Commit d4e48e3d authored by Alan Maguire's avatar Alan Maguire Committed by Andrii Nakryiko
Browse files

module, bpf: Store BTF base pointer in struct module 



...as this will allow split BTF modules with a base BTF
representation (rather than the full vmlinux BTF at time of
BTF encoding) to resolve their references to kernel types in a
way that is more resilient to small changes in kernel types.

This will allow modules that are not built every time the kernel
is to provide more resilient BTF, rather than have it invalidated
every time BTF ids for core kernel types change.

Fields are ordered to avoid holes in struct module.

Signed-off-by: default avatarAlan Maguire <alan.maguire@oracle.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Reviewed-by: default avatarLuis Chamberlain <mcgrof@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240620091733.1967885-3-alan.maguire@oracle.com
parent d1cf8408

include/linux/module.h

+2 −0
Original line number Diff line number Diff line
@@ -509,7 +509,9 @@ struct module { 
#endif

#ifdef CONFIG_DEBUG_INFO_BTF_MODULES

	unsigned int btf_data_size;

	unsigned int btf_base_data_size;

	void *btf_data;

	void *btf_base_data;

#endif

#ifdef CONFIG_JUMP_LABEL

	struct jump_entry *jump_entries;

kernel/module/main.c

+4 −1
Original line number Diff line number Diff line
@@ -2166,6 +2166,8 @@ static int find_module_sections(struct module *mod, struct load_info *info) 
#endif

#ifdef CONFIG_DEBUG_INFO_BTF_MODULES

	mod->btf_data = any_section_objs(info, ".BTF", 1, &mod->btf_data_size);

	mod->btf_base_data = any_section_objs(info, ".BTF.base", 1,

					      &mod->btf_base_data_size);

#endif

#ifdef CONFIG_JUMP_LABEL

	mod->jump_entries = section_objs(info, "__jump_table",
@@ -2590,8 +2592,9 @@ static noinline int do_init_module(struct module *mod) 
	}



#ifdef CONFIG_DEBUG_INFO_BTF_MODULES

	/* .BTF is not SHF_ALLOC and will get removed, so sanitize pointer */

	/* .BTF is not SHF_ALLOC and will get removed, so sanitize pointers */

	mod->btf_data = NULL;

	mod->btf_base_data = NULL;

#endif

	/*

	 * We want to free module_init, but be aware that kallsyms may be