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Message-Id: <1635510465-20469-2-git-send-email-jianhua.ljh@gmail.com>
Date: Fri, 29 Oct 2021 20:27:45 +0800
From: Janet Liu <jianhua.ljh@...il.com>
To: catalin.marinas@....com, will@...nel.org
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
orson.zhai@...soc.com
Subject: [PATCH v1 2/2] arm64: kprobes: add support for KPROBES_ON_FTRACE
From: Janet Liu <janet.liu@...soc.com>
This patch allow kprobes on ftrace call sites. This optimization
avoids use of a trap with regular kprobes.
This depends on HAVE_DYNAMIC_FTRACE_WITH_REGS which depends on
"patchable-function-entry" options which is only implemented with newer
toolchains.
Signed-off-by: Janet Liu <janet.liu@...soc.com>
---
arch/arm64/Kconfig | 1 +
arch/arm64/kernel/probes/Makefile | 1 +
arch/arm64/kernel/probes/ftrace.c | 73 ++++++++++++++++++++++++++++++++++++++
arch/arm64/kernel/probes/kprobes.c | 27 ++++++++++++++
4 files changed, 102 insertions(+)
create mode 100644 arch/arm64/kernel/probes/ftrace.c
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index ab07251..c3fd0dd 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -200,6 +200,7 @@ config ARM64
select HAVE_SYSCALL_TRACEPOINTS
select HAVE_KPROBES
select HAVE_OPTPROBES
+ 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 c77c92a..d9b204f 100644
--- a/arch/arm64/kernel/probes/Makefile
+++ b/arch/arm64/kernel/probes/Makefile
@@ -3,5 +3,6 @@ obj-$(CONFIG_KPROBES) += kprobes.o decode-insn.o \
kprobes_trampoline.o \
simulate-insn.o
obj-$(CONFIG_OPTPROBES) += opt.o opt_head.o
+obj-$(CONFIG_KPROBES_ON_FTRACE) += ftrace.o
obj-$(CONFIG_UPROBES) += uprobes.o decode-insn.o \
simulate-insn.o
diff --git a/arch/arm64/kernel/probes/ftrace.c b/arch/arm64/kernel/probes/ftrace.c
new file mode 100644
index 0000000..46ea92e
--- /dev/null
+++ b/arch/arm64/kernel/probes/ftrace.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-2.0-only
+//
+// Dynamic Ftrace based Kprobes Optimization
+//
+// Copyright (C) 2021, Unisoc Inc.
+// Author: Janet Liu <janet.liu@...soc.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*/
+void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
+ struct ftrace_ops *ops, struct ftrace_regs *fregs)
+{
+ struct kprobe *p;
+ struct kprobe_ctlblk *kcb;
+ struct pt_regs *regs = ftrace_get_regs(fregs);
+ int bit;
+
+ bit = ftrace_test_recursion_trylock(ip, parent_ip);
+ if (bit < 0)
+ return;
+
+ preempt_disable_notrace();
+ p = get_kprobe((kprobe_opcode_t *)ip);
+ if (unlikely(!p) || kprobe_disabled(p))
+ goto end;
+
+ 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);
+
+ __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 nop
+ */
+ instruction_pointer_set(regs,
+ (unsigned long)p->addr + MCOUNT_INSN_SIZE);
+ 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);
+ }
+end:
+ preempt_enable_notrace();
+ ftrace_test_recursion_unlock(bit);
+}
+NOKPROBE_SYMBOL(kprobe_ftrace_handler);
+
+int arch_prepare_kprobe_ftrace(struct kprobe *p)
+{
+ p->ainsn.api.insn = NULL;
+ p->ainsn.api.restore = 0;
+ return 0;
+}
diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
index 6dbcc89..3d371d3 100644
--- a/arch/arm64/kernel/probes/kprobes.c
+++ b/arch/arm64/kernel/probes/kprobes.c
@@ -417,6 +417,33 @@ int __kprobes arch_trampoline_kprobe(struct kprobe *p)
return 0;
}
+kprobe_opcode_t __kprobes *kprobe_lookup_name(const char *name, unsigned int offset)
+{
+ kprobe_opcode_t *addr;
+
+ addr = (kprobe_opcode_t *)kallsyms_lookup_name(name);
+#ifdef CONFIG_KPROBES_ON_FTRACE
+ if (addr && !offset) {
+ unsigned long faddr;
+
+ faddr = ftrace_location_range((unsigned long)addr,
+ (unsigned long)addr + 8);
+ if (faddr)
+ addr = (kprobe_opcode_t *)faddr;
+ }
+#endif
+ return addr;
+}
+
+bool __kprobes arch_kprobe_on_func_entry(unsigned long offset)
+{
+#ifdef CONFIG_KPROBES_ON_FTRACE
+ return offset <= 8;
+#else
+ return !offset;
+#endif
+}
+
int __init arch_init_kprobes(void)
{
register_kernel_break_hook(&kprobes_break_hook);
--
1.9.1
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