x86/traps: Use cpu_entry_area instead of orig_ist

The orig_ist[] array is a shadow copy of the IST array in the TSS. The
reason why it exists is that older kernels used two TSS variants with
different pointers into the debug stack. orig_ist[] contains the real
starting points.

There is no point anymore to do so because the same information can be
retrieved using the base address of the cpu entry area mapping and the
offsets of the various exception stacks.

No functional change. Preparation for removing orig_ist.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20190414160144.784487230@linutronix.de

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 0524e1d74f245338e1a4ee39b812a466690a9924..06c089513d39872c85300716e8b0bf6de703dbd4 100644 (file)
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -28,6 +28,7 @@
 #include <asm/mmu_context.h>           /* vma_pkey()                   */
 #include <asm/efi.h>                   /* efi_recover_from_page_fault()*/
 #include <asm/desc.h>                  /* store_idt(), ...             */
+#include <asm/cpu_entry_area.h>                /* exception stack              */
 
 #define CREATE_TRACE_POINTS
 #include <asm/trace/exceptions.h>
@@ -793,7 +794,7 @@ no_context(struct pt_regs *regs, unsigned long error_code,
        if (is_vmalloc_addr((void *)address) &&
            (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) ||
             address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) {
-               unsigned long stack = this_cpu_read(orig_ist.ist[ESTACK_DF]) - sizeof(void *);
+               unsigned long stack = __this_cpu_ist_top_va(DF) - sizeof(void *);
                /*
                 * We're likely to be running with very little stack space
                 * left.  It's plausible that we'd hit this condition but