Re: [RFC PATCH 2/6] testing/pkeys: Don't use uninitialized variable

On Mon, Jun 13, 2022 at 03:48:56PM -0700, Mehta, Sohil wrote:

On 6/10/2022 4:35 PM, ira.weiny@intel.com wrote:

quoted

diff --git a/tools/testing/selftests/vm/protection_keys.c b/tools/testing/selftests/vm/protection_keys.c
index d0183c381859..43e47de19c0d 100644
--- a/tools/testing/selftests/vm/protection_keys.c
+++ b/tools/testing/selftests/vm/protection_keys.c

@@ -1225,9 +1225,9 @@ void test_pkey_alloc_exhaust(int *ptr, u16 pkey)
  		int new_pkey;
  		dprintf1("%s() alloc loop: %d\n", __func__, i);
  		new_pkey = alloc_pkey();
-		dprintf4("%s()::%d, err: %d pkey_reg: 0x%016llx"
+		dprintf4("%s()::%d, errno: %d pkey_reg: 0x%016llx"

What is errno referring to over here?  There are a few things happening in
alloc_pkey().

Good point, but the only system call in alloc_pkey() is pkey_alloc() so it will
be the errno from there.

In test_pkey_alloc_exhaust() we are expecting the errno to be from pkey_alloc()

...
                if ((new_pkey == -1) && (errno == ENOSPC)) {
...

I guess it would show the latest error that happened. Does
errno need to be set to 0 before the call?

Maybe.  Now that I look again errno is printed just below at level 2.

                dprintf2("%s() errno: %d ENOSPC: %d\n", __func__, errno, ENOSPC);

I missed that.

Also, would it be useful to print the return value (new_pkey) from
alloc_pkey() here?

Yea that might be useful.  Perhaps change err to new_pkey instead since errno
is already printed.

Ira

quoted

  				" shadow: 0x%016llx\n",
-				__func__, __LINE__, err, __read_pkey_reg(),
+				__func__, __LINE__, errno, __read_pkey_reg(),
  				shadow_pkey_reg);
  		read_pkey_reg(); /* for shadow checking */
  		dprintf2("%s() errno: %d ENOSPC: %d\n", __func__, errno, ENOSPC);

Sohil