Adds a new test that tries to attach a program to fentry of two
functions of the same name, one located in vmlinux and the other in
bpf_testmod.
To avoid conflicts with existing tests, a new function
"bpf_fentry_shadow_test" was created both in vmlinux and in bpf_testmod.
The previous commit fixed a bug which caused this test to fail. The
verifier would always use the vmlinux function's address as the target
trampoline address, hence trying to create two trampolines for a single
address, which is forbidden.
Signed-off-by: Viktor Malik <vmalik@xxxxxxxxxx>
---
net/bpf/test_run.c | 5 +
.../selftests/bpf/bpf_testmod/bpf_testmod.c | 6 +
.../bpf/prog_tests/module_attach_shadow.c | 131 ++++++++++++++++++
3 files changed, 142 insertions(+)
create mode 100644 tools/testing/selftests/bpf/prog_tests/module_attach_shadow.c
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index b766a84c8536..7d46e8adbc96 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -558,6 +558,11 @@ long noinline bpf_kfunc_call_test4(signed char a, short b, int c, long d)
return (long)a + (long)b + (long)c + d;
}
+int noinline bpf_fentry_shadow_test(int a)
+{
+ return a + 1;
+}
+
struct prog_test_member1 {
int a;
};
diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
index 46500636d8cd..c478b14fdea1 100644
--- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
+++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
@@ -229,6 +229,12 @@ static const struct btf_kfunc_id_set bpf_testmod_kfunc_set = {
.set = &bpf_testmod_check_kfunc_ids,
};
+noinline int bpf_fentry_shadow_test(int a)
+{
+ return a + 2;
+}
+EXPORT_SYMBOL_GPL(bpf_fentry_shadow_test);
+
extern int bpf_fentry_test1(int a);
static int bpf_testmod_init(void)
diff --git a/tools/testing/selftests/bpf/prog_tests/module_attach_shadow.c b/tools/testing/selftests/bpf/prog_tests/module_attach_shadow.c
new file mode 100644
index 000000000000..a75d2cdde928
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/module_attach_shadow.c
@@ -0,0 +1,131 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2022 Red Hat */
+#include <test_progs.h>
+#include <bpf/btf.h>
+#include "bpf/libbpf_internal.h"
+#include "cgroup_helpers.h"
+
+static const char *module_name = "bpf_testmod";
+static const char *symbol_name = "bpf_fentry_shadow_test";
+
+static int get_bpf_testmod_btf_fd(void)
+{
+ struct bpf_btf_info info;
+ char name[64];
+ __u32 id = 0, len;
+ int err, fd;
+
+ while (true) {
+ err = bpf_btf_get_next_id(id, &id);
+ if (err) {
+ log_err("failed to iterate BTF objects");
+ return err;
+ }
+
+ fd = bpf_btf_get_fd_by_id(id);
+ if (fd < 0) {
+ if (errno == ENOENT)
+ continue; /* expected race: BTF was unloaded */
+ err = -errno;
+ log_err("failed to get FD for BTF object #%d", id);
+ return err;
+ }
+
+ len = sizeof(info);
+ memset(&info, 0, sizeof(info));
+ info.name = ptr_to_u64(name);
+ info.name_len = sizeof(name);
+
+ err = bpf_obj_get_info_by_fd(fd, &info, &len);
+ if (err) {
+ err = -errno;
+ log_err("failed to get info for BTF object #%d", id);
+ close(fd);
+ return err;
+ }
+
+ if (strcmp(name, module_name) == 0)
+ return fd;
+
+ close(fd);
+ }
+ return -ENOENT;
+}
+
+void test_module_fentry_shadow(void)
+{
+ struct btf *vmlinux_btf = NULL, *mod_btf = NULL;
+ int err, i;
+ int btf_fd[2] = {};
+ int prog_fd[2] = {};
+ int link_fd[2] = {};
+ __s32 btf_id[2] = {};
+
+ const struct bpf_insn trace_program[] = {
+ BPF_MOV64_IMM(BPF_REG_0, 0),
+ BPF_EXIT_INSN(),
+ };
+
+ LIBBPF_OPTS(bpf_prog_load_opts, load_opts,
+ .expected_attach_type = BPF_TRACE_FENTRY,
+ );
+
+ LIBBPF_OPTS(bpf_test_run_opts, test_opts);
+
+ vmlinux_btf = btf__load_vmlinux_btf();
+ if (!ASSERT_OK_PTR(vmlinux_btf, "load_vmlinux_btf"))
+ return;
+
+ btf_fd[1] = get_bpf_testmod_btf_fd();
+ if (!ASSERT_GT(btf_fd[1], 0, "get_bpf_testmod_btf_fd"))
+ goto out;
+
+ mod_btf = btf_get_from_fd(btf_fd[1], vmlinux_btf);
+ if (!ASSERT_OK_PTR(mod_btf, "btf_get_from_fd"))
+ goto out;
+
+ btf_id[0] = btf__find_by_name_kind(vmlinux_btf, symbol_name, BTF_KIND_FUNC);
+ if (!ASSERT_GT(btf_id[0], 0, "btf_find_by_name"))
+ goto out;
+
+ btf_id[1] = btf__find_by_name_kind(mod_btf, symbol_name, BTF_KIND_FUNC);
+ if (!ASSERT_GT(btf_id[1], 0, "btf_find_by_name"))
+ goto out;
+
+ for (i = 0; i < 2; i++) {
+ load_opts.attach_btf_id = btf_id[i];
+ load_opts.attach_btf_obj_fd = btf_fd[i];
+ prog_fd[i] = bpf_prog_load(BPF_PROG_TYPE_TRACING, NULL, "GPL",
+ trace_program,
+ sizeof(trace_program) / sizeof(struct bpf_insn),
+ &load_opts);
+ if (!ASSERT_GE(prog_fd[i], 0, "bpf_prog_load"))
+ goto out;
+
+ // If the verifier incorrectly resolves addresses of the
+ // shadowed functions and uses the same address for both the
+ // vmlinux and the bpf_testmod functions, this will fail on
+ // attempting to create two trampolines for the same address,
+ // which is forbidden.
+ link_fd[i] = bpf_link_create(prog_fd[i], 0, BPF_TRACE_FENTRY, NULL);
+ if (!ASSERT_GE(link_fd[i], 0, "bpf_link_create"))
+ goto out;
+ }
+
+ err = bpf_prog_test_run_opts(prog_fd[0], &test_opts);
+ ASSERT_OK(err, "running test");
+
+out:
+ if (vmlinux_btf)
+ btf__free(vmlinux_btf);
+ if (mod_btf)
+ btf__free(mod_btf);
+ for (i = 0; i < 2; i++) {
+ if (btf_fd[i])
+ close(btf_fd[i]);
+ if (prog_fd[i])
+ close(prog_fd[i]);
+ if (link_fd[i])
+ close(link_fd[i]);
+ }
+}
--
2.39.1
