[Buildroot] meaning of BR2_arm_dunno

[Buildroot] meaning of BR2_arm_dunno

[Sven Neumann]

Hi,

I wonder if anyone could explain to me the purpose of BR2_arm_dunno as
used in target/Config.in.arch. The reason I am asking is that we've run
into the problem of ending up with a misconfigured gcc (as reported
earlier on this list). I would like to find out how this can be avoided
in the future, but I seem to be unable to understand the mechanism that
selects the default values for BR2_GCC_TARGET_TUNE, BR2_GCC_TARGET_ARCH
and BR2_GCC_TARGET_ABI.


Sven

[Buildroot] meaning of BR2_arm_dunno

[Peter Korsgaard]

>>>>> "Sven" == Sven Neumann <s.neumann@phase-zero.de> writes:

 Sven> Hi,

 Sven> I wonder if anyone could explain to me the purpose of
 Sven> BR2_arm_dunno as used in target/Config.in.arch. The reason I am
 Sven> asking is that we've run into the problem of ending up with a
 Sven> misconfigured gcc (as reported earlier on this list). I would
 Sven> like to find out how this can be avoided in the future, but I
 Sven> seem to be unable to understand the mechanism that selects the
 Sven> default values for BR2_GCC_TARGET_TUNE, BR2_GCC_TARGET_ARCH and
 Sven> BR2_GCC_TARGET_ABI.

It takes a bit of searching as the lines have moved around the tree a
few times, but they were originally added by Bernhard in r19040 with
the nice commit message:

- populate some BR2_GCC_TARGET_ARCH, BR2_GCC_TARGET_ABI, BR2_GCC_TARGET_TUNE defaults (hand-waving mode, of course untested.. ;)

In other words it seems pretty half baked. Taking a look at Bernhard's
git tree I see he has:

        default apcs-gnu        if BR2_ARM_OABI
        default atpcs           if BR2_arm_dunno
        default aapcs           if BR2_arm_dunno
        default aapcs-linux     if BR2_ARM_EABI

Which confusingly comes from the following commit:

commit 7f7aac5d32ba677e8be386afa6ca121af00fbf1a
Author: Bernhard Fischer <rep.dot.nop@gmail.com>
Date:   Thu Sep 18 23:47:23 2008 +0200

    remove dependency on iwmmxt

Could you give it a try with those 2 lines changed?

-- 
Bye, Peter Korsgaard

[Buildroot] meaning of BR2_arm_dunno

[Sven Neumann]

Hi,

On Thu, 2009-01-29 at 16:46 +0100, Peter Korsgaard wrote:

>         default apcs-gnu        if BR2_ARM_OABI
>         default atpcs           if BR2_arm_dunno
>         default aapcs           if BR2_arm_dunno
>         default aapcs-linux     if BR2_ARM_EABI

That looks more reasonable to me and it is in line with what was
suggested on the linux-arm-kernel mailing-list, see
http://lists.arm.linux.org.uk/lurker/message/20090124.152540.2d9a4947.en.html

As you can see from the linked thread, the compiler we ended up with
works nicely for userspace, but it cannot be used to build a kernel. It
may be a good idea to set BR2_GCC_TARGET_ABI to aapcs-linux even if
BR2_iwmmxt is selected.

> Could you give it a try with those 2 lines changed?

What exactly do you want me to try? I guess I would have to remove
my .config and go thru menuconfig, select ARM iwmmxt and then check what
gets sets for BR2_GCC_TARGET_TUNE, BR2_GCC_TARGET_ARCH and
BR2_GCC_TARGET_ABI? Is that correct?


Sven

[Buildroot] meaning of BR2_arm_dunno

[Peter Korsgaard]

>>>>> "Sven" == Sven Neumann <s.neumann@phase-zero.de> writes:

Hi,

 >> default apcs-gnu        if BR2_ARM_OABI
 >> default atpcs           if BR2_arm_dunno
 >> default aapcs           if BR2_arm_dunno
 >> default aapcs-linux     if BR2_ARM_EABI

 Sven> As you can see from the linked thread, the compiler we ended up
 Sven> with works nicely for userspace, but it cannot be used to build
 Sven> a kernel. It may be a good idea to set BR2_GCC_TARGET_ABI to
 Sven> aapcs-linux even if BR2_iwmmxt is selected.

Ok, thanks.

 >> Could you give it a try with those 2 lines changed?

 Sven> What exactly do you want me to try? I guess I would have to
 Sven> remove my .config and go thru menuconfig, select ARM iwmmxt and
 Sven> then check what gets sets for BR2_GCC_TARGET_TUNE,
 Sven> BR2_GCC_TARGET_ARCH and BR2_GCC_TARGET_ABI? Is that correct?

I meant with the apcs-gnu for OABI, and aapcs-linux for EABI, wasn't
that your original problem?

-- 
Bye, Peter Korsgaard

[Buildroot] meaning of BR2_arm_dunno

[Sven Neumann]

Hi,

On Thu, 2009-01-29 at 16:46 +0100, Peter Korsgaard wrote:

>         default apcs-gnu        if BR2_ARM_OABI
>         default atpcs           if BR2_arm_dunno
>         default aapcs           if BR2_arm_dunno
>         default aapcs-linux     if BR2_ARM_EABI
> 
> [...]
> Could you give it a try with those 2 lines changed?

Does not work for my configuration. The error when compiling gcc is:

  Unknown ABI used in --with-abi=aapcs-linux

The relevant bits from my .config are:

BR2_iwmmxt=y
BR2_ARM_TYPE="ARM_IWMMXT"
# BR2_ARM_OABI is not set
BR2_ARM_EABI=y
BR2_ARCH="arm"
BR2_ENDIAN="LITTLE"
BR2_GCC_TARGET_TUNE="iwmmxt"
BR2_GCC_TARGET_ARCH="iwmmxt"
BR2_GCC_TARGET_ABI="aapcs-linux"
BR2_GCC_VERSION="4.3.2"

Anything else you want me to try ?


