Commit 09e679c2 authored by Tiezhu Yang's avatar Tiezhu Yang Committed by Huacai Chen
Browse files

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: default avatarJeff Xie <xiehuan09@gmail.com>
Signed-off-by: default avatarTiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: default avatarHuacai Chen <chenhuacai@loongson.cn>
parent 3f553686

arch/loongarch/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/loongarch/kernel/ftrace_dyn.c

+64 −0
Original line number Diff line number Diff line
@@ -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 */