kernel: add MODULE_ALLOW_BTF_MISMATCH option

BTF mismatch can occur for a separately-built module even when the ABI
is otherwise compatible and nothing else would prevent successfully
loading. Add a new config to control how mismatches are handled. By
default, preserve the current behavior of refusing to load the
module. If MODULE_ALLOW_BTF_MISMATCH is enabled, load the module but
ignore its BTF information.

Signed-off-by: Tianling Shen <cnsztl@immortalwrt.org>

diff --git a/config/Config-kernel.in b/config/Config-kernel.in
index 3a2189d63aff00848c468c466605ebf0617bc2a6..6c5e6a967a52988dfb4b26b4dbfd3ee9f97deaa4 100644 (file)
--- a/config/Config-kernel.in
+++ b/config/Config-kernel.in
@@ -373,6 +373,16 @@ config KERNEL_DEBUG_INFO_BTF
 
          Required to run BPF CO-RE applications.
 
+config KERNEL_MODULE_ALLOW_BTF_MISMATCH
+       bool "Allow loading modules with non-matching BTF type info"
+       depends on KERNEL_DEBUG_INFO_BTF
+       help
+         For modules whose split BTF does not match vmlinux, load without
+         BTF rather than refusing to load. The default behavior with
+         module BTF enabled is to reject modules with such mismatches;
+         this option will still load module BTF where possible but ignore
+         it when a mismatch is found.
+
 config KERNEL_DEBUG_INFO_REDUCED
        bool "Reduce debugging information"
        default y