linux-kernel - Re: [PATCH 3/3] vmalloc: Add debugfs modfraginfo

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Message-ID: <CAG48ez1QbKgoBCb-M=L+M5DJHj0URhNvS34h+Ax6RudckgCEEA@mail.gmail.com>
Date:   Thu, 21 Jun 2018 14:32:38 +0200
From:   Jann Horn <jannh@...gle.com>
To:     rick.p.edgecombe@...el.com
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        kristen.c.accardi@...el.com, Dave Hansen <dave.hansen@...el.com>,
        arjan.van.de.ven@...el.com
Subject: Re: [PATCH 3/3] vmalloc: Add debugfs modfraginfo

On Thu, Jun 21, 2018 at 12:12 AM Rick Edgecombe
<rick.p.edgecombe@...el.com> wrote:
> Add debugfs file "modfraginfo" for providing info on module space
> fragmentation.  This can be used for determining if loadable module
> randomization is causing any problems for extreme module loading situations,
> like huge numbers of modules or extremely large modules.
>
> Sample output when RANDOMIZE_BASE and X86_64 is configured:
> Largest free space:             847253504
> External Memory Fragementation: 20%
> Allocations in backup area:     0
>
> Sample output otherwise:
> Largest free space:             847253504
> External Memory Fragementation: 20%
[...]
> +       seq_printf(m, "Largest free space:\t\t%lu\n", largest_free);
> +       if (total_free)
> +               seq_printf(m, "External Memory Fragementation:\t%lu%%\n",

"Fragmentation"

> +                       100-(100*largest_free/total_free));
> +       else
> +               seq_puts(m, "External Memory Fragementation:\t0%%\n");

"Fragmentation"

[...]
> +static const struct file_operations debug_module_frag_operations = {
> +       .open       = proc_module_frag_debug_open,
> +       .read       = seq_read,
> +       .llseek     = seq_lseek,
> +       .release    = single_release,
> +};
>
> +static void debug_modfrag_init(void)
> +{
> +       debugfs_create_file("modfraginfo", 0x0400, NULL, NULL,
> +                       &debug_module_frag_operations);

0x0400 is 02000, which is the setgid bit. I think you meant to type 0400?