Date: Mon, 30 Jul 2007 00:17:37 -0700 (PDT) From: Don Lewis <truckman@FreeBSD.org> To: jhb@FreeBSD.org Cc: cvs-src@FreeBSD.org, src-committers@FreeBSD.org, cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/i386/i386 trap.c Message-ID: <200707300717.l6U7HcNC089641@gw.catspoiler.org> In-Reply-To: <200707270819.08197.jhb@freebsd.org>
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On 27 Jul, John Baldwin wrote: > On Friday 27 July 2007 06:42:20 am Don Lewis wrote: >> On 13 Jun, John Baldwin wrote: >> > jhb 2007-06-13 22:37:48 UTC >> > >> > FreeBSD src repository >> > >> > Modified files: >> > sys/i386/i386 trap.c >> > Log: >> > Don't clobber tf_err with the eva from a page fault as the page fault >> > address is saved in ksi_addr already. >> > >> > PR: i386/101379 >> > Submitted by: Tijl Coosemans : tijl ulyssis org >> > >> > Revision Changes Path >> > 1.306 +0 -3 src/sys/i386/i386/trap.c >> >> This change appears to have broken the garbage collector in >> ports/lang/pm3-base, which means that cvsup no longer works on -CURRENT. >> The garbage collector uses the old sigvec() interface, and counts on >> getting the fault address from the sc_err field in struct sigcontext, >> which is copied from tf_err. >> >> The Modula-3 source code for the handler and the sigvec() call is in >> pm3-1.1.15/libs/m3core/src/runtime/FreeBSD4/RTHeapDep.m3 under the port >> work directory. Since Modula-3 compiler uses this code, the compiler is >> bootstrapped from a version of this file that has already been >> translated to i386 assembly language. The latter lives in >> pm3-1.1.15/boot-FreeBSD4/m3core/FreeBSD4/RTHeapDep.ms. >> >> Modifying the assembly code to convert it to use sigaction() and to pull >> the fault address out of the siginfo structure is left as an exercise >> for someone more masochistic than me. > > Assuming wine doesn't use sigvec() this should work. I noticed while looking > at this that ddb's backtrace had some special handling that assumes tf_err == > faulting address as well. :-/ > > Index: machdep.c > =================================================================== > RCS file: /usr/cvs/src/sys/i386/i386/machdep.c,v > retrieving revision 1.657 > diff -u -r1.657 machdep.c > --- machdep.c 6 Jun 2007 07:35:07 -0000 1.657 > +++ machdep.c 27 Jul 2007 12:17:22 -0000 > @@ -352,7 +352,12 @@ > sf.sf_siginfo.si_sc.sc_pc = regs->tf_eip; > sf.sf_siginfo.si_sc.sc_ps = regs->tf_eflags; > sf.sf_siginfo.si_sc.sc_trapno = regs->tf_trapno; > - sf.sf_siginfo.si_sc.sc_err = regs->tf_err; > + > + /* > + * XXX: Some old binaries using sigvec() such as cvsup depend > + * on this. > + */ > + sf.sf_siginfo.si_sc.sc_err = (register_t)ksi->ksi_addr; > > /* > * If we're a vm86 process, we want to save the segment registers. After installing this patch, the bootstrap in the pm3-base port still fails. I installed pm3-base from the 6-STABLE package, and it isn't able to compile any of the other ports. I suspect the reason for the latter is that it is new enough to use sendsig() and not osendsig(). This makes sense because osendsig is a COMPAT_43 function and the binary is a lot newer than that. To preserve the "kludge" ABI as much as possible, I think it would be necessary to move the assignment to sc_err into the if-else block that checks to see if the signal handler was installed with the SA_SIGIFNO flag, and to make the same change in sendsig(), osendsig(), and freebsd4_sendsig(). This will break the wine port unless it uses SA_SIGINFO. As an alternative, I've got a set of patches to pm3-base to get it working on -CURRENT. It wasn't too hard to fix the bootstrap to use the "undocumented 4th arg" to the signal handler that is mentioned in i386/include/sigframe.h. The rest of the patches change the low-level Module-3 code to use sigaction() with the SA_SIGINFO flag instead of using a mixture of sigaction() (without SA_SIGINFO) and sigvec(). I'll post the patches for testing once I've had a chance to clean them up some more.
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