Date: Sun, 30 Jul 2006 18:34:11 +0200 From: Tijl Coosemans <tijl@ulyssis.org> To: kmacy@fsmware.com Cc: freebsd-hackers@freebsd.org Subject: Re: i386 page fault clobbers error code in trap frame Message-ID: <200607301834.16657.tijl@ulyssis.org> In-Reply-To: <b1fa29170607291257h43592826j75513b465074f115@mail.gmail.com> References: <200607292110.37733.tijl@ulyssis.org> <b1fa29170607291257h43592826j75513b465074f115@mail.gmail.com>
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On Saturday 29 July 2006 21:57, Kip Macy wrote:
> Looking at siginfo it isn't clear that there is a "right way" to
> provide SIGSEGV, eva, and the error code.
>
> _fault._trapno should contain the machine's error code and si_signo
> should contain SIGSEGV, and si_addr contains the faulting pc. Maybe
> one could abuse si_code to contain eva. Sorry for asking a question
> that has already been answered but where is eva being put currently?
si_addr doesn't contain the faulting pc, it contains the address that=20
caused the page fault (i.e. eva). pc at the time of the fault is stored=20
in the sigcontext as sc_eip.
But siginfo is ok. The problem is in sigcontext (mostly a copy of=20
trapframe), where sc_err is incorrect. However, it appears that all the=20
relevant code has changed significantly in CURRENT to the point that=20
the offending line can simply be removed. It would be nice if somebody=20
could review/verify/test this, because I don't have CURRENT installed=20
at the moment.
=2D-- sys/i386/i386/trap.c.orig Sun Jul 30 18:27:21 2006
+++ sys/i386/i386/trap.c Sun Jul 30 18:27:56 2006
@@ -777,9 +777,6 @@
return (-1);
}
=2D /* kludge to pass faulting virtual address to sendsig */
=2D frame->tf_err =3D eva;
=2D
return((rv =3D=3D KERN_PROTECTION_FAILURE) ? SIGBUS : SIGSEGV);
}
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