x86/traps: Enable all exception handler callbacks early

Now that early_fixup_exception() has pt_regs, we can just call
fixup_exception() from it.  This will make fancy exception handlers
work early.

Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: KVM list <kvm@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: xen-devel <Xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/20fc047d926150cb08cb9b9f2923519b07ec1a15.1459605520.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/mm/extable.c

@@ -88,10 +88,6 @@ extern unsigned int early_recursion_flag;
 /* Restricted version used during very early boot */
 void __init early_fixup_exception(struct pt_regs *regs, int trapnr)
 {
-	const struct exception_table_entry *e;
-	unsigned long new_ip;
-	ex_handler_t handler;
-
 	/* Ignore early NMIs. */
 	if (trapnr == X86_TRAP_NMI)
 		return;
@@ -102,19 +98,8 @@ void __init early_fixup_exception(struct pt_regs *regs, int trapnr)
 	if (regs->cs != __KERNEL_CS)
 		goto fail;
 
-	e = search_exception_tables(regs->ip);
-	if (!e)
-		goto fail;
-
-	new_ip  = ex_fixup_addr(e);
-	handler = ex_fixup_handler(e);
-
-	/* special handling not supported during early boot */
-	if (handler != ex_handler_default)
-		goto fail;
-
-	regs->ip = new_ip;
-	return;
+	if (fixup_exception(regs, trapnr))
+		return;
 
 fail:
 	early_printk("PANIC: early exception 0x%02x IP %lx:%lx error %lx cr2 0x%lx\n",