On Fri, Dec 23, 2016 at 5:37 PM, Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx> 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 <luto@xxxxxxxxxx> > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > Cc: H. Peter Anvin <hpa@xxxxxxxxx> > Cc: Borislav Petkov <bp@xxxxxxx> > Cc: Brian Gerst <brgerst@xxxxxxxxx> > Cc: Chen Yucong <slaoub@xxxxxxxxx> > Cc: Chris Metcalf <cmetcalf@xxxxxxxxxxxx> > Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> > Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx> > Cc: Huang Rui <ray.huang@xxxxxxx> > Cc: Jiri Slaby <jslaby@xxxxxxx> > Cc: Jonathan Corbet <corbet@xxxxxxx> > Cc: Michael S. Tsirkin <mst@xxxxxxxxxx> > Cc: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Cc: Ravi V. Shankar <ravi.v.shankar@xxxxxxxxx> > Cc: Shuah Khan <shuah@xxxxxxxxxx> > Cc: Vlastimil Babka <vbabka@xxxxxxx> > Cc: Tony Luck <tony.luck@xxxxxxxxx> > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx> > Cc: Liang Z. Li <liang.z.li@xxxxxxxxx> > Cc: Alexandre Julliard <julliard@xxxxxxxxxx> > Cc: Stas Sergeev <stsp@xxxxxxx> > Cc: x86@xxxxxxxxxx > Cc: linux-msdos@xxxxxxxxxxxxxxx > Signed-off-by: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx> > --- > 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 majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
