crypto: testmgr - don't generate WARN for missing modules

This userspace command:
    modprobe tcrypt
or
    modprobe tcrypt mode=0

runs all the tcrypt test cases numbered <200 (i.e., all the
test cases calling tcrypt_test() and returning return values).

Tests are sparsely numbered from 0 to 1000. For example:
    modprobe tcrypt mode=12
tests sha512, and
    modprobe tcrypt mode=152
tests rfc4543(gcm(aes))) - AES-GCM as GMAC

The test manager generates WARNING crashdumps every time it attempts
a test using an algorithm that is not available (not built-in to the
kernel or available as a module):

    alg: skcipher: failed to allocate transform for ecb(arc4): -2
    ------------[ cut here ]-----------
    alg: self-tests for ecb(arc4) (ecb(arc4)) failed (rc=-2)
    WARNING: CPU: 9 PID: 4618 at crypto/testmgr.c:5777
alg_test+0x30b/0x510
    [50 more lines....]

    ---[ end trace 0000000000000000 ]---

If the kernel is compiled with CRYPTO_USER_API_ENABLE_OBSOLETE
disabled (the default), then these algorithms are not compiled into
the kernel or made into modules and trigger WARNINGs:
    arc4 tea xtea khazad anubis xeta seed

Additionally, any other algorithms that are not enabled in .config
will generate WARNINGs. In RHEL 9.0, for example, the default
selection of algorithms leads to 16 WARNING dumps.

One attempt to fix this was by modifying tcrypt_test() to check
crypto_has_alg() and immediately return 0 if crypto_has_alg() fails,
rather than proceed and return a non-zero error value that causes
the caller (alg_test() in crypto/testmgr.c) to invoke WARN().
That knocks out too many algorithms, though; some combinations
like ctr(des3_ede) would work.

Instead, change the condition on the WARN to ignore a return
value is ENOENT, which is the value returned when the algorithm
or combination of algorithms doesn't exist. Add a pr_warn to
communicate that information in case the WARN is skipped.

This approach allows algorithm tests to work that are combinations,
not provided by one driver, like ctr(blowfish).

Result - no more WARNINGs:
modprobe tcrypt
[  115.541765] tcrypt: testing md5
[  115.556415] tcrypt: testing sha1
[  115.570463] tcrypt: testing ecb(des)
[  115.585303] cryptomgr: alg: skcipher: failed to allocate transform for ecb(des): -2
[  115.593037] cryptomgr: alg: self-tests for ecb(des) using ecb(des) failed (rc=-2)
[  115.593038] tcrypt: testing cbc(des)
[  115.610641] cryptomgr: alg: skcipher: failed to allocate transform for cbc(des): -2
[  115.618359] cryptomgr: alg: self-tests for cbc(des) using cbc(des) failed (rc=-2)
...

Signed-off-by: Robert Elliott <elliott@hpe.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/testmgr.c

@@ -5830,8 +5830,11 @@ test_done:
 			      driver, alg,
 			      fips_enabled ? "fips" : "panic_on_fail");
 		}
-		WARN(1, "alg: self-tests for %s (%s) failed (rc=%d)",
-		     driver, alg, rc);
+		pr_warn("alg: self-tests for %s using %s failed (rc=%d)",
+			alg, driver, rc);
+		WARN(rc != -ENOENT,
+		     "alg: self-tests for %s using %s failed (rc=%d)",
+		     alg, driver, rc);
 	} else {
 		if (fips_enabled)
 			pr_info("alg: self-tests for %s (%s) passed\n",