[PATCH PREVIEW RFC 5/6] base: bootcache: Add bootcache memory backend

[acampanella-thegoodpenguin <acampanella@thegoodpenguin.co.uk>]

From: Marc Kelly <mkelly@thegoodpenguin.co.uk>

bootcache_backend_memory provides a simple memory based backend that can
inject data found stored in a reserved-memory block into the bootcache
framework.

Signed-off-by: Marc Kelly <mkelly@thegoodpenguin.co.uk>
---
 drivers/base/Kconfig                    |   7 +
 drivers/base/Makefile                   |   1 +
 drivers/base/bootcache_backend_memory.c | 220 ++++++++++++++++++++++++++++++++
 3 files changed, 228 insertions(+)

diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index 1303364993ff4bf7fbbc210243dc6dc48fb1bd83..00c0ea6fa31f2d9a8863c93218a4db7ff87f9c0a 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -95,6 +95,13 @@ config BOOTCACHE
 		  A simple backend for testing and development.
 		  It does not persist any data externally.
 
+	config BOOTCACHE_BACKEND_MEMORY
+		bool "Memory backend"
+		help
+		  A backend that reads the cache data from reserved system memory.
+		  The reserved memory block is defined in the device tree and is
+		  assumed to be populated by the bootloader.
+
 	endchoice
 	endif
 
