ARM: 8022/1: ftrace: work with CONFIG_DEBUG_SET_MODULE_RONX

Make ftrace work with CONFIG_DEBUG_SET_MODULE_RONX by making module text
writable around the place where ftrace does its work, like it is done on
x86 in the patch which introduced CONFIG_DEBUG_SET_MODULE_RONX,
84e1c6bb ("x86: Add RO/NX protection for loadable kernel modules").
Tested-by: NMitchel Humpherys <mitchelh@codeaurora.org>
Signed-off-by: NRabin Vincent <rabin@rab.in>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/kernel/ftrace.c

@@ -14,6 +14,7 @@
 
 #include <linux/ftrace.h>
 #include <linux/uaccess.h>
+#include <linux/module.h>
 
 #include <asm/cacheflush.h>
 #include <asm/opcodes.h>
@@ -63,6 +64,18 @@ static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
 }
 #endif
 
+int ftrace_arch_code_modify_prepare(void)
+{
+	set_all_modules_text_rw();
+	return 0;
+}
+
+int ftrace_arch_code_modify_post_process(void)
+{
+	set_all_modules_text_ro();
+	return 0;
+}
+
 static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
 {
 	return arm_gen_branch_link(pc, addr);