target-ppc: Support dump for little endian ppc64

target-ppc: Support dump for little endian ppc64

Fix ppc64 arch specific dump code to support all combinations of little/big
endian hosts/guests. FWIW the current code is broken for altivec registers
when guest and host have a different endianness: these 128-bit registers
are written to guest memory as a two 64-bit entities and we should also swap
them.

Unit testing was done with the following program provided by Tom Musta:

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>

int main(int argc, char** argv)
{

__uint128_t v = ((__uint128_t)0x0001020304050607ull << 64) |
0x08090a0b0c0d0e0full;

register void * vptr asm ("r11");
vptr = &v;

for(;;)
asm volatile ("lvx 30,0,11" );
}

When sending SIGABRT to this program and examining the core file, we get:

- ppc64  : 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
- ppc64le: 0f 0e 0d 0c 0b 0a 09 08 07 06 05 04 03 02 01 00

We expect to find the very same layout in the QEMU dump since they are
real core files. This is what we get:

- ppc64 host, ppc64 guest   : 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
- ppc64 host, ppc64le guest : 0f 0e 0d 0c 0b 0a 09 08 07 06 05 04 03 02 01 00
- x86_64 host, ppc64 guest  : 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
- x86_64 host, ppc64le guest: 0f 0e 0d 0c 0b 0a 09 08 07 06 05 04 03 02 01 00

We introduce a NoteFuncArg type to avoid adding extra arguments to all note
functions.

Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
[ rebased on top of current master branch,
  introduced NoteFuncArg,
  use new cpu_to_dump{16,32,64} endian helpers,
  fix altivec support,
  Greg Kurz <gkurz@linux.vnet.ibm.com> ]
Reviewed-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Signed-off-by: Alexander Graf <agraf@suse.de>