Re: [PATCH] ARM: Use different linker path for hardfloat ABI

[Richard Guenther <richard.guenther@gmail.com>]

On Tue, Apr 3, 2012 at 12:45 PM, Richard Earnshaw <rearnsha@arm.com> wrote:
> On 03/04/12 10:29, Andrew Haley wrote:
>> On 04/02/2012 10:06 PM, dann frazier wrote:
>>> On Fri, Mar 30, 2012 at 06:52:34PM +0100, Richard Earnshaw wrote:
>>>> On 29/03/12 20:34, dann frazier wrote:
>>>>> This is an updated version of a patch Debian and Ubuntu are using to
>>>>> use an alternate linker path for hardfloat binaries. The difference
>>>>> with this one is that it covers the case where no float flag
>>>>> was passed in, defaulting to the softfloat path.
>>>>>
>>>>> 2012-03-29  dann frazier <dann.frazier@canonical.com>
>>>>>
>>>>>    * config/arm/linux-elf.h: Use alternate linker path
>>>>>           for hardfloat ABI
>>>>>
>>>>> Index: gcc/config/arm/linux-elf.h
>>>>> ===================================================================
>>>>> --- gcc/config/arm/linux-elf.h     (revision 185708)
>>>>> +++ gcc/config/arm/linux-elf.h     (working copy)
>>>>> @@ -59,14 +59,21 @@
>>>>>
>>>>>  #define LIBGCC_SPEC "%{mfloat-abi=soft*:-lfloat} -lgcc"
>>>>>
>>>>> -#define GLIBC_DYNAMIC_LINKER "/lib/ld-linux.so.2"
>>>>> +#define LINUX_DYNAMIC_LINKER_SF "/lib/ld-linux.so.3"
>>>>> +#define LINUX_DYNAMIC_LINKER_HF "/lib/arm-linux-gnueabihf/ld-linux.so.3"
>>>>>
>>>>>  #define LINUX_TARGET_LINK_SPEC  "%{h*} \
>>>>>     %{static:-Bstatic} \
>>>>>     %{shared:-shared} \
>>>>>     %{symbolic:-Bsymbolic} \
>>>>>     %{rdynamic:-export-dynamic} \
>>>>> -   -dynamic-linker " GNU_USER_DYNAMIC_LINKER " \
>>>>> +   %{msoft-float:-dynamic-linker " LINUX_DYNAMIC_LINKER_SF "} \
>>>>> +   %{mfloat-abi=soft*:-dynamic-linker " LINUX_DYNAMIC_LINKER_SF "} \
>>>>> +   %{mhard-float:-dynamic-linker " LINUX_DYNAMIC_LINKER_HF "} \
>>>>> +   %{mfloat-abi=hard:-dynamic-linker " LINUX_DYNAMIC_LINKER_HF "} \
>>>>> +   %{!mfloat-abi: \
>>>>> +     %{!msoft-float: \
>>>>> +       %{!mhard-float:-dynamic-linker " LINUX_DYNAMIC_LINKER_SF "}}} \
>>>>>     -X \
>>>>>     %{mbig-endian:-EB} %{mlittle-endian:-EL}" \
>>>>>     SUBTARGET_EXTRA_LINK_SPEC
>>>>>
>>>>
>>>> Looks to me as though this will break the old Linux ABI.  While we've
>>>> marked that as deprecated, it hasn't been removed as yet.  So I think
>>>> this patch either needs to wait until that removal has taken place, or
>>>> provide the relevant updates to maintain the old ABI support.
>>>
>>> Thanks for your review. You're right, this does appear to break the
>>> old ABI - that was a misunderstanding on my part. I think this fixes
>>> the problem:
>>
>> But what about those of us who are using hard-float but not the
>> Debian liker path?  It'll break, surely.  This looks to be like
>> it's Debian-specific.
>>
>
> Are you trying to tell me that some distros are using /lib/ld-linux.so.3
> directly for hard-float?  Sigh, you distro guys need to start talking to
> each other, rather than just going of inventing things ...
>
> If, so then there's only one way to sort out this mess.
>
> /lib/arm-linux-gnueabi/ld-linux.so.3  Location of soft-float loader
> /lib/arm-linux-gnueabihf/ld-linux.so.3 Location of hard-float loader
> /lib/ld-linux.so.3 legacy symlink to one of the above.
>
> Or something of this nature.
>
> All this is outside of GCC's remit though and I'm not in a position to
> drive any of it through.
>
> :-( :-( :-(

Now, I wonder why the dynamic linker cannot figure out the ABI itself
by means of using ELF flags or so?

Richard.

> R.
>
>