[U-Boot] [PATCH 5/5] lib: Enable private libgcc by default

Marek Vasut
2016-03-24T19:14:15Z

On 03/24/2016 08:08 PM, Sergey Kubushyn wrote:
> On Thu, 24 Mar 2016, Marek Vasut wrote:
>
>> On 03/24/2016 07:43 PM, Sergey Kubushyn wrote:
>>> On Thu, 24 Mar 2016, Sergey Kubushyn wrote:
>>>
>>>> On Thu, 24 Mar 2016, Marek Vasut wrote:
>>>>
>>>>> On 03/24/2016 12:54 AM, Sergey Kubushyn wrote:
>>>>>> On Thu, 24 Mar 2016, Marek Vasut wrote:
>>>>>>>> On 03/24/2016 12:47 AM, Sergey Kubushyn wrote:
>>>>>>>> On Thu, 24 Mar 2016, Marek Vasut wrote:
>>>>>>>>>>>> On 03/24/2016 12:08 AM, Tom Rini wrote:
>>>>>>>>>> On Wed, Mar 23, 2016 at 04:02:07PM -0700, Sergey Kubushyn
>>>>> wrote:
>>>>>>>>>>> On Wed, 23 Mar 2016, Tom Rini wrote:
>>>>>>>>>>>>>>>>>> On Wed, Mar 23, 2016 at 06:08:45PM +0100,
>>>>> Albert ARIBAUD > > > > > > > wrote:
>>>>>>>>>>>>> Hello Tom,
>>>>>>>>>>>>>>>>>>>>> On Wed, 23 Mar 2016 09:22:38 -0400,
>>>>> Tom Rini > > > > > > > > <trini@konsulko.com>
>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>> On Wed, Mar 23, 2016 at 01:53:35PM +0100, Albert
>>>>> ARIBAUD > > > > > > > > > wrote:
>>>>>>>>>>>>>>> Hello Marek,
>>>>>>>>>>>>>>>>>>>>>>>>> On Sun, 20 Mar 2016 17:15:34
>>>>> +0100, Marek Vasut > > > > > > > > > > <marex@denx.de>
>>>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>>> This patch decouples U-Boot binary from the >
>>>>>>>>>>>>>>> toolchain on
>>>>>>>>>>>>>>>> systems where
>>>>>>>>>>>>>>>> private libgcc is available. Instead of
>>>>> pulling in > > > > > > > > > > > functions
>>>>>>>>>>>>>>>> provided
>>>>>>>>>>>>>>>> by the libgcc from the toolchain, U-Boot will
>>>>> use > > > > > > > > > > > it's own set
>>>>>>>>>>>>>>>> of libgcc
>>>>>>>>>>>>>>>> functions. These functions are usually
>>>>> imported from > > > > > > > > > > > Linux
>>>>>>>>>>>>>>>> kernel, which
>>>>>>>>>>>>>>>> also uses it's own libgcc functions instead of
>>>>> the > > > > > > > > > > > ones
>>>>>>>>>>>>>>>> provided by the
>>>>>>>>>>>>>>>> toolchain.
>>>>>>>>>>>>>>>>>>>>>>>>>>> This patch solves a
>>>>> rather common problem. The > > > > > > > > > > > toolchain can
>>>>>>>>>>>>>>>> usually
>>>>>>>>>>>>>>>> generate code for many variants of target > >
>>>>>>>>>>>>>> architecture and
>>>>>>>>>>>>>>>> often even
>>>>>>>>>>>>>>>> different endianness. The libgcc on the other
>>>>> hand > > > > > > > > > > > is usually
>>>>>>>>>>>>>>>> compiled
>>>>>>>>>>>>>>>> for one particular configuration and the
>>>>> functions > > > > > > > > > > > provided by
>>>>>>>>>>>>>>>> it may
>>>>>>>>>>>>>>>> or may not be suited for use in U-Boot. This
>>>>> can > > > > > > > > > > > manifest in
>>>>>>>>>>>>>>>> two ways,
>>>>>>>>>>>>>>>> either the U-Boot fails to compile altogether
>>>>> and > > > > > > > > > > > linker will
>>>>>>>>>>>>>>>> complain
>>>>>>>>>>>>>>>> or, in the much worse case, the resulting
>>>>> U-Boot > > > > > > > > > > > will build,
>>>>>>>>>>>>>>>> but will
>>>>>>>>>>>>>>>> misbehave in very subtle and hard to debug ways.
>>>>>>>>>>>>>>>>>>>>>>>>> I don't think using private
>>>>> libgcc by default is a > > > > > > > > > > good idea.
>>>>>>>>>>>>>>>>>>>>>>>>> U-Boot's private libgcc is
>>>>> not a feature of U-Boot, > > > > > > > > > > but a fix
>>>>>>>>>>>>>>> for some
>>>>>>>>>>>>>>> cases where a target cannot properly link with
>>>>> the > > > > > > > > > > libgcc
>>>>>>>>>>>>>>> provided by
>>>>>>>>>>>>>>> the (specific release of the) GCC toolchain in
>>>>> use. > > > > > > > > > > Using
>>>>>>>>>>>>>>> private libgcc
>>>>>>>>>>>>>>> to other cases than these does not fix or
>>>>> improve > > > > > > > > > > anything; those
>>>>>>>>>>>>>>> other cases were working and did not require any
>>>>> fix > > > > > > > > > > in this
>>>>>>>>>>>>>>> respect.
>>>>>>>>>>>>>>>>>>>>>>> This isn't true, exactly. If
>>>>> using clang for example > > > > > > > > > everyone
