linux-kernel - Re: [PATCH] dcache: Define DNAME_INLINE

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Message-ID: <b932c4b8-a45d-4da3-8ef9-f45055830609@linux.dev>
Date: Tue, 20 May 2025 11:26:08 -0700
From: Yonghong Song <yonghong.song@...ux.dev>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>,
 Al Viro <viro@...iv.linux.org.uk>
Cc: Tiezhu Yang <yangtiezhu@...ngson.cn>,
 Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
 Linux-Fsdevel <linux-fsdevel@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
 loongarch@...ts.linux.dev, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] dcache: Define DNAME_INLINE_LEN as a number directly



On 5/20/25 1:04 AM, Alexei Starovoitov wrote:
> On Tue, May 20, 2025 at 1:23 AM Al Viro <viro@...iv.linux.org.uk> wrote:
>> On Tue, May 20, 2025 at 02:47:07PM +0800, Tiezhu Yang wrote:
>>> When executing the bcc script, there exists the following error
>>> on LoongArch and x86_64:
>> NOTABUG.  You can't require array sizes to contain no arithmetics,
>> including sizeof().  Well, you can, but don't expect your requests
>> to be satisfied.
>>
>>> How to reproduce:
>>>
>>> git clone https://github.com/iovisor/bcc.git
>>> mkdir bcc/build; cd bcc/build
>>> cmake ..
>>> make
>>> sudo make install
>>> sudo /usr/share/bcc/tools/filetop
>> So fix the script.  Or report it to whoever wrote it, if it's
>> not yours.
> +1
>
>> I'm sorry, but we are NOT going to accomodate random parsers
>> poking inside the kernel-internal headers and failing to
>> actually parse the language they are written in.
>>
>> If you want to exfiltrate a constant, do what e.g. asm-offsets is
>> doing.  Take a look at e.g.  arch/loongarch/kernel/asm-offsets.c
>> and check what ends up in include/generated/asm-offsets.h - the
>> latter is entirely produced out of the former.
>>
>> The trick is to have inline asm that would spew a recognizable
>> line when compiled into assembler, with the value(s) you want
>> substituted into it.  See include/linux/kbuild.h for the macros.
>>
>> Then you pick these lines out of generated your_file.s - no need
>> to use python, sed(1) will do just fine.  See filechk_offsets in
>> scripts/Makefile.lib for that part.
> None of it is necessary.
>
> Tiezhu,
>
> bcc's tools/filetop.py is really old and obsolete.
> It's not worth fixing. I'd delete it.
> Use bcc's libbpf-tools/filetop instead.

Tiezhu, please check whether libbpf-tools/filetop satisfied your need or 
not. Thanks!