linux-kernel - [PATCHv2 58/59] x86/mktme: Document the MKTME API for anonymous memory encryption

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Message-Id: <20190731150813.26289-59-kirill.shutemov@linux.intel.com>
Date:   Wed, 31 Jul 2019 18:08:12 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...capital.net>,
        David Howells <dhowells@...hat.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Kai Huang <kai.huang@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Alison Schofield <alison.schofield@...el.com>,
        linux-mm@...ck.org, kvm@...r.kernel.org, keyrings@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCHv2 58/59] x86/mktme: Document the MKTME API for anonymous memory encryption

From: Alison Schofield <alison.schofield@...el.com>

Signed-off-by: Alison Schofield <alison.schofield@...el.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 Documentation/x86/mktme/index.rst         |  1 +
 Documentation/x86/mktme/mktme_encrypt.rst | 56 +++++++++++++++++++++++
 2 files changed, 57 insertions(+)
 create mode 100644 Documentation/x86/mktme/mktme_encrypt.rst

diff --git a/Documentation/x86/mktme/index.rst b/Documentation/x86/mktme/index.rst
index 8cf2b7d62091..ca3c76adc596 100644
--- a/Documentation/x86/mktme/index.rst
+++ b/Documentation/x86/mktme/index.rst
@@ -9,3 +9,4 @@ Multi-Key Total Memory Encryption (MKTME)
    mktme_mitigations
    mktme_configuration
    mktme_keys
+   mktme_encrypt
diff --git a/Documentation/x86/mktme/mktme_encrypt.rst b/Documentation/x86/mktme/mktme_encrypt.rst
new file mode 100644
index 000000000000..6dc8ae11f1cb
--- /dev/null
+++ b/Documentation/x86/mktme/mktme_encrypt.rst
@@ -0,0 +1,56 @@
+MKTME API: system call encrypt_mprotect()
+=========================================
+
+Synopsis
+--------
+int encrypt_mprotect(void \*addr, size_t len, int prot, key_serial_t serial);
+
+Where *key_serial_t serial* is the serial number of a key allocated
+using the MKTME Key Service.
+
+Description
+-----------
+    encrypt_mprotect() encrypts the memory pages containing any part
+    of the address range in the interval specified by addr and len.
+
+    encrypt_mprotect() supports the legacy mprotect() behavior plus
+    the enabling of memory encryption. That means that in addition
+    to encrypting the memory, the protection flags will be updated
+    as requested in the call.
+
+    The *addr* and *len* must be aligned to a page boundary.
+
+    The caller must have *KEY_NEED_VIEW* permission on the key.
+
+    The memory that is to be protected must be mapped *ANONYMOUS*.
+
+Errors
+------
+    In addition to the Errors returned from legacy mprotect()
+    encrypt_mprotect will return:
+
+    ENOKEY *serial* parameter does not represent a valid key.
+
+    EINVAL *len* parameter is not page aligned.
+
+    EACCES Caller does not have *KEY_NEED_VIEW* permission on the key.
+
+EXAMPLE
+--------
+  Allocate an MKTME Key::
+        serial = add_key("mktme", "name", "type=cpu algorithm=aes-xts-128" @u
+
+  Map ANONYMOUS memory::
+        ptr = mmap(NULL, size, PROT_NONE, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
+
+  Protect memory::
+        ret = syscall(SYS_encrypt_mprotect, ptr, size, PROT_READ|PROT_WRITE,
+                      serial);
+
+  Use the encrypted memory
+
+  Free memory::
+        ret = munmap(ptr, size);
+
+  Free the key resource::
+        ret = keyctl(KEYCTL_INVALIDATE, serial);
-- 
2.21.0