[PATCH v3 6/7] powerpc: kprobes: emulate instructions on kprobe handler re-entry

From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
To: Michael Ellerman <mpe@ellerman.id.au>, Ingo Molnar <mingo@kernel.org>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: [PATCH v3 6/7] powerpc: kprobes: emulate instructions on kprobe handler re-entry
Date: Wed, 19 Apr 2017 18:21:05 +0530	[thread overview]
Message-ID: <0d4193a90e4b2ad3cd2ef33d41228b80a2ac9f91.1492604782.git.naveen.n.rao@linux.vnet.ibm.com> (raw)
In-Reply-To: <cover.1492604782.git.naveen.n.rao@linux.vnet.ibm.com>
In-Reply-To: <cover.1492604782.git.naveen.n.rao@linux.vnet.ibm.com>

On kprobe handler re-entry, try to emulate the instruction rather than
single stepping always.

Acked-by: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
---
 arch/powerpc/kernel/kprobes.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 46e8c1e03ce4..067e9863bfdf 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -276,6 +276,14 @@ int __kprobes kprobe_handler(struct pt_regs *regs)
 			kprobes_inc_nmissed_count(p);
 			prepare_singlestep(p, regs);
 			kcb->kprobe_status = KPROBE_REENTER;
+			if (p->ainsn.boostable >= 0) {
+				ret = try_to_emulate(p, regs);
+
+				if (ret > 0) {
+					restore_previous_kprobe(kcb);
+					return 1;
+				}
+			}
 			return 1;
 		} else {
 			if (*addr != BREAKPOINT_INSTRUCTION) {
-- 
2.12.1
