From 09e679c28a4def4ea8d4f618503c1d55c355ae5c Mon Sep 17 00:00:00 2001
From: Tiezhu Yang <yangtiezhu@loongson.cn>
Date: Sat, 25 Feb 2023 15:52:57 +0800
Subject: [PATCH] LoongArch: Add kprobes on ftrace support
Add kprobe_ftrace_handler() and arch_prepare_kprobe_ftrace() to support
kprobes on ftrace, the code is similar with x86 and riscv.
Here is a simple example:
# echo 'p:myprobe kernel_clone' > /sys/kernel/debug/tracing/kprobe_events
# echo 'r:myretprobe kernel_clone $retval' >> /sys/kernel/debug/tracing/kprobe_events
# echo 1 > /sys/kernel/debug/tracing/events/kprobes/myprobe/enable
# echo 1 > /sys/kernel/debug/tracing/events/kprobes/myretprobe/enable
# echo 1 > /sys/kernel/debug/tracing/tracing_on
# cat /sys/kernel/debug/tracing/trace
# tracer: nop
#
# entries-in-buffer/entries-written: 2/2 #P:4
#
# _-----=> irqs-off/BH-disabled
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / _-=> migrate-disable
# |||| / delay
# TASK-PID CPU# ||||| TIMESTAMP FUNCTION
# | | | ||||| | |
bash-488 [002] ..... 2041.190681: myprobe: (kernel_clone+0x0/0x40c)
bash-488 [002] ..... 2041.190788: myretprobe: (__do_sys_clone+0x84/0xb8 <- kernel_clone) arg1=0x200
Tested-by: Jeff Xie <xiehuan09@gmail.com>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
arch/loongarch/Kconfig | 1 +
arch/loongarch/kernel/ftrace_dyn.c | 64 ++++++++++++++++++++++++++++++
2 files changed, 65 insertions(+)
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index d90bb47f1dc3e..7fd51257e0ed4 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -107,6 +107,7 @@ config LOONGARCH
select HAVE_IRQ_EXIT_ON_IRQ_STACK
select HAVE_IRQ_TIME_ACCOUNTING
select HAVE_KPROBES
+ select HAVE_KPROBES_ON_FTRACE
select HAVE_KRETPROBES
select HAVE_MOD_ARCH_SPECIFIC
select HAVE_NMI
diff --git a/arch/loongarch/kernel/ftrace_dyn.c b/arch/loongarch/kernel/ftrace_dyn.c
index 0f07591cab309..4a3ef8516ccc6 100644
--- a/arch/loongarch/kernel/ftrace_dyn.c
+++ b/arch/loongarch/kernel/ftrace_dyn.c
@@ -6,6 +6,7 @@
*/
#include <linux/ftrace.h>
+#include <linux/kprobes.h>
#include <linux/uaccess.h>
#include <asm/inst.h>
@@ -271,3 +272,66 @@ int ftrace_disable_ftrace_graph_caller(void)
}
#endif /* CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS */
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
+#ifdef CONFIG_KPROBES_ON_FTRACE
+/* Ftrace callback handler for kprobes -- called under preepmt disabled */
+void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
+ struct ftrace_ops *ops, struct ftrace_regs *fregs)
+{
+ int bit;
+ struct pt_regs *regs;
+ struct kprobe *p;
+ struct kprobe_ctlblk *kcb;
+
+ bit = ftrace_test_recursion_trylock(ip, parent_ip);
+ if (bit < 0)
+ return;
+
+ p = get_kprobe((kprobe_opcode_t *)ip);
+ if (unlikely(!p) || kprobe_disabled(p))
+ goto out;
+
+ regs = ftrace_get_regs(fregs);
+ if (!regs)
+ 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);
+
+ __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->csr_era)
+ * 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->csr_era. 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.insn = NULL;
+ return 0;
+}
+#endif /* CONFIG_KPROBES_ON_FTRACE */
--
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