powerpc/ftrace: Use patch_instruction instead of probe_kernel_write()

The patch_instruction() interface is made to modify kernel text. It is
safer to use that then the probe_kernel_write() when modifying kernel
code.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/ftrace.c

@@ -63,11 +63,9 @@ ftrace_modify_code(unsigned long ip, unsigned int old, unsigned int new)
 		return -EINVAL;
 
 	/* replace the text with the new text */
-	if (probe_kernel_write((void *)ip, &new, MCOUNT_INSN_SIZE))
+	if (patch_instruction((unsigned int *)ip, new))
 		return -EPERM;
 
-	flush_icache_range(ip, ip + 8);
-
 	return 0;
 }
 
@@ -212,12 +210,9 @@ __ftrace_make_nop(struct module *mod,
 	 */
 	op = 0x48000008;	/* b +8 */
 
-	if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))
+	if (patch_instruction((unsigned int *)ip, op))
 		return -EPERM;
 
-
-	flush_icache_range(ip, ip + 8);
-
 	return 0;
 }
 
@@ -286,11 +281,9 @@ __ftrace_make_nop(struct module *mod,
 
 	op = PPC_INST_NOP;
 
-	if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))
+	if (patch_instruction((unsigned int *)ip, op))
 		return -EPERM;
 
-	flush_icache_range(ip, ip + 8);
-
 	return 0;
 }
 #endif /* PPC64 */
@@ -426,11 +419,9 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 
 	pr_devel("write to %lx\n", rec->ip);
 
-	if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))
+	if (patch_instruction((unsigned int *)ip, op))
 		return -EPERM;
 
-	flush_icache_range(ip, ip + 8);
-
 	return 0;
 }
 #endif /* CONFIG_PPC64 */