c
> 	prototypes.
> 	* gdbserver/target.c (read_inferior_memory)
> 	(write_inferior_memory): New functions.
> 	* gdbserver/target.h (read_inferior_memory)
> 	(write_inferior_memory): Change macros to prototypes.
> 	(struct target_ops): Update comments.  Add const to write_memory
> 	definition.

-- 
Daniel Jacobowitz                           Carnegie Mellon University
MontaVista Software                         Debian GNU/Linux Developer