Re: [PATCH] [gdb] Fix assert in delete_breakpoint

[Luis Machado <luis.machado@arm.com>]

On 11/14/23 15:09, Simon Marchi wrote:
> On 11/13/23 10:26, Tom de Vries wrote:
>> On a pinebook (aarch64 with 64-bit kernel and 32-bit userland) with test-case
>> gdb.base/gdb-sigterm.exp I run into:
>> ...
>> intrusive_list.h:458: internal-error: erase_element: \
>>   Assertion `elem_node->prev != INTRUSIVE_LIST_UNLINKED_VALUE' failed.^M
>> ...
>>
>> Fix this similar to:
>> - commit c0afd99439f ("[gdb/tui] Fix assert in ~gdbpy_tui_window_maker"), and
>> - commit 995a34b1772 ("Guard against frame.c destructors running before
>>   frame-info.c's"
>> by checking is_linked () before attempting to remove from breakpoint_chain.
>>
>> Tested on the pinebook and x86_64-linux.
>>
>> PR gdb/31061
>> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31061
> 
> Hi Tom,
> 
> Did you dig a little bit to understand why this happened specifically
> with this setup, and that it's indeed expected that the breakpoint is
> not in the breakpoint chain?  The stack trace you showed contains (with
> names demangled):
> 
>     0xaae1d42b delete_breakpoint(breakpoint*)^M
>             /home/rock/gdb/src/gdb/breakpoint.c:12636^M
>     0xab1ed045 delete_thread_breakpoint^M
>             /home/rock/gdb/src/gdb/thread.c:98^M
>     0xab1ed0ab delete_single_step_breakpoints(thread_info*)^M
>             /home/rock/gdb/src/gdb/thread.c:123^M
>     0xab021e81 delete_thread_infrun_breakpoints^M
>             /home/rock/gdb/src/gdb/infrun.c:3733^M
>     0xab021edd for_each_just_stopped_thread^M
>             /home/rock/gdb/src/gdb/infrun.c:3752^M
>     0xab021f79 delete_just_stopped_threads_infrun_breakpoints^M
>             /home/rock/gdb/src/gdb/infrun.c:3768^M
> 
> It looks like this is specific to architectures that use software
> single stepping?  Does "32-bit userland on 64-bit kernel on aarch64" use
> software single stepping, like 32-bit ARM?

Given AArch64 supports hardware single-stepping, I'd expect 32-bit userspace
running on 64-bit Linux Kernel to also support it.