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>

1 files changed, 18 insertions, 2 deletions

diff --git a/arch/arm/kernel/kprobes.c b/arch/arm/kernel/kprobes.c
index 0e47d3d67427..0df2d6d57c04 100644
--- 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;