[PATCH bpf-next v2 03/31] selftests/bpf: Query BPF_MAX_TRAMP_LINKS using BTF

Ilya Leoshkevich
2023-01-28T00:07:28Z

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>
---
.../selftests/bpf/prog_tests/fexit_stress.c | 22 +++++++----
.../bpf/prog_tests/trampoline_count.c | 18 +++++++--
tools/testing/selftests/bpf/test_progs.c | 38 +++++++++++++++++++
tools/testing/selftests/bpf/test_progs.h | 2 +
4 files changed, 69 insertions(+), 11 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/fexit_stress.c b/tools/testing/selftests/bpf/prog_tests/fexit_stress.c
index 5a7e6011f6bf..596536def43d 100644
--- 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 564b75bc087f..416addbb9d8e 100644
--- a/tools/testing/selftests/bpf/prog_tests/trampoline_count.c
+++ b/tools/testing/selftests/bpf/prog_tests/trampoline_count.c
@@ -2,7 +2,11 @@
#define _GNU_SOURCE
#include <test_progs.h>

+#if defined(__s390x__)
+#define MAX_TRAMP_PROGS 27
+#else
#define MAX_TRAMP_PROGS 38
+#endif

struct inst {
struct bpf_object *obj;
@@ -37,14 +41,21 @@ 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 +102,5 @@ void serial_test_trampoline_count(void)
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 4716e38e153a..a9b7a649bb4f 100644
--- 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 3f058dfadbaf..d5d51ec97ec8 100644
--- 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"
--
2.39.1