linux-kernel - Re: [PATCH v4] vmlinux.lds: account for destructor sections

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Message-ID: <CACT4Y+a6DnHitSQrEsy311Tn5-oeUse7aTrB9-=PTOx1afxavA@mail.gmail.com>
Date:	Fri, 1 Jul 2016 17:20:31 +0200
From:	Dmitry Vyukov <dvyukov@...gle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	stable <stable@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"x86@...nel.org" <x86@...nel.org>, Arnd Bergmann <arnd@...db.de>,
	linux-arch@...r.kernel.org,
	Andrey Ryabinin <ryabinin.a.a@...il.com>
Cc:	kasan-dev <kasan-dev@...glegroups.com>,
	Alexander Potapenko <glider@...gle.com>,
	Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH v4] vmlinux.lds: account for destructor sections

On Fri, Jul 1, 2016 at 5:19 PM, Dmitry Vyukov <dvyukov@...gle.com> wrote:
> If CONFIG_KASAN is enabled and gcc is configured with
> --disable-initfini-array and/or gold linker is used,
> gcc emits .ctors/.dtors and .text.startup/.text.exit
> sections instead of .init_array/.fini_array.
> .dtors section is not explicitly accounted in the linker
> script and messes vvar/percpu layout. Want:
>
> ffffffff822bfd80 D _edata
> ffffffff822c0000 D __vvar_beginning_hack
> ffffffff822c0000 A __vvar_page
> ffffffff822c0080 0000000000000098 D vsyscall_gtod_data
> ffffffff822c1000 A __init_begin
> ffffffff822c1000 D init_per_cpu__irq_stack_union
> ffffffff822c1000 A __per_cpu_load
> ffffffff822d3000 D init_per_cpu__gdt_page
>
> Got:
>
> ffffffff8279a600 D _edata
> ffffffff8279b000 A __vvar_page
> ffffffff8279c000 A __init_begin
> ffffffff8279c000 D init_per_cpu__irq_stack_union
> ffffffff8279c000 A __per_cpu_load
> ffffffff8279e000 D __vvar_beginning_hack
> ffffffff8279e080 0000000000000098 D vsyscall_gtod_data
> ffffffff827ae000 D init_per_cpu__gdt_page
>
> This happens because __vvar_page and .vvar get different
> addresses in arch/x86/kernel/vmlinux.lds.S:
>
>         . = ALIGN(PAGE_SIZE);
>         __vvar_page = .;
>
>         .vvar : AT(ADDR(.vvar) - LOAD_OFFSET) {
>                 /* work around gold bug 13023 */
>                 __vvar_beginning_hack = .;
>
> Discard .dtors/.fini_array/.text.exit, since we don't call dtors.
> Merge .text.startup into init text.
>
> Cc: <stable@...r.kernel.org> # v4.0+
> Reviewed-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
> Signed-off-by: Dmitry Vyukov <dvyukov@...gle.com>
>
> ---
>
> Changes since v1:
>  - discard .dtors
>  - don't define .mem sections
>
> Changes since v2:
>  - use 'vmlinux.lds' subsystem prefix instead of 'kasan'
>
> Changes since v3:
>  - add 'Cc: <stable@...r.kernel.org> # v4.0+' tag
>  - CC linux-kernel@...r.kernel.org,akpm@...ux-foundation.org


Andrew, can you please take this to mm tree?