selftests/bpf: Add testing of log_buf==NULL condition for BPF_PROG_LOAD

Add few extra test conditions to validate that it's ok to pass
log_buf==NULL and log_size==0 to BPF_PROG_LOAD command with the intent
to get log_true_size without providing a buffer.

Test that log_buf==NULL condition *does not* return -ENOSPC.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Lorenz Bauer <lmb@isovalent.com>
Link: https://lore.kernel.org/bpf/20230406234205.323208-19-andrii@kernel.org

diff --git a/tools/testing/selftests/bpf/prog_tests/verifier_log.c b/tools/testing/selftests/bpf/prog_tests/verifier_log.c
index 2ec82fc..9ae0ac6 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/verifier_log.c
+++ b/tools/testing/selftests/bpf/prog_tests/verifier_log.c
@@ -178,26 +178,47 @@ static void verif_log_subtest(const char *name, bool expect_load_error, int log_
        opts.log_buf = logs.buf;
        opts.log_level = log_level | 8; /* BPF_LOG_FIXED */
        opts.log_size = sizeof(logs.buf);
+       opts.log_true_size = 0;
        res = load_prog(&opts, expect_load_error);
        ASSERT_NEQ(res, -ENOSPC, "prog_load_res_fixed");
 
        log_true_sz_fixed = opts.log_true_size;
        ASSERT_GT(log_true_sz_fixed, 0, "log_true_sz_fixed");
 
+       /* (FIXED, NULL) get actual log size */
+       opts.log_buf = NULL;
+       opts.log_level = log_level | 8; /* BPF_LOG_FIXED */
+       opts.log_size = 0;
+       opts.log_true_size = 0;
+       res = load_prog(&opts, expect_load_error);
+       ASSERT_NEQ(res, -ENOSPC, "prog_load_res_fixed_null");
+       ASSERT_EQ(opts.log_true_size, log_true_sz_fixed, "log_sz_fixed_null_eq");
+
        /* (ROLLING) get actual log size */
        opts.log_buf = logs.buf;
        opts.log_level = log_level;
        opts.log_size = sizeof(logs.buf);
+       opts.log_true_size = 0;
        res = load_prog(&opts, expect_load_error);
        ASSERT_NEQ(res, -ENOSPC, "prog_load_res_rolling");
 
        log_true_sz_rolling = opts.log_true_size;
        ASSERT_EQ(log_true_sz_rolling, log_true_sz_fixed, "log_true_sz_eq");
 
+       /* (ROLLING, NULL) get actual log size */
+       opts.log_buf = NULL;
+       opts.log_level = log_level;
+       opts.log_size = 0;
+       opts.log_true_size = 0;
+       res = load_prog(&opts, expect_load_error);
+       ASSERT_NEQ(res, -ENOSPC, "prog_load_res_rolling_null");
+       ASSERT_EQ(opts.log_true_size, log_true_sz_rolling, "log_true_sz_null_eq");
+
        /* (FIXED) expect -ENOSPC for one byte short log */
        opts.log_buf = logs.buf;
        opts.log_level = log_level | 8; /* BPF_LOG_FIXED */
        opts.log_size = log_true_sz_fixed - 1;
+       opts.log_true_size = 0;
        res = load_prog(&opts, true /* should fail */);
        ASSERT_EQ(res, -ENOSPC, "prog_load_res_too_short_fixed");
 
@@ -205,6 +226,7 @@ static void verif_log_subtest(const char *name, bool expect_load_error, int log_
        opts.log_buf = logs.buf;
        opts.log_level = log_level | 8; /* BPF_LOG_FIXED */
        opts.log_size = log_true_sz_fixed;
+       opts.log_true_size = 0;
        res = load_prog(&opts, expect_load_error);
        ASSERT_NEQ(res, -ENOSPC, "prog_load_res_just_right_fixed");
 
@@ -219,6 +241,7 @@ static void verif_log_subtest(const char *name, bool expect_load_error, int log_
        opts.log_buf = logs.buf;
        opts.log_level = log_level;
        opts.log_size = log_true_sz_rolling;
+       opts.log_true_size = 0;
        res = load_prog(&opts, expect_load_error);
        ASSERT_NEQ(res, -ENOSPC, "prog_load_res_just_right_rolling");