KEYCTL_LINK
Creates a link from the keyring to the key. Arguments
ecx | Key serial number.
edx | Keyring serial number. It may be one of the following special values:
`KEY_SPEC_THREAD_KEYRING` | `Caller's thread-specific keyring.`
`KEY_SPEC_PROCESS_KEYRING` | `Caller's process-specific keyring.`
`KEY_SPEC_SESSION_KEYRING` | `Caller's session-specific keyring.`
`KEY_SPEC_USER_KEYRING` | `Caller's UID-specific keyring.`
`KEY_SPEC_USER_SESSION_KEYRING` | `Caller's UID-session keyring.`
`KEY_SPEC_GROUP_KEYRING` | `Caller's GID-specific keyring.`
`KEY_SPEC_REQKEY_AUTH_KEY` | `This specifies the authorization key created by request_key() and passed to the process it spawns to generate a key. If a valid keyring ID is passed in, then this will simply be returned if the key exists; an error will be issued if it doesn't exist.`
Return values If the system call succeeds the return value is 0. If the system call fails the return value is one of the following errno values:
`-ENOKEY` | `No matching key or keyring was found.`
`-EKEYEXPIRED` | `The keyring specified has expired.`
`-EKEYREVOKED` | `The keyring specified had been revoked.`
`-EACCES` | `The keyring exists, but is not writable or linkable by the calling process.`
`-ENOMEM` | `Insufficient memory to create a key.`
`-EDQUOT` | `Expanding the keyring would exceed the keyring owner's quota.`
`-ENOTDIR` | `edx is not a valid keyring.`
`-ENFILE` | `Keyring is full.`
`-ELOOP` | `Nesting of the keyrings is too deep.`
`-EDEADLK` | `The link would introduce a cycle in the current nesting of the keyrings.`
Remarks The process must have write permission on the keyring and must have link permission on the key.