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scripts: Exclude Rust CUs with pahole
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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: Rust-for-Linux#735 [3]

Co-developed-by: Eric Curtin <[email protected]>
Signed-off-by: Eric Curtin <[email protected]>
Signed-off-by: Martin Rodriguez Reboredo <[email protected]>
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YakoYakoYokuYoku committed Jan 11, 2023
1 parent 84b0fc2 commit dcc5038
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Showing 3 changed files with 14 additions and 1 deletion.
2 changes: 1 addition & 1 deletion init/Kconfig
Original file line number Diff line number Diff line change
Expand Up @@ -1913,7 +1913,7 @@ 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.
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9 changes: 9 additions & 0 deletions lib/Kconfig.debug
Original file line number Diff line number Diff line change
Expand Up @@ -364,6 +364,15 @@ 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
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4 changes: 4 additions & 0 deletions scripts/pahole-flags.sh
Original file line number Diff line number Diff line change
Expand Up @@ -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}

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