linux-kernel - [PATCH 4/4] arm64: implement KPROBES_ON

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Date:   Mon, 19 Aug 2019 11:38:10 +0000
From:   Jisheng Zhang <Jisheng.Zhang@...aptics.com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Steven Rostedt <rostedt@...dmis.org>
CC:     "x86@...nel.org" <x86@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH 4/4] arm64: implement KPROBES_ON_FTRACE

This patch implements KPROBES_ON_FTRACE for arm64.

~ # mount -t debugfs debugfs /sys/kernel/debug/
~ # cd /sys/kernel/debug/
/sys/kernel/debug # echo 'p _do_fork' > tracing/kprobe_events

before the patch:

/sys/kernel/debug # cat kprobes/list
ffffff801009ff7c  k  _do_fork+0x4    [DISABLED]

after the patch:

/sys/kernel/debug # cat kprobes/list
ffffff801009ff7c  k  _do_fork+0x4    [DISABLED][FTRACE]

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@...aptics.com>
---
 arch/arm64/Kconfig                |  1 +
 arch/arm64/kernel/probes/Makefile |  1 +
 arch/arm64/kernel/probes/ftrace.c | 16 ++++++++++++++++
 3 files changed, 18 insertions(+)
 create mode 100644 arch/arm64/kernel/probes/ftrace.c

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 663392d1eae2..928700f15e23 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -167,6 +167,7 @@ config ARM64
 	select HAVE_STACKPROTECTOR
 	select HAVE_SYSCALL_TRACEPOINTS
 	select HAVE_KPROBES
+	select HAVE_KPROBES_ON_FTRACE
 	select HAVE_KRETPROBES
 	select HAVE_GENERIC_VDSO
 	select IOMMU_DMA if IOMMU_SUPPORT
diff --git a/arch/arm64/kernel/probes/Makefile b/arch/arm64/kernel/probes/Makefile
index 8e4be92e25b1..4020cfc66564 100644
--- a/arch/arm64/kernel/probes/Makefile
+++ b/arch/arm64/kernel/probes/Makefile
@@ -4,3 +4,4 @@ obj-$(CONFIG_KPROBES)		+= kprobes.o decode-insn.o	\
 				   simulate-insn.o
 obj-$(CONFIG_UPROBES)		+= uprobes.o decode-insn.o	\
 				   simulate-insn.o
+obj-$(CONFIG_KPROBES_ON_FTRACE)	+= ftrace.o
diff --git a/arch/arm64/kernel/probes/ftrace.c b/arch/arm64/kernel/probes/ftrace.c
new file mode 100644
index 000000000000..1fe8f105e02e
--- /dev/null
+++ b/arch/arm64/kernel/probes/ftrace.c
@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Dynamic Ftrace based Kprobes Optimization
+ *
+ * Copyright (C) 2019 Synaptics Incorporated
+ *
+ * Author: Jisheng Zhang <jszhang@...nel.org>
+ */
+
+#include <linux/kprobes.h>
+
+int arch_prepare_kprobe_ftrace(struct kprobe *p)
+{
+	p->ainsn.api.insn = NULL;
+	return 0;
+}
-- 
2.23.0.rc1