[PATCH 4/4] arm64: implement KPROBES_ON_FTRACE

[Jisheng Zhang]

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.zh...@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/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 <jszh...@kernel.org>
+ */
+
+#include <linux/kprobes.h>
+
+int arch_prepare_kprobe_ftrace(struct kprobe *p)
+{
+       p->ainsn.api.insn = NULL;
+       return 0;
+}
-- 
2.23.0.rc1