netdev - Re: [PATCH bpf-next 2/3] bpf: emit RECORD_MMAP events for bpf prog load/unload

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Message-ID: <20180920084424.GN24124@hirez.programming.kicks-ass.net>
Date:   Thu, 20 Sep 2018 10:44:24 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Alexei Starovoitov <ast@...nel.org>
Cc:     "David S . Miller" <davem@...emloft.net>, daniel@...earbox.net,
        acme@...nel.org, netdev@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH bpf-next 2/3] bpf: emit RECORD_MMAP events for bpf prog
 load/unload

On Wed, Sep 19, 2018 at 03:39:34PM -0700, Alexei Starovoitov wrote:
>  void bpf_prog_kallsyms_del(struct bpf_prog *fp)
>  {
> +	unsigned long symbol_start, symbol_end;
> +	/* mmap_record.filename cannot be NULL and has to be u64 aligned */
> +	char buf[sizeof(u64)] = {};
> +
>  	if (!bpf_prog_kallsyms_candidate(fp))
>  		return;
>  
>  	spin_lock_bh(&bpf_lock);
>  	bpf_prog_ksym_node_del(fp->aux);
>  	spin_unlock_bh(&bpf_lock);
> +	bpf_get_prog_addr_region(fp, &symbol_start, &symbol_end);
> +	perf_event_mmap_bpf_prog(symbol_start, symbol_end - symbol_start,
> +				 buf, sizeof(buf));
>  }

So perf doesn't normally issue unmap events.. We've talked about doing
that, but so far it's never really need needed I think.

I feels a bit weird to start issuing unmap events for this.