Commit 5e214f2e authored by Connor O'Brien's avatar Connor O'Brien Committed by Daniel Borkmann
Browse files

bpf: Add config to allow loading modules with BTF mismatches 



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 Kconfig 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.

Suggested-by: default avatarYonghong Song <yhs@fb.com>
Suggested-by: default avatarMichal Suchánek <msuchanek@suse.de>
Signed-off-by: default avatarConnor O'Brien <connoro@google.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarShung-Hsi Yu <shung-hsi.yu@suse.com>
Acked-by: default avatarSong Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/CAADnVQJ+OVPnBz8z3vNu8gKXX42jCUqfuvhWAyCQDu8N_yqqwQ@mail.gmail.com
Link: https://lore.kernel.org/bpf/20220223012814.1898677-1-connoro@google.com
parent dda7596c

kernel/bpf/btf.c

+2 −1
Original line number Diff line number Diff line
@@ -6398,6 +6398,7 @@ static int btf_module_notify(struct notifier_block *nb, unsigned long op, 
			pr_warn("failed to validate module [%s] BTF: %ld\n",

				mod->name, PTR_ERR(btf));

			kfree(btf_mod);

			if (!IS_ENABLED(CONFIG_MODULE_ALLOW_BTF_MISMATCH))

				err = PTR_ERR(btf);

			goto out;

		}

lib/Kconfig.debug

+10 −0
Original line number Diff line number Diff line
@@ -339,6 +339,16 @@ config DEBUG_INFO_BTF_MODULES 
	help

	  Generate compact split BTF type information for kernel modules.



config MODULE_ALLOW_BTF_MISMATCH

	bool "Allow loading modules with non-matching BTF type info"

	depends on DEBUG_INFO_BTF_MODULES

	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 GDB_SCRIPTS

	bool "Provide GDB scripts for kernel debugging"

	help