Messages in this thread | | | Subject | Re: [PATCH 2.5.73] Signal stack fixes #1 introduce PF_SS_ACTIVE | From | (Eric W. Biederman) | Date | 05 Jul 2003 19:27:22 -0600 |
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Linus Torvalds <torvalds@osdl.org> writes:
> On Fri, 4 Jul 2003, Jörn Engel wrote: > > > > So some application has it's signal handler on the signal stack and > > instead of returning to the kernel, it detect where it left off before > > the signal, mangles the last two stack frames, and goes back directly? > > Yeah, basically a lot of old threading stuff did the equivalent of > longjump by hand. > > It is entirely possible that they do not do this out of signal handlers, > since that has its own set of problems anyway, and one of the reasons for > doing co-operative user level threading is to not need locking, and thus > you never want to do any thread switching asynchronously (eg from a signal > context). > > So I'm not saying that your patch will necessarily break stuff, I'm just > pointing out that it was actually done the way it is done on purpose.
I would have to double check but I am pretty certain dosemu does this when running dpmi applications. An alternative stack is setup for signals so we get a stack we can control, and if we want to return to dosemu instead of the dpmi application we must change the stack we return to.
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