linux-kernel - Re: [PATCH v3 perf, bpf-next 1/4] perf, bpf: Introduce PERF_RECORD_BPF

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Date:   Wed, 12 Dec 2018 16:49:18 +0000
From:   Song Liu <songliubraving@...com>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     lkml <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        Kernel Team <Kernel-team@...com>,
        "acme@...nel.org" <acme@...nel.org>
Subject: Re: [PATCH v3 perf, bpf-next 1/4] perf, bpf: Introduce
 PERF_RECORD_BPF_EVENT



> On Dec 12, 2018, at 4:06 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> 
> On Tue, Dec 11, 2018 at 03:33:47PM -0800, Song Liu wrote:
>> +static void perf_event_bpf_output(struct perf_event *event,
>> +				   void *data)
>> +{
>> +	struct perf_bpf_event *bpf_event = data;
>> +	struct perf_output_handle handle;
>> +	struct perf_sample_data sample;
>> +	char name[KSYM_NAME_LEN];
>> +	int name_len;
>> +	int ret;
>> +
>> +	if (!perf_event_bpf_match(event))
>> +		return;
>> +
>> +	/* get prog name and round up to 64 bit aligned */
>> +	bpf_get_prog_name(bpf_event->prog, name);
>> +	name_len = strlen(name) + 1;
>> +	while (!IS_ALIGNED(name_len, sizeof(u64)))
>> +		name[name_len++] = '\0';
> 
> Does this not require something like:
> 
> 	BUILD_BUG_ON(KSYM_NAME_LEN % sizeof(u64));

Yeah, this makes sense. I will add this in next version. 

Thanks,
Song