[Freeswitch-dev] Freeswitch on ARM, Memory alignment issues

[M D]

On Tue, 18 Jan 2011 12:54:53 -0500
Michael Jerris <mike at jerris.com> wrote:

In general, should I conclude that this issue has not been encountered
before?

> take a look at swith_types.h 645-710.  This is what you would need to
> do cross platform to align stuff.
If I understood you correctly, you mean to point out a general cross
platform issue and how it is dealt with withing freeswitch code. Right?
Just to complete the info, the ARM processor is running Little-Endian.
The code/settings/dialplan worked fine on a x86 linux machine, also
little endian. Probably nothing new, but I thought I should fill in the
details.

> I am surprised the first way isn't
> aligned already, the first proposed change wont be cross platform,
> the second, if that works, should be fine (as long as you free it
> later of course) but I am unsure if that will actually work cross
> platform.  The trick here is to figure out how to fix it once for all
> platforms.
> 
> Mike


I expected that the original code would be aligned too. It just wasn't,
atleast with gcc 4.3.3 + Code Sourcery enhancements. In gcc 4.4.5 ( I
think, I don't have access to my development machine at the moment.)
using the switch -falign-functions did align the buffer buf at a 32-bit
boundary. Of course align-functions does not ensure that all uint8_t
buffers would be aligned. 

Perhaps a conditional define would be more suitable fix, considering
all platforms. As far as I can tell, the memory alignment requirement
is ARM specific, which restricts this issue to gcc/linux. So in pseudo
code

#define ALIGN_ON_ARM
ifdef GCC
ifdef arm
#undef ALIGN_ON_ARM
#define ALIGN_ON_ARM __attribute__ (aligned(4))
#endif
#endif

and then in the source code

uint8_t buf[260] ALIGN_ON_ARM = {0};

Would something along these lines work? The only issue is that it would
touch a lot of the code. The use of structures with a uint8 buffer
is likely widely used within freeswitch. 

-m

> On Jan 18, 2011, at 12:35 PM, M D wrote:
> 
> > Summary:
> > Has anyone looked at/actively looking at the 32-bit boundary memory
> > alignment requirement for the ARM architecture?
> >