netdev - Re: [PATCH v2 bpf-next 0/7] bpf, printk: add BTF-based type printing

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 13 May 2020 15:48:17 -0700
From:   Joe Perches <joe@...ches.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Alan Maguire <alan.maguire@...cle.com>
Cc:     ast@...nel.org, daniel@...earbox.net, bpf@...r.kernel.org,
        linux@...musvillemoes.dk, arnaldo.melo@...il.com, yhs@...com,
        kafai@...com, songliubraving@...com, andriin@...com,
        john.fastabend@...il.com, kpsingh@...omium.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v2 bpf-next 0/7] bpf, printk: add BTF-based type printing

On Wed, 2020-05-13 at 15:24 -0700, Alexei Starovoitov wrote:
> On Tue, May 12, 2020 at 06:56:38AM +0100, Alan Maguire wrote:
> > The printk family of functions support printing specific pointer types
> > using %p format specifiers (MAC addresses, IP addresses, etc).  For
> > full details see Documentation/core-api/printk-formats.rst.
> > 
> > This patchset proposes introducing a "print typed pointer" format
> > specifier "%pT"; the argument associated with the specifier is of
> > form "struct btf_ptr *" which consists of a .ptr value and a .type
> > value specifying a stringified type (e.g. "struct sk_buff") or
> > an .id value specifying a BPF Type Format (BTF) id identifying
> > the appropriate type it points to.
> > 
> >   pr_info("%pT", BTF_PTR_TYPE(skb, "struct sk_buff"));
> > 
> > ...gives us:
> > 
> > (struct sk_buff){
> >  .transport_header = (__u16)65535,
> >  .mac_header = (__u16)65535,
> >  .end = (sk_buff_data_t)192,
> >  .head = (unsigned char *)000000007524fd8b,
> >  .data = (unsigned char *)000000007524fd8b,
> 
> could you add "0x" prefix here to make it even more C like
> and unambiguous ?

linux pointers are not emitted with an 0x prefix

(ie: pointers do not use SPECIAL in lib/vsprintf.c)