[PATCH] docs: Document pahole v1.26 requirement for KF_IMPLICIT_ARGS kfuncs

[zhidao su <soolaugust@gmail.com>]

Since Linux 7.0, kfuncs annotated with KF_IMPLICIT_ARGS require pahole
v1.26 or later. Without it, such kfuncs have incorrect BTF prototypes in
vmlinux, causing BPF programs to fail with 'func_proto incompatible with
vmlinux' error.

This affects all sched_ext kfuncs (e.g. scx_bpf_create_dsq,
scx_bpf_dispatch) and other KF_IMPLICIT_ARGS kfuncs across the kernel.
Ubuntu 24.04 LTS ships pahole v1.25 by default, causing 23/30 sched_ext
selftests to fail on affected systems.

Document this requirement in Documentation/process/changes.rst so users
understand the failure mode and can upgrade pahole appropriately.

Signed-off-by: zhidao su <suzhidao@xiaomi.com>
---
 Documentation/process/changes.rst | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/process/changes.rst b/Documentation/process/changes.rst
index 6b373e193548..141a4576c24d 100644
--- a/Documentation/process/changes.rst
+++ b/Documentation/process/changes.rst
@@ -145,6 +145,11 @@ Since Linux 5.2, if CONFIG_DEBUG_INFO_BTF is selected, the build system
 generates BTF (BPF Type Format) from DWARF in vmlinux, a bit later from kernel
 modules as well.  This requires pahole v1.22 or later.
 
+Since Linux 7.0, kfuncs annotated with KF_IMPLICIT_ARGS require pahole v1.26
+or later.  Without it, such kfuncs will have incorrect BTF prototypes in
+vmlinux, causing BPF programs to fail to load with a "func_proto incompatible
+with vmlinux" error.  Many sched_ext kfuncs are affected.
+
 It is found in the 'dwarves' or 'pahole' distro packages or from
 https://fedorapeople.org/~acme/dwarves/.
 
-- 
2.43.0