x86/asm, x86/microcode: Add __PAGE_OFFSET_BASE define on 32-bit

... in order to avoid #ifdeffery in code computing the ASLR randomization
offset. Remove that #ifdeffery in the microcode loader.

Suggested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nicolai Stange <nicstange@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Garnier <thgarnie@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160727120939.GA18911@nazgul.tnic
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/page_32_types.h

@@ -13,7 +13,8 @@
  * If you want more physical memory than this then see the CONFIG_HIGHMEM4G
  * and CONFIG_HIGHMEM64G options in the kernel configuration.
  */
-#define __PAGE_OFFSET		_AC(CONFIG_PAGE_OFFSET, UL)
+#define __PAGE_OFFSET_BASE	_AC(CONFIG_PAGE_OFFSET, UL)
+#define __PAGE_OFFSET		__PAGE_OFFSET_BASE
 
 #define __START_KERNEL_map	__PAGE_OFFSET
 

arch/x86/kernel/cpu/microcode/intel.c

@@ -818,13 +818,11 @@ void load_ucode_intel_ap(void)
 	if (blobs_p->valid) {
 		start = blobs_p->start;
 
-#ifdef CONFIG_RANDOMIZE_MEMORY
 		/*
 		 * Pay attention to CONFIG_RANDOMIZE_MEMORY=y as it shuffles
 		 * physmem mapping too and there we have the initrd.
 		 */
 		start += PAGE_OFFSET - __PAGE_OFFSET_BASE;
-#endif
 	}
 
 	collect_cpu_info_early(&uci);