ARM: kprobes: Decode 32-bit Thumb hint instructions

For hints which may have observable effects, like SEV (send event), we
use kprobe_emulate_none which emulates the hint by executing the
original instruction.

For NOP we simulate the instruction using kprobe_simulate_nop, which
does nothing. As probes execute with interrupts disabled this is also
used for hints which may block for an indefinite time, like WFE (wait
for event).

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

diff --git a/arch/arm/kernel/kprobes-thumb.c b/arch/arm/kernel/kprobes-thumb.c
index 554578b..27f83a3 100644 (file)
--- a/arch/arm/kernel/kprobes-thumb.c
+++ b/arch/arm/kernel/kprobes-thumb.c
@@ -37,6 +37,32 @@ static inline unsigned long __kprobes thumb_probe_pc(struct kprobe *p)
        return (unsigned long)p->addr - 1 + 4;
 }
 
+static const union decode_item t32_table_1111_0xxx___1[] = {
+       /* Branches and miscellaneous control                           */
+
+       /* YIELD                1111 0011 1010 xxxx 10x0 x000 0000 0001 */
+       DECODE_OR       (0xfff0d7ff, 0xf3a08001),
+       /* SEV                  1111 0011 1010 xxxx 10x0 x000 0000 0100 */
+       DECODE_EMULATE  (0xfff0d7ff, 0xf3a08004, kprobe_emulate_none),
+       /* NOP                  1111 0011 1010 xxxx 10x0 x000 0000 0000 */
+       /* WFE                  1111 0011 1010 xxxx 10x0 x000 0000 0010 */
+       /* WFI                  1111 0011 1010 xxxx 10x0 x000 0000 0011 */
+       DECODE_SIMULATE (0xfff0d7fc, 0xf3a08000, kprobe_simulate_nop),
+
+       DECODE_END
+};
+
+const union decode_item kprobe_decode_thumb32_table[] = {
+
+       /*
+        * Branches and miscellaneous control
+        *                      1111 0xxx xxxx xxxx 1xxx xxxx xxxx xxxx
+        */
+       DECODE_TABLE    (0xf8008000, 0xf0008000, t32_table_1111_0xxx___1),
+
+       DECODE_END
+};
+
 static void __kprobes
 t16_simulate_bxblx(struct kprobe *p, struct pt_regs *regs)
 {
@@ -551,5 +577,5 @@ thumb32_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn *asi)
 {
        asi->insn_singlestep = thumb32_singlestep;
        asi->insn_check_cc = thumb_check_cc;
-       return INSN_REJECTED;
+       return kprobe_decode_insn(insn, asi, kprobe_decode_thumb32_table, true);
 }