linux-kernel - Re: [PATCH v7 01/25] kallsyms: avoid hardcoding the buffer size

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Message-ID: <CANiq72=K4eC5EX9M8YRzL5Uy9onoTzha9rki-XZ3enSPy0p+UQ@mail.gmail.com>
Date:   Tue, 24 May 2022 18:21:14 +0200
From:   Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To:     Jarkko Sakkinen <jarkko@...nel.org>
Cc:     Miguel Ojeda <ojeda@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        rust-for-linux <rust-for-linux@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH v7 01/25] kallsyms: avoid hardcoding the buffer size

On Mon, May 23, 2022 at 9:46 PM Jarkko Sakkinen <jarkko@...nel.org> wrote:
>
> "Declare KSY_NAME_LEN, which describes the maximum length for a kernel
> symbol read by kallsyms from the input.  In read_symbol(), define the
> buffer to be of length "KSY_NAME_LEN + 1", which includes the terminator
> character."
>
> would be better.

Note that the patch is not declaring `KSYM_NAME_LEN`, but a new
constant for a fairly arbitrarily sized for an input buffer.

I am all for detailed commit messages, and I agree this can be
expanded. However, I think the first sentence of what you wrote should
be part of the docs of the constant, and the second one sounds like it
could be a comment on the code. Something like "Introduce
KSYM_NAME_LEN_BUFFER in place of the previously hardcoded size of the
input buffer (...)" would be better for a reviewer.

> You must split this then into two patches:

Note that the size is not really being increased in a meaningful way
-- the important bit is the introduction of the relationship between
constants. The changes are all meant as a replacement for the
previously hardcoded constant, so I don't think the split is a "must",
but we can do it.

We can even split this into 3 patches: clean up the unneeded `sizeof`,
replace (and, importantly, document) the hardcoded constant, and
finally introduce the relationship.

Thanks for taking a look!

Cheers,
Miguel