linux-kernel - Re: [PATCH 2/3] e820_update_range(): Allow specifying ULLONG

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Date:	Tue, 24 Jun 2008 13:01:26 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Bernhard Walle" <bwalle@...e.de>, "Ingo Molnar" <mingo@...e.hu>
Cc:	x86@...nel.org, vgoyal@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] e820_update_range(): Allow specifying ULLONG_MAX

On Tue, Jun 24, 2008 at 7:35 AM, Bernhard Walle <bwalle@...e.de> wrote:
> Allow the specifying of ULLONG_MAX to limit the whole E820 map from the
> specified start to the end. Without the patch, there would be integer
> overflows.
>
>
> Signed-off-by: Bernhard Walle <bwalle@...e.de>
> ---
>  arch/x86/kernel/e820.c |   11 +++++++++--
>  1 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index e466073..7d1109b 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -397,6 +397,9 @@ int __init copy_e820_map(struct e820entry *biosmap, int nr_map)
>        return __copy_e820_map(biosmap, nr_map);
>  }
>
> +/*
> + * Pass size == ULLONG_MAX to update until the end.
> + */
>  u64 __init e820_update_range(u64 start, u64 size, unsigned old_type,
>                                unsigned new_type)
>  {
> @@ -412,14 +415,18 @@ u64 __init e820_update_range(u64 start, u64 size, unsigned old_type,
>                        continue;
>                /* totally covered? */
>                if (ei->addr >= start &&
> -                   (ei->addr + ei->size) <= (start + size)) {
> +                   (((ei->addr + ei->size) <= (start + size)) ||
> +                           (size == ULLONG_MAX))) {
>                        ei->type = new_type;
>                        real_updated_size += ei->size;
>                        continue;
>                }
>                /* partially covered */
>                final_start = max(start, ei->addr);
> -               final_end = min(start + size, ei->addr + ei->size);
> +               if (size == ULLONG_MAX)
> +                       final_end = ei->addr + ei->size;
> +               else
> +                       final_end = min(start + size, ei->addr + ei->size);
>                if (final_start >= final_end)
>                        continue;
>                ei->size -= final_end - final_start;
> --


it seems we should let the caller to use
e820_update_range(start, ULLONG_MAX - size,....)

so you don't need to touch this func.

YH
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