linux-kernel - Re: [PATCH v5 perf,bpf 09/15] perf, bpf: save btf information as headers to perf.data

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Date:   Mon, 4 Mar 2019 14:52:17 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Song Liu <songliubraving@...com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        ast@...nel.org, daniel@...earbox.net, kernel-team@...com,
        peterz@...radead.org, acme@...hat.com, jolsa@...nel.org,
        namhyung@...nel.org
Subject: Re: [PATCH v5 perf,bpf 09/15] perf, bpf: save btf information as
 headers to perf.data

On Wed, Feb 27, 2019 at 09:06:37PM -0800, Song Liu wrote:

SNIP

>  
> +static int process_bpf_btf(struct feat_fd *ff, void *data __maybe_unused)
> +{
> +	struct perf_env *env = &ff->ph->env;
> +	u32 count, i;
> +
> +	if (do_read_u32(ff, &count))
> +		return -1;
> +
> +	down_write(&env->bpf_progs.lock);
> +
> +	for (i = 0; i < count; ++i) {
> +		struct btf_node *node;
> +		u32 id, data_size;
> +
> +		if (do_read_u32(ff, &id))
> +			return -1;
> +		if (do_read_u32(ff, &data_size))
> +			return -1;
> +
> +		node = malloc(sizeof(struct btf_node) + data_size);
> +		if (!node)
> +			return -1;
> +
> +		node->id = id;
> +		node->data_size = data_size;
> +
> +		if (__do_read(ff, node->data, data_size)) {
> +			free(node);
> +			return -1;
> +		}
> +
> +		/* endian mismatch, drop the btf, continue */
> +		if (ff->ph->needs_swap) {
> +			free(node);
> +			continue;
> +		}

again, we can check for needs_swap in the begining,
display warning and skip the loop in here

perhaps we should warn just once for all the bpf data
missed when needs_swap is set

jirka