linux-kernel - Re: [PATCH] kprobes: fix compilation when KPROBE

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Date:   Mon, 8 Apr 2019 09:55:19 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Sven Schnelle <svens@...ckframe.org>
Cc:     linux-kernel@...r.kernel.org,
        "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: Re: [PATCH] kprobes: fix compilation when KPROBE_EVENTS is enabled
 without kretpobes

On Sat,  6 Apr 2019 17:55:43 +0200
Sven Schnelle <svens@...ckframe.org> wrote:

> While implementing kprobes on PA-RISC (without kretprobes) compilation
> fails when CONFIG_KPROBE_EVENTS is enabled:
> 
> kernel/trace/trace_kprobe.o: in function `trace_kprobe_create':
> kernel/trace/trace_kprobe.c:666: undefined reference to `kprobe_on_func_entry'
> kernel/trace/trace_kprobe.o: in function `trace_kprobe_on_func_entry':
> kernel/trace/trace_kprobe.c:167: undefined reference to `kprobe_on_func_entry'
> kernel/trace/trace_kprobe.c:167: undefined reference to `kprobe_on_func_entry'
> make: *** [Makefile:1029: vmlinux] Error 1
> 
> Given the fact that these functions have no dependencies on kretprobes i think
> they should be moved out of the #ifdef CONFIG_KRETPROBES block.

Ah, I got it. Yes, this function had been introduced for kretprobe (because
kretprobe must be the entry of functions) but is used for kprobe_event and
bpf now.

It should be moved out of CONFIG_KPROBE_EVENTS.

Acked-by: Masami Hiramatsu <mhiramat@...nel.org>

Thank you,

> 
> Signed-off-by: Sven Schnelle <svens@...ckframe.org>
> Cc: "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>
> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Masami Hiramatsu <mhiramat@...nel.org>
> ---
>  kernel/kprobes.c | 39 ++++++++++++++++++++-------------------
>  1 file changed, 20 insertions(+), 19 deletions(-)
> 
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index c83e54727131..10a7e67fea67 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -1819,6 +1819,26 @@ unsigned long __weak arch_deref_entry_point(void *entry)
>  	return (unsigned long)entry;
>  }
>  
> +bool __weak arch_kprobe_on_func_entry(unsigned long offset)
> +{
> +	return !offset;
> +}
> +
> +bool kprobe_on_func_entry(kprobe_opcode_t *addr, const char *sym,
> +			  unsigned long offset)
> +{
> +	kprobe_opcode_t *kp_addr = _kprobe_addr(addr, sym, offset);
> +
> +	if (IS_ERR(kp_addr))
> +		return false;
> +
> +	if (!kallsyms_lookup_size_offset((unsigned long)kp_addr, NULL, &offset) ||
> +					 !arch_kprobe_on_func_entry(offset))
> +		return false;
> +
> +	return true;
> +}
> +
>  #ifdef CONFIG_KRETPROBES
>  /*
>   * This kprobe pre_handler is registered with every kretprobe. When probe
> @@ -1875,25 +1895,6 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs)
>  }
>  NOKPROBE_SYMBOL(pre_handler_kretprobe);
>  
> -bool __weak arch_kprobe_on_func_entry(unsigned long offset)
> -{
> -	return !offset;
> -}
> -
> -bool kprobe_on_func_entry(kprobe_opcode_t *addr, const char *sym, unsigned long offset)
> -{
> -	kprobe_opcode_t *kp_addr = _kprobe_addr(addr, sym, offset);
> -
> -	if (IS_ERR(kp_addr))
> -		return false;
> -
> -	if (!kallsyms_lookup_size_offset((unsigned long)kp_addr, NULL, &offset) ||
> -						!arch_kprobe_on_func_entry(offset))
> -		return false;
> -
> -	return true;
> -}
> -
>  int register_kretprobe(struct kretprobe *rp)
>  {
>  	int ret = 0;
> -- 
> 2.20.1
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>