On Wed, 2017-03-08 at 19:53 +0300, Stas Sergeev wrote: > 08.03.2017 19:46, Andy Lutomirski пишет: > >> No no, since I meant prot mode, this is not what I need. > >> I would never need to disable UMIP as to allow the > >> prot mode apps to do SLDT. Instead it would be good > >> to have an ability to provide a replacement for the dummy > >> emulation that is currently being proposed for kernel. > >> All is needed for this, is just to deliver a SIGSEGV. > > That's what I meant. Turning off FIXUP_UMIP would leave UMIP on but > > turn off the fixup, so you'd get a SIGSEGV indicating #GP (or a vm86 > > GP exit). > But then I am confused with the word "compat" in > your "COMPAT_MASK0_X86_UMIP_FIXUP" and > "sys_adjust_compat_mask(int op, int word, u32 mask);" > > Leaving UMIP on and only disabling a fixup doesn't > sound like a compat option to me. I would expect > compat to disable it completely. I guess that the _UMIP_FIXUP part makes it clear that emulation, not UMIP is disabled, allowing the SIGSEGV be delivered to the user space program. Would having a COMPAT_MASK0_X86_UMIP_FIXUP to disable emulation and a COMPAT_MASK0_X86_UMIP to disable UMIP make sense? Also, wouldn't having a COMPAT_MASK0_X86_UMIP to disable UMIP defeat its purpose? Applications could simply use this compat mask to bypass UMIP and gain access to the instructions it protects. Thanks and BR, Ricardo -- 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
