829adda597
This patch adds support for kprobes on ftrace call sites to avoids
much of the overhead with regular kprobes. Try it with simple
steps:
echo 'p:myprobe sys_clone a0=%a0 a1=%a1 stack_val=+4($stack)' > /sys/kernel/de
bug/tracing/kprobe_events
echo 1 > /sys/kernel/debug/tracing/events/kprobes/enable
cat /sys/kernel/debug/tracing/trace
tracer: nop
entries-in-buffer/entries-written: 1/1 #P:1
_-----=> irqs-off
/ _----=> need-resched
| / _---=> hardirq/softirq
|| / _--=> preempt-depth
||| / delay
TASK-PID CPU# |||| TIMESTAMP FUNCTION
| | | |||| | |
sh-92 [000] .... 369.899962: myprobe: (sys_clone+0x0/0x28) a0=0x1200011 a1=0x0 stack_val=0x201c20ffffffe0
cat /sys/kernel/debug/kprobes/list
ffffffe00020b584 k sys_clone+0x0 [FTRACE]
^^^^^^
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
54 lines
1.4 KiB
C
54 lines
1.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/kprobes.h>
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/* Ftrace callback handler for kprobes -- called under preepmt disabed */
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void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
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struct ftrace_ops *ops, struct ftrace_regs *regs)
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{
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struct kprobe *p;
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struct kprobe_ctlblk *kcb;
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p = get_kprobe((kprobe_opcode_t *)ip);
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if (unlikely(!p) || kprobe_disabled(p))
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return;
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kcb = get_kprobe_ctlblk();
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if (kprobe_running()) {
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kprobes_inc_nmissed_count(p);
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} else {
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unsigned long orig_ip = instruction_pointer(&(regs->regs));
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instruction_pointer_set(&(regs->regs), ip);
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__this_cpu_write(current_kprobe, p);
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kcb->kprobe_status = KPROBE_HIT_ACTIVE;
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if (!p->pre_handler || !p->pre_handler(p, &(regs->regs))) {
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/*
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* Emulate singlestep (and also recover regs->pc)
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* as if there is a nop
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*/
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instruction_pointer_set(&(regs->regs),
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(unsigned long)p->addr + MCOUNT_INSN_SIZE);
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if (unlikely(p->post_handler)) {
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kcb->kprobe_status = KPROBE_HIT_SSDONE;
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p->post_handler(p, &(regs->regs), 0);
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}
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instruction_pointer_set(&(regs->regs), orig_ip);
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}
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/*
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* If pre_handler returns !0, it changes regs->pc. We have to
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* skip emulating post_handler.
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*/
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__this_cpu_write(current_kprobe, NULL);
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}
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}
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NOKPROBE_SYMBOL(kprobe_ftrace_handler);
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int arch_prepare_kprobe_ftrace(struct kprobe *p)
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{
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p->ainsn.api.insn = NULL;
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return 0;
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}
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