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Commit 94254930 authored by Jon Medhurst's avatar Jon Medhurst Committed by Nicolas Pitre
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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: default avatarJon Medhurst <tixy@yxit.co.uk>
Signed-off-by: default avatarNicolas Pitre <nicolas.pitre@linaro.org>
parent 20e8155e

arch/arm/kernel/kprobes-decode.c

+24 −0
Original line number Diff line number Diff line
@@ -1225,6 +1225,30 @@ space_cccc_001x(kprobe_opcode_t insn, struct arch_specific_insn *asi) 
	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 :