ARM: 7334/1: add jump label support

Add the arch-specific code to support jump labels for ARM and Thumb-2.

This code will only be activated on compilers that are capable of
building it.  It has been tested with GCC 4.6 patched with the patch
from GCC bug 48637.

Cc: Jason Baron <jbaron@redhat.com>
Signed-off-by: Rabin Vincent <rabin@rab.in>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

3 files changed, 50 insertions, 0 deletions

diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index 8c63ee8d3c4..1b7d9a39097 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -38,6 +38,7 @@ obj-$(CONFIG_HAVE_ARM_SCU)	+= smp_scu.o
 obj-$(CONFIG_HAVE_ARM_TWD)      += smp_twd.o
 obj-$(CONFIG_DYNAMIC_FTRACE)    += ftrace.o insn.o
 obj-$(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
 obj-$(CONFIG_KPROBES)           += kprobes.o kprobes-common.o patch.o
 ifdef CONFIG_THUMB2_KERNEL
diff --git a/arch/arm/kernel/insn.h b/arch/arm/kernel/insn.h
index 994d60fd3ff..e96065da4da 100644
--- a/arch/arm/kernel/insn.h
+++ b/arch/arm/kernel/insn.h
@@ -1,6 +1,16 @@
 #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);
 
diff --git a/arch/arm/kernel/jump_label.c b/arch/arm/kernel/jump_label.c
new file mode 100644
index 00000000000..4ce4f789446
--- /dev/null
+++ b/arch/arm/kernel/jump_label.c
@@ -0,0 +1,39 @@
+#include <linux/kernel.h>
+#include <linux/jump_label.h>
+
+#include "insn.h"
+#include "patch.h"
+
+#ifdef HAVE_JUMP_LABEL
+
+static void __arch_jump_label_transform(struct jump_entry *entry,
+                                        enum jump_label_type type,
+                                        bool is_static)
+{
+        void *addr = (void *)entry->code;
+        unsigned int insn;
+
+        if (type == JUMP_LABEL_ENABLE)
+                insn = arm_gen_branch(entry->code, entry->target);
+        else
+                insn = arm_gen_nop();
+
+        if (is_static)
+                __patch_text(addr, insn);
+        else
+                patch_text(addr, insn);
+}
+
+void arch_jump_label_transform(struct jump_entry *entry,
+                               enum jump_label_type type)
+{
+        __arch_jump_label_transform(entry, type, false);
+}
+
+void arch_jump_label_transform_static(struct jump_entry *entry,
+                                      enum jump_label_type type)
+{
+        __arch_jump_label_transform(entry, type, true);
+}
+
+#endif