linux-kernel - Re: [PATCH 5/5] x86: if kernel .text .data .bss are not marked as E820

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Date:	Fri, 24 Aug 2012 18:23:48 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Jacob Shin <jacob.shin@....com>
Cc:	X86-ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>, Tejun Heo <tj@...nel.org>,
	Dave Young <dyoung@...hat.com>,
	Chao Wang <chaowang@...hat.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Andreas Herrmann <andreas.herrmann3@....com>,
	Borislav Petkov <borislav.petkov@....com>
Subject: Re: [PATCH 5/5] x86: if kernel .text .data .bss are not marked as
 E820_RAM, complain and fix

On Fri, Aug 24, 2012 at 4:55 PM, Jacob Shin <jacob.shin@....com> wrote:
> There could be cases where user supplied memmap=exactmap memory
> mappings do not mark the region where the kernel .text .data and
> .bss reside as E820_RAM as reported here:
>
> https://lkml.org/lkml/2012/8/14/86
>
> Handle it by complaining, and adding the range back into the e820.
>
> Signed-off-by: Jacob Shin <jacob.shin@....com>
> ---
>  arch/x86/kernel/setup.c |   15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 4217fb4..b84aceb5 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -926,6 +926,21 @@ void __init setup_arch(char **cmdline_p)
>         insert_resource(&iomem_resource, &data_resource);
>         insert_resource(&iomem_resource, &bss_resource);
>
> +       /*
> +        * Complain if .text .data and .bss are not marked as E820_RAM and
> +        * attempt to fix it by adding the range. We may have a confused BIOS,
> +        * or the user may have incorrectly supplied it via memmap=exactmap. If
> +        * we really are running on top non-RAM, we will crash later anyways.
> +        */
> +       if (!e820_all_mapped(code_resource.start, bss_resource.end, E820_RAM)) {
> +               pr_warn(".text .data .bss are not marked as E820_RAM!\n");
> +
> +               e820_add_region(code_resource.start,
> +                               bss_resource.end - code_resource.start + 1,
> +                               E820_RAM);
> +               sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);

           this sanitze_e820_map could be spared. trim_bios_range will
that always.

> +       }
> +
>         trim_bios_range();
>  #ifdef CONFIG_X86_32
>         if (ppro_with_ram_bug()) {

also should use brk_limit instead of bss_resource.end. aka need to
keep the map for brk area.

Thanks

Yinghai
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