ARM: kprobes: Decode 16-bit Thumb PC- and SP-relative address instructions

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

1 files changed, 33 insertions, 0 deletions

diff --git a/arch/arm/kernel/kprobes-thumb.c b/arch/arm/kernel/kprobes-thumb.c
index 632a5e8f5977..2b30828d5f0c 100644
--- a/arch/arm/kernel/kprobes-thumb.c
+++ b/arch/arm/kernel/kprobes-thumb.c
@@ -74,6 +74,28 @@ t16_simulate_ldrstr_sp_relative(struct kprobe *p, struct pt_regs *regs)
                 base[index] = regs->uregs[rt];
 }
 
+static void __kprobes
+t16_simulate_reladr(struct kprobe *p, struct pt_regs *regs)
+{
+        kprobe_opcode_t insn = p->opcode;
+        unsigned long base = (insn & 0x800) ? regs->ARM_sp
+                                            : (thumb_probe_pc(p) & ~3);
+        long offset = insn & 0xff;
+        int rt = (insn >> 8) & 0x7;
+        regs->uregs[rt] = base + offset * 4;
+}
+
+static void __kprobes
+t16_simulate_add_sp_imm(struct kprobe *p, struct pt_regs *regs)
+{
+        kprobe_opcode_t insn = p->opcode;
+        long imm = insn & 0x7f;
+        if (insn & 0x80) /* SUB */
+                regs->ARM_sp -= imm * 4;
+        else /* ADD */
+                regs->ARM_sp += imm * 4;
+}
+
 static unsigned long __kprobes
 t16_emulate_loregs(struct kprobe *p, struct pt_regs *regs)
 {
@@ -154,6 +176,10 @@ t16_decode_hiregs(kprobe_opcode_t insn, struct arch_specific_insn *asi)
 static const union decode_item t16_table_1011[] = {
         /* Miscellaneous 16-bit instructions                */
 
+        /* ADD (SP plus immediate)      1011 0000 0xxx xxxx */
+        /* SUB (SP minus immediate)     1011 0000 1xxx xxxx */
+        DECODE_SIMULATE (0xff00, 0xb000, t16_simulate_add_sp_imm),
+
         /*
          * If-Then, and hints
          *                              1011 1111 xxxx xxxx
@@ -274,6 +300,13 @@ const union decode_item kprobe_decode_thumb16_table[] = {
         DECODE_SIMULATE (0xf000, 0x9000, t16_simulate_ldrstr_sp_relative),
 
         /*
+         * Generate PC-/SP-relative address
+         * ADR (literal)                1010 0xxx xxxx xxxx
+         * ADD (SP plus immediate)      1010 1xxx xxxx xxxx
+         */
+        DECODE_SIMULATE (0xf000, 0xa000, t16_simulate_reladr),
+
+        /*
          * Miscellaneous 16-bit instructions
          *                              1011 xxxx xxxx xxxx
          */