[PATCHv2 stable 6.1 0/2] btf, scripts: Update pahole options

[PATCHv2 stable 6.1 0/2] btf, scripts: Update pahole options

[Jiri Olsa]

hi,
we need to be able to use latest pahole options for 6.1 kernels,
updating the scripts/pahole-flags.sh with that (clean backports).

thanks,
jirka

v2 changes:
  - added missing SOB

---
Alan Maguire (1):
      bpf: Add --skip_encoding_btf_inconsistent_proto, --btf_gen_optimized to pahole flags for v1.25

Martin Rodriguez Reboredo (1):
      btf, scripts: Exclude Rust CUs with pahole

 init/Kconfig            | 2 +-
 lib/Kconfig.debug       | 9 +++++++++
 scripts/pahole-flags.sh | 7 +++++++
 3 files changed, 17 insertions(+), 1 deletion(-)

[PATCHv2 stable 6.1 1/2] btf, scripts: Exclude Rust CUs with pahole

[Jiri Olsa]

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

commit c1177979af9c616661a126a80dd486ad0543b836 upstream.

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 [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]
Link: https://lore.kernel.org/bpf/20230111152050.559334-1-yakoyoku@gmail.com
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 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 de255842f5d0..148704640252 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1914,7 +1914,7 @@ 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 4db0199651f5..95541b99aa8e 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -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
diff --git a/scripts/pahole-flags.sh b/scripts/pahole-flags.sh
index 0d99ef17e4a5..1f1f1d397c39 100755
--- 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}
-- 
2.43.0

[PATCHv2 stable 6.1 2/2] bpf: Add --skip_encoding_btf_inconsistent_proto, --btf_gen_optimized to pahole flags for v1.25

[Jiri Olsa]

From: Alan Maguire <alan.maguire@oracle.com>

commit 7b99f75942da332e3f4f865e55a10fec95a30d4f upstream.

v1.25 of pahole supports filtering out functions with multiple inconsistent
function prototypes or optimized-out parameters from the BTF representation.
These present problems because there is no additional info in BTF saying which
inconsistent prototype matches which function instance to help guide attachment,
and functions with optimized-out parameters can lead to incorrect assumptions
about register contents.

So for now, filter out such functions while adding BTF representations for
functions that have "."-suffixes (foo.isra.0) but not optimized-out parameters.
This patch assumes that below linked changes land in pahole for v1.25.

Issues with pahole filtering being too aggressive in removing functions
appear to be resolved now, but CI and further testing will confirm.

Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20230510130241.1696561-1-alan.maguire@oracle.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 scripts/pahole-flags.sh | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/scripts/pahole-flags.sh b/scripts/pahole-flags.sh
index 1f1f1d397c39..728d55190d97 100755
--- a/scripts/pahole-flags.sh
+++ b/scripts/pahole-flags.sh
@@ -23,5 +23,8 @@ if [ "${pahole_ver}" -ge "124" ]; then
 	# see PAHOLE_HAS_LANG_EXCLUDE
 	extra_paholeopt="${extra_paholeopt} --lang_exclude=rust"
 fi
+if [ "${pahole_ver}" -ge "125" ]; then
+	extra_paholeopt="${extra_paholeopt} --skip_encoding_btf_inconsistent_proto --btf_gen_optimized"
+fi
 
 echo ${extra_paholeopt}
-- 
2.43.0

Re: [PATCHv2 stable 6.1 0/2] btf, scripts: Update pahole options

[Greg KH]

On Wed, Jan 17, 2024 at 02:35:18PM +0100, Jiri Olsa wrote:
> hi,
> we need to be able to use latest pahole options for 6.1 kernels,
> updating the scripts/pahole-flags.sh with that (clean backports).
> 
> thanks,
> jirka
> 
> v2 changes:
>   - added missing SOB
> 
> ---
> Alan Maguire (1):
>       bpf: Add --skip_encoding_btf_inconsistent_proto, --btf_gen_optimized to pahole flags for v1.25
> 
> Martin Rodriguez Reboredo (1):
>       btf, scripts: Exclude Rust CUs with pahole
> 
>  init/Kconfig            | 2 +-
>  lib/Kconfig.debug       | 9 +++++++++
>  scripts/pahole-flags.sh | 7 +++++++
>  3 files changed, 17 insertions(+), 1 deletion(-)
> 

All now queued up, thanks.

greg k-h