linux-kernel - Re: [PATCH v7 1/3] x86/mm: Adapt MODULES

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Message-ID: <20170316081013.GB7815@gmail.com>
Date:   Thu, 16 Mar 2017 09:10:13 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Thomas Garnier <thgarnie@...gle.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Jonathan Corbet <corbet@....net>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Kees Cook <keescook@...omium.org>,
        Juergen Gross <jgross@...e.com>,
        Andy Lutomirski <luto@...nel.org>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>, zijun_hu <zijun_hu@....com>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Andy Lutomirski <luto@...capital.net>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Jiri Kosina <jikos@...nel.org>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
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        Josh Poimboeuf <jpoimboe@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, kasan-dev@...glegroups.com,
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        kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH v7 1/3] x86/mm: Adapt MODULES_END based on Fixmap section
 size


* Thomas Garnier <thgarnie@...gle.com> wrote:

> This patch aligns MODULES_END to the beginning of the Fixmap section.
> It optimizes the space available for both sections. The address is
> pre-computed based on the number of pages required by the Fixmap
> section.
> 
> It will allow GDT remapping in the Fixmap section. The current
> MODULES_END static address does not provide enough space for the kernel
> to support a large number of processors.
> 
> Signed-off-by: Thomas Garnier <thgarnie@...gle.com>
> ---
> Based on next-20170308
> ---
>  Documentation/x86/x86_64/mm.txt         | 5 ++++-
>  arch/x86/include/asm/pgtable_64_types.h | 3 ++-
>  arch/x86/kernel/module.c                | 1 +
>  arch/x86/mm/dump_pagetables.c           | 1 +
>  arch/x86/mm/kasan_init_64.c             | 1 +
>  mm/vmalloc.c                            | 1 +

> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -35,6 +35,7 @@
>  #include <linux/uaccess.h>
>  #include <asm/tlbflush.h>
>  #include <asm/shmparam.h>
> +#include <asm/fixmap.h>
>  
>  #include "internal.h"

Note that asm/fixmap.h is an x86-ism that isn't present in many other 
architectures, so this hunk will break the build.

To make progress with these patches I've fixed it up with an ugly #ifdef 
CONFIG_X86, but it needs a real solution instead before this can be pushed 
upstream.

Thanks,

	Ingo

=====================>
 mm/vmalloc.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index dabea6a29fad..b7d2a23349f4 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -35,7 +35,10 @@
 #include <linux/uaccess.h>
 #include <asm/tlbflush.h>
 #include <asm/shmparam.h>
-#include <asm/fixmap.h>
+
+#ifdef CONFIG_X86
+# include <asm/fixmap.h>
+#endif
 
 #include "internal.h"