imx6ULL memcpy issue in RTEMS 5

[Ian Caddy]

Hi All,

I am trying to get a imx6ULL custom BSP running on RTEMS 5.  I am 
working through some startup issues between u-boot and RTEMS and I think 
I have most of them squared away now.

During the RTEMS higher level init, the IMFS is inited and as part of 
that, /dev is created.  When creating the node for the "dev" directory, in:

rtems/cpukit/libfs/src/imfs/imfs_creat.c:56

it performs a memcpy to place the name into the node->name:

memcpy(RTEMS_DECONST(char *, node->name), name, namelen);

where:

node->name = 0x8031c4B8

name = "dev" @ 0x8029aff1

namelen = 3

At the lowest level memcpy calls:

gcc-7.3.0/newlib/libc/machine/arm/memcpy-armv7a.S

which at line 236 performs a half word load from the source (which is 
not aligned, not the name address above):

  ldrhcs tmp1, [src], #2

and I get a data abort as src = 0x8029aff1 which is a const string and 
has no reason to be word (or half word) aligned.

I pretty much copied the build tree, from the imx BSP (which is based on 
an imx7 I think from memory) as the imx6ULL is a Cortex-A7 single core 
proceessor, using the ARMv7-A architecture.

Some places have been saying that I need to check whether or not the 
particular processor support non-aligned access, but the imx 
documentation is not that great and points to the ARM documentation 
which is more generalised.

There seemed to be a similar issue on the GNU embedded toolchain mailing 
list:

https://answers.launchpad.net/gcc-arm-embedded/+question/289328

I can provide more detailed information if anyone is interested.

We are going to need to be able to support unaligned access for memcpy 
on both the source and destination, so I was hoping someone might be 
able to point me in the correct direction to fix it?

regards,

Ian Caddy