linux-kernel - Re: [PATCH 01/17] kallsyms: support big kernel symbols (2-byte lengths)

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Message-ID: <YOIicc94zvSjrKfe@casper.infradead.org>
Date:   Sun, 4 Jul 2021 22:04:49 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     ojeda@...nel.org
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        rust-for-linux@...r.kernel.org, linux-kbuild@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Alex Gaynor <alex.gaynor@...il.com>,
        Geoffrey Thomas <geofft@...reload.com>,
        Finn Behrens <me@...enk.de>,
        Adam Bratschi-Kaye <ark.email@...il.com>,
        Wedson Almeida Filho <wedsonaf@...gle.com>
Subject: Re: [PATCH 01/17] kallsyms: support big kernel symbols (2-byte
 lengths)

On Sun, Jul 04, 2021 at 10:27:40PM +0200, ojeda@...nel.org wrote:
> From: Miguel Ojeda <ojeda@...nel.org>
> 
> Rust symbols can become quite long due to namespacing introduced
> by modules, types, traits, generics, etc.
> 
> Increasing to 255 is not enough in some cases, and therefore
> we need to introduce 2-byte lengths to the symbol table. We call
> these "big" symbols.
> 
> In order to avoid increasing all lengths to 2 bytes (since most
> of them only require 1 byte, including many Rust ones), we use
> length zero to mark "big" symbols in the table.

What happened to my suggestion from last time of encoding symbols < 128
as 0-127 and symbols larger than that as (data[0] - 128) * 256 +
data[1]) ?