Re: [PATCH 5/5] ARM: asm-source.exp link options in case of armv7b target

[Victor Kamensky <victor.kamensky@linaro.org>]

Hi Yao,

On 23 October 2014 23:05, Yao Qi <yao@codesourcery.com> wrote:
> Victor Kamensky <victor.kamensky@linaro.org> writes:
>
>> +    "armv7b-*-*" {
>> +     set asm-arch arm
>> +     append link-flags " -be8"
>> +    }
>
> We can't tell whether "-be8" is needed from the target triplet.
> Considering multi-lib, "-be8" is needed for one multilib, but not
> for the other.

Any executable/library that runs on big endian V7 *must* be linked
with -be8 option. Otherwise it simply won't run. In any other multilib
option vfp, neon, etc -be8 must be set. Basically, in big endian case
gcc/gas generates data and instructions in big endian
format but ARM V7 requires that instruction should be little endian
format. It is linker that does instructions byte swap. If -be8 flag
is not passed during link while running on ARM V7 big endian target
executable with crash with SIGILL. If link happens through gcc, then
-be8 always passed for non relocatable code by compiler. In this
particular case link happens directly with linker and -be8 is not
default, so it is needed. One may argue that -be8 for final
executables in ARM V7 BE target should be default even for
linker, but it is not the current case ...

Also note that you have plenty examples in the same test
gdb/testsuite/gdb.asm/asm-source.exp
that do very similar things. For example:

    "powerpc64le-*" {
        set asm-arch powerpc64le
        set asm-flags "-a64 -I${srcdir}/${subdir} $obj_include"
        append link-flags " -m elf64lppc"
    }

Why "-m elf64lppc" is set for powerpc64le target? I suspect
by very similar reasons.

> Maybe, you can fix your problem by running tests via LDFLAGS_FOR_TARGET,
>
> $ make check RUNTESTFLAGS='LDFLAGS_FOR_TARGET=-be8'
>
> or you can create your own board file foo.exp, and add
>
> set_board_info ldflags  "-be8"

I don't feel very strong about it, and definitely I can workaround
this issue or just ignore the failure. It just seemed that it was very
easy to fix.

If you are still not convinced by above argument, yes,
let's just drop it. Please let me know you final thoughts. We
will proceed accordingly. I am fine either way.

Thanks,
Victor

> $ make check RUNTESTFLAGS='--target_board=foo'
>
> --
> Yao (齐尧)