Sven

[Buildroot] meaning of BR2_arm_dunno

[Sven Neumann]

Hi,

On Fri, 2009-01-30 at 11:01 +0100, Sven Neumann wrote:

> Does not work for my configuration. The error when compiling gcc is:
> 
>   Unknown ABI used in --with-abi=aapcs-linux

Might be related to
http://gcc.gnu.org/ml/gcc-patches/2008-09/msg01500.html

BR2_GCC_TARGET_ABI="aapcs" seems to be accepted. I will try to compile
my tree with this option now and also check if I can build a recent
kernel using the compiler that results from this build...


Sven

[Buildroot] meaning of BR2_arm_dunno

[Peter Korsgaard]

>>>>> "Sven" == Sven Neumann <s.neumann@phase-zero.de> writes:

Hi,

 Sven> Might be related to
 Sven> http://gcc.gnu.org/ml/gcc-patches/2008-09/msg01500.html

Ahh, our good friend Bernhard ;)

 Sven> BR2_GCC_TARGET_ABI="aapcs" seems to be accepted. I will try to compile
 Sven> my tree with this option now and also check if I can build a recent
 Sven> kernel using the compiler that results from this build...

Ok, thanks, otherwise I'll take the gcc patch so aapcs-linux works.

-- 
Bye, Peter Korsgaard

[Buildroot] meaning of BR2_arm_dunno

[Sven Neumann]

Hi,

On Fri, 2009-01-30 at 11:23 +0100, Peter Korsgaard wrote:

>  Sven> BR2_GCC_TARGET_ABI="aapcs" seems to be accepted. I will try to compile
>  Sven> my tree with this option now and also check if I can build a recent
>  Sven> kernel using the compiler that results from this build...
> 
> Ok, thanks, otherwise I'll take the gcc patch so aapcs-linux works.

I've successfully built the system, booted it and run some tests. I also
verified that I can build 2.6.29-rc3 using the kernel created by this
build. Attached is a patch with the change.


Sven


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[Buildroot] meaning of BR2_arm_dunno

[Peter Korsgaard]

>>>>> "Sven" == Sven Neumann <s.neumann@phase-zero.de> writes:

 Sven> Hi,
 Sven> On Fri, 2009-01-30 at 11:23 +0100, Peter Korsgaard wrote:

 Sven> BR2_GCC_TARGET_ABI="aapcs" seems to be accepted. I will try to compile
 Sven> my tree with this option now and also check if I can build a recent
 Sven> kernel using the compiler that results from this build...
 >> 
 >> Ok, thanks, otherwise I'll take the gcc patch so aapcs-linux works.

 Sven> I've successfully built the system, booted it and run some tests. I also
 Sven> verified that I can build 2.6.29-rc3 using the kernel created by this
 Sven> build. Attached is a patch with the change.

Thanks, but I think the correct thing is to use aapcs-linux (E.G. so
it also works with older toolchains), and patch gcc 4.3.2 to accept
that (like Bernhard already did).

I've checked in that patch already and will fix up the stuff in
Config.in.arch now.

Thanks for testing it.

-- 
Bye, Peter Korsgaard

[Buildroot] meaning of BR2_arm_dunno

[Bernhard Reutner-Fischer]

On Fri, Jan 30, 2009 at 12:28:52PM +0100, Peter Korsgaard wrote:
>>>>>> "Sven" == Sven Neumann <s.neumann@phase-zero.de> writes:
>
> Sven> Hi,
> Sven> On Fri, 2009-01-30 at 11:23 +0100, Peter Korsgaard wrote:
>
> Sven> BR2_GCC_TARGET_ABI="aapcs" seems to be accepted. I will try to compile
> Sven> my tree with this option now and also check if I can build a recent
> Sven> kernel using the compiler that results from this build...
> >> 
> >> Ok, thanks, otherwise I'll take the gcc patch so aapcs-linux works.
>
> Sven> I've successfully built the system, booted it and run some tests. I also
> Sven> verified that I can build 2.6.29-rc3 using the kernel created by this
> Sven> build. Attached is a patch with the change.
>
>Thanks, but I think the correct thing is to use aapcs-linux (E.G. so
>it also works with older toolchains), and patch gcc 4.3.2 to accept
>that (like Bernhard already did).

I think this is/will be fixed in gcc-4.4.0 and 4.3.3
>
>I've checked in that patch already and will fix up the stuff in
>Config.in.arch now.

As already mentioned several times somewhere else, you should synch
(these parts of) your tree against improvements that went into my
tree. This poor guy wouldn't have been bitten by this issue, fwiw.

[Buildroot] meaning of BR2_arm_dunno

[Peter Korsgaard]

>>>>> "Bernhard" == Bernhard Reutner-Fischer <rep.dot.nop@gmail.com> writes:

Hi,

 >> Thanks, but I think the correct thing is to use aapcs-linux (E.G. so
 >> it also works with older toolchains), and patch gcc 4.3.2 to accept
 >> that (like Bernhard already did).

 Bernhard> I think this is/will be fixed in gcc-4.4.0 and 4.3.3

Ok, good.

 >> I've checked in that patch already and will fix up the stuff in
 >> Config.in.arch now.

 Bernhard> As already mentioned several times somewhere else, you
 Bernhard> should synch (these parts of) your tree against
 Bernhard> improvements that went into my tree. This poor guy wouldn't
 Bernhard> have been bitten by this issue, fwiw.

It's a question of time, you are more than welcome to help and send
patches to the list ;)

-- 
Bye, Peter Korsgaard