Is this bug really still present in modern CPUs? This change breaks running 16-bit apps in Wine. I have a few really old games I like to play on occasion, and I don't have a copy of Win 3.11 to put in a VM.
On Fri, Apr 11, 2014 at 1:36 PM, tip-bot for H. Peter Anvin <tip...@zytor.com> wrote: > Commit-ID: b3b42ac2cbae1f3cecbb6229964a4d48af31d382 > Gitweb: http://git.kernel.org/tip/b3b42ac2cbae1f3cecbb6229964a4d48af31d382 > Author: H. Peter Anvin <h...@linux.intel.com> > AuthorDate: Sun, 16 Mar 2014 15:31:54 -0700 > Committer: H. Peter Anvin <h...@linux.intel.com> > CommitDate: Fri, 11 Apr 2014 10:10:09 -0700 > > x86-64, modify_ldt: Ban 16-bit segments on 64-bit kernels > > The IRET instruction, when returning to a 16-bit segment, only > restores the bottom 16 bits of the user space stack pointer. We have > a software workaround for that ("espfix") for the 32-bit kernel, but > it relies on a nonzero stack segment base which is not available in > 32-bit mode. > > Since 16-bit support is somewhat crippled anyway on a 64-bit kernel > (no V86 mode), and most (if not quite all) 64-bit processors support > virtualization for the users who really need it, simply reject > attempts at creating a 16-bit segment when running on top of a 64-bit > kernel. > > Cc: Linus Torvalds <torva...@linux-foundation.org> > Signed-off-by: H. Peter Anvin <h...@linux.intel.com> > Link: http://lkml.kernel.org/n/tip-kicdm89kzw9lldryb1br9...@git.kernel.org > Cc: <sta...@vger.kernel.org> > --- > arch/x86/kernel/ldt.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c > index ebc9873..af1d14a 100644 > --- a/arch/x86/kernel/ldt.c > +++ b/arch/x86/kernel/ldt.c > @@ -229,6 +229,17 @@ static int write_ldt(void __user *ptr, unsigned long > bytecount, int oldmode) > } > } > > + /* > + * On x86-64 we do not support 16-bit segments due to > + * IRET leaking the high bits of the kernel stack address. > + */ > +#ifdef CONFIG_X86_64 > + if (!ldt_info.seg_32bit) { > + error = -EINVAL; > + goto out_unlock; > + } > +#endif > + > fill_ldt(&ldt, &ldt_info); > if (oldmode) > ldt.avl = 0; > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
