linux-kernel - Re: [RFC PATCH bpf-next 0/6] bpf, printk: add BTF-based type printing

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Message-ID: <alpine.LRH.2.21.2004171803550.29397@localhost>
Date:   Fri, 17 Apr 2020 18:06:16 +0100 (BST)
From:   Alan Maguire <alan.maguire@...cle.com>
To:     Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
cc:     Alan Maguire <alan.maguire@...cle.com>, ast@...nel.org,
        daniel@...earbox.net, yhs@...com, kafai@...com,
        songliubraving@...com, andriin@...com, john.fastabend@...il.com,
        kpsingh@...omium.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [RFC PATCH bpf-next 0/6] bpf, printk: add BTF-based type
 printing

On Fri, 17 Apr 2020, Arnaldo Carvalho de Melo wrote:

> Em Fri, Apr 17, 2020 at 11:42:34AM +0100, Alan Maguire escreveu:
> > To give a flavour for what the printed-out data looks like,
> > here we use pr_info() to display a struct sk_buff *.  Note
> > we specify the 'N' modifier to show type field names:
> > 
> >   struct sk_buff *skb = alloc_skb(64, GFP_KERNEL);
> > 
> >   pr_info("%pTN<struct sk_buff>", skb);
> > 
> > ...gives us:
> > 
> > {{{.next=00000000c7916e9c,.prev=00000000c7916e9c,{.dev=00000000c7916e9c|.dev_scratch=0}}|.rbnode={.__rb_parent_color=0,.rb_right=00000000c7916e9c,.rb_left=00000000c7916e9c}|.list={.next=00000000c7916e9c,.prev=00000000c7916e9c}},{.sk=00000000c7916e9c|.ip_defrag_offset=0},{.tstamp=0|.skb_mstamp_ns=0},.cb=['\0'],{{._skb_refdst=0,.destructor=00000000c7916e9c}|.tcp_tsorted_anchor={.next=00000000c7916e9c,.prev=00000000c7916e9c}},._nfct=0,.len=0,.data_len=0,.mac_len=0,.hdr_len=0,.queue_mapping=0,.__cloned_offset=[],.cloned=0x0,.nohdr=0x0,.fclone=0x0,.peeked=0x0,.head_frag=0x0,.pfmemalloc=0x0,.active_extensions=0,.headers_start=[],.__pkt_type_offset=[],.pkt_type=0x0,.ignore_df=0x0,.nf_trace=0x0,.ip_summed=0x0,.ooo_okay=0x0,.l4_hash=0x0,.sw_hash=0x0,.wifi_acked_valid=0x0,.wifi_acked=0x0,.no_fcs=0x0,.encapsulation=0x0,.encap_hdr_csum=0x0,.csum_valid=0x0,.__pkt_vlan_present_offset=[],.vlan_present=0x0,.csum_complete_sw=0x0,.csum_level=0x0,.csum_not_inet=0x0,.dst_pending_co
> 
> One suggestion, to make this more compact, one could have %pTNz<struct
> sk_buff>" that wouldn't print any integral type member that is zeroed
> :-)
>

That's a great idea, thanks Arnaldo! I'll add that.

Alan
 
> - Arnaldo
>