Re: Unable to build a BEAGLEBOARD kernel

[Matt Thomas <matt%3am-software.com@localhost>]

On Oct 5, 2012, at 12:02 AM, David Laight wrote:

> On Sun, Sep 16, 2012 at 09:47:34PM +0000, Pierre Pronchery wrote:
>>              Hi current-users@, port-arm@,
>> 
>> I am currently unable to build an evbarm kernel for the Beagleboard; it 
>> fails with the following error:
>> 
>> === BEGIN PASTE ===
>>    compile  BEAGLEBOARD/arm32_kvminit.o
>> cc1: warnings being treated as errors
>> /home/khorben/Projects/netbsd/src/sys/arch/arm/arm32/arm32_kvminit.c: In 
>> function 'arm32_kernel_vm_init':
>> /home/khorben/Projects/netbsd/src/sys/arch/arm/arm32/
>> arm32_kvminit.c:359:1: error: not protecting local variables: variable 
>> length buffer
> 
> Generally variable length buffers are not a good idea in the kernel.
> There is very limited stack space so you have to know about the largest
> possible value - which means you might as well allocate it.

Given arm has 4KB of stack space, and the amount of text+data is unknown, the 
variable stack based approach was best.  If stack-protector can't protect 
against much declarations, it implementation is incomplete and its use in this 
case should be disabled (as has been done).