[PATCH] kprobes: enable funcions only for required arch

Kernel/kprobes.c defines get_insn_slot() and free_insn_slot() which are
currently required _only_ for x86_64 and powerpc (which has no-exec support).

FYI, get{free}_insn_slot() functions manages the memory page which is mapped
as executable, required for instruction emulation.

This patch moves those two functions under __ARCH_WANT_KPROBES_INSN_SLOT and
defines __ARCH_WANT_KPROBES_INSN_SLOT in arch specific kprobes.h file.
Signed-off-by: NAnil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

include/asm-powerpc/kprobes.h

@@ -30,6 +30,8 @@
 #include <linux/ptrace.h>
 #include <linux/percpu.h>
 
+#define  __ARCH_WANT_KPROBES_INSN_SLOT
+
 struct pt_regs;
 
 typedef unsigned int kprobe_opcode_t;

include/asm-x86_64/kprobes.h

@@ -27,6 +27,8 @@
 #include <linux/ptrace.h>
 #include <linux/percpu.h>
 
+#define  __ARCH_WANT_KPROBES_INSN_SLOT
+
 struct pt_regs;
 
 typedef u8 kprobe_opcode_t;

kernel/kprobes.c

@@ -52,6 +52,7 @@ static DEFINE_SPINLOCK(kprobe_lock);	/* Protects kprobe_table */
 DEFINE_SPINLOCK(kretprobe_lock);	/* Protects kretprobe_inst_table */
 static DEFINE_PER_CPU(struct kprobe *, kprobe_instance) = NULL;
 
+#ifdef __ARCH_WANT_KPROBES_INSN_SLOT
 /*
  * kprobe->ainsn.insn points to the copy of the instruction to be
  * single-stepped. x86_64, POWER4 and above have no-exec support and
@@ -151,6 +152,7 @@ void __kprobes free_insn_slot(kprobe_opcode_t *slot)
 		}
 	}
 }
+#endif
 
 /* We have preemption disabled.. so it is safe to use __ versions */
 static inline void set_kprobe_instance(struct kprobe *kp)