linux-kernel - Re: [PATCH 2/2] lib/vsprintf: reduce space taken by no_hash

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Date:   Thu, 11 Mar 2021 21:46:16 -0600
From:   Timur Tabi <timur@...nel.org>
To:     Marco Elver <elver@...gle.com>
Cc:     Petr Mladek <pmladek@...e.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH 2/2] lib/vsprintf: reduce space taken by no_hash_pointers warning

On Mon, Mar 8, 2021 at 4:51 AM Marco Elver <elver@...gle.com> wrote:
> If we do __initconst change we need to manually remove the duplicate
> lines because we're asking the compiler to create a large array (and
> there's no more auto-dedup). If we do not remove the duplicate lines,
> the __initconst-only approach would create a larger image and result
> in subtly increased memory consumption during init. The additional
> code together with manual dedup should offset that. (I can split this
> patch as Andy suggests, but first need confirmation what people
> actually want.)
>
> I have no idea what the right trade-off is, and appeal to Geert to
> suggest what would be acceptable to him.

Maybe we can have only the message itself wrapped in an #ifdef CONFIG_
of some kind.  For example:

+#ifndef CONFIG_CC_OPTIMIZE_FOR_SIZE
       pr_warn("**********************************************************\n");
       pr_warn("**   NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE NOTICE   **\n");
       pr_warn("**                                                      **\n");
       pr_warn("** This system shows unhashed kernel memory addresses   **\n");
...
+#endif

       return 0;
}

In other words, if space is really constrained, then don't include the
message.  Or maybe just include part of the message.