btf, scripts: Exclude Rust CUs with pahole

Version 1.24 of pahole has the capability to exclude compilation units (CUs)
of specific languages [1] [2]. Rust, as of writing, is not currently supported
by pahole and if it's used with a build that has BTF debugging enabled it
results in malformed kernel and module binaries [3]. So it's better for pahole
to exclude Rust CUs until support for it arrives.

Co-developed-by: Eric Curtin <ecurtin@redhat.com>
Signed-off-by: Eric Curtin <ecurtin@redhat.com>
Signed-off-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Eric Curtin <ecurtin@redhat.com>
Reviewed-by: Neal Gompa <neal@gompa.dev>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?id=49358dfe2aaae4e90b072332c3e324019826783f
Link: https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?id=8ee363790b7437283c53090a85a9fec2f0b0fbc4
Link: https://github.com/Rust-for-Linux/linux/issues/735
Link: https://lore.kernel.org/bpf/20230111152050.559334-1-yakoyoku@gmail.com

diff --git a/init/Kconfig b/init/Kconfig
index 7e5c3dd..c93f19d 100644 (file)
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1935,7 +1935,7 @@ config RUST
        depends on !MODVERSIONS
        depends on !GCC_PLUGINS
        depends on !RANDSTRUCT
-       depends on !DEBUG_INFO_BTF
+       depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE
        select CONSTRUCTORS
        help
          Enables Rust support in the kernel.

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 881c3f8..335411e 100644 (file)
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -389,6 +389,15 @@ config PAHOLE_HAS_BTF_TAG
          btf_decl_tag) or not. Currently only clang compiler implements
          these attributes, so make the config depend on CC_IS_CLANG.
 
+config PAHOLE_HAS_LANG_EXCLUDE
+       def_bool PAHOLE_VERSION >= 124
+       help
+         Support for the --lang_exclude flag which makes pahole exclude
+         compilation units from the supplied language. Used in Kbuild to
+         omit Rust CUs which are not supported in version 1.24 of pahole,
+         otherwise it would emit malformed kernel and module binaries when
+         using DEBUG_INFO_BTF_MODULES.
+
 config DEBUG_INFO_BTF_MODULES
        def_bool y
        depends on DEBUG_INFO_BTF && MODULES && PAHOLE_HAS_SPLIT_BTF

diff --git a/scripts/pahole-flags.sh b/scripts/pahole-flags.sh
index 0d99ef1..1f1f1d3 100755 (executable)
--- a/scripts/pahole-flags.sh
+++ b/scripts/pahole-flags.sh
@@ -19,5 +19,9 @@ fi
 if [ "${pahole_ver}" -ge "122" ]; then
        extra_paholeopt="${extra_paholeopt} -j"
 fi
+if [ "${pahole_ver}" -ge "124" ]; then
+       # see PAHOLE_HAS_LANG_EXCLUDE
+       extra_paholeopt="${extra_paholeopt} --lang_exclude=rust"
+fi
 
 echo ${extra_paholeopt}