Re: [PATCH v5] libbpf: kprobe.multi: Filter with available_filter_functions

[Jiri Olsa <olsajiri@gmail.com>]

On Fri, May 26, 2023 at 10:10:47AM +0800, Jackie Liu wrote:

SNIP

> -resolve_kprobe_multi_cb(unsigned long long sym_addr, char sym_type,
> -			const char *sym_name, void *ctx)
> +kallsyms_resolve_kprobe_multi_cb(unsigned long long sym_addr, char sym_type,
> +				 const char *sym_name, void *ctx)
>  {
>  	struct kprobe_multi_resolve *res = ctx;
>  	int err;
> @@ -10431,8 +10438,8 @@ resolve_kprobe_multi_cb(unsigned long long sym_addr, char sym_type,
>  	if (!glob_match(sym_name, res->pattern))
>  		return 0;
>  
> -	err = libbpf_ensure_mem((void **) &res->addrs, &res->cap, sizeof(unsigned long),
> -				res->cnt + 1);
> +	err = libbpf_ensure_mem((void **) &res->addrs, &res->cap,
> +				sizeof(unsigned long), res->cnt + 1);

hum, looks like this is just formatting change, AFAICS we don't need that 

>  	if (err)
>  		return err;
>  
> @@ -10440,6 +10447,75 @@ resolve_kprobe_multi_cb(unsigned long long sym_addr, char sym_type,
>  	return 0;
>  }
>  

SNIP

> +
> +static void kprobe_multi_resolve_free(struct kprobe_multi_resolve *res)
> +{
> +	while (res->syms && res->cnt)
> +		free((char *)res->syms[--res->cnt]);
> +
> +	free(res->syms);
> +	free(res->addrs);

we should set cnt and cap to zero for the fallback sake

> +}
> +
>  struct bpf_link *
>  bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
>  				      const char *pattern,
> @@ -10476,13 +10552,20 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
>  		return libbpf_err_ptr(-EINVAL);
>  
>  	if (pattern) {
> -		err = libbpf_kallsyms_parse(resolve_kprobe_multi_cb, &res);
> -		if (err)
> -			goto error;
> +		err = libbpf_available_kprobes_parse(ftrace_resolve_kprobe_multi_cb,
> +						     &res);
> +		if (err) {
> +			/* fallback to kallsyms */

we need to call kprobe_multi_resolve_free in here and set
cnt/cap to zero in kprobe_multi_resolve_free

jirka

> +			err = libbpf_kallsyms_parse(kallsyms_resolve_kprobe_multi_cb,
> +						    &res);
> +			if (err)
> +				goto error;
> +		}
>  		if (!res.cnt) {
>  			err = -ENOENT;
>  			goto error;
>  		}
> +		syms = res.syms;
>  		addrs = res.addrs;
>  		cnt = res.cnt;
>  	}
> @@ -10511,12 +10594,12 @@ bpf_program__attach_kprobe_multi_opts(const struct bpf_program *prog,
>  		goto error;
>  	}
>  	link->fd = link_fd;
> -	free(res.addrs);
> +	kprobe_multi_resolve_free(&res);
>  	return link;
>  
>  error:
>  	free(link);
> -	free(res.addrs);
> +	kprobe_multi_resolve_free(&res);
>  	return libbpf_err_ptr(err);
>  }
>  
> -- 
> 2.25.1
>