[RFC v2 04/13] x86/mm: Add helper functions for MKTME memory encryption keys

[Alison Schofield <alison.schofield@intel.com>]

Define a global mapping structure to manage the mapping of userspace
Keys to hardware KeyIDs in MKTME (Multi-Key Total Memory Encryption).
Implement helper functions that access this mapping structure.

The helpers will be used by these MKTME API's:
 >  Key Service API: security/keys/mktme_keys.c
 >  encrypt_mprotect() system call: mm/mprotect.c

Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/include/asm/mktme.h | 12 ++++++
 arch/x86/mm/mktme.c          | 91 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 103 insertions(+)

diff --git a/arch/x86/include/asm/mktme.h b/arch/x86/include/asm/mktme.h
index f05baa15e6f6..dbb49909d665 100644
--- a/arch/x86/include/asm/mktme.h
+++ b/arch/x86/include/asm/mktme.h
@@ -12,6 +12,18 @@ extern phys_addr_t mktme_keyid_mask;
 extern int mktme_nr_keyids;
 extern int mktme_keyid_shift;
 
+/* Manage mappings between hardware KeyIDs and userspace Keys */
+extern int mktme_map_alloc(void);
+extern void mktme_map_free(void);
+extern void mktme_map_lock(void);
+extern void mktme_map_unlock(void);
+extern int mktme_map_mapped_keyids(void);
+extern void mktme_map_set_keyid(int keyid, void *key);
+extern void mktme_map_free_keyid(int keyid);
+extern int mktme_map_keyid_from_key(void *key);
+extern void *mktme_map_key_from_keyid(int keyid);
+extern int mktme_map_get_free_keyid(void);
+
 DECLARE_STATIC_KEY_FALSE(mktme_enabled_key);
 static inline bool mktme_enabled(void)
 {
diff --git a/arch/x86/mm/mktme.c b/arch/x86/mm/mktme.c
index c81727540e7c..34224d4e3f45 100644
--- a/arch/x86/mm/mktme.c
+++ b/arch/x86/mm/mktme.c
@@ -40,6 +40,97 @@ int __vma_keyid(struct vm_area_struct *vma)
 	return (prot & mktme_keyid_mask) >> mktme_keyid_shift;
 }
 
+/*
+ * struct mktme_map and the mktme_map_* functions manage the mapping
+ * of userspace Keys to hardware KeyIDs. These are used by the MKTME Key
+ * Service API and the encrypt_mprotect() system call.
+ */
+
+struct mktme_mapping {
+	struct mutex	lock;		/* protect this map & HW state */
+	unsigned int	mapped_keyids;
+	void		*key[];
+};
+
+struct mktme_mapping *mktme_map;
+
+static inline long mktme_map_size(void)
+{
+	long size = 0;
+
+	size += sizeof(*mktme_map);
+	size += sizeof(mktme_map->key[0]) * (mktme_nr_keyids + 1);
+	return size;
+}
+
+int mktme_map_alloc(void)
+{
+	mktme_map = kvzalloc(mktme_map_size(), GFP_KERNEL);
+	if (!mktme_map)
+		return 0;
+	mutex_init(&mktme_map->lock);
+	return 1;
+}
+
+void mktme_map_free(void)
+{
+	kvfree(mktme_map);
+}
+
+void mktme_map_lock(void)
+{
+	mutex_lock(&mktme_map->lock);
+}
+
+void mktme_map_unlock(void)
+{
+	mutex_unlock(&mktme_map->lock);
+}
+
+int mktme_map_mapped_keyids(void)
+{
+	return mktme_map->mapped_keyids;
+}
+
+void mktme_map_set_keyid(int keyid, void *key)
+{
+	mktme_map->key[keyid] = key;
+	mktme_map->mapped_keyids++;
+}
+
+void mktme_map_free_keyid(int keyid)
+{
+	mktme_map->key[keyid] = 0;
+	mktme_map->mapped_keyids--;
+}
+
+int mktme_map_keyid_from_key(void *key)
+{
+	int i;
+
+	for (i = 1; i <= mktme_nr_keyids; i++)
+		if (mktme_map->key[i] == key)
+			return i;
+	return 0;
+}
+
+void *mktme_map_key_from_keyid(int keyid)
+{
+	return mktme_map->key[keyid];
+}
+
+int mktme_map_get_free_keyid(void)
+{
+	int i;
+
+	if (mktme_map->mapped_keyids < mktme_nr_keyids) {
+		for (i = 1; i <= mktme_nr_keyids; i++)
+			if (mktme_map->key[i] == 0)
+				return i;
+	}
+	return 0;
+}
+
 /* Prepare page to be used for encryption. Called from page allocator. */
 void __prep_encrypted_page(struct page *page, int order, int keyid, bool zero)
 {
-- 
2.14.1