kprobes: Ensure blacklist data is aligned

ARC Linux (not supporting native unaligned access) was failing
to boot because __start_kprobe_blacklist was not aligned.

This was because per generated vmlinux.lds it was emitted right
next to .rodata with strings etc hence could be randomly
unaligned.

Fix that by ensuring a word alignment. While 4 would suffice for
32bit arches and problem at hand, it is probably better to put 8.

| Path: (null) CPU: 0 PID: 1 Comm: swapper Not tainted
| 3.15.0-rc3-next-20140430 #2
| task: 8f044000 ti: 8f01e000 task.ti: 8f01e000
|
| [ECR   ]: 0x00230400 => Misaligned r/w from 0x800fb0d3
| [EFA   ]: 0x800fb0d3
| [BLINK ]: do_one_initcall+0x86/0x1bc
| [ERET  ]: init_kprobes+0x52/0x120

Signed-off-by: Vineet Gupta <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>
Cc: anton Kolesov <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

Author: Vineet Gupta

include/asm-generic/vmlinux.lds.h

@@ -110,7 +110,8 @@
 #endif
 
 #ifdef CONFIG_KPROBES
-#define KPROBE_BLACKLIST()	VMLINUX_SYMBOL(__start_kprobe_blacklist) = .; \
+#define KPROBE_BLACKLIST()	. = ALIGN(8);				      \
+				VMLINUX_SYMBOL(__start_kprobe_blacklist) = .; \
 				*(_kprobe_blacklist)			      \
 				VMLINUX_SYMBOL(__stop_kprobe_blacklist) = .;
 #else