Date: Sat, 26 Dec 1998 14:22:19 +1030 (CST) From: Mark Newton <newton@atdot.dotat.org> To: cvs-all@FreeBSD.ORG, freebsd-hackers@FreeBSD.ORG Subject: LDT entries - Proposed change Message-ID: <199812260352.OAA01444@atdot.dotat.org>
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I'd like to make some low-level changes over the next couple of days to support the svr4 emulator which I'll be committing after new-year. Synopsis of problem: Sun bug ID 1251858 describes how Sun changed the system call semantics of Solaris between 2.5.1 and 2.6. System calls are still done by means of an intersegment jump into one of the system's LDT entries; FreeBSD has historically supported system call execution through LDT entries 0 and 16 (for iBCS2 COFF and BSDI emulation respectively), but Solaris 2.6 uses LDT entry 4. Unfortunately, FreeBSD has historically used LDT entry 4 for user process data. I have a patch for sys/i386/include/segments.h and sys/i386/i386/machdep.c which changes LUDATA_SEL from 4 to 5 (why 5? Why not?) and provides for system call entries via LDT entry 4 (termed LSOL26CALLS_SEL at present). I'm running this kernel at the moment with no ill effects, and I'd like to commit the change at some point over the next couple of days. Does anyone know of any applications using USER_LDT which might be in love with entry 5 already? Does anyone know of any BadThings(tm) which will occur if LUDATA_SEL is moved to entry 5? If I don't get back any bad feedback I'll commit the change shortly before new-year. In the meantime, a patch against 3.0-RELEASE which makes the change is at http://www.freebsd.org/~newton/freebsd-svr4/segpatch if anyone wants to see it. Cheers, - mark -------------------------------------------------------------------- I tried an internal modem, newton@atdot.dotat.org but it hurt when I walked. Mark Newton ----- Voice: +61-4-1958-3414 ------------- Fax: +61-8-83034403 ----- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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