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

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Date:   Thu, 21 Mar 2019 14:17:46 -0400
From:   Qian Cai <cai@....pw>
To:     Catalin Marinas <catalin.marinas@....com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        kvm-ppc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH] kmemleak: powerpc: skip scanning holes in the .bss
 section

On Thu, 2019-03-21 at 17:19 +0000, Catalin Marinas wrote:
> The 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.
> 
> Acked-by: Michael Ellerman <mpe@...erman.id.au> (powerpc)
> Reported-by: Qian Cai <cai@....pw>
> Signed-off-by: Catalin Marinas <catalin.marinas@....com>

Tested-by: Qian Cai <cai@....pw>