bpf: fix selftests/bpf test_kmod.sh failure when CONFIG_BPF_JIT_ALWAYS_ON=y

With CONFIG_BPF_JIT_ALWAYS_ON is defined in the config file,
tools/testing/selftests/bpf/test_kmod.sh failed like below:
[root@localhost bpf]# ./test_kmod.sh
sysctl: setting key "net.core.bpf_jit_enable": Invalid argument
[ JIT enabled:0 hardened:0 ]
[ 132.175681] test_bpf: #297 BPF_MAXINSNS: Jump, gap, jump, ... FAIL to prog_create err=-524 len=4096
[ 132.458834] test_bpf: Summary: 348 PASSED, 1 FAILED, [340/340 JIT'ed]
[ JIT enabled:1 hardened:0 ]
[ 133.456025] test_bpf: #297 BPF_MAXINSNS: Jump, gap, jump, ... FAIL to prog_create err=-524 len=4096
[ 133.730935] test_bpf: Summary: 348 PASSED, 1 FAILED, [340/340 JIT'ed]
[ JIT enabled:1 hardened:1 ]
[ 134.769730] test_bpf: #297 BPF_MAXINSNS: Jump, gap, jump, ... FAIL to prog_create err=-524 len=4096
[ 135.050864] test_bpf: Summary: 348 PASSED, 1 FAILED, [340/340 JIT'ed]
[ JIT enabled:1 hardened:2 ]
[ 136.442882] test_bpf: #297 BPF_MAXINSNS: Jump, gap, jump, ... FAIL to prog_create err=-524 len=4096
[ 136.821810] test_bpf: Summary: 348 PASSED, 1 FAILED, [340/340 JIT'ed]
[root@localhost bpf]#

The test_kmod.sh load/remove test_bpf.ko multiple times with different
settings for sysctl net.core.bpf_jit_{enable,harden}. The failed test #297
of test_bpf.ko is designed such that JIT always fails.

Commit 290af86629b2 (bpf: introduce BPF_JIT_ALWAYS_ON config)
introduced the following tightening logic:
...
if (!bpf_prog_is_dev_bound(fp->aux)) {
fp = bpf_int_jit_compile(fp);
#ifdef CONFIG_BPF_JIT_ALWAYS_ON
if (!fp->jited) {
*err = -ENOTSUPP;
return fp;
}
#endif
...
With this logic, Test #297 always gets return value -ENOTSUPP
when CONFIG_BPF_JIT_ALWAYS_ON is defined, causing the test failure.

This patch fixed the failure by marking Test #297 as expected failure
when CONFIG_BPF_JIT_ALWAYS_ON is defined.

Fixes: 290af86629b2 (bpf: introduce BPF_JIT_ALWAYS_ON config)
Signed-off-by: Yonghong Song <[e-mail]>
Signed-off-by: Daniel Borkmann <[e-mail]>

lib/test_bpf.c

···
 		__u32 result;
 	} test[MAX_SUBTESTS];
 	int (*fill_helper)(struct bpf_test *self);
+	int expected_errcode; /* used when FLAG_EXPECTED_FAIL is set in the aux */
 	__u8 frag_data[MAX_DATA];
 	int stack_depth; /* for eBPF only, since tests don't call verifier */
 };
···
 		},
 		CLASSIC | FLAG_NO_DATA | FLAG_EXPECTED_FAIL,
 		{ },
-		{ }
+		{ },
+		.fill_helper = NULL,
+		.expected_errcode = -EINVAL,
 	},
 	{
 		"check: div_k_0",
···
 		},
 		CLASSIC | FLAG_NO_DATA | FLAG_EXPECTED_FAIL,
 		{ },
-		{ }
+		{ },
+		.fill_helper = NULL,
+		.expected_errcode = -EINVAL,
 	},
 	{
 		"check: unknown insn",
···
 		},
 		CLASSIC | FLAG_EXPECTED_FAIL,
 		{ },
-		{ }
+		{ },
+		.fill_helper = NULL,
+		.expected_errcode = -EINVAL,
 	},
 	{
 		"check: out of range spill/fill",
···
 		},
 		CLASSIC | FLAG_NO_DATA | FLAG_EXPECTED_FAIL,
 		{ },
-		{ }
+		{ },
+		.fill_helper = NULL,
+		.expected_errcode = -EINVAL,
 	},
 	{
 		"JUMPS + HOLES",
···
 		CLASSIC | FLAG_NO_DATA | FLAG_EXPECTED_FAIL,
 		{ },
 		{ },
+		.fill_helper = NULL,
+		.expected_errcode = -EINVAL,
 	},
 	{
 		"check: LDX + RET X",
···
 		CLASSIC | FLAG_NO_DATA | FLAG_EXPECTED_FAIL,
 		{ },
 		{ },
+		.fill_helper = NULL,
+		.expected_errcode = -EINVAL,
 	},
 	{	/* Mainly checking JIT here. */
 		"M[]: alt STX + LDX",
···
 		CLASSIC | FLAG_NO_DATA | FLAG_EXPECTED_FAIL,
 		{ },
 		{ },
+		.fill_helper = NULL,
+		.expected_errcode = -EINVAL,
 	},
 	{	/* Passes checker but fails during runtime. */
 		"LD [SKF_AD_OFF-1]",
···
 		{ },
 		{ },
 		.fill_helper = bpf_fill_maxinsns4,
+		.expected_errcode = -EINVAL,
 	},
 	{	/* Mainly checking JIT here. */
 		"BPF_MAXINSNS: Very long jump",
···
 	{
 		"BPF_MAXINSNS: Jump, gap, jump, ...",
 		{ },
+#ifdef CONFIG_BPF_JIT_ALWAYS_ON
+		CLASSIC | FLAG_NO_DATA | FLAG_EXPECTED_FAIL,
+#else
 		CLASSIC | FLAG_NO_DATA,
+#endif
 		{ },
 		{ { 0, 0xababcbac } },
 		.fill_helper = bpf_fill_maxinsns11,
+		.expected_errcode = -ENOTSUPP,
 	},
 	{
 		"BPF_MAXINSNS: ld_abs+get_processor_id",
···
 
 		*err = bpf_prog_create(&fp, &fprog);
 		if (tests[which].aux & FLAG_EXPECTED_FAIL) {
-			if (*err == -EINVAL) {
+			if (*err == tests[which].expected_errcode) {
 				pr_cont("PASS\n");
 				/* Verifier rejected filter as expected. */
 				*err = 0;