From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Joe Perches <joe@perches.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 4/7] printk: add type-printing %pT format specifier which uses BTF
Date: Wed, 13 May 2020 16:07:56 -0700 [thread overview]
Message-ID: <CAADnVQK8osy9W8-u-K=ucqe5q-+Uik41fBw6d-SfG-m6rgVwDQ@mail.gmail.com> (raw)
In-Reply-To: <1b63a6b193073674b6e0f9f95c62ce2af1b977cc.camel@perches.com>
On Wed, May 13, 2020 at 4:05 PM Joe Perches <joe@perches.com> wrote:
>
> On Tue, 2020-05-12 at 06:56 +0100, Alan Maguire wrote:
> > printk supports multiple pointer object type specifiers (printing
> > netdev features etc). Extend this support using BTF to cover
> > arbitrary types. "%pT" specifies the typed format, and the pointer
> > argument is a "struct btf_ptr *" where struct btf_ptr is as follows:
> >
> > struct btf_ptr {
> > void *ptr;
> > const char *type;
> > u32 id;
> > };
> >
> > Either the "type" string ("struct sk_buff") or the BTF "id" can be
> > used to identify the type to use in displaying the associated "ptr"
> > value. A convenience function to create and point at the struct
> > is provided:
> >
> > printk(KERN_INFO "%pT", BTF_PTR_TYPE(skb, struct sk_buff));
> >
> > When invoked, BTF information is used to traverse the sk_buff *
> > and display it. Support is present for structs, unions, enums,
> > typedefs and core types (though in the latter case there's not
> > much value in using this feature of course).
> >
> > Default output is indented, but compact output can be specified
> > via the 'c' option. Type names/member values can be suppressed
> > using the 'N' option. Zero values are not displayed by default
> > but can be using the '0' option. Pointer values are obfuscated
> > unless the 'x' option is specified. As an example:
> >
> > struct sk_buff *skb = alloc_skb(64, GFP_KERNEL);
> > 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 *)000000006b71155a,
> > .data = (unsigned char *)000000006b71155a,
> > .truesize = (unsigned int)768,
> > .users = (refcount_t){
> > .refs = (atomic_t){
> > .counter = (int)1,
>
> Given
>
> #define BTF_INT_ENCODING(VAL) (((VAL) & 0x0f000000) >> 24)
>
> Maybe
>
> #define BTF_INT_SIGNED (1 << 0)
> #define BTF_INT_CHAR (1 << 1)
> #define BTF_INT_BOOL (1 << 2)
>
> could be extended to include
>
> #define BTF_INT_HEX (1 << 3)
>
> So hex values can be appropriately pretty-printed.
Nack to that.
next prev parent reply other threads:[~2020-05-13 23:08 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 [this message]
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
2020-05-14 17:46 ` Alan Maguire
2020-05-15 18:59 ` Yonghong Song
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