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Commit 9233c1ee authored by Maneesh Soni's avatar Maneesh Soni Committed by Ralf Baechle
Browse files

MIPS Kprobes: Deny probes on ll/sc instructions 



As ll/sc instruction are for atomic read-modify-write operations, allowing
probes on top of these insturctions is a bad idea.

Signed-off-by: default avatarVictor Kamensky <kamensky@cisco.com>
Signed-off-by: default avatarManeesh Soni <manesoni@cisco.com>
Cc: David Daney <david.daney@cavium.com>
Cc: ananth@in.ibm.com
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2912/


Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
parent 41dde781

arch/mips/kernel/kprobes.c

+31 −0
Original line number Diff line number Diff line
@@ -113,6 +113,30 @@ static int __kprobes insn_has_delayslot(union mips_instruction insn) 
	return 0;

}



/*

 * insn_has_ll_or_sc function checks whether instruction is ll or sc

 * one; putting breakpoint on top of atomic ll/sc pair is bad idea;

 * so we need to prevent it and refuse kprobes insertion for such

 * instructions; cannot do much about breakpoint in the middle of

 * ll/sc pair; it is upto user to avoid those places

 */

static int __kprobes insn_has_ll_or_sc(union mips_instruction insn)

{

	int ret = 0;



	switch (insn.i_format.opcode) {

	case ll_op:

	case lld_op:

	case sc_op:

	case scd_op:

		ret = 1;

		break;

	default:

		break;

	}

	return ret;

}



int __kprobes arch_prepare_kprobe(struct kprobe *p)

{

	union mips_instruction insn;
@@ -121,6 +145,13 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p) 


	insn = p->addr[0];



	if (insn_has_ll_or_sc(insn)) {

		pr_notice("Kprobes for ll and sc instructions are not"

			  "supported\n");

		ret = -EINVAL;

		goto out;

	}



	if (insn_has_delayslot(insn)) {

		pr_notice("Kprobes for branch and jump instructions are not"

			  "supported\n");