libstb/secvar: add secvar api implementation

This patch provides the OPAL runtime service frontend for the host OS to
retrieve secure variables, and append new ones for processing on the
next reboot. These calls operate on the internal abstraction or utilize
the platform-provided driver hooks, and therefore this API should not
need to be updated to support changes in storage or backend drivers.

Included are the following functions:
 - opal_secvar_get()
 - opal_secvar_get_next()
 - opal_secvar_enqueue_update()

opal_secvar_get() retrieves the data blob associated with a given key.
The data buffer may be set to NULL to only query for variable size. This
runtime service only operates on the variable bank.

opal_secvar_get_next() can be used to iterate through the list of
variable keys in the variable bank. Supplying an empty key (or zero key
length) returns the key of the first variable in the variable bank.
Supplying a valid key returns the key of the next variable in sequence.

opal_secvar_enqueue_update() provides a method for the host OS to submit
a new variable for processing on next boot, by appending it to the
update bank. As this does not affect the variable bank, appending a
variable via this runtime service will not affect the output of the
previous set of functions. The update queue is only processed during
secvar initialization.

Signed-off-by: Eric Richter <erichte@linux.ibm.com>
[oliver: style fixes]
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
---
V2:
 - removed opal_secvar_backend, replaced by DT node
 - removed unnecessary argument casting
 - all calls return OPAL_RESOURCE if secvar failed to init

V3:
 - remove metadata from API parameters
 - remove opal_secvar_get_size
 - change enqueue to replace an update with a repeat name, rather
    than enqueueing the duplicate
 - change enqueue to unstage an update matching a key if size is zero
 - make all key parameters const where possible
 - rename key_size to key_buf_size in _get_next
 - fix leaking node when enqueue could not allocate the secvar

V4:
 - enqueue update now uses secvar alloc/realloc
 - use storage-defined max var size instead of hardcoded constant

ccan/list/list.h

@@ -523,4 +523,42 @@ static inline struct list_node *list_node_from_off_(void *ptr, size_t off)
 	(container_off_var(var, member) +		\
 	 check_type(var->member, struct list_node))
 
+
+#if HAVE_TYPEOF
+#define list_typeof(var) typeof(var)
+#else
+#define list_typeof(var) void *
+#endif
+
+
+/* Returns member, or NULL if at end of list. */
+static inline void *list_entry_or_null(const struct list_head *h,
+                                      const struct list_node *n,
+                                      size_t off)
+{
+       if (n == &h->n)
+               return NULL;
+       return (char *)n - off;
+}
+
+/**
+ * list_next - get the next entry in a list
+ * @h: the list_head
+ * @i: a pointer to an entry in the list.
+ * @member: the list_node member of the structure
+ *
+ * If @i was the last entry in the list, returns NULL.
+ *
+ * Example:
+ *     struct child *second;
+ *     second = list_next(&parent->children, first, list);
+ *     if (!second)
+ *             printf("No second child!\n");
+ */
+#define list_next(h, i, member)                                                \
+       ((list_typeof(i))list_entry_or_null(list_debug(h),              \
+                                           (i)->member.next,           \
+                                           list_off_var_((i), member)))
+
+
 #endif /* CCAN_LIST_H */

include/opal-api.h

@@ -222,7 +222,10 @@
 #define OPAL_MPIPL_UPDATE			173
 #define OPAL_MPIPL_REGISTER_TAG			174
 #define OPAL_MPIPL_QUERY_TAG			175
-#define OPAL_LAST				175
+#define OPAL_SECVAR_GET				176
+#define OPAL_SECVAR_GET_NEXT			177
+#define OPAL_SECVAR_ENQUEUE_UPDATE		178
+#define OPAL_LAST				178
 
 #define QUIESCE_HOLD			1 /* Spin all calls at entry */
 #define QUIESCE_REJECT			2 /* Fail all calls with OPAL_BUSY */

libstb/secvar/Makefile.inc

@@ -9,6 +9,7 @@ include $(SECVAR_DIR)/storage/Makefile.inc
 include $(SECVAR_DIR)/backend/Makefile.inc
 
 SECVAR_SRCS = secvar_main.c secvar_util.c secvar_devtree.c
+SECVAR_SRCS = secvar_main.c secvar_util.c secvar_devtree.c secvar_api.c
 SECVAR_OBJS = $(SECVAR_SRCS:%.c=%.o)
 SECVAR = $(SECVAR_DIR)/built-in.a
 

