bpf: Add BTF_ID_LIST_GLOBAL in btf_ids.h

Existing BTF_ID_LIST used a local static variable
to store btf_ids. This patch provided a new macro
BTF_ID_LIST_GLOBAL to store btf_ids in a global
variable which can be shared among multiple files.

The existing BTF_ID_LIST is still retained.
Two reasons. First, BTF_ID_LIST is also used to build
btf_ids for helper arguments which typically
is an array of 5. Since typically different
helpers have different signature, it makes
little sense to share them. Second, some
current computed btf_ids are indeed local.
If later those btf_ids are shared between
different files, they can use BTF_ID_LIST_GLOBAL then.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Link: https://lore.kernel.org/bpf/20200720163401.1393159-1-yhs@fb.com

diff --git a/include/linux/btf_ids.h b/include/linux/btf_ids.h
index 1cdb569..77ab45b 100644 (file)
--- a/include/linux/btf_ids.h
+++ b/include/linux/btf_ids.h
@@ -57,17 +57,20 @@ asm(                                                        \
  * .zero 4
  *
  */
-#define __BTF_ID_LIST(name)                            \
+#define __BTF_ID_LIST(name, scope)                     \
 asm(                                                   \
 ".pushsection " BTF_IDS_SECTION ",\"a\";       \n"     \
-".local " #name ";                             \n"     \
+"." #scope " " #name ";                        \n"     \
 #name ":;                                      \n"     \
 ".popsection;                                  \n");   \
 
 #define BTF_ID_LIST(name)                              \
-__BTF_ID_LIST(name)                                    \
+__BTF_ID_LIST(name, local)                             \
 extern u32 name[];
 
+#define BTF_ID_LIST_GLOBAL(name)                       \
+__BTF_ID_LIST(name, globl)
+
 /*
  * The BTF_ID_UNUSED macro defines 4 zero bytes.
  * It's used when we want to define 'unused' entry
@@ -90,6 +93,7 @@ asm(                                                  \
 #define BTF_ID_LIST(name) static u32 name[5];
 #define BTF_ID(prefix, name)
 #define BTF_ID_UNUSED
+#define BTF_ID_LIST_GLOBAL(name) u32 name[1];
 
 #endif /* CONFIG_DEBUG_INFO_BTF */
 

diff --git a/tools/include/linux/btf_ids.h b/tools/include/linux/btf_ids.h
index 1cdb569..77ab45b 100644 (file)
--- a/tools/include/linux/btf_ids.h
+++ b/tools/include/linux/btf_ids.h
@@ -57,17 +57,20 @@ asm(                                                        \
  * .zero 4
  *
  */
-#define __BTF_ID_LIST(name)                            \
+#define __BTF_ID_LIST(name, scope)                     \
 asm(                                                   \
 ".pushsection " BTF_IDS_SECTION ",\"a\";       \n"     \
-".local " #name ";                             \n"     \
+"." #scope " " #name ";                        \n"     \
 #name ":;                                      \n"     \
 ".popsection;                                  \n");   \
 
 #define BTF_ID_LIST(name)                              \
-__BTF_ID_LIST(name)                                    \
+__BTF_ID_LIST(name, local)                             \
 extern u32 name[];
 
+#define BTF_ID_LIST_GLOBAL(name)                       \
+__BTF_ID_LIST(name, globl)
+
 /*
  * The BTF_ID_UNUSED macro defines 4 zero bytes.
  * It's used when we want to define 'unused' entry
@@ -90,6 +93,7 @@ asm(                                                  \
 #define BTF_ID_LIST(name) static u32 name[5];
 #define BTF_ID(prefix, name)
 #define BTF_ID_UNUSED
+#define BTF_ID_LIST_GLOBAL(name) u32 name[1];
 
 #endif /* CONFIG_DEBUG_INFO_BTF */
 

diff --git a/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c b/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
index 22d83bb..3b127ca 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
+++ b/tools/testing/selftests/bpf/prog_tests/resolve_btfids.c
@@ -28,7 +28,17 @@ struct symbol test_symbols[] = {
        { "func",    BTF_KIND_FUNC,    -1 },
 };
 
-BTF_ID_LIST(test_list)
+BTF_ID_LIST(test_list_local)
+BTF_ID_UNUSED
+BTF_ID(typedef, S)
+BTF_ID(typedef, T)
+BTF_ID(typedef, U)
+BTF_ID(struct,  S)
+BTF_ID(union,   U)
+BTF_ID(func,    func)
+
+extern __u32 test_list_global[];
+BTF_ID_LIST_GLOBAL(test_list_global)
 BTF_ID_UNUSED
 BTF_ID(typedef, S)
 BTF_ID(typedef, T)
@@ -94,18 +104,25 @@ static int resolve_symbols(void)
 
 int test_resolve_btfids(void)
 {
-       unsigned int i;
+       __u32 *test_list, *test_lists[] = { test_list_local, test_list_global };
+       unsigned int i, j;
        int ret = 0;
 
        if (resolve_symbols())
                return -1;
 
-       /* Check BTF_ID_LIST(test_list) IDs */
-       for (i = 0; i < ARRAY_SIZE(test_symbols) && !ret; i++) {
-               ret = CHECK(test_list[i] != test_symbols[i].id,
-                           "id_check",
-                           "wrong ID for %s (%d != %d)\n", test_symbols[i].name,
-                           test_list[i], test_symbols[i].id);
+       /* Check BTF_ID_LIST(test_list_local) and
+        * BTF_ID_LIST_GLOBAL(test_list_global) IDs
+        */
+       for (j = 0; j < ARRAY_SIZE(test_lists); j++) {
+               test_list = test_lists[j];
+               for (i = 0; i < ARRAY_SIZE(test_symbols) && !ret; i++) {
+                       ret = CHECK(test_list[i] != test_symbols[i].id,
+                                   "id_check",
+                                   "wrong ID for %s (%d != %d)\n",
+                                   test_symbols[i].name,
+                                   test_list[i], test_symbols[i].id);
+               }
        }
 
        return ret;