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From: Joe Perches <joe@perches.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Alan Maguire <alan.maguire@oracle.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>, bpf <bpf@vger.kernel.org>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>,
	Yonghong Song <yhs@fb.com>, Martin KaFai Lau <kafai@fb.com>,
	Song Liu <songliubraving@fb.com>,
	Andrii Nakryiko <andriin@fb.com>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@chromium.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Network Development <netdev@vger.kernel.org>
Subject: Re: [PATCH v2 bpf-next 0/7] bpf, printk: add BTF-based type printing
Date: Wed, 13 May 2020 16:23:42 -0700	[thread overview]
Message-ID: <e09c45fac7bb688e5e248449594625eda97a2791.camel@perches.com> (raw)
In-Reply-To: <CAADnVQLPSvRCO-xxW+Rcz4bzLM-DXjSzm8AwhyogrNTufBdoNw@mail.gmail.com>

On Wed, 2020-05-13 at 15:50 -0700, Alexei Starovoitov wrote:
> On Wed, May 13, 2020 at 3:48 PM Joe Perches <joe@perches.com> wrote:
> > 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
> 
> So? This is not at all comparable to %p

Then why is x used to obfuscate?



  reply	other threads:[~2020-05-13 23:23 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-12  5:56 [PATCH v2 bpf-next 0/7] bpf, printk: add BTF-based type printing Alan Maguire
2020-05-12  5:56 ` [PATCH v2 bpf-next 1/7] bpf: provide function to get vmlinux BTF information Alan Maguire
2020-05-12  5:56 ` [PATCH v2 bpf-next 2/7] bpf: move to generic BTF show support, apply it to seq files/strings Alan Maguire
2020-05-13 23:04   ` Yonghong Song
2020-05-18  9:46     ` Alan Maguire
2020-05-19  6:21       ` Yonghong Song
2020-05-12  5:56 ` [PATCH v2 bpf-next 3/7] checkpatch: add new BTF pointer format specifier Alan Maguire
2020-05-12  5:56 ` [PATCH v2 bpf-next 4/7] printk: add type-printing %pT format specifier which uses BTF Alan Maguire
2020-05-13 23:05   ` Joe Perches
2020-05-13 23:07     ` Alexei Starovoitov
2020-05-13 23:22       ` Joe Perches
2020-05-14 23:43         ` Joe Perches
2020-05-15  0:09           ` Alexei Starovoitov
2020-05-15  0:21             ` Joe Perches
2020-05-14  0:45   ` Yonghong Song
2020-05-14 22:37     ` Alan Maguire
2020-05-15  0:39       ` Yonghong Song
2020-05-12  5:56 ` [PATCH v2 bpf-next 5/7] printk: extend test_printf to test %pT BTF-based format specifier Alan Maguire
2020-05-12  5:56 ` [PATCH v2 bpf-next 6/7] bpf: add support for %pT format specifier for bpf_trace_printk() helper Alan Maguire
2020-05-14  0:53   ` Yonghong Song
2020-05-18  9:10     ` Alan Maguire
2020-05-18 14:47       ` Yonghong Song
2020-05-12  5:56 ` [PATCH v2 bpf-next 7/7] bpf: add tests for %pT format specifier Alan Maguire
2020-05-15  0:21   ` Andrii Nakryiko
2020-05-13 22:24 ` [PATCH v2 bpf-next 0/7] bpf, printk: add BTF-based type printing Alexei Starovoitov
2020-05-13 22:48   ` Joe Perches
2020-05-13 22:50     ` Alexei Starovoitov
2020-05-13 23:23       ` Joe Perches [this message]
2020-05-14 17:46   ` Alan Maguire
2020-05-15 18:59   ` Yonghong Song

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