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Groups > linux.kernel > #1190677
| From | "Jan Beulich" <JBeulich@suse.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH v3 2/3] x86/ldt: Make modify_ldt optional |
| Date | 2015-07-23 09:20 +0200 |
| Message-ID | <pPiXn-88k-1@gated-at.bofh.it> (permalink) |
| References | <pPiXn-88k-3@gated-at.bofh.it> <pP7Si-qJ-27@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
>>> On 22.07.15 at 21:23, <luto@kernel.org> wrote: > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -1015,6 +1015,7 @@ config VM86 > config X86_16BIT > bool "Enable support for 16-bit segments" if EXPERT > default y > + depends on MODIFY_LDT_SYSCALL > ---help--- > This option is required by programs like Wine to run 16-bit > protected mode legacy code on x86 processors. Disabling > @@ -2053,6 +2054,22 @@ config CMDLINE_OVERRIDE > This is used to work around broken boot loaders. This should > be set to 'N' under normal conditions. > > +config MODIFY_LDT_SYSCALL > + bool "Enable the LDT (local descriptor table)" if EXPERT > + default y > + ---help--- > + Linux can allow user programs to install a per-process x86 > + Local Descriptor Table (LDT) using the modify_ldt(2) system > + call. This is required to run 16-bit or segmented code such as > + DOSEMU or some Wine programs. It is also used by some very old > + threading libraries. > + > + Enabling this feature adds a small amount of overhead to > + context switches and increases the low-level kernel attack > + surface. Disabling it removes the modify_ldt(2) system call. > + > + Saying 'N' here may make sense for embedded or server kernels. > + I think it would be better to place this ahead of the one being made dependent on it, to avoid the user being prompted for X86_16BIT despite it possibly becoming unavailable (when this one gets set to n). Jan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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Re: [PATCH v3 2/3] x86/ldt: Make modify_ldt optional "Jan Beulich" <JBeulich@suse.com> - 2015-07-23 09:20 +0200
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