ARM: kprobes: Add emulation of hint instructions like NOP and WFI
Being able to probe NOP instructions is useful for hard-coding probeable
locations and is used by the kprobes test code.
Signed-off-by: Jon Medhurst <tixy@yxit.co.uk>
Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
diff --git a/arch/arm/kernel/kprobes-decode.c b/arch/arm/kernel/kprobes-decode.c
index 6bed8b0..03b85ad 100644
--- a/arch/arm/kernel/kprobes-decode.c
+++ b/arch/arm/kernel/kprobes-decode.c
@@ -1225,6 +1225,30 @@
if ((insn & 0x0fb00000) == 0x03000000)
return prep_emulate_rd12_modify(insn, asi);
+ /* hints : cccc 0011 0010 0000 xxxx xxxx xxxx xxxx */
+ if ((insn & 0x0fff0000) == 0x03200000) {
+ unsigned op2 = insn & 0x000000ff;
+ if (op2 == 0x01 || op2 == 0x04) {
+ /* YIELD : cccc 0011 0010 0000 xxxx xxxx 0000 0001 */
+ /* SEV : cccc 0011 0010 0000 xxxx xxxx 0000 0100 */
+ asi->insn[0] = insn;
+ asi->insn_handler = emulate_none;
+ return INSN_GOOD;
+ } else if (op2 <= 0x03) {
+ /* NOP : cccc 0011 0010 0000 xxxx xxxx 0000 0000 */
+ /* WFE : cccc 0011 0010 0000 xxxx xxxx 0000 0010 */
+ /* WFI : cccc 0011 0010 0000 xxxx xxxx 0000 0011 */
+ /*
+ * We make WFE and WFI true NOPs to avoid stalls due
+ * to missing events whilst processing the probe.
+ */
+ asi->insn_handler = emulate_nop;
+ return INSN_GOOD_NO_SLOT;
+ }
+ /* For DBG and unallocated hints it's safest to reject them */
+ return INSN_REJECTED;
+ }
+
/*
* MSR : cccc 0011 0x10 xxxx xxxx xxxx xxxx xxxx
* ALU op with S bit and Rd == 15 :