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Subject[PATCH] arm64/kprobe: add support for KPROBES_ON_FTRACE
Date
Allow KPROBES to use the ftrace infrastructure.
This depends on HAVE_DYNAMIC_FTRACE_WITH_REGS
which introduce by :
commit 3b23e4991fb6 ("arm64: implement ftrace with regs")

Based on the x86 code by Masami.

With:
# cd /sys/kernel/debug/tracing
# echo 'p _do_fork+0x4' > kprobe_events

before patch:
# cat ../kprobes/list
sh: write error: Invalid argument

after patch:
# cat ../kprobes/list
ffffa00016aa9d4c k _do_fork+0x4 [FTRACE]

Signed-off-by: Cheng Jian <cj.chengjian@huawei.com>
---
.../debug/kprobes-on-ftrace/arch-support.txt | 2 +-
arch/arm64/Kconfig | 1 +
arch/arm64/kernel/probes/Makefile | 2 +
arch/arm64/kernel/probes/ftrace.c | 65 +++++++++++++++++++
4 files changed, 69 insertions(+), 1 deletion(-)
create mode 100644 arch/arm64/kernel/probes/ftrace.c

diff --git a/Documentation/features/debug/kprobes-on-ftrace/arch-support.txt b/Documentation/features/debug/kprobes-on-ftrace/arch-support.txt
index 4fae0464ddff..f9dd9dd91e0c 100644
--- a/Documentation/features/debug/kprobes-on-ftrace/arch-support.txt
+++ b/Documentation/features/debug/kprobes-on-ftrace/arch-support.txt
@@ -9,7 +9,7 @@
| alpha: | TODO |
| arc: | TODO |
| arm: | TODO |
- | arm64: | TODO |
+ | arm64: | ok |
| c6x: | TODO |
| csky: | TODO |
| h8300: | TODO |
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index b1b4476ddb83..d613be9c2346 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -144,6 +144,7 @@ config ARM64
select HAVE_DYNAMIC_FTRACE
select HAVE_DYNAMIC_FTRACE_WITH_REGS \
if $(cc-option,-fpatchable-function-entry=2)
+ select HAVE_KPROBES_ON_FTRACE if HAVE_DYNAMIC_FTRACE_WITH_REGS
select HAVE_EFFICIENT_UNALIGNED_ACCESS
select HAVE_FAST_GUP
select HAVE_FTRACE_MCOUNT_RECORD
diff --git a/arch/arm64/kernel/probes/Makefile b/arch/arm64/kernel/probes/Makefile
index 8e4be92e25b1..45a9d916a47d 100644
--- a/arch/arm64/kernel/probes/Makefile
+++ b/arch/arm64/kernel/probes/Makefile
@@ -4,3 +4,5 @@ obj-$(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..f89bfaa3e5f3
--- /dev/null
+++ b/arch/arm64/kernel/probes/ftrace.c
@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Dynamic Ftrace based Kprobes Optimization
+ *
+ * Copyright (C) Hitachi Ltd., 2012
+ * Copyright (C) 2019 Huawei Inc.
+ * Copyright 2019 Cheng Jian <cj.chengjian@huawei.com>
+ */
+#include <linux/kprobes.h>
+#include <linux/ptrace.h>
+#include <linux/hardirq.h>
+#include <linux/preempt.h>
+#include <linux/ftrace.h>
+
+
+/* Ftrace callback handler for kprobes -- called under preepmt disabed */
+void kprobe_ftrace_handler(unsigned long pc, unsigned long parent_pc,
+ struct ftrace_ops *ops, struct pt_regs *regs)
+{
+ struct kprobe *p;
+ struct kprobe_ctlblk *kcb;
+
+ /* Preempt is disabled by ftrace */
+ p = get_kprobe((kprobe_opcode_t *)pc);
+ if (unlikely(!p) || kprobe_disabled(p))
+ return;
+
+ kcb = get_kprobe_ctlblk();
+ if (kprobe_running()) {
+ kprobes_inc_nmissed_count(p);
+ } else {
+ /*
+ * On ARM64, recg->pc is *before* this instruction for the
+ * pre handler.
+ */
+ regs->pc -= MCOUNT_INSN_SIZE;
+
+ __this_cpu_write(current_kprobe, p);
+ kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+ if (!p->pre_handler || !p->pre_handler(p, regs)) {
+ /*
+ * Emulate singlestep (and also recover regs->ip)
+ * as if there is a nop
+ */
+ regs->pc += MCOUNT_INSN_SIZE;
+ if (unlikely(p->post_handler)) {
+ kcb->kprobe_status = KPROBE_HIT_SSDONE;
+ p->post_handler(p, regs, 0);
+ }
+ }
+ /*
+ * If pre_handler returns !0, it changes regs->ip. We have to
+ * skip emulating post_handler.
+ */
+ __this_cpu_write(current_kprobe, NULL);
+ }
+}
+NOKPROBE_SYMBOL(kprobe_ftrace_handler);
+
+int arch_prepare_kprobe_ftrace(struct kprobe *p)
+{
+ p->ainsn.api.insn = NULL;
+
+ return 0;
+}
--
2.17.1
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