Re: python-injected silent breakpoints broken since 1a853c52

[Joel Brobecker <brobecker at adacore dot com>]

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.

Thank you!
-- 
Joel