Re: [PATCH-for-5.0] roms/edk2-funcs.sh: Use available GCC for ARM/Aarch64 targets

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 12/5/19 5:13 PM, Laszlo Ersek wrote:
> Hi Phil,
> 
> (+Ard)
> 
> On 12/04/19 23:12, Philippe Mathieu-Daudé wrote:
>> Centos 7.7 only provides cross GCC 4.8.5, but the script forces
>> us to use GCC5. Since the same machinery is valid to check the
>> GCC version, remove the $emulation_target check.
>>
>>    $ cat /etc/redhat-release
>>    CentOS Linux release 7.7.1908 (Core)
>>
>>    $ aarch64-linux-gnu-gcc -v 2>&1 | tail -1
>>    gcc version 4.8.5 20150623 (Red Hat 4.8.5-16) (GCC)
> 
> this patch is not correct, in my opinion. ARM / AARCH64 support in edk2
> requires GCC5 as a minimum. It was never tested with an earlier
> toolchain, to my understanding. Not on my part, anyway.
> 
> To be more precise: when I tested cross-gcc toolchains earlier than
> that, the ArmVirtQemu builds always failed. Minimally, those toolchains
> didn't recognize some of the AARCH64 system registers.
> 
> If CentOS 7.7 does not provide a suitable (>=GCC5) toolchain, then we
> can't build ArmVirtQemu binaries on CentOS 7.7, in my opinion.
> 
> Personally, on my RHEL7 laptop, over time I've used the following
> toolchains, to satisfy the GCC5 requirement of ArmVirtQemu (which
> requirement I took as experimental evidence):
> 
> - Initially (last quarter of 2014), I used binary distributions --
>    tarballs -- of cross-binutils and cross-gcc, from Linaro.
> 
> - Later (last quarter of 2016), I rebuilt some SRPMs that were at the
>    time Fedora-only for RHEL7. Namely:
> 
>    - cross-binutils-2.27-3.fc24
>      https://koji.fedoraproject.org/koji/buildinfo?buildID=801348
> 
>    - gcc-6.1.1-2.fc24
>      https://koji.fedoraproject.org/koji/buildinfo?buildID=761767
> 
> - Most recently, I've been using cross-binutils updated from EPEL7:
> 
>    - cross-binutils-2.27-9.el7.1
>      https://koji.fedoraproject.org/koji/buildinfo?buildID=918474
> 
> To my knowledge, there is still no suitable cross-compiler available on
> RHEL7, from any trustworthy RPM repository. So, to this day, I use
> gcc-6.1.1-2 for cross-building ArmVirtQemu, on my RHEL7 laptop.
> 
> Again: I believe it does not matter if the gcc-4.8.5-based
> cross-compiler in CentOS 7 "happens" to work. That's a compiler that I
> have never tested with, or vetted for, upstream ArmVirtQemu.
> 
> Now, I realize that in edk2, we have stuff like
> 
>    GCC48_AARCH64_CC_FLAGS
> 
> in "BaseTools/Conf/tools_def.template" -- coming from commit
> 7a9dbf2c94d1 ("BaseTools/Conf/tools_def.template: drop ARM/AARCH support
> from GCC46/GCC47", 2019-01-08). That doesn't change the fact that I've
> never built or tested ArmVirtQemu with such a compiler. And so this
> patch makes me quite uncomfortable.
> 
> If that rules out CentOS 7 as a QEMU project build / CI platform for the
> bundled ArmVirtQemu binaries, then we need a more recent platform
> (perhaps CentOS 8, not sure).

Unfortunately CentOS 8 is not available as a Docker image, which is a 
convenient way to build EDK2 in a CI.

