[PATCH] Fix ctrl-c when debugging WOW64 processes
Hannes Domani
ssbssa@yahoo.de
Thu Sep 17 20:23:45 GMT 2020
Am Donnerstag, 17. September 2020, 22:00:29 MESZ hat Simon Marchi <simark@simark.ca> Folgendes geschrieben:
> On 2020-09-17 2:03 p.m., Hannes Domani via Gdb-patches wrote:
> > DebugBreakProcess starts a new thread in the target process with the
> > entry point DbgUiRemoteBreakin, where an int3 triggers a breakpoint
> > exception for gdb.
> >
> > But this uses DbgUiRemoteBreakin of the 64bit ntdll.dll even for
> > WOW64 processes.
> > It stops in 64bit code, Wow64GetThreadContext reports a wrong pc without
> > the int3, and gdb lets the target process continue.
> >
> > So this uses DbgUiRemoteBreakin of the 32bit ntdll.dll as the thread
> > entry point for WOW64 processes instead.
>
> Interesting. Is there any reference somewhere that explains that things
> must be done this way when a 64 bit process is debugging a 32 bit
> process?
Sadly, I could find no real reference for this.
It took me quite a few hours to debug/understand this problem.
> In any case, the patch is OK, with the formatting nits below fixed.
>
> > @@ -1522,9 +1524,36 @@ ctrl_c_handler (DWORD event_type)
> > if (!new_console && !attach_flag)
> > return TRUE;
> >
> > - if (!DebugBreakProcess (current_process_handle))
> > - warning (_("Could not interrupt program. "
> > - "Press Ctrl-c in the program console."));
> > +#ifdef __x86_64__
> > + if (wow64_process)
> > + {
> > + /* Call DbgUiRemoteBreakin of the 32bit ntdll.dll in the target process.
> > + DebugBreakProcess would call the one of the 64bit ntdll.dll, which
> > + can't be correctly handled by gdb. */
> > + if (!wow64_dbgbreak)
>
> wow64_dbgbreak == nullptr
>
>
> > + {
> > + CORE_ADDR addr;
> > + if (!find_minimal_symbol_address ("ntdll!DbgUiRemoteBreakin",
> > + &addr, 0))
> > + wow64_dbgbreak = (void *) addr;
> > + }
> > +
> > + if (wow64_dbgbreak)
>
>
> wow64_dbgbreak != nullptr
Pushed with these changes, thanks.
Hannes
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