From: Andrii Nakryiko andrii@kernel.org
[ Upstream commit 635599bace259a2c42741c3ea61bfa7be6f15556 ]
If some of the subtests use module BTFs through ksyms, they will cause bpf_prog to take a refcount on bpf_testmod module, which will prevent it from successfully unloading. Module's refcnt is decremented when bpf_prog is freed, which generally happens in RCU callback. So we need to trigger syncronize_rcu() in the kernel, which can be achieved nicely with membarrier(MEMBARRIER_CMD_SHARED) or membarrier(MEMBARRIER_CMD_GLOBAL) syscall. So do that in kernel_sync_rcu() and make it available to other test inside the test_progs. This synchronize_rcu() is called before attempting to unload bpf_testmod.
Fixes: 9f7fa225894c ("selftests/bpf: Add bpf_testmod kernel module for testing") Suggested-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Andrii Nakryiko andrii@kernel.org Signed-off-by: Alexei Starovoitov ast@kernel.org Acked-by: Yonghong Song yhs@fb.com Acked-by: Hao Luo haoluo@google.com Link: https://lore.kernel.org/bpf/20210112075520.4103414-5-andrii@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- .../selftests/bpf/prog_tests/btf_map_in_map.c | 33 ------------------- tools/testing/selftests/bpf/test_progs.c | 11 +++++++ tools/testing/selftests/bpf/test_progs.h | 1 + 3 files changed, 12 insertions(+), 33 deletions(-)
diff --git a/tools/testing/selftests/bpf/prog_tests/btf_map_in_map.c b/tools/testing/selftests/bpf/prog_tests/btf_map_in_map.c index 76ebe4c250f11..eb90a6b8850d2 100644 --- a/tools/testing/selftests/bpf/prog_tests/btf_map_in_map.c +++ b/tools/testing/selftests/bpf/prog_tests/btf_map_in_map.c @@ -20,39 +20,6 @@ static __u32 bpf_map_id(struct bpf_map *map) return info.id; }
-/* - * Trigger synchronize_rcu() in kernel. - * - * ARRAY_OF_MAPS/HASH_OF_MAPS lookup/update operations trigger synchronize_rcu() - * if looking up an existing non-NULL element or updating the map with a valid - * inner map FD. Use this fact to trigger synchronize_rcu(): create map-in-map, - * create a trivial ARRAY map, update map-in-map with ARRAY inner map. Then - * cleanup. At the end, at least one synchronize_rcu() would be called. - */ -static int kern_sync_rcu(void) -{ - int inner_map_fd, outer_map_fd, err, zero = 0; - - inner_map_fd = bpf_create_map(BPF_MAP_TYPE_ARRAY, 4, 4, 1, 0); - if (CHECK(inner_map_fd < 0, "inner_map_create", "failed %d\n", -errno)) - return -1; - - outer_map_fd = bpf_create_map_in_map(BPF_MAP_TYPE_ARRAY_OF_MAPS, NULL, - sizeof(int), inner_map_fd, 1, 0); - if (CHECK(outer_map_fd < 0, "outer_map_create", "failed %d\n", -errno)) { - close(inner_map_fd); - return -1; - } - - err = bpf_map_update_elem(outer_map_fd, &zero, &inner_map_fd, 0); - if (err) - err = -errno; - CHECK(err, "outer_map_update", "failed %d\n", err); - close(inner_map_fd); - close(outer_map_fd); - return err; -} - static void test_lookup_update(void) { int map1_fd, map2_fd, map3_fd, map4_fd, map5_fd, map1_id, map2_id; diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c index 7d077d48cadd0..213628ee721c1 100644 --- a/tools/testing/selftests/bpf/test_progs.c +++ b/tools/testing/selftests/bpf/test_progs.c @@ -11,6 +11,7 @@ #include <signal.h> #include <string.h> #include <execinfo.h> /* backtrace */ +#include <linux/membarrier.h>
#define EXIT_NO_TEST 2 #define EXIT_ERR_SETUP_INFRA 3 @@ -370,8 +371,18 @@ static int delete_module(const char *name, int flags) return syscall(__NR_delete_module, name, flags); }
+/* + * Trigger synchronize_rcu() in kernel. + */ +int kern_sync_rcu(void) +{ + return syscall(__NR_membarrier, MEMBARRIER_CMD_SHARED, 0, 0); +} + static void unload_bpf_testmod(void) { + if (kern_sync_rcu()) + fprintf(env.stderr, "Failed to trigger kernel-side RCU sync!\n"); if (delete_module("bpf_testmod", 0)) { if (errno == ENOENT) { if (env.verbosity > VERBOSE_NONE) diff --git a/tools/testing/selftests/bpf/test_progs.h b/tools/testing/selftests/bpf/test_progs.h index 115953243f623..e49e2fdde9425 100644 --- a/tools/testing/selftests/bpf/test_progs.h +++ b/tools/testing/selftests/bpf/test_progs.h @@ -219,6 +219,7 @@ int bpf_find_map(const char *test, struct bpf_object *obj, const char *name); int compare_map_keys(int map1_fd, int map2_fd); int compare_stack_ips(int smap_fd, int amap_fd, int stack_trace_len); int extract_build_id(char *build_id, size_t size); +int kern_sync_rcu(void);
#ifdef __x86_64__ #define SYS_NANOSLEEP_KPROBE_NAME "__x64_sys_nanosleep"