On Wed, Apr 27, 2011 at 12:12:12PM -0700, Mike Dunn wrote:
> On 04/27/2011 09:42 AM, Eric Cooper wrote:
> > 1. In gdb, I can step and continue, but I can't halt. Once I've
> > continued, typing ^C does nothing. (Typing it a second time just
> > makes gdb offer to quit.) I can still halt from the openocd telnet
> > client.
>
> That's odd. I've never experienced this. I'm a little behind the latest in
> git. Recently introduced bug in gdb server code? In gdb?
I'm using:
GNU gdb (Sourcery G++ Lite 2010q1-188) 7.0.50.20100218-cvs
> BTW, be careful using openocd through telnet while gdb is connected. Openocd
> assumes exclusive use of one or the other, and does things like clear all
> existing breakpoints when gdb connects. It could be confusing the issue for
> you.
I tried with no telnet client connected, just gdb, and got the same behavior.
Maybe I'll have to run arm-gdb under gdb to find out what's going on ...
> > 2. Breakpoints don't work. I can set one in either the telnet client
> > or gdb without any error message. But when I continue execution, the
> > program never halts at the breakpoint.
>
> Have you tried hardware breakpoints as well?
Yes, apparently that doesn't work on this chip:
Info : feroceon.cpu: hardware has 1 breakpoint/watchpoint unit
When I try, I get this:
> bp 0x07f7c2e4 4 hw
no watchpoint unit available for hardware breakpoint
can't add breakpoint: resource not available
> You should be able to verify that the software breakpoint was
> succesfully inserted by doing a 'mdw' or 'arm disassemble' at the
> breakpoint address and seeing if the original instruction was
> replaced with the bkpt instruction.
It all seems OK:
> arm disassemble 0x07f7c2e4
0x07f7c2e4 0xe5d03014 LDRB r3, [r0, #0x14]
> bp 0x07f7c2e4 4
breakpoint set at 0x07f7c2e4
> arm disassemble 0x07f7c2e4
0x07f7c2e4 0xe1200070 BKPT 0x0000
> resume
(breakpoint not hit, despite execution going through there)
> halt
target state: halted
target halted in ARM state due to debug-request, current mode:
Supervisor
cpsr: 0x400000d3 pc: 0x07f7c2e8
MMU: disabled, D-Cache: disabled, I-Cache: enabled
> arm disassemble 0x07f7c2e4
0x07f7c2e4 0xe1200070 BKPT 0x0000
I think it must still be executing the unmodified instruction out of
the i-cache. Shouldn't openocd flush that when it sets a software
breakpoint?
--
Eric Cooper e c c @ c m u . e d u
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