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

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Date:	Tue, 24 Jun 2008 13:21:44 -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 1:01 PM, Yinghai Lu <yhlu.kernel@...il.com> wrote:
> 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.

or add sanitary check before using size in this func like
if (size > ULLONG_MAX - start)
     size = ULLONG_MAX - start;

e820_remove_range need to the same thing

YH
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