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Date:      Thu, 22 Feb 2001 23:29:10 +0200
From:      Mark Murray <mark@grondar.za>
To:        John Baldwin <jhb@FreeBSD.org>
Cc:        cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org
Subject:   Re: cvs commit: src/sys/i386/i386 trap.c 
Message-ID:  <200102222128.f1MLSS119499@gratis.grondar.za>
In-Reply-To: <200102221935.f1MJZLx89084@freefall.freebsd.org> ; from John Baldwin <jhb@FreeBSD.org>  "Thu, 22 Feb 2001 11:35:21 PST."
References:  <200102221935.f1MJZLx89084@freefall.freebsd.org> 

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>   The p_md.md_regs member of proc is used in signal handling to reference
>   the the original trapframe of the syscall, trap, or interrupt that entered
>   the kernel.  Before SMPng, ast's were handled via a psuedo trap at the
>   end of doerti.  With the SMPng commit, ast's were broken out into a
>   separate ast() function that was called from doreti to match the behavior
>   of other architectures.  Unfortunately, when this was done, the
>   p_md.md_regs member of curproc was not updateda in ast(), thus when
>   signals are handled by userret() after an interrupt that returns to
>   userland, we end up using a stale trapframe that will result in the
>   registers from the old trapframe overwriting the real trapframe and
>   smashing all the registers right before we return to usermode.  The saved
>   %cs:%eip from where we were in usermode are saved in the trapframe for
>   example.

Does this fix any intersting panics? I have a (patched) kernel that
panics (GPF) in doreti. Is this inspired by anything of that ilk?

M
-- 
Mark Murray
Warning: this .sig is umop ap!sdn

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