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index dc87c21cd79468045878c4b3cef5714c12f65ec4..d818e72df290e6772297345efc71082adc04e1f2 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -10,6 +10,7 @@ obj-y			:= component.o core.o bus.o dd.o syscore.o \
 obj-$(CONFIG_AUXILIARY_BUS) += auxiliary.o
 obj-$(CONFIG_BOOTCACHE)    += bootcache.o
 obj-$(CONFIG_BOOTCACHE_BACKEND_TEST)    += bootcache_backend_test.o
+obj-$(CONFIG_BOOTCACHE_BACKEND_MEMORY)    += bootcache_backend_memory.o
 obj-$(CONFIG_DEVTMPFS)	+= devtmpfs.o
 obj-y			+= power/
 obj-$(CONFIG_ISA_BUS_API)	+= isa.o
diff --git a/drivers/base/bootcache_backend_memory.c b/drivers/base/bootcache_backend_memory.c
new file mode 100644
index 0000000000000000000000000000000000000000..d7a83ce2725bc7aa5f37d5fc3dcd7bea753e4d68
--- /dev/null
+++ b/drivers/base/bootcache_backend_memory.c
@@ -0,0 +1,220 @@
+// SPDX-License-Identifier: GPL-2.0
+#define DEBUG 1
+#include <linux/unaligned.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/hashtable.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/of_reserved_mem.h>
+#include <linux/platform_device.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/kobject.h>
+#include <linux/sysfs.h>
+
+#include <linux/bootcache.h>
+
+#define DRIVER_NAME "bootcache_memory_backend"
+#define BOOTCACHE_MAGIC ('B' << 24 | 'C' << 16 | 'H' << 8 | 'E')
+#define BOOTCACHE_MINSIZE 4096
+
+/*
+ * This defines a cache entry as stored.
+ */
+struct cache_memory_store_entry {
+	u32 key_length;
+	u32 data_length;
+	u8 data_type;
+	u8 data[];
+} __packed;
+
+/*
+ * The in memory store of multiple cache entries.
+ */
+struct cache_memory_store {
+	u32 magic;
+	u32 entry_count;
+	struct cache_memory_store_entry entries[];
+} __packed;
+
+struct reserved_mem *rmem;
+
+/*
+ * This function processes the loaded data and adds each entry to the
+ * system cache via the callbck.
+ */
+static int memory_backend_load_cache(void)
+{
+	const struct cache_memory_store *store;
+	const u8 *current_ptr;
+	const void *max_address;
+	u32 entry_count;
+	int i;
+	int ret;
+
+	if (!rmem) {
+		pr_warn("%s: No bootcache was found\n", DRIVER_NAME);
+		return 0;
+	}
+
+	store = ioremap(rmem->base, rmem->size);
+	if (!store) {
+		pr_warn("%s: Unable to map reserved memory 0x%llx\n", DRIVER_NAME, rmem->base);
+		return -ENOMEM;
+	}
+	max_address = store + rmem->size;
+	current_ptr = (const unsigned char *)store->entries;
+	entry_count = get_unaligned(&store->entry_count);
+
+	for (i = 0; i < entry_count; i++) {
+		struct cache_memory_store_entry *entry;
+		struct bootcache_entry *new_entry = NULL;
+		size_t data_length, key_length;
+		u8 *src, *dest;
+		int j;
+
+		entry = (struct cache_memory_store_entry *)current_ptr;
+		data_length = get_unaligned(&entry->data_length);
+		key_length = get_unaligned(&entry->key_length);
+
+		/* Check if will go outside the bounds */
+		if ((current_ptr + sizeof(struct cache_memory_store_entry) +
+				data_length + key_length + 1) > max_address) {
+			ret = -ENOMEM;
+			goto error;
+		}
+
+		new_entry = kzalloc(sizeof(*new_entry), GFP_KERNEL);
+		if (!new_entry) {
+			ret = -ENOMEM;
+			goto error;
+		}
+
+		new_entry->len = data_length;
+		new_entry->key = kzalloc(key_length+1, GFP_KERNEL);
+		new_entry->data = kzalloc(data_length, GFP_KERNEL);
+
+		if (!new_entry->key || !new_entry->data) {
+			pr_err("%s: Memory Allocation error creating new_entry data\n",
+				DRIVER_NAME);
+			kfree(new_entry->key);
+			kfree(new_entry->data);
+			kfree(new_entry);
+			ret = -ENOMEM;
+			goto error;
+		}
+		/*
+		 * Source data is potentially unaligned, so we copy it with the correct
+		 * access functions
+		 */
+		src = &entry->data[0];
+		dest = new_entry->key;
+		for (j = 0; j < key_length; j++)
+			*dest++ = get_unaligned(src++);
+
+		src = &entry->data[key_length+1];
+		dest = new_entry->data;
+		for (j = 0; j < data_length; j++)
+			*dest++ = get_unaligned(src++);
+
+		pr_debug("%s: Setting up Entry (%d) with key: %s, data length is %zu\n",
+			DRIVER_NAME, i, new_entry->key, new_entry->len);
+
+		/* call the framework provided function */
+		ret = bootcache_add_entry(new_entry);
+		if (ret) {
+			kfree(new_entry->key);
+			kfree(new_entry->data);
+			kfree(new_entry);
+			ret = 0;
+		}
+
+		/* Sanity check we've got space for the next extry */
+
+		current_ptr += sizeof(struct cache_memory_store_entry) +
+			data_length + key_length + 1;
+		if (current_ptr + sizeof(struct cache_memory_store_entry)
+				> max_address) {
+			ret = ret = -ENOMEM;
+			goto error;
+		}
+	}
+
+error:
+	if (store)
+		iounmap((void *)store);
+
+	return ret;
+}
+
+static struct bootcache_info cache_info = {
+	.name = "memory",
+	.load_cache = memory_backend_load_cache,
+};
+
+static int bootcache_backend_probe(struct platform_device *pdev)
+{
+	int ret;
+	size_t table_size;
+	struct cache_memory_store *temp_store;
+	struct device_node *reserved_mem_node;
+
+	/* Check for the front end being ready */
+
+	pr_debug("%s: %s\n", DRIVER_NAME, __func__);
+
+	reserved_mem_node = of_parse_phandle(pdev->dev.of_node, "memory-region", 0);
+	if (reserved_mem_node) {
+		rmem = of_reserved_mem_lookup(reserved_mem_node);
+		of_node_put(reserved_mem_node);
+	}
+
+	if (!rmem) {
+		pr_err("%s: Failed to find reserved memory region.\n", DRIVER_NAME);
+		return -ENOMEM;
+	}
+	pr_debug("%s: Found reserved cache memory block (%s):\n", DRIVER_NAME, rmem->name);
+	pr_debug("%s:  Physical Address: 0x%llx\n", DRIVER_NAME, rmem->base);
+	pr_debug("%s:  Size: 0x%llx (%llu bytes)\n", DRIVER_NAME, rmem->size,
+		rmem->size);
+
+	if (rmem->size < BOOTCACHE_MINSIZE) {
+		pr_err("%s: reserved memory too small (%llu bytes)\n", DRIVER_NAME, rmem->size);
+		return -ENOMEM;
+	}
+
+	ret = bootcache_register_backend(&cache_info);
+
+	if (ret < 0) {
+		pr_err("%s: bootcache_register_backend() failed with error %d\n",
+			DRIVER_NAME, ret);
+		return ret;
+	}
+	pr_info("%s: Backend loaded\n", DRIVER_NAME);
+
+	return 0;
+}
+
+static const struct of_device_id bootcache_backend_driver_dt_ids[] = {
+	{ .compatible = "linux,backend-backend-memory", },
+	{ }
+};
+
+static struct platform_driver bootcache_memory_platform_driver = {
+	.probe		= bootcache_backend_probe,
+	.driver		= {
+		.name	= DRIVER_NAME,
+		.of_match_table = of_match_ptr(bootcache_backend_driver_dt_ids),
+	},
+};
+
+static int __init bootcache_backend_init(void)
+{
+	return platform_driver_register(&bootcache_memory_platform_driver);
+}
+
+core_initcall(bootcache_backend_init);

-- 
2.48.1