selftests/bpf: Query BPF_MAX_TRAMP_LINKS using BTF

Do not hard-code the value, since for s390x it will be smaller than
for x86.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/r/20230128000650.1516334-4-iii@linux.ibm.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/prog_tests/fexit_stress.c b/tools/testing/selftests/bpf/prog_tests/fexit_stress.c
index 5a7e601..596536d 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/fexit_stress.c
+++ b/tools/testing/selftests/bpf/prog_tests/fexit_stress.c
@@ -2,14 +2,19 @@
 /* Copyright (c) 2019 Facebook */
 #include <test_progs.h>
 
-/* that's kernel internal BPF_MAX_TRAMP_PROGS define */
-#define CNT 38
-
 void serial_test_fexit_stress(void)
 {
-       int fexit_fd[CNT] = {};
-       int link_fd[CNT] = {};
-       int err, i;
+       int bpf_max_tramp_links, err, i;
+       int *fd, *fexit_fd, *link_fd;
+
+       bpf_max_tramp_links = get_bpf_max_tramp_links();
+       if (!ASSERT_GE(bpf_max_tramp_links, 1, "bpf_max_tramp_links"))
+               return;
+       fd = calloc(bpf_max_tramp_links * 2, sizeof(*fd));
+       if (!ASSERT_OK_PTR(fd, "fd"))
+               return;
+       fexit_fd = fd;
+       link_fd = fd + bpf_max_tramp_links;
 
        const struct bpf_insn trace_program[] = {
                BPF_MOV64_IMM(BPF_REG_0, 0),
@@ -28,7 +33,7 @@ void serial_test_fexit_stress(void)
                goto out;
        trace_opts.attach_btf_id = err;
 
-       for (i = 0; i < CNT; i++) {
+       for (i = 0; i < bpf_max_tramp_links; i++) {
                fexit_fd[i] = bpf_prog_load(BPF_PROG_TYPE_TRACING, NULL, "GPL",
                                            trace_program,
                                            sizeof(trace_program) / sizeof(struct bpf_insn),
@@ -44,10 +49,11 @@ void serial_test_fexit_stress(void)
        ASSERT_OK(err, "bpf_prog_test_run_opts");
 
 out:
-       for (i = 0; i < CNT; i++) {
+       for (i = 0; i < bpf_max_tramp_links; i++) {
                if (link_fd[i])
                        close(link_fd[i]);
                if (fexit_fd[i])
                        close(fexit_fd[i]);
        }
+       free(fd);
 }

diff --git a/tools/testing/selftests/bpf/prog_tests/trampoline_count.c b/tools/testing/selftests/bpf/prog_tests/trampoline_count.c
index 564b75b..8fd4c0d 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/trampoline_count.c
+++ b/tools/testing/selftests/bpf/prog_tests/trampoline_count.c
@@ -2,8 +2,6 @@
 #define _GNU_SOURCE
 #include <test_progs.h>
 
-#define MAX_TRAMP_PROGS 38
-
 struct inst {
        struct bpf_object *obj;
        struct bpf_link   *link;
@@ -37,14 +35,21 @@ void serial_test_trampoline_count(void)
 {
        char *file = "test_trampoline_count.bpf.o";
        char *const progs[] = { "fentry_test", "fmod_ret_test", "fexit_test" };
-       struct inst inst[MAX_TRAMP_PROGS + 1] = {};
+       int bpf_max_tramp_links, err, i, prog_fd;
        struct bpf_program *prog;
        struct bpf_link *link;
-       int prog_fd, err, i;
+       struct inst *inst;
        LIBBPF_OPTS(bpf_test_run_opts, opts);
 
+       bpf_max_tramp_links = get_bpf_max_tramp_links();
+       if (!ASSERT_GE(bpf_max_tramp_links, 1, "bpf_max_tramp_links"))
+               return;
+       inst = calloc(bpf_max_tramp_links + 1, sizeof(*inst));
+       if (!ASSERT_OK_PTR(inst, "inst"))
+               return;
+
        /* attach 'allowed' trampoline programs */
-       for (i = 0; i < MAX_TRAMP_PROGS; i++) {
+       for (i = 0; i < bpf_max_tramp_links; i++) {
                prog = load_prog(file, progs[i % ARRAY_SIZE(progs)], &inst[i]);
                if (!prog)
                        goto cleanup;
@@ -91,4 +96,5 @@ cleanup:
                bpf_link__destroy(inst[i].link);
                bpf_object__close(inst[i].obj);
        }
+       free(inst);
 }

diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
index c5f8521..6d5e302 100644 (file)
--- a/tools/testing/selftests/bpf/test_progs.c
+++ b/tools/testing/selftests/bpf/test_progs.c
@@ -17,6 +17,7 @@
 #include <sys/select.h>
 #include <sys/socket.h>
 #include <sys/un.h>
+#include <bpf/btf.h>
 
 static bool verbose(void)
 {
@@ -967,6 +968,43 @@ int write_sysctl(const char *sysctl, const char *value)
        return 0;
 }
 
+int get_bpf_max_tramp_links_from(struct btf *btf)
+{
+       const struct btf_enum *e;
+       const struct btf_type *t;
+       __u32 i, type_cnt;
+       const char *name;
+       __u16 j, vlen;
+
+       for (i = 1, type_cnt = btf__type_cnt(btf); i < type_cnt; i++) {
+               t = btf__type_by_id(btf, i);
+               if (!t || !btf_is_enum(t) || t->name_off)
+                       continue;
+               e = btf_enum(t);
+               for (j = 0, vlen = btf_vlen(t); j < vlen; j++, e++) {
+                       name = btf__str_by_offset(btf, e->name_off);
+                       if (name && !strcmp(name, "BPF_MAX_TRAMP_LINKS"))
+                               return e->val;
+               }
+       }
+
+       return -1;
+}
+
+int get_bpf_max_tramp_links(void)
+{
+       struct btf *vmlinux_btf;
+       int ret;
+
+       vmlinux_btf = btf__load_vmlinux_btf();
+       if (!ASSERT_OK_PTR(vmlinux_btf, "vmlinux btf"))
+               return -1;
+       ret = get_bpf_max_tramp_links_from(vmlinux_btf);
+       btf__free(vmlinux_btf);
+
+       return ret;
+}
+
 #define MAX_BACKTRACE_SZ 128
 void crash_handler(int signum)
 {

diff --git a/tools/testing/selftests/bpf/test_progs.h b/tools/testing/selftests/bpf/test_progs.h
index 3f058df..d5d51ec 100644 (file)
--- a/tools/testing/selftests/bpf/test_progs.h
+++ b/tools/testing/selftests/bpf/test_progs.h
@@ -394,6 +394,8 @@ int kern_sync_rcu(void);
 int trigger_module_test_read(int read_sz);
 int trigger_module_test_write(int write_sz);
 int write_sysctl(const char *sysctl, const char *value);
+int get_bpf_max_tramp_links_from(struct btf *btf);
+int get_bpf_max_tramp_links(void);
 
 #ifdef __x86_64__
 #define SYS_NANOSLEEP_KPROBE_NAME "__x64_sys_nanosleep"