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Message-Id: <20220728020250.1699-1-iecedge@gmail.com>
Date: Thu, 28 Jul 2022 02:02:50 +0000
From: Jianlin Lv <iecedge@...il.com>
To: corbet@....net, catalin.marinas@....com, will@...nel.org,
rostedt@...dmis.org, mingo@...hat.com, naveen.n.rao@...ux.ibm.com,
anil.s.keshavamurthy@...el.com, davem@...emloft.net,
mhiramat@...nel.org, arnd@...db.de, zhengzengkai@...wei.com
Cc: iecedge@...il.com, jianlv@...y.com, linux-kernel@...r.kernel.org,
linux-doc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: [PATCH] arm64/kprobes: Add support for KPROBES_ON_FTRACE
This is the arm64 version of ftrace-based kprobes to avoid the overhead
with regular kprobes, by using the ftrace infrastructure.
Signed-off-by: Jianlin Lv <iecedge@...il.com>
---
.../debug/kprobes-on-ftrace/arch-support.txt | 2 +-
arch/arm64/Kconfig | 1 +
arch/arm64/kernel/probes/Makefile | 1 +
arch/arm64/kernel/probes/kprobes-ftrace.c | 81 +++++++++++++++++++
include/linux/kprobes.h | 2 +
kernel/kprobes.c | 4 +-
6 files changed, 88 insertions(+), 3 deletions(-)
create mode 100644 arch/arm64/kernel/probes/kprobes-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 b3697f4c806e..fadbd4513c91 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 |
| csky: | ok |
| hexagon: | TODO |
| ia64: | TODO |
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 1652a9800ebe..7271d97e035a 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -204,6 +204,7 @@ 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..dab2fa4dba81 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) += kprobes-ftrace.o
diff --git a/arch/arm64/kernel/probes/kprobes-ftrace.c b/arch/arm64/kernel/probes/kprobes-ftrace.c
new file mode 100644
index 000000000000..fcfa6b6533a0
--- /dev/null
+++ b/arch/arm64/kernel/probes/kprobes-ftrace.c
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Dynamic Ftrace based Kprobes Optimization
+ *
+ * Copyright (C) Hitachi Ltd., 2012
+ */
+#include <linux/kprobes.h>
+
+int arch_check_ftrace_location(struct kprobe *p)
+{
+ unsigned long addr = (unsigned long)p->addr;
+
+ /* ftrace location at the BL in the callsite (<function-entry> + AARCH64_INSN_SIZE) */
+ if (ftrace_location(addr) == (addr + AARCH64_INSN_SIZE)) {
+#ifdef CONFIG_KPROBES_ON_FTRACE
+ p->flags |= KPROBE_FLAG_FTRACE;
+#else /* !CONFIG_KPROBES_ON_FTRACE */
+ return -EINVAL;
+#endif
+ }
+ return 0;
+}
+
+/* Ftrace callback handler for kprobes */
+void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
+ struct ftrace_ops *ops, struct ftrace_regs *fregs)
+{
+ struct pt_regs *regs;
+ struct kprobe *p;
+ struct kprobe_ctlblk *kcb;
+ int bit;
+
+ bit = ftrace_test_recursion_trylock(ip, parent_ip);
+ if (bit < 0)
+ return;
+
+ regs = ftrace_get_regs(fregs);
+ p = get_kprobe((kprobe_opcode_t *) (ip - AARCH64_INSN_SIZE));
+ if (unlikely(!p) || kprobe_disabled(p))
+ goto out;
+
+ kcb = get_kprobe_ctlblk();
+ if (kprobe_running()) {
+ kprobes_inc_nmissed_count(p);
+ } else {
+ unsigned long orig_ip = instruction_pointer(regs);
+
+ instruction_pointer_set(regs, ip - AARCH64_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->pc)
+ * as if there is a 4byte nop
+ */
+ instruction_pointer_set(regs, ip);
+ if (unlikely(p->post_handler)) {
+ kcb->kprobe_status = KPROBE_HIT_SSDONE;
+ p->post_handler(p, regs, 0);
+ }
+ instruction_pointer_set(regs, orig_ip);
+ }
+
+ /*
+ * If pre_handler returns !0, it changes regs->pc. We have to
+ * skip emulating post_handler.
+ */
+ __this_cpu_write(current_kprobe, NULL);
+ }
+out:
+ ftrace_test_recursion_unlock(bit);
+}
+NOKPROBE_SYMBOL(kprobe_ftrace_handler);
+
+int arch_prepare_kprobe_ftrace(struct kprobe *p)
+{
+ p->ainsn.api.insn = NULL;
+ return 0;
+}
+
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 55041d2f884d..83a479908029 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -392,6 +392,8 @@ static inline int arch_prepare_kprobe_ftrace(struct kprobe *p)
}
#endif /* CONFIG_KPROBES_ON_FTRACE */
+int arch_check_ftrace_location(struct kprobe *p);
+
/* Get the kprobe at this addr (if any) - called with preemption disabled */
struct kprobe *get_kprobe(void *addr);
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index f214f8c088ed..34754c2fe14e 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1534,7 +1534,7 @@ static inline int warn_kprobe_rereg(struct kprobe *p)
return ret;
}
-static int check_ftrace_location(struct kprobe *p)
+int __weak arch_check_ftrace_location(struct kprobe *p)
{
unsigned long addr = (unsigned long)p->addr;
@@ -1553,7 +1553,7 @@ static int check_kprobe_address_safe(struct kprobe *p,
{
int ret;
- ret = check_ftrace_location(p);
+ ret = arch_check_ftrace_location(p);
if (ret)
return ret;
jump_label_lock();
--
2.25.1
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