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selftests/bpf: Test direct reading/writing read-only percpu_array map

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Verify these two cases:

1. Direct reading the data of read-only percpu data's percpu_array map
   is allowed.
2. Direct writing the data of read-only percpu data's percpu_array map
   is disallowed.

Assisted-by: Codex:gpt-5.5-xhigh
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260813152324.97937-9-leon.hwang@linux.dev
This commit is contained in:
Leon Hwang
2026-08-13 23:23:21 +08:00
committed by Andrii Nakryiko
parent 4c9241bd73
commit 3993d5beef
1 changed files with 90 additions and 0 deletions
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90
tools/testing/selftests/bpf/prog_tests/global_data_init.c
View File

@@ -236,6 +236,92 @@ static void test_global_percpu_data_lskel(void)
test_global_percpu_data_lskel__destroy(lskel);
}
static int create_rdonly_percpu_array(void)
{
LIBBPF_OPTS(bpf_map_create_opts, map_opts,
.map_flags = BPF_F_RDONLY_PROG,
);
int key = 0, map_fd, err;
__u64 value = 0;
map_fd = bpf_map_create(BPF_MAP_TYPE_PERCPU_ARRAY, "percpu_ro_map", sizeof(int),
sizeof(__u64), 1, &map_opts);
if (!ASSERT_GE(map_fd, 0, "bpf_map_create"))
return -1;
err = bpf_map_update_elem(map_fd, &key, &value, BPF_F_ALL_CPUS);
if (!ASSERT_OK(err, "bpf_map_update_elem"))
goto out;
err = bpf_map_freeze(map_fd);
if (!ASSERT_OK(err, "bpf_map_freeze"))
goto out;
return map_fd;
out:
close(map_fd);
return -1;
}
static void test_global_percpu_data_rdonly_direct_read(void)
{
/*
* Raw instructions with manually prepared rdonly percpu_array map
* for testing direct-read global percpu data, because libbpf
* doesn't have rdonly internal percpu_array map support for
* global percpu data.
*/
struct bpf_insn insns[] = {
BPF_LD_MAP_VALUE(BPF_REG_1, 0, 0),
BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, 0),
BPF_EXIT_INSN(),
};
int map_fd, prog_fd;
map_fd = create_rdonly_percpu_array();
if (map_fd < 0)
return;
insns[0].imm = map_fd;
prog_fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, "percpu_ro_prog", "GPL", insns,
ARRAY_SIZE(insns), NULL);
if (ASSERT_GE(prog_fd, 0, "bpf_prog_load"))
close(prog_fd);
close(map_fd);
}
static void test_global_percpu_data_rdonly_direct_write(void)
{
LIBBPF_OPTS(bpf_prog_load_opts, prog_opts);
/* See the comment in test_global_percpu_data_rdonly_direct_read() */
struct bpf_insn insns[] = {
BPF_LD_MAP_VALUE(BPF_REG_1, 0, 0),
BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1, 0),
BPF_ST_MEM(BPF_DW, BPF_REG_1, 0, 0),
BPF_EXIT_INSN(),
};
char log_buf[256] = {};
int map_fd, prog_fd;
prog_opts.log_buf = log_buf;
prog_opts.log_size = sizeof(log_buf);
prog_opts.log_level = 1;
map_fd = create_rdonly_percpu_array();
if (map_fd < 0)
return;
insns[0].imm = map_fd;
prog_fd = bpf_prog_load(BPF_PROG_TYPE_SOCKET_FILTER, "percpu_ro_prog", "GPL", insns,
ARRAY_SIZE(insns), &prog_opts);
if (!ASSERT_LT(prog_fd, 0, "bpf_prog_load"))
close(prog_fd);
else
ASSERT_HAS_SUBSTR(log_buf, "write into map forbidden", "verifier log");
close(map_fd);
}
void test_global_percpu_data(void)
{
if (!feat_supported(NULL, FEAT_PERCPU_DATA)) {
@@ -247,4 +333,8 @@ void test_global_percpu_data(void)
test_global_percpu_data_init();
if (test__start_subtest("lskel"))
test_global_percpu_data_lskel();
if (test__start_subtest("rdonly_direct_read"))
test_global_percpu_data_rdonly_direct_read();
if (test__start_subtest("rdonly_direct_write"))
test_global_percpu_data_rdonly_direct_write();
}