nvmem: rmem: add CRC validation for Mobileye EyeQ5 NVMEM

Mobileye EyeQ5 has a non-volatile memory region which
gets used to store MAC addresses. Its format includes
a prefix 12-byte header and a suffix 4-byte CRC.

Add an optional ->checksum() callback inside match data;
it runs CRC32 onto the content.

Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20241230143035.265518-7-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/nvmem/rmem.c b/drivers/nvmem/rmem.c
index ca89c2689031534ff316a48e03360aeec823b025..b39d628cb60a1c657f8a71df9e50f428d2662a53 100644 (file)
--- a/drivers/nvmem/rmem.c
+++ b/drivers/nvmem/rmem.c
@@ -3,11 +3,13 @@
  * Copyright (C) 2020 Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
  */
 
+#include <linux/crc32.h>
 #include <linux/io.h>
 #include <linux/module.h>
 #include <linux/nvmem-provider.h>
 #include <linux/of_reserved_mem.h>
 #include <linux/platform_device.h>
+#include <linux/slab.h>
 
 struct rmem {
        struct device *dev;
@@ -15,6 +17,18 @@ struct rmem {
        struct reserved_mem *mem;
 };
 
+struct rmem_match_data {
+       int (*checksum)(struct rmem *priv);
+};
+
+struct __packed rmem_eyeq5_header {
+       u32 magic;
+       u32 version;
+       u32 size;
+};
+
+#define RMEM_EYEQ5_MAGIC       ((u32)0xDABBAD00)
+
 static int rmem_read(void *context, unsigned int offset,
                     void *val, size_t bytes)
 {
@@ -47,10 +61,66 @@ static int rmem_read(void *context, unsigned int offset,
        return 0;
 }
 
+static int rmem_eyeq5_checksum(struct rmem *priv)
+{
+       void *buf __free(kfree) = NULL;
+       struct rmem_eyeq5_header header;
+       u32 computed_crc, *target_crc;
+       size_t data_size;
+       int ret;
+
+       ret = rmem_read(priv, 0, &header, sizeof(header));
+       if (ret)
+               return ret;
+
+       if (header.magic != RMEM_EYEQ5_MAGIC)
+               return -EINVAL;
+
+       /*
+        * Avoid massive kmalloc() if header read is invalid;
+        * the check would be done by the next rmem_read() anyway.
+        */
+       if (header.size > priv->mem->size)
+               return -EINVAL;
+
+       /*
+        *           0 +-------------------+
+        *             | Header (12 bytes) | \
+        *             +-------------------+ |
+        *             |                   | | data to be CRCed
+        *             |        ...        | |
+        *             |                   | /
+        *   data_size +-------------------+
+        *             |   CRC (4 bytes)   |
+        * header.size +-------------------+
+        */
+
+       buf = kmalloc(header.size, GFP_KERNEL);
+       if (!buf)
+               return -ENOMEM;
+
+       ret = rmem_read(priv, 0, buf, header.size);
+       if (ret)
+               return ret;
+
+       data_size = header.size - sizeof(*target_crc);
+       target_crc = buf + data_size;
+       computed_crc = crc32(U32_MAX, buf, data_size) ^ U32_MAX;
+
+       if (computed_crc == *target_crc)
+               return 0;
+
+       dev_err(priv->dev,
+               "checksum failed: computed %#x, expected %#x, header (%#x, %#x, %#x)\n",
+               computed_crc, *target_crc, header.magic, header.version, header.size);
+       return -EINVAL;
+}
+
 static int rmem_probe(struct platform_device *pdev)
 {
        struct nvmem_config config = { };
        struct device *dev = &pdev->dev;
+       const struct rmem_match_data *match_data = device_get_match_data(dev);
        struct reserved_mem *mem;
        struct rmem *priv;
 
@@ -73,10 +143,22 @@ static int rmem_probe(struct platform_device *pdev)
        config.size = mem->size;
        config.reg_read = rmem_read;
 
+       if (match_data && match_data->checksum) {
+               int ret = match_data->checksum(priv);
+
+               if (ret)
+                       return ret;
+       }
+
        return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &config));
 }
 
+static const struct rmem_match_data rmem_eyeq5_match_data = {
+       .checksum = rmem_eyeq5_checksum,
+};
+
 static const struct of_device_id rmem_match[] = {
+       { .compatible = "mobileye,eyeq5-bootloader-config", .data = &rmem_eyeq5_match_data },
        { .compatible = "nvmem-rmem", },
        { /* sentinel */ },
 };