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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>
This commit is contained in:
Tiezhu Yang 2023-02-25 15:52:57 +08:00 committed by Huacai Chen
parent 3f55368600
commit 09e679c28a
2 changed files with 65 additions and 0 deletions
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1
arch/loongarch/Kconfig
View File

@ -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

64
arch/loongarch/kernel/ftrace_dyn.c
View File

@ -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 */