[PATCH v3 2/2] selftests/powerpc: Add a test of the switch_endian() syscall

[Michael Ellerman]

On Mon, 2015-03-16 at 16:30 +0530, Anshuman Khandual wrote:
> On 03/16/2015 12:27 PM, Michael Ellerman wrote:
> > This adds a test of the switch_endian() syscall we added in the previous
> > commit.
> > 
> > We test it by calling the endian switch syscall, and then executing some
> > code in the other endian to check everything went as expected. That code
> > checks registers we expect to be maintained are, and then writes to
> > stdout. If the endian switch failed to happen that code sequence will be
> > illegal and cause the test to abort.
> > 
> > We then switch back to the original endian, do the same checks and
> > finally write a success message and exit(0).
> > 
> > Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
> 
> Hey Michael,
> 
> Did a quick test, passes on LE but seems like failing on BE.
> 
> On LE:
> 
> Hello wrong-endian world
> Hello right-endian world
> success: switch_endian_test
> 
> on BE:
> 
> Hello wrong-endian world (returns 176)
> 
> The previous version of the test was passing both on LE
> and BE (after applying the compiler trick in the assembly)

Hmm, odd. Works for me:

$ uname -a
Linux bebuntu 4.0.0-rc3-00002-g9dd2601a490a #1 SMP Fri Mar 13 15:52:11 AEDT 2015 ppc64 ppc64 ppc64 GNU/Linux
$ make
cc -O2 -Wall -g -nostdlib -m64   -c -o check.o check.S
objcopy -j .text --reverse-bytes=4 -O binary check.o check-reversed.o
hexdump -v -e '/1 ".byte 0x%02X\n"' check-reversed.o > check-reversed.S
cc -O2 -Wall -g -nostdlib -m64    switch_endian_test.S check-reversed.S   -o switch_endian_test
$ ./switch_endian_test 
Hello wrong-endian world
Hello right-endian world
success: switch_endian_test


What are you seeing exactly?

cheers