From: Randolph Chung <randolph@tausq.org>
To: Carlos O'Donell <carlos@baldric.uwo.ca>
Cc: James Bottomley <James.Bottomley@steeleye.com>,
parisc-linux@lists.parisc-linux.org
Subject: [parisc-linux] Re: syscall restart block.
Date: Sun, 12 Sep 2004 17:05:11 -0700 [thread overview]
Message-ID: <20040913000511.GU28659@tausq.org> (raw)
In-Reply-To: <20040912184553.GT1854@baldric.uwo.ca>
> If we move stack trampolines to the gateway pagethen signals can't be
> delivered to the returning process during the trampoline walk (signals
> are not allowed to be delivered for processes on the gateway page). So
> it fixes our hole too.
>
> It also allows us to interpret PT_GNU_STACK properly, since the kernel
> no longer needs to execute a trampoline on the users stack. The
> toolchain can now correctly mark the stack as non-exec.
>
> I only just realized we still had this hole and it might manifest itself
> under heavy signal load.
i think the analysis is correct, but i don't like the solution! :-)
various pieces of software (gcc, gdb) need to be able to read and
analyze the signal trampoline for unwinding. putting the trampoline
onto the gateway page will break these applications, because the
gateway page is not readable by the user.
randolph
--
Randolph Chung
Debian GNU/Linux Developer, hppa/ia64 ports
http://www.tausq.org/
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next prev parent reply other threads:[~2004-09-13 0:05 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-09-12 18:45 [parisc-linux] syscall restart block Carlos O'Donell
2004-09-12 21:36 ` James Bottomley
2004-09-13 0:05 ` Randolph Chung [this message]
2004-09-13 16:03 ` [parisc-linux] [RFC] hppa needs a vDSO? Solves signal trampolines and opens up new possibilities Carlos O'Donell
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