name: 'Enable BTF'
description: 'Enable CONFIG_DEBUG_INFO_BTF and apply libbpf feature-detection fix for android12-5.10'
inputs:
  version:
    description: 'Kernel config version (e.g., android12-5.10)'
    required: true
  kernel_version:
    description: 'Kernel version (e.g., 5.10)'
    required: true
  sublevel:
    description: 'Kernel sublevel'
    required: true

runs:
  using: 'composite'
  steps:
    - name: Apply libbpf feature-detection fix (android12-5.10)
      shell: bash
      working-directory: ${{ github.workspace }}/kernel/common
      if: ${{ inputs.version == 'android12-5.10' && fromJSON(inputs.sublevel) > 43 }}
      run: |
        set -euo pipefail
        patch -p1 -N < ${{ github.action_path }}/patches/0001-libbpf-remove-feature-detection-BTF.patch

    - name: Apply resolve_btfids linker-flag fix (android12-5.10)
      shell: bash
      working-directory: ${{ github.workspace }}/kernel/common
      if: ${{ inputs.version == 'android12-5.10' && fromJSON(inputs.sublevel) > 43 }}
      run: |
        set -euo pipefail
        patch -p1 -N < ${{ github.action_path }}/patches/0002-resolve_btfids-inherit-host-linker-flags.patch

    - name: Apply xdp_buff BTF-emit fix (android12-5.10)
      shell: bash
      working-directory: ${{ github.workspace }}/kernel/common
      if: ${{ inputs.version == 'android12-5.10' && fromJSON(inputs.sublevel) > 43 }}
      run: |
        set -euo pipefail
        # bpf_types.h references struct xdp_buff via
        # BTF_ID_LIST_SINGLE(bpf_xdp_output_btf_ids) in net/core/filter.c, but
        # the oldest sublevels (5.10.43) never emit xdp_buff into vmlinux BTF,
        # so resolve_btfids aborts with "unresolved symbol xdp_buff". Force BTF
        # emission with BTF_TYPE_EMIT in net/core/xdp.c, which includes
        # <net/xdp.h> (the struct must be COMPLETE at the emit point, so it
        # cannot live in filter.c where xdp_buff is only forward-declared).
        # The patch also adds #include <linux/btf.h> so BTF_TYPE_EMIT is
        # declared in xdp.c (filter.c already pulls it in).
        # Idempotent/harmless on newer sublevels.
        patch -p1 -N < ${{ github.action_path }}/patches/0003-btf-emit-xdp-buff.patch

    - name: Apply resolve_btfids ELF_T_WORD endian fix (android12-5.10)
      shell: bash
      working-directory: ${{ github.workspace }}/kernel/common
      if: ${{ inputs.version == 'android12-5.10' && fromJSON(inputs.sublevel) > 43 }}
      run: |
        set -euo pipefail
        # Backport of upstream 61e8aeda9398 ("bpf: Fix libelf endian handling
        # in resolv_btfids"). The .BTF_ids section content defaults to
        # ELF_T_BYTE, so libelf does no per-word translation when
        # resolve_btfids patches the section back with elf_update(); without
        # ELF_T_WORD the BTF_ID entries (e.g. xdp_buff) are handled as raw
        # bytes and resolution fails with "FAILED unresolved symbol xdp_buff".
        # Sublevels >= 66 (2021-11+) already carry this fix in-tree, so only
        # patch when it is missing (sublevel-43 trees: 2021-10 and lower) to
        # stay idempotent under `set -e`.
        if ! grep -q 'd_type = ELF_T_WORD' tools/bpf/resolve_btfids/main.c; then
          patch -p1 -N < ${{ github.action_path }}/patches/0004-resolve_btfids-elf-word.patch
        else
          echo "resolve_btfids already has the ELF_T_WORD fix; skipping"
        fi

    - name: Expose host dd for hermetic BTF generation (android12-5.10)
      shell: bash
      working-directory: ${{ github.workspace }}/kernel/common
      if: ${{ inputs.version == 'android12-5.10' && fromJSON(inputs.sublevel) > 43 }}
      run: |
        set -euo pipefail
        # The hermetic toolchain PATH (build.config.common -> HERMETIC_TOOLCHAIN=1)
        # has no /usr/bin, so coreutils 'dd' is missing. gen_btf in
        # scripts/link-vmlinux.sh:253 does `printf ... | dd of=...`; without dd the
        # pipeline fails and the build aborts with "Failed to generate BTF".
        # ADDITIONAL_HOST_TOOLS is honored by build/_setup_env.sh (symlinked into
        # the hermetic host_tools dir, which IS on the PATH). Echo it into the
        # build config so both Normal and Bypass build.sh runs pick it up.
        grep -q '^ADDITIONAL_HOST_TOOLS=' build.config.gki.aarch64 || \
          echo 'ADDITIONAL_HOST_TOOLS="${ADDITIONAL_HOST_TOOLS} dd"' >> build.config.gki.aarch64

