From 4134e6b029b26028ae1f50d9081b1878f267ac18 Mon Sep 17 00:00:00 2001
From: Ben Hutchings <benh@debian.org>
Date: Wed, 2 Mar 2022 21:22:28 +0100
Subject: [PATCH] module: Avoid ABI changes when debug info is disabled

Forwarded: not-needed

CI builds are done with debug info disabled, but this removes some
members from struct module and replaces some BTF-related exports with
static definitions.  This causes builds to fail if there is an ABI
reference for the current ABI.

- Add a new config symbol DEBUG_INFO_BTF_MODULES_NOOP which can be
  enabled when DEBUG_INFO is not enabled
- When the symbol is enabled:
  - Define the BTF-related members of struct module
  - Export the no-op definitions of BTF-related functions
  - Define and export the same BTF-related static lists


Gbp-Pq: Topic debian
Gbp-Pq: Name module-avoid-abi-changes-when-debug-info-is-disabled.patch
---
 include/linux/btf.h    |  2 +-
 include/linux/module.h |  2 +-
 kernel/bpf/btf.c       | 24 ++++++++++++++++++++++++
 lib/Kconfig.debug      | 10 ++++++++++
 4 files changed, 36 insertions(+), 2 deletions(-)

diff --git a/include/linux/btf.h b/include/linux/btf.h
index 0e1b6281fd8..eee42c114a9 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -250,7 +250,7 @@ struct kfunc_btf_id_list {
 	struct mutex mutex;
 };
 
-#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+#if defined(CONFIG_DEBUG_INFO_BTF_MODULES) || defined(CONFIG_DEBUG_INFO_BTF_MODULES_NOOP)
 void register_kfunc_btf_id_set(struct kfunc_btf_id_list *l,
 			       struct kfunc_btf_id_set *s);
 void unregister_kfunc_btf_id_set(struct kfunc_btf_id_list *l,
diff --git a/include/linux/module.h b/include/linux/module.h
index c9f1200b231..5a7bea7348b 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -470,7 +470,7 @@ struct module {
 	unsigned int num_bpf_raw_events;
 	struct bpf_raw_event_map *bpf_raw_events;
 #endif
-#ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+#if defined(CONFIG_DEBUG_INFO_BTF_MODULES) || defined(CONFIG_DEBUG_INFO_BTF_MODULES_NOOP)
 	unsigned int btf_data_size;
 	void *btf_data;
 #endif
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index c9da250fee3..58e52de4554 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6436,6 +6436,30 @@ bool bpf_check_mod_kfunc_call(struct kfunc_btf_id_list *klist, u32 kfunc_id,
 	return false;
 }
 
+#elif defined(CONFIG_DEBUG_INFO_BTF_MODULES_NOOP)
+
+void register_kfunc_btf_id_set(struct kfunc_btf_id_list *l,
+			       struct kfunc_btf_id_set *s)
+{
+}
+EXPORT_SYMBOL_GPL(register_kfunc_btf_id_set);
+
+void unregister_kfunc_btf_id_set(struct kfunc_btf_id_list *l,
+				 struct kfunc_btf_id_set *s)
+{
+}
+EXPORT_SYMBOL_GPL(unregister_kfunc_btf_id_set);
+
+bool bpf_check_mod_kfunc_call(struct kfunc_btf_id_list *klist, u32 kfunc_id,
+			      struct module *owner)
+{
+	return false;
+}
+
+#endif /* CONFIG_DEBUG_INFO_BTF_MODULES */
+
+#if defined(CONFIG_DEBUG_INFO_BTF_MODULES) || defined(CONFIG_DEBUG_INFO_BTF_MODULES_NOOP)
+
 #define DEFINE_KFUNC_BTF_ID_LIST(name)                                         \
 	struct kfunc_btf_id_list name = { LIST_HEAD_INIT(name.list),           \
 					  __MUTEX_INITIALIZER(name.mutex) };   \
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 5e14e32056a..a7cad165c81 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -343,6 +343,16 @@ config GDB_SCRIPTS
 
 endif # DEBUG_INFO
 
+if !DEBUG_INFO
+
+config DEBUG_INFO_BTF_MODULES_NOOP
+	bool "Provide no-op BTF ABI to modules"
+	help
+	  Enable this option instead of DEBUG_INFO_BTF to avoid an ABI
+	  change when debug info is disabled.
+
+endif
+
 config FRAME_WARN
 	int "Warn for stack frames larger than"
 	range 0 8192
-- 
2.30.2