kaiser: cleanups while trying for gold link

While trying to get our gold link to work, four cleanups:
matched the gdt_page declaration to its definition;
in fiddling unsuccessfully with PERCPU_INPUT(), lined up backslashes;
lined up the backslashes according to convention in percpu-defs.h;
deleted the unused irq_stack_pointer addition to irq_stack_union.

Sad to report that aligning backslashes does not appear to help gold
align to 8192: but while these did not help, they are worth keeping.
Acked-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

CVE-2017-5754
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

arch/x86/include/asm/desc.h

@@ -43,7 +43,7 @@ struct gdt_page {
 	struct desc_struct gdt[GDT_ENTRIES];
 } __attribute__((aligned(PAGE_SIZE)));
 
-DECLARE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page);
+DECLARE_PER_CPU_PAGE_ALIGNED_USER_MAPPED(struct gdt_page, gdt_page);
 
 static inline struct desc_struct *get_cpu_gdt_table(unsigned int cpu)
 {

arch/x86/include/asm/processor.h

@@ -333,11 +333,6 @@ union irq_stack_union {
 		char gs_base[40];
 		unsigned long stack_canary;
 	};
-
-	struct {
-		char irq_stack_pointer[64];
-		char unused[IRQ_STACK_SIZE - 64];
-	};
 };
 
 DECLARE_PER_CPU_FIRST(union irq_stack_union, irq_stack_union) __visible;

include/asm-generic/vmlinux.lds.h

@@ -725,7 +725,6 @@
  */
 #define PERCPU_INPUT(cacheline)						\
 	VMLINUX_SYMBOL(__per_cpu_start) = .;				\
-	\
 	VMLINUX_SYMBOL(__per_cpu_user_mapped_start) = .;		\
 	*(.data..percpu..first)						\
 	. = ALIGN(cacheline);						\
@@ -734,7 +733,6 @@
 	. = ALIGN(PAGE_SIZE);						\
 	*(.data..percpu..user_mapped..page_aligned)			\
 	VMLINUX_SYMBOL(__per_cpu_user_mapped_end) = .;			\
-	\
 	. = ALIGN(PAGE_SIZE);						\
 	*(.data..percpu..page_aligned)					\
 	. = ALIGN(cacheline);						\