diff mbox series

[bpf,v2,1/3] bpf: Make CONFIG_DEBUG_INFO_BTF depend upon CONFIG_BPF_SYSCALL

Message ID 20211122144742.477787-2-memxor@gmail.com (mailing list archive)
State Accepted
Commit d9847eb8be3d895b2b5f514fdf3885d47a0b92a2
Delegated to: BPF
Headers show
Series Fixes for kfunc-mod regressions and warnings | expand

Checks

Context Check Description
netdev/tree_selection success Clearly marked for bpf
netdev/fixes_present success Fixes tag present in non-next series
netdev/subject_prefix success Link
netdev/cover_letter success Series has a cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 103 this patch: 103
netdev/cc_maintainers warning 7 maintainers not CCed: kafai@fb.com songliubraving@fb.com john.fastabend@gmail.com yhs@fb.com akpm@linux-foundation.org netdev@vger.kernel.org kpsingh@kernel.org
netdev/build_clang success Errors and warnings before: 39 this patch: 39
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 107 this patch: 107
netdev/checkpatch warning CHECK: struct mutex definition without comment
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-PR fail PR summary
bpf/vmtest-bpf fail VM_Test

Commit Message

Kumar Kartikeya Dwivedi Nov. 22, 2021, 2:47 p.m. UTC 
Vinicius Costa Gomes reported [0] that build fails when
CONFIG_DEBUG_INFO_BTF is enabled and CONFIG_BPF_SYSCALL is disabled.
This leads to btf.c not being compiled, and then no symbol being present
in vmlinux for the declarations in btf.h. Since BTF is not useful
without enabling BPF subsystem, disallow this combination.

However, theoretically disabling both now could still fail, as the
symbol for kfunc_btf_id_list variables is not available. This isn't a
problem as the compiler usually optimizes the whole register/unregister
call, but at lower optimization levels it can fail the build in linking
stage.

Fix that by adding dummy variables so that modules taking address of
them still work, but the whole thing is a noop.

  [0]: https://lore.kernel.org/bpf/20211110205418.332403-1-vinicius.gomes@intel.com

Fixes: 14f267d95fe4 ("bpf: btf: Introduce helpers for dynamic BTF set registration")
Reported-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 include/linux/btf.h | 14 ++++++++++----
 kernel/bpf/btf.c    |  9 ++-------
 lib/Kconfig.debug   |  1 +
 3 files changed, 13 insertions(+), 11 deletions(-)

Comments

Song Liu Nov. 26, 2021, 7:06 a.m. UTC | #1 
On Mon, Nov 22, 2021 at 6:47 AM Kumar Kartikeya Dwivedi
<memxor@gmail.com> wrote:
>
> Vinicius Costa Gomes reported [0] that build fails when
> CONFIG_DEBUG_INFO_BTF is enabled and CONFIG_BPF_SYSCALL is disabled.
> This leads to btf.c not being compiled, and then no symbol being present
> in vmlinux for the declarations in btf.h. Since BTF is not useful
> without enabling BPF subsystem, disallow this combination.
>
> However, theoretically disabling both now could still fail, as the
> symbol for kfunc_btf_id_list variables is not available. This isn't a
> problem as the compiler usually optimizes the whole register/unregister
> call, but at lower optimization levels it can fail the build in linking
> stage.
>
> Fix that by adding dummy variables so that modules taking address of
> them still work, but the whole thing is a noop.
>
>   [0]: https://lore.kernel.org/bpf/20211110205418.332403-1-vinicius.gomes@intel.com
>
> Fixes: 14f267d95fe4 ("bpf: btf: Introduce helpers for dynamic BTF set registration")
> Reported-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

Acked-by: Song Liu <songliubraving@fb.com>
diff mbox series

Patch

diff --git a/include/linux/btf.h b/include/linux/btf.h
index 203eef993d76..0e1b6281fd8f 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -245,7 +245,10 @@  struct kfunc_btf_id_set {
 	struct module *owner;
 };
 
-struct kfunc_btf_id_list;
+struct kfunc_btf_id_list {
+	struct list_head list;
+	struct mutex mutex;
+};
 
 #ifdef CONFIG_DEBUG_INFO_BTF_MODULES
 void register_kfunc_btf_id_set(struct kfunc_btf_id_list *l,
@@ -254,6 +257,9 @@  void unregister_kfunc_btf_id_set(struct kfunc_btf_id_list *l,
 				 struct kfunc_btf_id_set *s);
 bool bpf_check_mod_kfunc_call(struct kfunc_btf_id_list *klist, u32 kfunc_id,
 			      struct module *owner);
+
+extern struct kfunc_btf_id_list bpf_tcp_ca_kfunc_list;
+extern struct kfunc_btf_id_list prog_test_kfunc_list;
 #else
 static inline void register_kfunc_btf_id_set(struct kfunc_btf_id_list *l,
 					     struct kfunc_btf_id_set *s)
@@ -268,13 +274,13 @@  static inline bool bpf_check_mod_kfunc_call(struct kfunc_btf_id_list *klist,
 {
 	return false;
 }
+
+static struct kfunc_btf_id_list bpf_tcp_ca_kfunc_list __maybe_unused;
+static struct kfunc_btf_id_list prog_test_kfunc_list __maybe_unused;
 #endif
 
 #define DEFINE_KFUNC_BTF_ID_SET(set, name)                                     \
 	struct kfunc_btf_id_set name = { LIST_HEAD_INIT(name.list), (set),     \
 					 THIS_MODULE }
 
-extern struct kfunc_btf_id_list bpf_tcp_ca_kfunc_list;
-extern struct kfunc_btf_id_list prog_test_kfunc_list;
-
 #endif
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index dbc3ad07e21b..ea3df9867cec 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -6346,11 +6346,6 @@  BTF_ID_LIST_GLOBAL_SINGLE(btf_task_struct_ids, struct, task_struct)
 
 /* BTF ID set registration API for modules */
 
-struct kfunc_btf_id_list {
-	struct list_head list;
-	struct mutex mutex;
-};
-
 #ifdef CONFIG_DEBUG_INFO_BTF_MODULES
 
 void register_kfunc_btf_id_set(struct kfunc_btf_id_list *l,
@@ -6389,8 +6384,6 @@  bool bpf_check_mod_kfunc_call(struct kfunc_btf_id_list *klist, u32 kfunc_id,
 	return false;
 }
 
-#endif
-
 #define DEFINE_KFUNC_BTF_ID_LIST(name)                                         \
 	struct kfunc_btf_id_list name = { LIST_HEAD_INIT(name.list),           \
 					  __MUTEX_INITIALIZER(name.mutex) };   \
@@ -6398,3 +6391,5 @@  bool bpf_check_mod_kfunc_call(struct kfunc_btf_id_list *klist, u32 kfunc_id,
 
 DEFINE_KFUNC_BTF_ID_LIST(bpf_tcp_ca_kfunc_list);
 DEFINE_KFUNC_BTF_ID_LIST(prog_test_kfunc_list);
+
+#endif
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 9ef7ce18b4f5..596bb5e4790c 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -316,6 +316,7 @@  config DEBUG_INFO_BTF
 	bool "Generate BTF typeinfo"
 	depends on !DEBUG_INFO_SPLIT && !DEBUG_INFO_REDUCED
 	depends on !GCC_PLUGIN_RANDSTRUCT || COMPILE_TEST
+	depends on BPF_SYSCALL
 	help
 	  Generate deduplicated BTF type information from DWARF debug info.
 	  Turning this on expects presence of pahole tool, which will convert