> I think it's also educational to check the origin of the code that your
> patch proposes to remove. Most recently it was moved around from a
> different place, in QEMU commit 65a109ab4b1a ('roms: lift
> "edk2-funcs.sh" from "tests/uefi-test-tools/build.sh"', 2019-04-17).
> 
> In that commit, for some reason I didn't keep the original code comments
> (perhaps it would have been too difficult or messy to preserve the
> comments sanely with the restructured / factored-out code). But, they
> went like this (originally from commit 77db55fc8155,
> "tests/uefi-test-tools: add build scripts", 2019-02-21):
> 
> # Expose cross_prefix (which is possibly empty) to the edk2 tools. While at it,
> # determine the suitable edk2 toolchain as well.
> # - For ARM and AARCH64, edk2 only offers the GCC5 toolchain tag, which covers
> #   the gcc-5+ releases.
> # - For IA32 and X64, edk2 offers the GCC44 through GCC49 toolchain tags, in
> #   addition to GCC5. Unfortunately, the mapping between the toolchain tags and
> #   the actual gcc releases isn't entirely trivial. Run "git-blame" on
> #   "OvmfPkg/build.sh" in edk2 for more information.
> # And, because the above is too simple, we have to assign cross_prefix to an
> # edk2 build variable that is specific to both the toolchain tag and the target
> # architecture.
> 
> So... unless Ard feels it is really totally safe to retro-actively rely
> on the gcc-4.8.5-based compiler in CentOS 7, I'd rather we picked a more
> recent build platform (OS) instead. For example, we build ArmVirtQemu on
> RHEL8 regularly, so that's a reality-based "plus" for CentOS 8.
> 
> 
> Independently of all of the above, the OVMF toolchain selection logic
> that this patch proposes to reuse with ArmVirtQemu, is *really*
> x86-specific. Please run "git blame" on "OvmfPkg/build.sh" in upstream
> edk2, to see where the various branches come from (as the comments in
> this shell script suggest as well). There had been mess like commit
> 656ac0c7d8ea ('Revert "OvmfPkg/build.sh: select the GCC49 toolchain
> settings for gcc-7.*"', 2017-08-25).

Thanks for all the pointers, very educative indeed :)

I'll see other setups I can use with GCC5+ available.

I still have to figure if there are free tier CI with less limitations 
than Travis/Shippable/GitLab, so we can keep the full EDK2 build output log.

> Thanks,
> Laszlo
> 
>>
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>> ---
>> Patch to review with --ignore-all-space
>> ---
>>   roms/edk2-funcs.sh | 48 +++++++++++++++++++---------------------------
>>   1 file changed, 20 insertions(+), 28 deletions(-)
>>
>> diff --git a/roms/edk2-funcs.sh b/roms/edk2-funcs.sh
>> index 3f4485b201..a455611c0d 100644
>> --- a/roms/edk2-funcs.sh
>> +++ b/roms/edk2-funcs.sh
>> @@ -135,35 +135,27 @@ qemu_edk2_get_toolchain()
>>       return 1
>>     fi
>>
>> -  case "$emulation_target" in
>> -    (arm|aarch64)
>> -      printf 'GCC5\n'
>> +  if ! cross_prefix=$(qemu_edk2_get_cross_prefix "$emulation_target"); then
>> +    return 1
>> +  fi
>> +
>> +  gcc_version=$("${cross_prefix}gcc" -v 2>&1 | tail -1 | awk '{print $3}')
>> +  # Run "git-blame" on "OvmfPkg/build.sh" in edk2 for more information on
>> +  # the mapping below.
>> +  case "$gcc_version" in
>> +    ([1-3].*|4.[0-7].*)
>> +      printf '%s: unsupported gcc version "%s"\n' \
>> +        "$program_name" "$gcc_version" >&2
>> +      return 1
>>         ;;
>> -
>> -    (i386|x86_64)
>> -      if ! cross_prefix=$(qemu_edk2_get_cross_prefix "$emulation_target"); then
>> -        return 1
>> -      fi
>> -
>> -      gcc_version=$("${cross_prefix}gcc" -v 2>&1 | tail -1 | awk '{print $3}')
>> -      # Run "git-blame" on "OvmfPkg/build.sh" in edk2 for more information on
>> -      # the mapping below.
>> -      case "$gcc_version" in
>> -        ([1-3].*|4.[0-7].*)
>> -          printf '%s: unsupported gcc version "%s"\n' \
>> -            "$program_name" "$gcc_version" >&2
>> -          return 1
>> -          ;;
>> -        (4.8.*)
>> -          printf 'GCC48\n'
>> -          ;;
>> -        (4.9.*|6.[0-2].*)
>> -          printf 'GCC49\n'
>> -          ;;
>> -        (*)
>> -          printf 'GCC5\n'
>> -          ;;
>> -      esac
>> +    (4.8.*)
>> +      printf 'GCC48\n'
>> +      ;;
>> +    (4.9.*|6.[0-2].*)
>> +      printf 'GCC49\n'
>> +      ;;
>> +    (*)
>> +      printf 'GCC5\n'
>>         ;;
>>     esac
>>   }
>>
> 
>