linux-kernel - Re: [RFC bpf-next 2/4] fprobe: Resolve symbols with kallsyms_lookup

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Date:   Fri, 8 Apr 2022 09:58:15 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>
Subject: Re: [RFC bpf-next 2/4] fprobe: Resolve symbols with
 kallsyms_lookup_names

On Thu,  7 Apr 2022 14:52:22 +0200
Jiri Olsa <jolsa@...nel.org> wrote:

> Using kallsyms_lookup_names to speed up symbols lookup
> in register_fprobe_syms API.

OK, this looks good to me.

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

Thank you!

> 
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---
>  kernel/kallsyms.c     |  2 +-
>  kernel/trace/fprobe.c | 23 ++---------------------
>  2 files changed, 3 insertions(+), 22 deletions(-)
> 
> diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
> index a3738ddf9e87..7d89da375c23 100644
> --- a/kernel/kallsyms.c
> +++ b/kernel/kallsyms.c
> @@ -230,7 +230,7 @@ unsigned long kallsyms_lookup_name(const char *name)
>  	return module_kallsyms_lookup_name(name);
>  }
>  
> -#ifdef CONFIG_LIVEPATCH
> +#if defined(CONFIG_LIVEPATCH) || defined(CONFIG_FPROBE)
>  /*
>   * Iterate over all symbols in vmlinux.  For symbols from modules use
>   * module_kallsyms_on_each_symbol instead.
> diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
> index 89d9f994ebb0..d466803dc2b2 100644
> --- a/kernel/trace/fprobe.c
> +++ b/kernel/trace/fprobe.c
> @@ -88,36 +88,17 @@ NOKPROBE_SYMBOL(fprobe_exit_handler);
>  /* Convert ftrace location address from symbols */
>  static unsigned long *get_ftrace_locations(const char **syms, int num)
>  {
> -	unsigned long addr, size;
>  	unsigned long *addrs;
> -	int i;
>  
>  	/* Convert symbols to symbol address */
>  	addrs = kcalloc(num, sizeof(*addrs), GFP_KERNEL);
>  	if (!addrs)
>  		return ERR_PTR(-ENOMEM);
>  
> -	for (i = 0; i < num; i++) {
> -		addr = kallsyms_lookup_name(syms[i]);
> -		if (!addr)	/* Maybe wrong symbol */
> -			goto error;
> +	if (!kallsyms_lookup_names(syms, num, addrs))
> +		return addrs;
>  
> -		/* Convert symbol address to ftrace location. */
> -		if (!kallsyms_lookup_size_offset(addr, &size, NULL) || !size)
> -			goto error;
> -
> -		addr = ftrace_location_range(addr, addr + size - 1);
> -		if (!addr) /* No dynamic ftrace there. */
> -			goto error;
> -
> -		addrs[i] = addr;
> -	}
> -
> -	return addrs;
> -
> -error:
>  	kfree(addrs);
> -
>  	return ERR_PTR(-ENOENT);
>  }
>  
> -- 
> 2.35.1
> 


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