The following reply was made to PR amd64/182740; it has been noted by GNATS.
From: [email protected] (dfilter service) To: [email protected] Cc: Subject: Re: amd64/182740: commit references a PR Date: Thu, 10 Oct 2013 19:51:45 +0000 (UTC) Author: jhb Date: Thu Oct 10 19:51:38 2013 New Revision: 256293 URL: http://svnweb.freebsd.org/changeset/base/256293 Log: Sanitize the %eflags returned by BIOS routines. Some BIOS routines enter protected mode and may leave protected-mode-specific flags like PSL_NT set when they return to real mode. This can cause a fault when BTX re-enters protected mode after the BIOS mode returns. PR: amd64/182740 Reported by: Julian Pidancet <[email protected]> Approved by: re (gjb) MFC after: 1 week Modified: head/sys/boot/i386/btx/btx/btx.S Modified: head/sys/boot/i386/btx/btx/btx.S ============================================================================== --- head/sys/boot/i386/btx/btx/btx.S Thu Oct 10 19:48:43 2013 (r256292) +++ head/sys/boot/i386/btx/btx/btx.S Thu Oct 10 19:51:38 2013 (r256293) @@ -41,6 +41,8 @@ .set PSL_RESERVED_DEFAULT,0x00000002 .set PSL_T,0x00000100 # Trap flag .set PSL_I,0x00000200 # Interrupt enable flag + .set PSL_D,0x00000400 # String instruction direction + .set PSL_NT,0x00004000 # Nested task flag .set PSL_VM,0x00020000 # Virtual 8086 mode flag .set PSL_AC,0x00040000 # Alignment check flag /* @@ -611,8 +613,8 @@ rret_tramp: movw $MEM_ESPR-0x08,%sp # R pushl %ds # regs pushl %es pushfl # Save %eflags - cli # Disable interrupts - std # String ops dec + pushl $PSL_RESERVED_DEFAULT|PSL_D # Use clean %eflags with + popfl # string ops dec xorw %ax,%ax # Reset seg movw %ax,%ds # regs movw %ax,%es # (%ss is already 0) @@ -675,6 +677,7 @@ rret_tramp.1: xorl %ecx,%ecx # Zero testl $V86F_FLAGS,%edx # User wants flags? jz rret_tramp.3 # No movl MEM_ESPR-0x3c,%eax # Read real mode flags + andl $~(PSL_T|PSL_NT),%eax # Clear unsafe flags movw %ax,-0x08(%esi) # Update user flags (low 16) /* * Return to the user task _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "[email protected]" _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-amd64 To unsubscribe, send any mail to "[email protected]"
