[tip:x86/irq] x86/traps: Use cpu_entry_area instead of orig_ist

[tip-bot for Thomas Gleixner]

Commit-ID:  d876b67343a648f3613506c7dbfed088fa0c875b
Gitweb:     https://git.kernel.org/tip/d876b67343a648f3613506c7dbfed088fa0c875b
Author:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Sun, 14 Apr 2019 17:59:50 +0200
Committer:  Borislav Petkov <bp@xxxxxxx>
CommitDate: Wed, 17 Apr 2019 13:01:59 +0200

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@xxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Cc: x86-ml <x86@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/20190414160144.784487230@xxxxxxxxxxxxx
---
 arch/x86/mm/fault.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 0524e1d74f24..06c089513d39 100644
--- 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