ARM: kprobes: enable OPTPROBES for ARM 32

This patch introduce kprobeopt for ARM 32.

Limitations:
 - Currently only kernel compiled with ARM ISA is supported.

 - Offset between probe point and optinsn slot must not larger than
   32MiB. Masami Hiramatsu suggests replacing 2 words, it will make
   things complex. Futher patch can make such optimization.

Kprobe opt on ARM is relatively simpler than kprobe opt on x86 because
ARM instruction is always 4 bytes aligned and 4 bytes long. This patch
replace probed instruction by a 'b', branch to trampoline code and then
calls optimized_callback(). optimized_callback() calls opt_pre_handler()
to execute kprobe handler. It also emulate/simulate replaced instruction.

When unregistering kprobe, the deferred manner of unoptimizer may leave
branch instruction before optimizer is called. Different from x86_64,
which only copy the probed insn after optprobe_template_end and
reexecute them, this patch call singlestep to emulate/simulate the insn
directly. Futher patch can optimize this behavior.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Will Deacon <will.deacon@arm.com>
Reviewed-by: Jon Medhurst (Tixy) <tixy@linaro.org>
Signed-off-by: Jon Medhurst <tixy@linaro.org>

4 files changed, 3 insertions, 34 deletions

diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index 9c51a433e025..902397dd1000 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -52,7 +52,7 @@ obj-$(CONFIG_FUNCTION_GRAPH_TRACER)	+= ftrace.o insn.o
 obj-$(CONFIG_JUMP_LABEL)        += jump_label.o insn.o patch.o
 obj-$(CONFIG_KEXEC)             += machine_kexec.o relocate_kernel.o
 # Main staffs in KPROBES are in arch/arm/probes/ .
-obj-$(CONFIG_KPROBES)           += patch.o
+obj-$(CONFIG_KPROBES)           += patch.o insn.o
 obj-$(CONFIG_OABI_COMPAT)       += sys_oabi-compat.o
 obj-$(CONFIG_ARM_THUMBEE)       += thumbee.o
 obj-$(CONFIG_KGDB)              += kgdb.o patch.o
diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
index b8c75e45a950..709ee1d6d4df 100644
--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -20,8 +20,7 @@
 #include <asm/cacheflush.h>
 #include <asm/opcodes.h>
 #include <asm/ftrace.h>
-
-#include "insn.h"
+#include <asm/insn.h>
 
 #ifdef CONFIG_THUMB2_KERNEL
 #define NOP             0xf85deb04      /* pop.w {lr} */
diff --git a/arch/arm/kernel/insn.h b/arch/arm/kernel/insn.h
deleted file mode 100644
index e96065da4dae..000000000000
--- a/arch/arm/kernel/insn.h
+++ /dev/null
@@ -1,29 +0,0 @@
-#ifndef __ASM_ARM_INSN_H
-#define __ASM_ARM_INSN_H
-
-static inline unsigned long
-arm_gen_nop(void)
-{
-#ifdef CONFIG_THUMB2_KERNEL
-        return 0xf3af8000; /* nop.w */
-#else
-        return 0xe1a00000; /* mov r0, r0 */
-#endif
-}
-
-unsigned long
-__arm_gen_branch(unsigned long pc, unsigned long addr, bool link);
-
-static inline unsigned long
-arm_gen_branch(unsigned long pc, unsigned long addr)
-{
-        return __arm_gen_branch(pc, addr, false);
-}
-
-static inline unsigned long
-arm_gen_branch_link(unsigned long pc, unsigned long addr)
-{
-        return __arm_gen_branch(pc, addr, true);
-}
-
-#endif
diff --git a/arch/arm/kernel/jump_label.c b/arch/arm/kernel/jump_label.c
index d8da075959bf..e39cbf488cfe 100644
--- a/arch/arm/kernel/jump_label.c
+++ b/arch/arm/kernel/jump_label.c
@@ -1,8 +1,7 @@
 #include <linux/kernel.h>
 #include <linux/jump_label.h>
 #include <asm/patch.h>
-
-#include "insn.h"
+#include <asm/insn.h>
 
 #ifdef HAVE_JUMP_LABEL