arm/ftrace: Use __patch_text()

Instead of flipping text protection, use the patch_text infrastructure
that uses a fixmap alias where required.

This removes the last user of set_all_modules_text_*().

Tested-by: Will Deacon <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

Author: Peter Zijlstra

arch/arm/kernel/Makefile

@@ -49,8 +49,8 @@ obj-$(CONFIG_HAVE_ARM_SCU)	+= smp_scu.o
 obj-$(CONFIG_HAVE_ARM_TWD)	+= smp_twd.o
 obj-$(CONFIG_ARM_ARCH_TIMER)	+= arch_timer.o
 obj-$(CONFIG_FUNCTION_TRACER)	+= entry-ftrace.o
-obj-$(CONFIG_DYNAMIC_FTRACE)	+= ftrace.o insn.o
-obj-$(CONFIG_FUNCTION_GRAPH_TRACER)	+= ftrace.o insn.o
+obj-$(CONFIG_DYNAMIC_FTRACE)	+= ftrace.o insn.o patch.o
+obj-$(CONFIG_FUNCTION_GRAPH_TRACER)	+= ftrace.o insn.o patch.o
 obj-$(CONFIG_JUMP_LABEL)	+= jump_label.o insn.o patch.o
 obj-$(CONFIG_KEXEC)		+= machine_kexec.o relocate_kernel.o
 # Main staffs in KPROBES are in arch/arm/probes/ .

arch/arm/kernel/ftrace.c

@@ -22,6 +22,7 @@
 #include <asm/ftrace.h>
 #include <asm/insn.h>
 #include <asm/set_memory.h>
+#include <asm/patch.h>
 
 #ifdef CONFIG_THUMB2_KERNEL
 #define	NOP		0xf85deb04	/* pop.w {lr} */
@@ -35,9 +36,7 @@ static int __ftrace_modify_code(void *data)
 {
 	int *command = data;
 
-	set_kernel_text_rw();
 	ftrace_modify_all_code(*command);
-	set_kernel_text_ro();
 
 	return 0;
 }
@@ -59,13 +58,11 @@ static unsigned long adjust_address(struct dyn_ftrace *rec, unsigned long addr)
 
 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();
 	/* Make sure any TLB misses during machine stop are cleared. */
 	flush_tlb_all();
 	return 0;
@@ -97,10 +94,7 @@ static int ftrace_modify_code(unsigned long pc, unsigned long old,
 			return -EINVAL;
 	}
 
-	if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE))
-		return -EPERM;
-
-	flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
+	__patch_text((void *)pc, new);
 
 	return 0;
 }