x86/entry: Fix assumptions that the HW TSS is at the beginning of cpu_tss

A future patch will move SYSENTER_stack to the beginning of cpu_tss
to help detect overflow.  Before this can happen, fix several code
paths that hardcode assumptions about the old layout.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Dave Hansen <dave.hansen@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Link: https://lkml.kernel.org/r/20171204150605.722425540@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 7 insertions, 6 deletions

diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c
index 84fcfde53f8f..50593e138281 100644
--- a/arch/x86/power/cpu.c
+++ b/arch/x86/power/cpu.c
@@ -165,12 +165,13 @@ static void fix_processor_context(void)
         struct desc_struct *desc = get_cpu_gdt_rw(cpu);
         tss_desc tss;
 #endif
-        set_tss_desc(cpu, t);   /*
-                                 * This just modifies memory; should not be
-                                 * necessary. But... This is necessary, because
-                                 * 386 hardware has concept of busy TSS or some
-                                 * similar stupidity.
-                                 */
+
+        /*
+         * This just modifies memory; should not be necessary. But... This is
+         * necessary, because 386 hardware has concept of busy TSS or some
+         * similar stupidity.
+         */
+        set_tss_desc(cpu, &t->x86_tss);
 
 #ifdef CONFIG_X86_64
         memcpy(&tss, &desc[GDT_ENTRY_TSS], sizeof(tss_desc));