Date: Sun, 27 Jun 1999 16:18:46 +1000 From: Bruce Evans <bde@zeta.org.au> To: bde@zeta.org.au, brdean@mindspring.com, freebsd-current@FreeBSD.ORG Subject: Re: kernel panic w/regard to setting io permissions bitmap Message-ID: <199906270618.QAA26124@godzilla.zeta.org.au>
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>>The panic occurs at 'swtch_com+0x6e: ltr %si'. At the time, %si is >>0x20, which indexes to what appears to be a busy tss (type=01011b) >>with a limit of 0x67. That instruction generates a general protection >>fault with an error code of 0. The current process was Idle. The busy tss seems to be the only problem. The busy bit in the tss descriptor should be clear when the ltr instruction is executed, because the descriptor has just been copied from an image whose busy bit is clear. This was broken in rev.1.332 of machdep.c by moving the initialisation of common_tssd to after the first ltr instruction, so that the busy bit in common_tssd is set. Bruce diff -c2 machdep.c~ machdep.c *** machdep.c~ Sat Jun 26 21:41:33 1999 --- machdep.c Sun Jun 27 15:52:07 1999 *************** *** 1643,1651 **** common_tss.tss_ss0 = GSEL(GDATA_SEL, SEL_KPL) ; common_tss.tss_ioopt = (sizeof common_tss) << 16; - gsel_tss = GSEL(GPROC0_SEL, SEL_KPL); - ltr(gsel_tss); - private_tss = 0; tss_gdt = &gdt[GPROC0_SEL].sd; common_tssd = *tss_gdt; dblfault_tss.tss_esp = dblfault_tss.tss_esp0 = dblfault_tss.tss_esp1 = --- 1643,1651 ---- common_tss.tss_ss0 = GSEL(GDATA_SEL, SEL_KPL) ; common_tss.tss_ioopt = (sizeof common_tss) << 16; tss_gdt = &gdt[GPROC0_SEL].sd; common_tssd = *tss_gdt; + private_tss = 0; + gsel_tss = GSEL(GPROC0_SEL, SEL_KPL); + ltr(gsel_tss); dblfault_tss.tss_esp = dblfault_tss.tss_esp0 = dblfault_tss.tss_esp1 = To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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