On Fri, Dec 23, 2016 at 5:37 PM, Ricardo Neri <[email protected]> wrote: > If the User-Mode Instruction Prevention CPU feature is available and > enabled, a general protection fault will be issued if the instructions > sgdt, sldt, sidt, str or smsw are executed from user-mode context > (CPL > 0). If the fault was caused by any of the instructions protected > by UMIP, fixup_umip_exceptino will emulate dummy results for these > instructions. > > Cc: Andy Lutomirski <[email protected]> > Cc: Andrew Morton <[email protected]> > Cc: H. Peter Anvin <[email protected]> > Cc: Borislav Petkov <[email protected]> > Cc: Brian Gerst <[email protected]> > Cc: Chen Yucong <[email protected]> > Cc: Chris Metcalf <[email protected]> > Cc: Dave Hansen <[email protected]> > Cc: Fenghua Yu <[email protected]> > Cc: Huang Rui <[email protected]> > Cc: Jiri Slaby <[email protected]> > Cc: Jonathan Corbet <[email protected]> > Cc: Michael S. Tsirkin <[email protected]> > Cc: Paul Gortmaker <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: Ravi V. Shankar <[email protected]> > Cc: Shuah Khan <[email protected]> > Cc: Vlastimil Babka <[email protected]> > Cc: Tony Luck <[email protected]> > Cc: Paolo Bonzini <[email protected]> > Cc: Liang Z. Li <[email protected]> > Cc: Alexandre Julliard <[email protected]> > Cc: Stas Sergeev <[email protected]> > Cc: [email protected] > Cc: [email protected] > Signed-off-by: Ricardo Neri <[email protected]> > --- > arch/x86/kernel/traps.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c > index bf0c6d0..5044fb3 100644 > --- a/arch/x86/kernel/traps.c > +++ b/arch/x86/kernel/traps.c > @@ -64,6 +64,7 @@ > #include <asm/trace/mpx.h> > #include <asm/mpx.h> > #include <asm/vm86.h> > +#include <asm/umip.h> > > #ifdef CONFIG_X86_64 > #include <asm/x86_init.h> > @@ -491,6 +492,9 @@ do_general_protection(struct pt_regs *regs, long > error_code) > RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); > cond_local_irq_enable(regs); > > + if (user_mode(regs) && !fixup_umip_exception(regs)) > + return; > +
I would do fixup_umip_exception(regs) == 0 to make it more obvious what's going on. Also, since you're allowing this in v8086 mode, I think this should have an explicit test in tools/testing/selftests/x86/entry_from_vm86.c. I *think* it will work fine, but the pt_regs handling in vm86 mode is quite scary and has been rewritten recently. -- To unsubscribe from this list: send the line "unsubscribe linux-msdos" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
