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GCC BPF support #164

Merged
merged 2 commits into from
Jan 16, 2025
Merged

GCC BPF support #164

merged 2 commits into from
Jan 16, 2025

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theihor
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@theihor theihor commented Dec 27, 2024

Successor of #144

@theihor theihor force-pushed the bpf-gcc branch 2 times, most recently from 6922229 to 83066ab Compare December 28, 2024 00:04
theihor added a commit to theihor/vmtest that referenced this pull request Dec 28, 2024
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Test libbpf/ci#164
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@theihor theihor force-pushed the bpf-gcc branch 3 times, most recently from 835e83e to ed0eb19 Compare January 10, 2025 20:40
@theihor theihor changed the title Add build-bpf-gcc action GCC BPF support Jan 10, 2025
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theihor commented Jan 10, 2025

@chantra this one makes GCC BPF specific changes. It should be reviewed/merged after #166

@theihor theihor requested a review from chantra January 10, 2025 20:42
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theihor added a commit to theihor/vmtest that referenced this pull request Jan 10, 2025
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Sync libbpf/ci#164
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theihor added a commit to theihor/vmtest that referenced this pull request Jan 10, 2025
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Sync libbpf/ci#164
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@theihor theihor force-pushed the bpf-gcc branch 5 times, most recently from a11be94 to b118b37 Compare January 14, 2025 21:51
chantra
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LGTM, I am just not sure if the BPF-GCC is complementary to the current bpf build, e.g after this build, we have 2 distinctive bpf objects, 1 for the llvm build, and one for the gcc one?

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theihor commented Jan 14, 2025

@chantra please see an explanation re these two questions below

I am just not sure if the BPF-GCC is complementary to the current bpf build, e.g after this build, we have 2 distinctive bpf objects, 1 for the llvm build, and one for the gcc one?

shouldn't we instead define a "bpf-toolchain" that defaults to llvm (current behaviour), and can potentially be changd to gcc and use this build? Or is this handled transparently by the "test_progs-bpf_gcc" target?

Yes, it's handled transparently in selftests/bpf/Makefile.

The "bpf-toolchain" doesn't really change when we set BPF_GCC. This is why I decided to not include the changes from #144 that add "bpf-toolchain" action arguments.

For example, let's say the CI toolchain-full is set to "llvm-17". So, the kernel is built with LLVM=-17 (see here), and the test_progs binaries are built with llvm-17 (not the default).

Now, on x86 BUILD_BPF_GCC is true, so BPF_GCC will be set to where freshly built gcc binaries are located. The test_progs-bpf_gcc binary is still built with clang 17 in this case (make target just uses $(CC)). What changes is:

  1. test_progs-bpf_gcc is built (by default it's not)
  2. The BPF objects for test_progs-bpf_gcc are built with provided GCC compiler. Later they are automagically included in the test runner binary as static arrays, IIRC.

So from the perspective of the CI, BPF_GCC is an additional test runner, built conditionally.

Now to the question wether we want to run this on all variants of the toolchain, I think yes. This way we are testing BPF emitted by GCC against kernels built by different toolchains.

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chantra commented Jan 16, 2025

Now to the question wether we want to run this on all variants of the toolchain, I think yes. This way we are testing BPF emitted by GCC against kernels built by different toolchains.

Thanks, yes, make sense.

@theihor
Add build-bpf-gcc action
c5c4c83 
A prerequisite for running selftests/bpf is a recent version of GCC
compiled for BPF backend.

Signed-off-by: Ihor Solodrai <[email protected]>
@theihor
kernel-build: build GCC BPF test runner on x86_64
12b93d1 
When BUILD_BPF_GCC is set in kernel-build, GCC BPF will be built and
BPF_GCC variable set for build-selftests. When BPF_GCC is set,
test_progs-bpf_gcc runner is built in selftests/bpf.

If test_progs-bpf_gcc is specified in KERNEL_TEST, it will be executed
by run-vmtest action.

Signed-off-by: Ihor Solodrai <[email protected]>
theihor added a commit to theihor/vmtest that referenced this pull request Jan 16, 2025
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Merge libbpf/ci#164
1af0d44 
Update kernel-build workflow and configs to run selftests/bpf with BPF
objects compiled with recent GCC BPF.

Signed-off-by: Ihor Solodrai <[email protected]>
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theihor commented Jan 16, 2025

vmtest CI passed: https://github.com/kernel-patches/vmtest/actions/runs/12814890364

Merging now.

@theihor theihor merged commit 236da0f into libbpf:main Jan 16, 2025
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theihor added a commit to kernel-patches/vmtest that referenced this pull request Jan 16, 2025
@theihor
GCC BPF support (#327)
ae60395 
Merge libbpf/ci#164

Update kernel-build workflow and configs to run selftests/bpf with BPF
objects compiled with recent GCC BPF.

Signed-off-by: Ihor Solodrai <[email protected]>
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