x86/entry: Convert double fault exception to IDTENTRY_DF

Convert #DF to IDTENTRY_DF
  - Implement the C entry point with DEFINE_IDTENTRY_DF
  - Emit the ASM stub with DECLARE_IDTENTRY_DF on 64bit
  - Remove the ASM idtentry in 64bit
  - Adjust the 32bit shim code
  - Fixup the XEN/PV code
  - Remove the old prototypes

No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200505135315.583415264@linutronix.de



diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index d302839..d983a0d 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -680,15 +680,9 @@
 	call	paranoid_entry
 	UNWIND_HINT_REGS
 
-	/* Read CR2 early */
-	GET_CR2_INTO(%r12);
-
-	TRACE_IRQS_OFF
-
 	movq	%rsp, %rdi		/* pt_regs pointer into first argument */
 	movq	ORIG_RAX(%rsp), %rsi	/* get error code into 2nd argument*/
 	movq	$-1, ORIG_RAX(%rsp)	/* no syscall to restart */
-	movq	%r12, %rdx		/* Move CR2 into 3rd argument */
 	call	\cfunc
 
 	jmp	paranoid_exit
@@ -918,7 +912,7 @@
 	/*
 	 * This may fault.  Non-paranoid faults on return to userspace are
 	 * handled by fixup_bad_iret.  These include #SS, #GP, and #NP.
-	 * Double-faults due to espfix64 are handled in do_double_fault.
+	 * Double-faults due to espfix64 are handled in exc_double_fault.
 	 * Other faults here are fatal.
 	 */
 	iretq
@@ -1073,8 +1067,6 @@
 
 idtentry	X86_TRAP_PF		page_fault		do_page_fault			has_error_code=1
 
-idtentry_df	X86_TRAP_DF		double_fault		do_double_fault
-
 #ifdef CONFIG_XEN_PV
 idtentry	512 /* dummy */		hypervisor_callback	xen_do_hypervisor_callback	has_error_code=0
 #endif