linux-kernel - RE: [PATCH v8 4/9] kallsyms: Reduce the memory occupied by kallsyms_seqs_of

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <bd30cbc9b7594261a7b9da26e9c98da4@AcuMS.aculab.com>
Date:   Wed, 2 Nov 2022 12:00:51 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Zhen Lei' <thunder.leizhen@...wei.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Petr Mladek <pmladek@...e.com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        "live-patching@...r.kernel.org" <live-patching@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Luis Chamberlain" <mcgrof@...nel.org>,
        "linux-modules@...r.kernel.org" <linux-modules@...r.kernel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        "Ingo Molnar" <mingo@...hat.com>
Subject: RE: [PATCH v8 4/9] kallsyms: Reduce the memory occupied by
 kallsyms_seqs_of_names[]

From: Zhen Lei
> Sent: 02 November 2022 08:49
> 
> kallsyms_seqs_of_names[] records the symbol index sorted by address, the
> maximum value in kallsyms_seqs_of_names[] is the number of symbols. And
> 2^24 = 16777216, which means that three bytes are enough to store the
> index. This can help us save (1 * kallsyms_num_syms) bytes of memory.

You can get the compiler to do the 'heavy lifting' for you.

struct uint24 {
    unsigned int val24:24;
} __attribute__((packed));

struct uint24 table[1024];

works fine.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)