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Commit 804dec5b authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Ingo Molnar
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kprobes/x86: Do not modify singlestep buffer while resuming 



Do not modify singlestep execution buffer (kprobe.ainsn.insn)
while resuming from single-stepping, instead, modifies
the buffer to add a jump back instruction at preparing
buffer.

Signed-off-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David S . Miller <davem@davemloft.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ye Xiaolong <xiaolong.ye@intel.com>
Link: http://lkml.kernel.org/r/149076361560.22469.1610155860343077495.stgit@devbox


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 17880e4d

arch/x86/kernel/kprobes/core.c

+20 −22
Original line number Diff line number Diff line
@@ -399,23 +399,36 @@ int __copy_instruction(u8 *dest, u8 *src) 
	return length;

}



/* Prepare reljump right after instruction to boost */

static void prepare_boost(struct kprobe *p, int length)

{

	if (can_boost(p->ainsn.insn, p->addr) &&

	    MAX_INSN_SIZE - length >= RELATIVEJUMP_SIZE) {

		/*

		 * These instructions can be executed directly if it

		 * jumps back to correct address.

		 */

		synthesize_reljump(p->ainsn.insn + length, p->addr + length);

		p->ainsn.boostable = 1;

	} else {

		p->ainsn.boostable = -1;

	}

}



static int arch_copy_kprobe(struct kprobe *p)

{

	int ret;

	int len;



	/* Copy an instruction with recovering if other optprobe modifies it.*/

	ret = __copy_instruction(p->ainsn.insn, p->addr);

	if (!ret)

	len = __copy_instruction(p->ainsn.insn, p->addr);

	if (!len)

		return -EINVAL;



	/*

	 * __copy_instruction can modify the displacement of the instruction,

	 * but it doesn't affect boostable check.

	 */

	if (can_boost(p->ainsn.insn, p->addr))

		p->ainsn.boostable = 0;

	else

		p->ainsn.boostable = -1;

	prepare_boost(p, len);



	/* Check whether the instruction modifies Interrupt Flag or not */

	p->ainsn.if_modifier = is_IF_modifier(p->ainsn.insn);
@@ -878,21 +891,6 @@ static void resume_execution(struct kprobe *p, struct pt_regs *regs, 
		break;

	}



	if (p->ainsn.boostable == 0) {

		if ((regs->ip > copy_ip) &&

		    (regs->ip - copy_ip) + 5 < MAX_INSN_SIZE) {

			/*

			 * These instructions can be executed directly if it

			 * jumps back to correct address.

			 */

			synthesize_reljump((void *)regs->ip,

				(void *)orig_ip + (regs->ip - copy_ip));

			p->ainsn.boostable = 1;

		} else {

			p->ainsn.boostable = -1;

		}

	}



	regs->ip += orig_ip - copy_ip;



no_change: