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From:   Jisheng Zhang <Jisheng.Zhang@synaptics.com>
To:     Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
        "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
        Steven Rostedt <rostedt@goodmis.org>
CC:     "x86@kernel.org" <x86@kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: [PATCH 4/4] arm64: implement KPROBES_ON_FTRACE
Thread-Topic: [PATCH 4/4] arm64: implement KPROBES_ON_FTRACE
Thread-Index: AQHVVoKTiZqAlY6xIUan+odTmeZEhQ==
Date:   Mon, 19 Aug 2019 11:38:10 +0000
Message-ID: <20190819192706.46ce2c1d@xhacker.debian>
References: <20190819192422.5ed79702@xhacker.debian>
In-Reply-To: <20190819192422.5ed79702@xhacker.debian>
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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@synaptics.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/M=
akefile
index 8e4be92e25b1..4020cfc66564 100644
--- a/arch/arm64/kernel/probes/Makefile
+++ b/arch/arm64/kernel/probes/Makefile
@@ -4,3 +4,4 @@ obj-$(CONFIG_KPROBES)		+=3D kprobes.o decode-insn.o	\
 				   simulate-insn.o
 obj-$(CONFIG_UPROBES)		+=3D uprobes.o decode-insn.o	\
 				   simulate-insn.o
+obj-$(CONFIG_KPROBES_ON_FTRACE)	+=3D ftrace.o
diff --git a/arch/arm64/kernel/probes/ftrace.c b/arch/arm64/kernel/probes/f=
trace.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@kernel.org>
+ */
+
+#include <linux/kprobes.h>
+
+int arch_prepare_kprobe_ftrace(struct kprobe *p)
+{
+	p->ainsn.api.insn =3D NULL;
+	return 0;
+}
--=20
2.23.0.rc1