ARM: kprobes: Add Thumb instruction decoding stubs

Extend arch_prepare_kprobe to support probing of Thumb code. For
the actual decoding of Thumb instructions, stub functions are
added which currently just reject the probe.

Signed-off-by: Jon Medhurst <tixy@yxit.co.uk>
Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>

diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index a22b8f1c7b14b10d8e10cdea6698fdd362c9dff4..f7887dc53c1f6ac8dbda79c63bfd331d51f67a4c 100644 (file)
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -38,7 +38,11 @@ obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o
 obj-$(CONFIG_FUNCTION_GRAPH_TRACER)    += ftrace.o
 obj-$(CONFIG_KEXEC)            += machine_kexec.o relocate_kernel.o
 obj-$(CONFIG_KPROBES)          += kprobes.o kprobes-common.o
+ifdef CONFIG_THUMB2_KERNEL
+obj-$(CONFIG_KPROBES)          += kprobes-thumb.o
+else
 obj-$(CONFIG_KPROBES)          += kprobes-arm.o
+endif
 obj-$(CONFIG_ATAGS_PROC)       += atags.o
 obj-$(CONFIG_OABI_COMPAT)      += sys_oabi-compat.o
 obj-$(CONFIG_ARM_THUMBEE)      += thumbee.o

diff --git a/arch/arm/kernel/kprobes-thumb.c b/arch/arm/kernel/kprobes-thumb.c
new file mode 100644 (file)
index 0000000..ac6b2d1
--- /dev/null
+++ b/arch/arm/kernel/kprobes-thumb.c
@@ -0,0 +1,26 @@
+/*
+ * arch/arm/kernel/kprobes-thumb.c
+ *
+ * Copyright (C) 2011 Jon Medhurst <tixy@yxit.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/kernel.h>
+#include <linux/kprobes.h>
+
+#include "kprobes.h"
+
+enum kprobe_insn __kprobes
+thumb16_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi)
+{
+       return INSN_REJECTED;
+}
+
+enum kprobe_insn __kprobes
+thumb32_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi)
+{
+       return INSN_REJECTED;
+}

diff --git a/arch/arm/kernel/kprobes.c b/arch/arm/kernel/kprobes.c
index 0e47d3d674277c137aabd1c4abab135e0dc13455..0df2d6d57c04036b753df962e5e2787ded45425f 100644 (file)
--- a/arch/arm/kernel/kprobes.c
+++ b/arch/arm/kernel/kprobes.c
@@ -51,16 +51,32 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
        kprobe_opcode_t insn;
        kprobe_opcode_t tmp_insn[MAX_INSN_SIZE];
        unsigned long addr = (unsigned long)p->addr;
+       kprobe_decode_insn_t *decode_insn;
        int is;
 
-       if (addr & 0x3 || in_exception_text(addr))
+       if (in_exception_text(addr))
                return -EINVAL;
 
+#ifdef CONFIG_THUMB2_KERNEL
+       addr &= ~1; /* Bit 0 would normally be set to indicate Thumb code */
+       insn = ((u16 *)addr)[0];
+       if (is_wide_instruction(insn)) {
+               insn <<= 16;
+               insn |= ((u16 *)addr)[1];
+               decode_insn = thumb32_kprobe_decode_insn;
+       } else
+               decode_insn = thumb16_kprobe_decode_insn;
+#else /* !CONFIG_THUMB2_KERNEL */
+       if (addr & 0x3)
+               return -EINVAL;
        insn = *p->addr;
+       decode_insn = arm_kprobe_decode_insn;
+#endif
+
        p->opcode = insn;
        p->ainsn.insn = tmp_insn;
 
-       switch (arm_kprobe_decode_insn(insn, &p->ainsn)) {
+       switch ((*decode_insn)(insn, &p->ainsn)) {
        case INSN_REJECTED:     /* not supported */
                return -EINVAL;
 

diff --git a/arch/arm/kernel/kprobes.h b/arch/arm/kernel/kprobes.h
index 406bb2da7fea74143c573473300b41849d2c2655..86abfabe83f291a985ca39ca1430c2bc48c5bb61 100644 (file)
--- a/arch/arm/kernel/kprobes.h
+++ b/arch/arm/kernel/kprobes.h
@@ -29,8 +29,21 @@ enum kprobe_insn {
        INSN_GOOD_NO_SLOT
 };
 
+typedef enum kprobe_insn (kprobe_decode_insn_t)(kprobe_opcode_t,
+                                               struct arch_specific_insn *);
+
+#ifdef CONFIG_THUMB2_KERNEL
+
+enum kprobe_insn thumb16_kprobe_decode_insn(kprobe_opcode_t,
+                                               struct arch_specific_insn *);
+enum kprobe_insn thumb32_kprobe_decode_insn(kprobe_opcode_t,
+                                               struct arch_specific_insn *);
+
+#else /* !CONFIG_THUMB2_KERNEL */
+
 enum kprobe_insn arm_kprobe_decode_insn(kprobe_opcode_t,
                                        struct arch_specific_insn *);
+#endif
 
 void __init arm_kprobe_decode_init(void);