libstb/secvar/secvar_api.c

@@ -0,0 +1,158 @@
+// SPDX-License-Identifier: Apache-2.0
+/* Copyright 2019 IBM Corp. */
+
+#ifndef pr_fmt
+#define pr_fmt(fmt) "SECVAR_API: " fmt
+#endif
+
+#include <opal.h>
+#include "secvar.h"
+
+
+static int64_t opal_secvar_get(const char *key, uint64_t key_len, void *data, uint64_t *data_size)
+{
+	struct secvar_node *node;
+	int64_t rc = OPAL_SUCCESS;
+
+	if (!secvar_enabled)
+		return OPAL_UNSUPPORTED;
+	if (!secvar_ready)
+		return OPAL_RESOURCE;
+	if (!key)
+		return OPAL_PARAMETER;
+	if (key_len == 0)
+		return OPAL_PARAMETER;
+	// Data size must be set, data is optional for size query
+	if (!data_size)
+		return OPAL_PARAMETER;
+
+	node = find_secvar(key, key_len, &variable_bank);
+	if (!node)
+		return OPAL_EMPTY; // Variable not found, bail early
+
+	if (!data)
+		rc = OPAL_SUCCESS;
+	else if (*data_size < node->var->data_size)
+		rc = OPAL_PARTIAL;
+	else
+		memcpy(data, node->var->data, node->var->data_size);
+
+	*data_size = node->var->data_size;
+
+	return rc;
+}
+opal_call(OPAL_SECVAR_GET, opal_secvar_get, 4);
+
+
+static int64_t opal_secvar_get_next(char *key, uint64_t *key_len, uint64_t key_buf_size)
+{
+	struct secvar_node *node;
+
+	if (!secvar_enabled)
+		return OPAL_UNSUPPORTED;
+	if (!secvar_ready)
+		return OPAL_RESOURCE;
+	if (!key_len)
+		return OPAL_PARAMETER;
+	if (key_buf_size == 0)
+		return OPAL_PARAMETER;
+	if (*key_len > SECVAR_MAX_KEY_LEN)
+		return OPAL_PARAMETER;
+	if (*key_len > key_buf_size)
+		return OPAL_PARAMETER;
+	if (!key)
+		return OPAL_PARAMETER;
+
+	if (!is_key_empty(key, *key_len)) {
+		node = find_secvar(key, *key_len, &variable_bank);
+		if (!node)
+			return OPAL_PARAMETER;
+
+		node = list_next(&variable_bank, node, link);
+	} else {
+		node = list_top(&variable_bank, struct secvar_node, link);
+	}
+
+	if (!node)
+		return OPAL_EMPTY;
+
+	if (key_buf_size < node->var->key_len) {
+		*key_len = node->var->key_len;
+		return OPAL_PARTIAL;
+	}
+
+	*key_len = node->var->key_len;
+	memcpy(key, node->var->key, node->var->key_len);
+
+	return OPAL_SUCCESS;
+}
+opal_call(OPAL_SECVAR_GET_NEXT, opal_secvar_get_next, 3);
+
+
+static int64_t opal_secvar_enqueue_update(const char *key, uint64_t key_len, void *data, uint64_t data_size)
+{
+	struct secvar_node *node;
+
+	if (!secvar_enabled)
+		return OPAL_UNSUPPORTED;
+	if (!secvar_ready)
+		return OPAL_RESOURCE;
+	if (!secvar_storage.write_bank)
+		return OPAL_HARDWARE;
+	if (!key)
+		return OPAL_PARAMETER;
+	if (key_len == 0)
+		return OPAL_PARAMETER;
+	if (key_len > SECVAR_MAX_KEY_LEN)
+		return OPAL_PARAMETER;
+	if ((!data) && (data_size != 0))
+		return OPAL_PARAMETER;
+	if (data_size > secvar_storage.max_var_size)
+		return OPAL_PARAMETER;
+
+	// Key should not be empty
+	if (is_key_empty(key, key_len))
+		return OPAL_PARAMETER;
+
+	node = find_secvar(key, key_len, &update_bank);
+
+	// Unstage an update
+	if (data_size == 0) {
+		if (!node)
+			return OPAL_EMPTY;
+
+		if (node->var)
+			free(node->var);
+		list_del(&node->link);
+		free(node);
+		goto out;
+	}
+
+	if (node) {
+		list_del(&node->link);
+		// Realloc var if too small
+		if (node->size < data_size) {
+			if (realloc_secvar(node, data_size))
+				return OPAL_NO_MEM;
+		} else {
+			memset(node->var, 0x00, sizeof(struct secvar) + node->var->data_size);
+		}
+	} else {
+		node = alloc_secvar(data_size);
+		if (!node)
+			return OPAL_NO_MEM;
+	}
+
+	memcpy(node->var->key, key, key_len);
+	node->var->key_len = key_len;
+	memcpy(node->var->data, data, data_size);
+	node->var->data_size = data_size;
+
+	list_add_tail(&update_bank, &node->link);
+
+out:
+	secvar_storage.write_bank(&update_bank, SECVAR_UPDATE_BANK);
+
+	return OPAL_SUCCESS;
+}
+opal_call(OPAL_SECVAR_ENQUEUE_UPDATE, opal_secvar_enqueue_update, 4);