Re: python-injected silent breakpoints broken since 1a853c52

[Jan Kiszka <jan dot kiszka at siemens dot com>]

On 2015-01-13 15:39, Joel Brobecker wrote:
> Jan,
> 
>> I've stumbled over a regression of gdb since commit 1a853c52 (make
>> "permanent breakpoints" per location and disableable). My gdb python
>> scripts [1] that load Linux kernel module symbols as the target loads
>> the modules now fail.
>>
>> The involved command is lx-symbols [2]. It installs a silent breakpoint
>> on a kernel function that is called when a module is loaded. Before
>> 1a853c52, the python callback was normally invoked and the target
>> continued to run. Since af48d08f (1a853c52 is not testable), the int3
>> instruction (I'm testing with x86) is left in the target, and garbage
>> instructions are executed, causing a kernel oops. The breakpoint is
>> apparently not properly skipped (remove, single-step, re-insert) when
>> resuming the target on return from LoadModuleBreakpoint.stop().
>>
>> I can provide more details on how to set up a reproduction case but I
>> would only gather them when desired as that is not straightforward.
>>
>> Jan
>>
>> [1] https://lkml.org/lkml/2014/11/20/531
>> [2]
>> http://git.kiszka.org/?p=linux.git;a=blob;f=scripts/gdb/linux/symbols.py;h=bf05e451c58666add299061046bf1ceb9e82f4ef;hb=d92098e7cf60d31ccd025e56d20c23917ccd0819
> 
> Thanks for the report!
> 
> Can you please open a PR at the following URL?
> https://sourceware.org/bugzilla/
> 
> There is a chance that we might consider this regression as
> release blocking for GDB 7.9 (planned for the near future),
> and having PR makes things a lot easier to track.

Done: https://sourceware.org/bugzilla/show_bug.cgi?id=17837

Jan

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