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

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Date:   Fri, 01 May 2020 17:25:13 -0700
From:   Joe Perches <joe@...ches.com>
To:     Alan Maguire <alan.maguire@...cle.com>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.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 Thu, 2020-04-30 at 03:03 -0700, Alan Maguire wrote:
> On Mon, 20 Apr 2020, Joe Perches wrote:

> > Here as well the individual field types don't contain
> > enough information to determine if a field should be
> > output as %x or %u.
> Right, we could add some more format modifiers for cases
> like that I guess.  Currently the display formats used are
> - numbers are represented as decimal
> - bitfields are represented in hex
> - pointers are obfuscated unless the 'x' option is used
> - char arrays are printed as chars if printable,
>   [ 'l', 'i', 'k', 'e', ' ', 't', 'h', 'i', 's' ]
> 
> I'd be happy to add more format specifiers to control
> these options, or tweak the defaults if needed. A
> "print numbers in hex" option seems worthwhile perhaps?

Or maybe add and use new typedefs like x8,x16,x32,x64 to the
bpf struct definitions where u8,u16,u32,u64 are %u and
x8,x16,x32,x64 are %x