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Re: [Qemu-ppc] [PATCH v2] Added uapi directory into linux-header

From: Alexander Graf
Subject: Re: [Qemu-ppc] [PATCH v2] Added uapi directory into linux-header
Date: Tue, 18 Dec 2012 11:38:55 +0100

On 18.12.2012, at 11:19, Bhushan Bharat-R65777 <address@hidden> wrote:

>>>>>>>>> +++ b/scripts/update-linux-headers.sh
>>>>>>>>> @@ -46,14 +46,26 @@ for arch in $ARCHLIST; do
>>>>>>>>> make -C "$linux" INSTALL_HDR_PATH="$tmpdir" SRCARCH=$arch
>>>>>>>>> headers_install
>>>>>>>>> +    if [ -e "$linux/arch/$arch/include/uapi" ] &&
>>>>>>>>> +        ! [ -e "$output/linux-headers/uapi" ] ; then
>>>>>>>>> +        mkdir "$output/linux-headers/uapi"
>>>>>>>> mkdir -p
>>>>>>>> But looking through this whole thing, it seems like the root
>>>>>>>> cause is actually different. We don't want any uapi directories
>>>>>>>> exposed to user space. So let's go back a step:
>>>>>>>> Why do we need the uapi include dir? Because some header is using it.
>>>>>>>> linux-headers/asm-powerpc/kvm_para.h:
>>>>>>> The kvm_para.h (also kvm.h) are now defined in include/uapi/asm/
>>>>>>> Is not this the correct thing that any header file in
>>>>>>> include/uapi/asm/ (in
>>>>>> this case kvm_para.h) includes another header file (epapr_hcalls.h)
>>>>>> in same directory?
>>>>>>> Also I think now only the uapi/asm/*.h files should be exposed to
>>>>>>> userspace
>>>>>> (QEMU here).
>>>>>> make headers_install should basically remove all the uapi magic and
>>>>>> give us normal backwards-compatible asm trees :).
>>>>> I am perfectly fine, How we can do this now :)
>>>> Well, for starters, do the headers work if you apply the patch I sent
>>>> in a previous mail plus the epapr_hcall.h copy? If so, then that's
>>>> the way to go :)
>>> Are you really sure that applying a patch and then syncing (or other way
>> round)  is the way you want to go ?
>> Yes, because I'm quite confident we're generating broken headers right now.
> Ok, so every time someone does the sync he/she has to do this? Also do we 
> think that sometime in future this will be taken care by make header_install?

That's the point.

The QEMU header sync is a hack that allows us to not use system headers. System 
headers could be outdated wrt features we want to support.

However, system headers get generated using make headers_install. And there we 
generate a header that refers to a uapi directory that doesn't exist after 

So the next time a distro updates their system headers, they get broken ones. 
That's what the patch against Linux is trying to fix.


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