linux-kernel - Re: [PATCH 3/5] perf tools: Parsing libbpf return value using err.h

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Date:	Tue, 3 Nov 2015 12:17:16 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Wang Nan <wangnan0@...wei.com>
Cc:	lizefan@...wei.com, pi3orama@....com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] perf tools: Parsing libbpf return value using err.h

Em Tue, Nov 03, 2015 at 10:44:44AM +0000, Wang Nan escreveu:
> In following patches libbpf would encode error code using return
> pointer instead of returnning a NULL pointer to indicate error. This
> patch makes a preperation to enable perf correctly receive error code
> from libbpf.
> 
> Signed-off-by: Wang Nan <wangnan0@...wei.com>
> Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
> ---
>  tools/perf/tests/llvm.c      | 2 +-
>  tools/perf/util/bpf-loader.c | 8 ++++----
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/perf/tests/llvm.c b/tools/perf/tests/llvm.c
> index 512d362..38e0d9a 100644
> --- a/tools/perf/tests/llvm.c
> +++ b/tools/perf/tests/llvm.c
> @@ -27,7 +27,7 @@ static int test__bpf_parsing(void *obj_buf, size_t obj_buf_sz)
>  	struct bpf_object *obj;
>  
>  	obj = bpf_object__open_buffer(obj_buf, obj_buf_sz, NULL);
> -	if (!obj)
> +	if (IS_ERR(obj) || !obj)

Well, since we've adopted IS_ERR() from the kernel, we better try to
follow how it is used there, no?

Since you move to use ERR_PTR(), you probably will never return NULL,
right? So whay the (|| !obj) part?

The kernel has an IS_ERR_OR_NULL() interface tho, trying to figure out
when that would be appropriate...

- Arnaldo

>  		return -1;
>  	bpf_object__close(obj);
>  	return 0;
> diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
> index 0c5d174..dd6fa27 100644
> --- a/tools/perf/util/bpf-loader.c
> +++ b/tools/perf/util/bpf-loader.c
> @@ -59,9 +59,9 @@ struct bpf_object *bpf__prepare_load(const char *filename, bool source)
>  	} else
>  		obj = bpf_object__open(filename);
>  
> -	if (!obj) {
> +	if (IS_ERR(obj) || !obj) {
>  		pr_debug("bpf: failed to load %s\n", filename);
> -		return ERR_PTR(-EINVAL);
> +		return !obj ? ERR_PTR(-EINVAL) : obj;
>  	}
>  
>  	return obj;
> @@ -96,9 +96,9 @@ config_bpf_program(struct bpf_program *prog)
>  	int err;
>  
>  	config_str = bpf_program__title(prog, false);
> -	if (!config_str) {
> +	if (IS_ERR(config_str) || !config_str) {
>  		pr_debug("bpf: unable to get title for program\n");
> -		return -EINVAL;
> +		return !config_str ? -EINVAL : PTR_ERR(config_str);
>  	}
>  
>  	priv = calloc(sizeof(*priv), 1);
> -- 
> 1.8.3.4
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