[PATCH 6.1.y] rust: Disallow BTF generation with Rust + LTO

[Miguel Ojeda <ojeda@kernel.org>]

From: Matthew Maurer <mmaurer@google.com>

commit 5daa0c35a1f0e7a6c3b8ba9cb721e7d1ace6e619 upstream.

The kernel cannot currently self-parse BTF containing Rust debug
information. pahole uses the language of the CU to determine whether to
filter out debug information when generating the BTF. When LTO is
enabled, Rust code can cross CU boundaries, resulting in Rust debug
information in CUs labeled as C. This results in a system which cannot
parse its own BTF.

Signed-off-by: Matthew Maurer <mmaurer@google.com>
Cc: stable@vger.kernel.org
Fixes: c1177979af9c ("btf, scripts: Exclude Rust CUs with pahole")
Link: https://lore.kernel.org/r/20250108-rust-btf-lto-incompat-v1-1-60243ff6d820@google.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
 init/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/init/Kconfig b/init/Kconfig
index 2825c8cfde3b..b6786ddc88a8 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1925,7 +1925,7 @@ config RUST
 	depends on !GCC_PLUGINS
 	depends on !RANDSTRUCT
 	depends on !SHADOW_CALL_STACK
-	depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE
+	depends on !DEBUG_INFO_BTF || (PAHOLE_HAS_LANG_EXCLUDE && !LTO)
 	help
 	  Enables Rust support in the kernel.
 
-- 
2.49.0