[PATCH bpf-next v5 09/11] selftests/bpf: Provide weak definitions for cross-test functions

Ricardo B. Marlière
2026-04-15T21:00:05Z

Some test files reference functions defined in other translation units that
may not be compiled when skeletons are missing. Replace forward
declarations of uprobe_multi_func_{1,2,3}() with weak no-op stubs so the
linker resolves them regardless of which objects are present.

Move stack_mprotect() from test_lsm.c into testing_helpers.c so it is
always available. The previous weak-stub approach returned 0, which would
cause callers expecting -1/EPERM to fail their assertions
deterministically. Having the real implementation in a shared utility
avoids this problem entirely.

Signed-off-by: Ricardo B. Marlière <rbm@suse.com>
---
.../testing/selftests/bpf/prog_tests/bpf_cookie.c | 17 +++++++++++------
tools/testing/selftests/bpf/prog_tests/iters.c | 3 +--
tools/testing/selftests/bpf/prog_tests/test_lsm.c | 22 ----------------------
tools/testing/selftests/bpf/testing_helpers.c | 17 +++++++++++++++++
tools/testing/selftests/bpf/testing_helpers.h | 1 +
5 files changed, 30 insertions(+), 30 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c b/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c
index 35adc3f6d443..5a864cd8ad1b 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c
@@ -252,10 +252,17 @@ static void kprobe_multi_attach_api_subtest(void)
kprobe_multi__destroy(skel);
}

-/* defined in prog_tests/uprobe_multi_test.c */
-void uprobe_multi_func_1(void);
-void uprobe_multi_func_2(void);
-void uprobe_multi_func_3(void);
+/*
+ * Weak uprobe target stubs. noinline is required because
+ * uprobe_multi_test_run() takes their addresses to configure the BPF
+ * program's attachment points; an inlined function has no stable
+ * address in the binary to probe. The strong definitions in
+ * uprobe_multi_test.c take precedence when that translation unit is
+ * linked.
+ */
+noinline __weak void uprobe_multi_func_1(void) {}
+noinline __weak void uprobe_multi_func_2(void) {}
+noinline __weak void uprobe_multi_func_3(void) {}

static void uprobe_multi_test_run(struct uprobe_multi *skel)
{
@@ -574,8 +581,6 @@ static void tracing_subtest(struct test_bpf_cookie *skel)
close(fmod_ret_fd);
}

-int stack_mprotect(void);
-
static void lsm_subtest(struct test_bpf_cookie *skel)
{
__u64 cookie;
diff --git a/tools/testing/selftests/bpf/prog_tests/iters.c b/tools/testing/selftests/bpf/prog_tests/iters.c
index a539980a2fbe..7c0b59fdf498 100644
--- a/tools/testing/selftests/bpf/prog_tests/iters.c
+++ b/tools/testing/selftests/bpf/prog_tests/iters.c
@@ -7,6 +7,7 @@
#include <unistd.h>
#include <malloc.h>
#include <stdlib.h>
+#include <linux/compiler.h>
#include <test_progs.h>
#include "cgroup_helpers.h"

@@ -202,8 +203,6 @@ static void subtest_task_iters(void)
iters_task__destroy(skel);
}

-extern int stack_mprotect(void);
-
static void subtest_css_task_iters(void)
{
struct iters_css_task *skel = NULL;
diff --git a/tools/testing/selftests/bpf/prog_tests/test_lsm.c b/tools/testing/selftests/bpf/prog_tests/test_lsm.c
index bdc4fc06bc5a..d7495efd4a56 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_lsm.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_lsm.c
@@ -5,36 +5,14 @@
*/

#include <test_progs.h>
-#include <sys/mman.h>
#include <sys/wait.h>
#include <unistd.h>
-#include <malloc.h>
-#include <stdlib.h>

#include "lsm.skel.h"
#include "lsm_tailcall.skel.h"

char *CMD_ARGS[] = {"true", NULL};

-#define GET_PAGE_ADDR(ADDR, PAGE_SIZE) \
- (char *)(((unsigned long) (ADDR + PAGE_SIZE)) & ~(PAGE_SIZE-1))
-
-int stack_mprotect(void)
-{
- void *buf;
- long sz;
- int ret;
-
- sz = sysconf(_SC_PAGESIZE);
- if (sz < 0)
- return sz;
-
- buf = alloca(sz * 3);
- ret = mprotect(GET_PAGE_ADDR(buf, sz), sz,
- PROT_READ | PROT_WRITE | PROT_EXEC);
- return ret;
-}
-
int exec_cmd(int *monitored_pid)
{
int child_pid, child_status;
diff --git a/tools/testing/selftests/bpf/testing_helpers.c b/tools/testing/selftests/bpf/testing_helpers.c
index 6fbe1e995660..3f7ae76c209b 100644
--- a/tools/testing/selftests/bpf/testing_helpers.c
+++ b/tools/testing/selftests/bpf/testing_helpers.c
@@ -5,6 +5,7 @@
#include <stdlib.h>
#include <string.h>
#include <errno.h>
+#include <sys/mman.h>
#include <bpf/bpf.h>
#include <bpf/libbpf.h>
#include "disasm.h"
@@ -516,3 +517,19 @@ bool is_jit_enabled(void)

return enabled;
}
+
+int stack_mprotect(void)
+{
+ void *buf;
+ long sz;
+ int ret;
+
+ sz = sysconf(_SC_PAGESIZE);
+ if (sz < 0)
+ return sz;
+
+ buf = alloca(sz * 3);
+ ret = mprotect((void *)(((unsigned long)(buf + sz)) & ~(sz - 1)), sz,
+ PROT_READ | PROT_WRITE | PROT_EXEC);
+ return ret;
+}
diff --git a/tools/testing/selftests/bpf/testing_helpers.h b/tools/testing/selftests/bpf/testing_helpers.h
index 2ca2356a0b58..2edc6fb7fc52 100644
--- a/tools/testing/selftests/bpf/testing_helpers.h
+++ b/tools/testing/selftests/bpf/testing_helpers.h
@@ -59,5 +59,6 @@ struct bpf_insn;
int get_xlated_program(int fd_prog, struct bpf_insn **buf, __u32 *cnt);
int testing_prog_flags(void);
bool is_jit_enabled(void);
+int stack_mprotect(void);

#endif /* __TESTING_HELPERS_H */

--
2.53.0