linux-kernel - Re: [PATCH 4.19 62/99] kmemleak: powerpc: skip scanning holes in the .bss section

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Date:   Tue, 7 May 2019 16:58:09 +0900
From:   Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@...hiba.co.jp>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Qian Cai <cai@....pw>, Paul Mackerras <paulus@...ba.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Avi Kivity <avi@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krcmar <rkrcmar@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH 4.19 62/99] kmemleak: powerpc: skip scanning holes in the
 .bss section

Hi,

On Mon, May 06, 2019 at 04:32:35PM +0200, Greg Kroah-Hartman wrote:
> [ Upstream commit 298a32b132087550d3fa80641ca58323c5dfd4d9 ]
> 
> Commit 2d4f567103ff ("KVM: PPC: Introduce kvm_tmp framework") adds
> kvm_tmp[] into the .bss section and then free the rest of unused spaces
> back to the page allocator.
> 
> kernel_init
>   kvm_guest_init
>     kvm_free_tmp
>       free_reserved_area
>         free_unref_page
>           free_unref_page_prepare
> 
> With DEBUG_PAGEALLOC=y, it will unmap those pages from kernel.  As the
> result, kmemleak scan will trigger a panic when it scans the .bss
> section with unmapped pages.
> 
> This patch creates dedicated kmemleak objects for the .data, .bss and
> potentially .data..ro_after_init sections to allow partial freeing via
> the kmemleak_free_part() in the powerpc kvm_free_tmp() function.
> 
> Link: http://lkml.kernel.org/r/20190321171917.62049-1-catalin.marinas@arm.com
> Signed-off-by: Catalin Marinas <catalin.marinas@....com>
> Reported-by: Qian Cai <cai@....pw>
> Acked-by: Michael Ellerman <mpe@...erman.id.au> (powerpc)
> Tested-by: Qian Cai <cai@....pw>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: Avi Kivity <avi@...hat.com>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Radim Krcmar <rkrcmar@...hat.com>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>  arch/powerpc/kernel/kvm.c |  7 +++++++
>  mm/kmemleak.c             | 16 +++++++++++-----
>  2 files changed, 18 insertions(+), 5 deletions(-)

This commit has other problems, so we also need the following commits:

commit dce5b0bdeec61bdbee56121ceb1d014151d5cab1
Author: Arnd Bergmann <arnd@...db.de>
Date:   Thu Apr 18 17:50:48 2019 -0700

    mm/kmemleak.c: fix unused-function warning

    The only references outside of the #ifdef have been removed, so now we
    get a warning in non-SMP configurations:

      mm/kmemleak.c:1404:13: error: unused function 'scan_large_block' [-Werror,-Wunused-function]

    Add a new #ifdef around it.

    Link: http://lkml.kernel.org/r/20190416123148.3502045-1-arnd@arndb.de
    Fixes: 298a32b13208 ("kmemleak: powerpc: skip scanning holes in the .bss section")
    Signed-off-by: Arnd Bergmann <arnd@...db.de>
    Acked-by: Catalin Marinas <catalin.marinas@....com>
    Cc: Vincent Whitchurch <vincent.whitchurch@...s.com>
    Cc: Michael Ellerman <mpe@...erman.id.au>
    Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>

Please apply this commit.

Best regards,
  Nobuhiro