linux-kernel - Re: [PATCH arm64/kexec] arm64: kexec_file: forbid kdump via kexec_file

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Date:   Fri, 7 Dec 2018 20:56:53 +0530
From:   Bhupesh Sharma <bhsharma@...hat.com>
To:     James Morse <james.morse@....com>
Cc:     linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devicetree@...r.kernel.org,
        kexec mailing list <kexec@...ts.infradead.org>,
        Will Deacon <will.deacon@....com>, robh+dt@...nel.org,
        AKASHI Takahiro <takahiro.akashi@...aro.org>,
        Catalin Marinas <catalin.marinas@....com>, dhowells@...hat.com,
        Vivek Goyal <vgoyal@...hat.com>, herbert@...dor.apana.org.au,
        davem@...emloft.net, Dave Young <dyoung@...hat.com>,
        Baoquan He <bhe@...hat.com>, arnd@...db.de,
        schwidefsky@...ibm.com, heiko.carstens@...ibm.com,
        prudo@...ux.ibm.com, Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        frowand.list@...il.com
Subject: Re: [PATCH arm64/kexec] arm64: kexec_file: forbid kdump via kexec_file_load()

Hi James,

On Fri, Dec 7, 2018 at 3:44 PM James Morse <james.morse@....com> wrote:
>
> Now that kexec_walk_memblock() can do the crash-kernel placement itself
> architectures that don't support kdump via kexe_file_load() need to
> explicitly forbid it.
>
> We don't support this on arm64 until the kernel can add the elfcorehdr
> and usable-memory-range fields to the DT. Without these the crash-kernel
> overwrites the previous kernel's memory during startup.
>
> Add a check to refuse crash image loading.
>
> Signed-off-by: James Morse <james.morse@....com>
> ---
>
> Context: http://lore.kernel.org/r/20181206155424.GA4422@arm.com
>
>  arch/arm64/kernel/kexec_image.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/arch/arm64/kernel/kexec_image.c b/arch/arm64/kernel/kexec_image.c
> index 1ad1d5f8f024..07bf740bea91 100644
> --- a/arch/arm64/kernel/kexec_image.c
> +++ b/arch/arm64/kernel/kexec_image.c
> @@ -47,6 +47,10 @@ static void *image_load(struct kimage *image,
>         struct kexec_segment *kernel_segment;
>         int ret;
>
> +       /* We don't support crash kernels yet. */
> +       if (image->type == KEXEC_TYPE_CRASH)
> +               return ERR_PTR(-EOPNOTSUPP);
> +
>         /*
>          * We require a kernel with an unambiguous Image header. Per
>          * Documentation/booting.txt, this is the case when image_size
> --
> 2.19.2
>

TBH, I would have loved the complete 'kexec_file_load' support to have
made way upstream for arm64 as well, but I understand that it is stuck
till we have an agreement on the DT side of things. So, refusing a
crash image loading in such a case makes sense for now.

So, please feel free to add:
Reviewed-by: Bhupesh Sharma <bhsharma@...hat.com>

Thanks,
Bhupesh