    - name: Build and use pahole >=1.26 for hermetic BTF generation (android12-5.10)
      shell: bash
      working-directory: ${{ github.workspace }}/kernel
      if: ${{ inputs.version == 'android12-5.10' && fromJSON(inputs.sublevel) > 43 }}
      run: |
        set -euo pipefail
        # android12-5.10 pins prebuilt pahole v1.19, which fails to recode the
        # DWARF types and DROPS symbols (e.g. xdp_buff) from the emitted BTF.
        # resolve_btfids then aborts with "FAILED unresolved symbol xdp_buff".
        # This is the exact failure Google/kernelci hit (see lore.kernel.org,
        # "kernelci failures due to pahole missing", Apr-Sep 2022): pahole emits
        # hundreds of MB of "namespace__recode_dwarf_types: couldn't find ..."
        # warnings and silently drops types. Even Ubuntu's apt pahole 1.25 still
        # cannot fully recode the 5.10.43 sublevel DWARF (5.10.66+ is fine).
        # Build the latest pahole from source (1.31, matching a working host)
        # and wrap the hermetic-path pahole to exec it.
        #
        # The wrapper also always injects --skip_encoding_btf_enum64 /
        # decl_tag / type_tag. Sublevels <=149 have no scripts/pahole-flags.sh
        # at all, so their link-vmlinux.sh calls pahole with no skip flags; the
        # old in-tree libbpf there only handles BTF kinds 1-15 and EINVALs on
        # enum64/decl_tag/type_tag. Newer sublevels pass --skip_encoding_btf_enum64
        # via pahole-flags.sh already; duplicate skip flags are harmless.
        sudo apt-get install -y -qq cmake gcc libdw-dev libelf-dev zlib1g-dev dwarves

        # Build pahole 1.31 from source (acmel/dwarves). Deterministic, self-hosted.
        # Release build type is required: the default Debug sets -Wall -Werror, and
        # the bundled libbpf/btf_encoder fail under newer GCC as -Werror.
        PAHOLE_SRC="$HOME/dwarves"
        rm -rf "$PAHOLE_SRC"
        git clone --depth 1 --branch v1.31 https://github.com/acmel/dwarves.git "$PAHOLE_SRC"
        mkdir -p "$PAHOLE_SRC/build"
        cd "$PAHOLE_SRC/build"
        cmake -D__LIB=lib -DCMAKE_INSTALL_PREFIX=/usr/local -DCMAKE_BUILD_TYPE=Release .. >/dev/null
        make -j"$(nproc)" pahole
        sudo make install pahole
        # pahole links against libdwarves*.so installed under /usr/local/lib;
        # regenerate the dynamic linker cache so the binary can find them.
        sudo ldconfig
        command -v pahole
        pahole --version

        HERMETIC_PAHOLE="${{ github.workspace }}/kernel/build/build-tools/path/linux-x86/pahole"
        REAL_PAHOLE="$(command -v pahole)"
        if [ -L "$HERMETIC_PAHOLE" ] || [ -f "$HERMETIC_PAHOLE" ]; then
          cat > "$HERMETIC_PAHOLE" <<EOF
        #!/bin/sh
        exec "$REAL_PAHOLE" --skip_encoding_btf_enum64 --skip_encoding_btf_decl_tag --skip_encoding_btf_type_tag "\$@"
        EOF
          chmod +x "$HERMETIC_PAHOLE"
          echo "Wrote wrapper $HERMETIC_PAHOLE -> $REAL_PAHOLE (skip enum64/decl_tag/type_tag)"
          "$HERMETIC_PAHOLE" --version
        else
          echo "WARNING: $HERMETIC_PAHOLE not found; leaving prebuilt pahole in place"
        fi

    - name: Enable BTF Config
      uses: ./.github/actions/set-kernel-config
      with:
        config_list: |
          CONFIG_DEBUG_INFO_BTF=y