| Message ID | 20210108220930.482456-5-andrii@kernel.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Support kernel module ksym variables | expand |
On 1/8/21 2:09 PM, Andrii Nakryiko wrote: > 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_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> Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: Hao Luo <haoluo@google.com> On Sun, Jan 10, 2021 at 8:05 PM Yonghong Song <yhs@fb.com> wrote: > > > > On 1/8/21 2:09 PM, Andrii Nakryiko wrote: > > 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_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> > > Acked-by: Yonghong Song <yhs@fb.com>
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 76ebe4c250f1..eb90a6b8850d 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 7d077d48cadd..e3fbca25696c 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_GLOBAL, 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 115953243f62..e49e2fdde942 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"
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_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> --- .../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(-)