ARM: kprobes: Decode 32-bit Thumb table branch instructions

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

1 files changed, 25 insertions, 0 deletions

diff --git a/arch/arm/kernel/kprobes-thumb.c b/arch/arm/kernel/kprobes-thumb.c
index 299dc3a33ad2..dfaea25c6069 100644
--- a/arch/arm/kernel/kprobes-thumb.c
+++ b/arch/arm/kernel/kprobes-thumb.c
@@ -37,6 +37,26 @@ static inline unsigned long __kprobes thumb_probe_pc(struct kprobe *p)
         return (unsigned long)p->addr - 1 + 4;
 }
 
+static void __kprobes
+t32_simulate_table_branch(struct kprobe *p, struct pt_regs *regs)
+{
+        kprobe_opcode_t insn = p->opcode;
+        unsigned long pc = thumb_probe_pc(p);
+        int rn = (insn >> 16) & 0xf;
+        int rm = insn & 0xf;
+
+        unsigned long rnv = (rn == 15) ? pc : regs->uregs[rn];
+        unsigned long rmv = regs->uregs[rm];
+        unsigned int halfwords;
+
+        if (insn & 0x10)
+                halfwords = ((u16 *)rnv)[rmv];
+        else
+                halfwords = ((u8 *)rnv)[rmv];
+
+        regs->ARM_pc = pc + 2 * halfwords;
+}
+
 static enum kprobe_insn __kprobes
 t32_decode_ldmstm(kprobe_opcode_t insn, struct arch_specific_insn *asi)
 {
@@ -117,6 +137,11 @@ static const union decode_item t32_table_1110_100x_x1xx[] = {
         DECODE_EMULATEX (0xff400000, 0xe9400000, t32_emulate_ldrdstrd,
                                                  REGS(NOPCWB, NOSPPC, NOSPPC, 0, 0)),
 
+        /* TBB                  1110 1000 1101 xxxx xxxx xxxx 0000 xxxx */
+        /* TBH                  1110 1000 1101 xxxx xxxx xxxx 0001 xxxx */
+        DECODE_SIMULATEX(0xfff000e0, 0xe8d00000, t32_simulate_table_branch,
+                                                 REGS(NOSP, 0, 0, 0, NOSPPC)),
+
         /* STREX                1110 1000 0100 xxxx xxxx xxxx xxxx xxxx */
         /* LDREX                1110 1000 0101 xxxx xxxx xxxx xxxx xxxx */
         /* STREXB               1110 1000 1100 xxxx xxxx xxxx 0100 xxxx */