>>>>>>>>>>>>>> needs to
>>>>>>>>>>>>>> enable this code. We're also using -fno-builtin >
>>>>>>>>>>>>> -ffreestanding
>>>>>>>>>>>>>> which
>>>>>>>>>>>>>> should limit the amount of interference from the >
>>>>>>>>>>>>> toolchain. And
>>>>>>>>>>>>>> we get
>>>>>>>>>>>>>> that.
>>>>>>>>>>>>>>>>>>>>> You mean clang does not produce
>>>>> self-sustained binaries?
>>>>>>>>>>>>>>>>>>> clang does not provide "libgcc", so
>>>>> there's no -lgcc > > > > > > > providing
>>>>>>>>>>>> all of
>>>>>>>>>>>> the functions that are (today) in:
>>>>>>>>>>>> _ashldi3.S _ashrdi3.S _divsi3.S _lshrdi3.S _modsi3.S
>>>>>>>>>>>> _udivsi3.S
>>>>>>>>>>>> _umodsi3.S div0.S _uldivmod.S
>>>>>>>>>>>> which aside from __modsi3 and __umodsi3 are all
>>>>> __aeabi_xxx
>>>>>>>>>>>>>>>>> There is also _udivmoddi4 pulled from libgcc
>>>>> for 64-bit > > > > > > division
>>>>>>>>>>> since we
>>>>>>>>>>> switched to 64-bit all around ARM. It comes from clock
>>>>>>>>>>> calculations for
>>>>>>>>>>> video, e.g. from drivers/video/ipu_common.c for i.MX6.
>>>>>>>>>>>>>>> Well, this is an example of why we both don't
>>>>> want libgcc ever > > > > > nor
>>>>>>>>>> do we
>>>>>>>>>> want to overly expand what we do offer. In this case
>>>>> isn't it > > > > > an
>>>>>>>>>> example of something that should be using lldiv/do_div/etc?
>>>>>>>>>>>>> I haven't seen the _udivmoddi4 emitted in my tests.
>>>>> Linux's libgcc > > > > copy
>>>>>>>>> also doesn't implement the function. Which toolchain do you
>>>>> use > > > > and
>>>>>>>>> which target did you compile?
>>>>>>>>>>> I'm using my own armv7hl-linux-gnueabi toolchain built
>>>>> for hard > > > float.
>>>>>>>> Linux
>>>>>>>> arm libgcc does have arch/arm/lib/div64.S file that provides
>>>>>>>> __do_div64()
>>>>>>>> function that is used by do_div() from include/asm/div64.h for
>>>>>>>> 32-bit
>>>>>>>> ARM
>>>>>>>> platform. Sure, arm64 has neither div64.h nor div64.S. We _DO_
>>>>> have
>>>>>>>> div64.h
>>>>>>>> (that is totally different from what Linux provides) but no
>>>>> div64.S > > > in
>>>>>>>> arch/arm/lib.
>>>>>>>>> In that case, we should just import div64.S from Linux on
>>>>> arm32 and be
>>>>>>> done with it ? Since we now have all the necessary macros thanks
>>>>> to > > the
>>>>>>> first four patches in this series, that should be trivial.
>>>>>>>>> What do you think? I can bake a patch real quick, so you can
>>>>> test it ?
>>>>>>> Sure I'll test it, no problems. Just bake the patch :)
>>>>>
>>>>> Done, give it a go please.
>>>>
>>>> OK, it didn't work, _udivmoddi4.o is still being pulled from libgcc.
>>>> I'm
>>>> analyzing it right now, will come up with more later today.
>>>
>>> OK, it requires a CONFIG_USE_PRIVATE_LIBGCC defined to use private
>>> libgcc,
>>> my bad -- thought it would be automatic. Having that defined makes build
>>> fail complaining about assembly syntax in div64.S:
>>>
>>> === Cut ===
>>> arch/arm/lib/div64.S: Assembler messages:
>>> arch/arm/lib/div64.S:185: Error: bad instruction `arm( orr r2,r2,r1,lsl
>>> ip)'
>>> arch/arm/lib/div64.S:186: Error: bad instruction `thumb( lsl r1,r1,ip)'
>>> arch/arm/lib/div64.S:187: Error: bad instruction `thumb( orr r2,r2,r1)'
>>> scripts/Makefile.build:316: recipe for target 'arch/arm/lib/div64.o'
>>> failed
>>> make[1]: *** [arch/arm/lib/div64.o] Error 1
>>> Makefile:1214: recipe for target 'arch/arm/lib' failed
>>> make: *** [arch/arm/lib] Error 2
>>> === Cut ===
>>>
>>> Probably something is missing in div64.h? The Linux one is totally
>>> different. Digging in right now...
>>
>> Are you building the stuff with all of these 5+1 patches ?
>
> Nope. Aren't those already in U-Boot master? I pulled the latest master and
> thought those were there. If not would you please send me those 5
> patches so
> I wouldn't have to hunt them through archives?

I'll send you all six off-list.

Best regards,
Marek Vasut