[PATCH v21 28/28] docs: x86/sgx: Document the enclave API

[Jarkko Sakkinen]

Document the enclave driver API i.e. the set of ioctl's used to create
and manage enclaves and set their privileges

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
---
 Documentation/x86/sgx/3.API.rst | 27 +++++++++++++++++++++++++++
 Documentation/x86/sgx/index.rst |  1 +
 2 files changed, 28 insertions(+)
 create mode 100644 Documentation/x86/sgx/3.API.rst

diff --git a/Documentation/x86/sgx/3.API.rst b/Documentation/x86/sgx/3.API.rst
new file mode 100644
index 000000000000..b113aeb05f54
--- /dev/null
+++ b/Documentation/x86/sgx/3.API.rst
@@ -0,0 +1,27 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===
+API
+===
+
+The enclave life-cycle starts by opening `/dev/sgx/enclave`. After this there is
+already a data structure inside kernel tracking the enclave that is initially
+uncreated. After this a set of ioctl's can be used to create, populate and
+initialize the enclave.
+
+You can close (if you want) the fd after you've mmap()'d. As long as the file is
+open the enclave stays alive so you might want to do that after you don't need
+it anymore. Even munmap() won't destruct the enclave if the file is open.
+Neither will closing the fd as long as you have mmap() done over the fd (even
+if it does not across the range defined in SECS).
+
+Finally, there is ioctl to authorize priviliged attributes:
+`SGX_IOC_ENCLAVE_SET_ATTRIBUTE`. Each of them is presented by a file inside
+`/dev/sgx/`. Right now there is only one such file `/dev/sgx/provision`, which
+controls the `PROVISON_KEY` attribute.
+
+.. kernel-doc:: arch/x86/kernel/cpu/sgx/driver/ioctl.c
+   :functions: sgx_ioc_enclave_create
+               sgx_ioc_enclave_add_page
+               sgx_ioc_enclave_init
+               sgx_ioc_enclave_set_attribute
diff --git a/Documentation/x86/sgx/index.rst b/Documentation/x86/sgx/index.rst
index 5d660e83d984..de0b78328611 100644
--- a/Documentation/x86/sgx/index.rst
+++ b/Documentation/x86/sgx/index.rst
@@ -15,3 +15,4 @@ potentially malicious.
 
    1.Architecture
    2.Kernel-internals
+   3.API
-- 
2.20.1