efi: Fix free_end build warning

Initialize the free_end variable to zero.  Fixes build warnings
like these:

  arch/arm64/kernel/efi.c: warning: ‘free_end’ may be used uninitialized in this function

Signed-off-by: Geoff Levand <geoff@infradead.org>
---
Got this with the latest arm64/for-next/core branch.  Please consider.

-Geoff 

 arch/arm64/kernel/efi.c | 1 +
 1 file changed, 1 insertion(+)

[Adding original authors]

On Wed, Nov 12, 2014 at 08:27:30PM +0000, Geoff Levand wrote:
> Initialize the free_end variable to zero.  Fixes build warnings
> like these:
> 
>   arch/arm64/kernel/efi.c: warning: ‘free_end’ may be used uninitialized in this function
> 
> Signed-off-by: Geoff Levand <geoff@infradead.org>
> ---
> Got this with the latest arm64/for-next/core branch.  Please consider.
> 
> -Geoff 
> 
>  arch/arm64/kernel/efi.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
> index 4f39a18..83fc53c 100644
> --- a/arch/arm64/kernel/efi.c
> +++ b/arch/arm64/kernel/efi.c
> @@ -239,6 +239,7 @@ static void __init free_boot_services(void)
>  	 * want to keep for UEFI.
>  	 */
>  
> +	free_end = 0;
>  	keep_end = 0;
>  	free_start = 0;

Whilst I can't see how free_end gets used uninitialized in this function,
the code is really hard to read and I'd like to get an Ack from one of the
people on CC before merging this, just in case GCC is actually telling us
something useful for a change.

Will

On 14 November 2014 11:22, Will Deacon <will.deacon@arm.com> wrote:
> [Adding original authors]
>
> On Wed, Nov 12, 2014 at 08:27:30PM +0000, Geoff Levand wrote:
>> Initialize the free_end variable to zero.  Fixes build warnings
>> like these:
>>
>>   arch/arm64/kernel/efi.c: warning: ‘free_end’ may be used uninitialized in this function
>>
>> Signed-off-by: Geoff Levand <geoff@infradead.org>
>> ---
>> Got this with the latest arm64/for-next/core branch.  Please consider.
>>
>> -Geoff
>>
>>  arch/arm64/kernel/efi.c | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
>> index 4f39a18..83fc53c 100644
>> --- a/arch/arm64/kernel/efi.c
>> +++ b/arch/arm64/kernel/efi.c
>> @@ -239,6 +239,7 @@ static void __init free_boot_services(void)
>>        * want to keep for UEFI.
>>        */
>>
>> +     free_end = 0;
>>       keep_end = 0;
>>       free_start = 0;
>
> Whilst I can't see how free_end gets used uninitialized in this function,
> the code is really hard to read and I'd like to get an Ack from one of the
> people on CC before merging this, just in case GCC is actually telling us
> something useful for a change.
>

We are planning to remove this code entirely in the 3.20 timeframe.
Freeing boot services will not be necessary any longer once we stop
reserving it in the first place, and I agree that the function is hard
to read. Also, it depends on the UEFI memory map being sorted, which
is not mandated by the spec so we can't actually rely on it. (Even if
it usually is the case)

So I don't object to this patch, if the warning is bothering people,
but perhaps we can just wait for the warning to go away once the new
stuff lands.

On Fri, Nov 14, 2014 at 10:29:59AM +0000, Ard Biesheuvel wrote:
> On 14 November 2014 11:22, Will Deacon <will.deacon@arm.com> wrote:
> > [Adding original authors]
> >
> > On Wed, Nov 12, 2014 at 08:27:30PM +0000, Geoff Levand wrote:
> >> Initialize the free_end variable to zero.  Fixes build warnings
> >> like these:
> >>
> >>   arch/arm64/kernel/efi.c: warning: ‘free_end’ may be used uninitialized in this function
> >>
> >> Signed-off-by: Geoff Levand <geoff@infradead.org>
> >> ---
> >> Got this with the latest arm64/for-next/core branch.  Please consider.
> >>
> >> -Geoff
> >>
> >>  arch/arm64/kernel/efi.c | 1 +
> >>  1 file changed, 1 insertion(+)
> >>
> >> diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
> >> index 4f39a18..83fc53c 100644
> >> --- a/arch/arm64/kernel/efi.c
> >> +++ b/arch/arm64/kernel/efi.c
> >> @@ -239,6 +239,7 @@ static void __init free_boot_services(void)
> >>        * want to keep for UEFI.
> >>        */
> >>
> >> +     free_end = 0;
> >>       keep_end = 0;
> >>       free_start = 0;
> >
> > Whilst I can't see how free_end gets used uninitialized in this function,
> > the code is really hard to read and I'd like to get an Ack from one of the
> > people on CC before merging this, just in case GCC is actually telling us
> > something useful for a change.
> >
> 
> We are planning to remove this code entirely in the 3.20 timeframe.
> Freeing boot services will not be necessary any longer once we stop
> reserving it in the first place, and I agree that the function is hard
> to read. Also, it depends on the UEFI memory map being sorted, which
> is not mandated by the spec so we can't actually rely on it. (Even if
> it usually is the case)
> 
> So I don't object to this patch, if the warning is bothering people,
> but perhaps we can just wait for the warning to go away once the new
> stuff lands.

Ok, thanks Ard. I think I'll leave it alone for now, then.

Will