Re: ptrace single-stepping change breaks Wine

Eric Pouech
2004-11-28T17:04:14Z

Jesse Allen a écrit :
> On Sun, Nov 21, 2004 at 10:23:41PM -0800, Linus Torvalds wrote:
>
>>Ok, how about this patch?
>>
>>It does basically two things:
>>
>> - it makes the x86 version of ptrace be a lot more careful about the TF
>> bit in eflags, and in particular it never touches it _unless_ the
>> tracer has explicitly asked for it (ie we set TF only when doing a
>> PTRACE_SINGESTEP, and we clear it only when it has been set by us, not
>> if it has been set by the program itself).
>>
>> This patch also cleans up the codepaths by doing all the common stuff
>> in set_singlestep()/clear_singlestep().
>>
>> - It clarifies signal handling, and makes it clear that we always push
>> the full eflags onto the signal stack, _except_ if the TF bit was set
>> by an external ptrace user, in which case we hide it so that the tracee
>> doesn't see it when it looks at its stack contents.
>>
>> It also adds a few comments, and makes it clear that the signal handler
>> itself is always set up with TF _clear_. But if we were single-stepped
>> into it, we will have notified the debugger, so the debugger obviously
>> can (and often will) decide to continue single-stepping.
>>
>>IMHO, this is a nice cleanup, and it also means that I can actually debug
>>my "program from hell":
>>
>> [torvalds@evo ~]$ gdb ./a.out
>> GNU gdb Red Hat Linux (6.1post-1.20040607.41rh)
>> Copyright 2004 Free Software Foundation, Inc.
>> GDB is free software, covered by the GNU General Public License, and you are
>> welcome to change it and/or distribute copies of it under certain conditions.
>> Type "show copying" to see the conditions.
>> There is absolutely no warranty for GDB. Type "show warranty" for details.
>> This GDB was configured as "i386-redhat-linux-gnu"...(no debugging symbols
>> found)...Using host libthread_db library "/lib/tls/libthread_db.so.1".
>>
>> (gdb) run
>> Starting program: /home/torvalds/a.out
>> Reading symbols from shared object read from target memory...(no debugging
>> symbols found)...done.
>> Loaded system supplied DSO at 0xffffe000
>> (no debugging symbols found)...(no debugging symbols found)...
>> Program received signal SIGTRAP, Trace/breakpoint trap.
>> 0x08048480 in main ()
>> (gdb) signal SIGTRAP
>> Continuing with signal SIGTRAP.
>>
>> Program received signal SIGTRAP, Trace/breakpoint trap.
>> 0x08048487 in main ()
>> (gdb) signal SIGTRAP
>> Continuing with signal SIGTRAP.
>>
>> Program received signal SIGTRAP, Trace/breakpoint trap.
>> 0x08048488 in smc ()
>> (gdb) signal SIGTRAP
>> Continuing with signal SIGTRAP.
>> Copy protected: ok
>>
>> Program exited with code 01.
>> (gdb)
>>
>>which I think is a sign that this patch actually fixes ptrace.
>>
>>Does this help with wine? I dunno. Maybe some wine people can comment..
>>
>
>
>
> For the wine app in question, it does make a difference. However, there is
> a new problem. The program gets stuck at the loading screen at 100% CPU.
> It's making a call to select, timing out, and then tries select again,
> repeats. It's waiting for something that seems to never happen.
>
> I've captured a log, "loop.log.bz2", and shortened to have only the relevent
> information after the CMS32_MUTEX is created. Look for occurances of
> "select()" -- I think the second one is where it starts. It's on my ftp if
> anyone wants to take a look. It probably can be compared to the working-
> version log where this doesn't occur, but it might be a pain to spot the
> working particular instance.

Hi Jesse
Any network issue on your side? I tried to traceroute resnet.disp.net, but no avail.
So I cannot have a look to you newest trace.

A+