[PATCH 05/16] UBUNTU: SAUCE: scripts: Exclude Rust CUs with pahole

[Andrea Righi]

From: Martin Rodriguez Reboredo <yakoyoku at gmail.com>

BugLink: https://bugs.launchpad.net/bugs/2007654

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.

Link: https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?id=49358dfe2aaae4e90b072332c3e324019826783f [1]
Link: https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?id=8ee363790b7437283c53090a85a9fec2f0b0fbc4 [2]
Link: https://github.com/Rust-for-Linux/linux/issues/735 [3]

Co-developed-by: Eric Curtin <ecurtin at redhat.com>
Signed-off-by: Eric Curtin <ecurtin at redhat.com>
Signed-off-by: Martin Rodriguez Reboredo <yakoyoku at gmail.com>
Acked-by: Miguel Ojeda <ojeda at kernel.org>
Tested-by: Eric Curtin <ecurtin at redhat.com>
Reviewed-by: Neal Gompa <neal at gompa.dev>
Acked-by: Arnaldo Carvalho de Melo <acme at redhat.com>
(cherry picked from https://lore.kernel.org/bpf/CANiq72mUOOeHgN8wM4d2Kf_XEEVCZNSOa5qxt08crPYV1TCQ-w@mail.gmail.com/T/)
Signed-off-by: Andrea Righi <andrea.righi at canonical.com>
---
 init/Kconfig            | 2 +-
 lib/Kconfig.debug       | 9 +++++++++
 scripts/pahole-flags.sh | 4 ++++
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/init/Kconfig b/init/Kconfig
index c29709b1c091..fea68d967df6 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1948,7 +1948,7 @@ 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 02ee440f7be3..3509115a0e85 100644
--- 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 d4f3d63cb434..5a413ea7b73c 100755
--- a/scripts/pahole-flags.sh
+++ b/scripts/pahole-flags.sh
@@ -19,6 +19,10 @@ 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
 
 if [ "${pahole_ver}" -ge "124" ]; then
 	extra_paholeopt="${extra_paholeopt} --skip_encoding_btf_enum64"
-- 
2.39.2