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Andy Lutomirski authored
For mysterious historical reasons, struct user_desc doesn't indicate whether segments are accessed. set_thread_area() has always programmed segments as non-accessed, so the first write will set the accessed bit. This will fault if the GDT is read-only. Fix it by making TLS segments start out accessed. If this ends up breaking something, we could, in principle, leave TLS segments non-accessed and fix them up when we get the page fault. I'd be surprised, though -- AFAIK all the nasty legacy segmented programs (DOSEMU, Wine, things that run on DOSEMU and Wine, etc.) do their nasty segmented things using the LDT and not the GDT. I assume this is mainly because old OSes (Linux and otherwise) didn't historically provide APIs to do nasty things in the GDT. Fixes: 45fc8757 ("x86: Make the GDT remapping read-only on 64-bit") Signed-off-by:
Andy Lutomirski <luto@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Thomas Garnier <thgarnie@google.com> Link: http://lkml.kernel.org/r/62b7748542df0164af7e0a5231283b9b13858c45.1489900519.git.luto@kernel.orgSigned-off-by:
Thomas Gleixner <tglx@linutronix.de>
5b781c7e