2014-12-26 12:23:13

by Alexander Kuleshov

[permalink] [raw]
Subject: [PATCH] x86: Remove excess calculations for heap_end_ptr

heap_end_ptr default value defined as _end+STACK_SZE-512, but
STACK_SIZE is already 512.

Signed-off-by: Alexander Kuleshov <[email protected]>
---
arch/x86/boot/header.S | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
index 16ef025..c69b870 100644
--- a/arch/x86/boot/header.S
+++ b/arch/x86/boot/header.S
@@ -342,7 +342,7 @@ ramdisk_size: .long 0 # its size in bytes
bootsect_kludge:
.long 0 # obsolete

-heap_end_ptr: .word _end+STACK_SIZE-512
+heap_end_ptr: .word _end
# (Header version 0x0201 or later)
# space from here (exclusive) down to
# end of setup code can be used by setup
--
2.2.1.201.gbbcefff


2014-12-26 14:35:38

by Jeremiah Mahler

[permalink] [raw]
Subject: Re: [PATCH] x86: Remove excess calculations for heap_end_ptr

Alexander,

On Fri, Dec 26, 2014 at 06:22:42PM +0600, Alexander Kuleshov wrote:
> heap_end_ptr default value defined as _end+STACK_SZE-512, but
STACK_SIZE

> STACK_SIZE is already 512.
>
> Signed-off-by: Alexander Kuleshov <[email protected]>
> ---
> arch/x86/boot/header.S | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
> index 16ef025..c69b870 100644
> --- a/arch/x86/boot/header.S
> +++ b/arch/x86/boot/header.S
> @@ -342,7 +342,7 @@ ramdisk_size: .long 0 # its size in bytes
> bootsect_kludge:
> .long 0 # obsolete
>
> -heap_end_ptr: .word _end+STACK_SIZE-512
> +heap_end_ptr: .word _end
> # (Header version 0x0201 or later)
> # space from here (exclusive) down to
> # end of setup code can be used by setup

So right now STACK_SIZE happens to be 512 so STACK_SIZE-512 is zero.
What happens if someone changes the size of STACK_SIZE?

This change doesn't fix any problem right now and creates potential
problems in the future.

> --
> 2.2.1.201.gbbcefff
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.tux.org/lkml/

--
- Jeremiah Mahler

2014-12-26 17:03:39

by Alexander Kuleshov

[permalink] [raw]
Subject: Re: [PATCH] x86: Remove excess calculations for heap_end_ptr

Yes, you're right,

At first i thought that it is just typo, and right after that i
thought about this case when somebody will change STACK_SIZE

2014-12-26 20:35 GMT+06:00 Jeremiah Mahler <[email protected]>:
> Alexander,
>
> On Fri, Dec 26, 2014 at 06:22:42PM +0600, Alexander Kuleshov wrote:
>> heap_end_ptr default value defined as _end+STACK_SZE-512, but
> STACK_SIZE
>
>> STACK_SIZE is already 512.
>>
>> Signed-off-by: Alexander Kuleshov <[email protected]>
>> ---
>> arch/x86/boot/header.S | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
>> index 16ef025..c69b870 100644
>> --- a/arch/x86/boot/header.S
>> +++ b/arch/x86/boot/header.S
>> @@ -342,7 +342,7 @@ ramdisk_size: .long 0 # its size in bytes
>> bootsect_kludge:
>> .long 0 # obsolete
>>
>> -heap_end_ptr: .word _end+STACK_SIZE-512
>> +heap_end_ptr: .word _end
>> # (Header version 0x0201 or later)
>> # space from here (exclusive) down to
>> # end of setup code can be used by setup
>
> So right now STACK_SIZE happens to be 512 so STACK_SIZE-512 is zero.
> What happens if someone changes the size of STACK_SIZE?
>
> This change doesn't fix any problem right now and creates potential
> problems in the future.
>
>> --
>> 2.2.1.201.gbbcefff
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>> the body of a message to [email protected]
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>> Please read the FAQ at http://www.tux.org/lkml/
>
> --
> - Jeremiah Mahler



--
_________________________
0xAX

2014-12-26 17:05:10

by H. Peter Anvin

[permalink] [raw]
Subject: Re: [PATCH] x86: Remove excess calculations for heap_end_ptr

Yes, the -512 is not related to STACK_SIZE, so this patch is wrong. NAK.

On December 26, 2014 9:03:38 AM PST, Alexander Kuleshov <[email protected]> wrote:
>Yes, you're right,
>
>At first i thought that it is just typo, and right after that i
>thought about this case when somebody will change STACK_SIZE
>
>2014-12-26 20:35 GMT+06:00 Jeremiah Mahler <[email protected]>:
>> Alexander,
>>
>> On Fri, Dec 26, 2014 at 06:22:42PM +0600, Alexander Kuleshov wrote:
>>> heap_end_ptr default value defined as _end+STACK_SZE-512, but
>> STACK_SIZE
>>
>>> STACK_SIZE is already 512.
>>>
>>> Signed-off-by: Alexander Kuleshov <[email protected]>
>>> ---
>>> arch/x86/boot/header.S | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
>>> index 16ef025..c69b870 100644
>>> --- a/arch/x86/boot/header.S
>>> +++ b/arch/x86/boot/header.S
>>> @@ -342,7 +342,7 @@ ramdisk_size: .long 0 # its
>size in bytes
>>> bootsect_kludge:
>>> .long 0 # obsolete
>>>
>>> -heap_end_ptr: .word _end+STACK_SIZE-512
>>> +heap_end_ptr: .word _end
>>> # (Header version 0x0201 or
>later)
>>> # space from here (exclusive)
>down to
>>> # end of setup code can be
>used by setup
>>
>> So right now STACK_SIZE happens to be 512 so STACK_SIZE-512 is zero.
>> What happens if someone changes the size of STACK_SIZE?
>>
>> This change doesn't fix any problem right now and creates potential
>> problems in the future.
>>
>>> --
>>> 2.2.1.201.gbbcefff
>>>
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe
>linux-kernel" in
>>> the body of a message to [email protected]
>>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>>> Please read the FAQ at http://www.tux.org/lkml/
>>
>> --
>> - Jeremiah Mahler

--
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