[PATCH stable 5.15] bpf: Add --skip_encoding_btf_inconsistent_proto, --btf_gen_optimized to pahole flags for v1.25

[PATCH stable 5.15] 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.

[ small context conflict because of not backported --lang_exclude=rust
option, which is not needed in 5.15 ]

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 d38fa6d84d62..5c724f697100 100755
--- a/scripts/pahole-flags.sh
+++ b/scripts/pahole-flags.sh
@@ -20,5 +20,8 @@ fi
 if [ "${pahole_ver}" -ge "124" ]; then
 	extra_paholeopt="${extra_paholeopt} --skip_encoding_btf_enum64"
 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: [PATCH stable 5.15] bpf: Add --skip_encoding_btf_inconsistent_proto, --btf_gen_optimized to pahole flags for v1.25

[Greg KH]

On Mon, Jan 22, 2024 at 09:03:29AM +0100, Jiri Olsa wrote:
> From: Alan Maguire <alan.maguire@oracle.com>
> 
> commit 7b99f75942da332e3f4f865e55a10fec95a30d4f upstream.
> 
> [ small context conflict because of not backported --lang_exclude=rust
> option, which is not needed in 5.15 ]
> 
> 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(+)

Now queued up, thanks.

greg k-h