From d4e48e3dd45017abdd69a19285d197de897ef44f Mon Sep 17 00:00:00 2001
From: Alan Maguire <alan.maguire@oracle.com>
Date: Thu, 20 Jun 2024 10:17:29 +0100
Subject: [PATCH] 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: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240620091733.1967885-3-alan.maguire@oracle.com
---
include/linux/module.h | 2 ++
kernel/module/main.c | 5 ++++-
2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/include/linux/module.h b/include/linux/module.h
index ffa1c603163c2..b79d926cae8a9 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -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;
diff --git a/kernel/module/main.c b/kernel/module/main.c
index d18a94b973e10..d9592195c5bbb 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -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
--
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