[PATCH v9 3/4] mtd: rawnand: Add support for secure regions in NAND memory
Manivannan Sadhasivam
manivannan.sadhasivam at linaro.org
Thu Apr 1 16:15:07 BST 2021
On a typical end product, a vendor may choose to secure some regions in
the NAND memory which are supposed to stay intact between FW upgrades.
The access to those regions will be blocked by a secure element like
Trustzone. So the normal world software like Linux kernel should not
touch these regions (including reading).
The regions are declared using a NAND chip DT property,
"secure-regions". So let's make use of this property in the raw NAND
core and skip access to the secure regions present in a system.
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam at linaro.org>
---
drivers/mtd/nand/raw/nand_base.c | 107 ++++++++++++++++++++++++++++++-
include/linux/mtd/rawnand.h | 14 ++++
2 files changed, 120 insertions(+), 1 deletion(-)
diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index c33fa1b1847f..c216d3eca915 100644
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -278,11 +278,50 @@ static int nand_block_bad(struct nand_chip *chip, loff_t ofs)
return 0;
}
+/**
+ * nand_region_is_secured() - Check if the region is secured
+ * @chip: NAND chip object
+ * @offset: Offset of the region to check
+ * @size: Size of the region to check
+ *
+ * Checks if the region is secured by comparing the offset and size with the
+ * list of secure regions obtained from DT. Returns true if the region is
+ * secured else false.
+ */
+static bool nand_region_is_secured(struct nand_chip *chip, loff_t offset, u64 size)
+{
+ int i;
+
+ /* Skip touching the secure regions if present */
+ for (i = 0; i < chip->nr_secure_regions; i++) {
+ const struct nand_secure_region *region = &chip->secure_regions[i];
+
+ if (offset + size <= region->offset ||
+ offset >= region->offset + region->size)
+ continue;
+
+ pr_debug("%s: Region 0x%llx - 0x%llx is secured!",
+ __func__, offset, offset + size);
+
+ return true;
+ }
+
+ return false;
+}
+
static int nand_isbad_bbm(struct nand_chip *chip, loff_t ofs)
{
+ struct mtd_info *mtd = nand_to_mtd(chip);
+ int last_page = ((mtd->erasesize - mtd->writesize) >>
+ chip->page_shift) & chip->pagemask;
+
if (chip->options & NAND_NO_BBM_QUIRK)
return 0;
+ /* Check if the region is secured */
+ if (nand_region_is_secured(chip, ofs, last_page))
+ return -EIO;
+
if (chip->legacy.block_bad)
return chip->legacy.block_bad(chip, ofs);
@@ -397,6 +436,10 @@ static int nand_do_write_oob(struct nand_chip *chip, loff_t to,
return -EINVAL;
}
+ /* Check if the region is secured */
+ if (nand_region_is_secured(chip, to, ops->ooblen))
+ return -EIO;
+
chipnr = (int)(to >> chip->chip_shift);
/*
@@ -565,6 +608,11 @@ static int nand_block_isreserved(struct mtd_info *mtd, loff_t ofs)
if (!chip->bbt)
return 0;
+
+ /* Check if the region is secured */
+ if (nand_region_is_secured(chip, ofs, 0))
+ return -EIO;
+
/* Return info from the table */
return nand_isreserved_bbt(chip, ofs);
}
@@ -3127,6 +3175,10 @@ static int nand_do_read_ops(struct nand_chip *chip, loff_t from,
int retry_mode = 0;
bool ecc_fail = false;
+ /* Check if the region is secured */
+ if (nand_region_is_secured(chip, from, readlen))
+ return -EIO;
+
chipnr = (int)(from >> chip->chip_shift);
nand_select_target(chip, chipnr);
@@ -3458,6 +3510,10 @@ static int nand_do_read_oob(struct nand_chip *chip, loff_t from,
pr_debug("%s: from = 0x%08Lx, len = %i\n",
__func__, (unsigned long long)from, readlen);
+ /* Check if the region is secured */
+ if (nand_region_is_secured(chip, from, readlen))
+ return -EIO;
+
stats = mtd->ecc_stats;
len = mtd_oobavail(mtd, ops);
@@ -3979,6 +4035,10 @@ static int nand_do_write_ops(struct nand_chip *chip, loff_t to,
return -EINVAL;
}
+ /* Check if the region is secured */
+ if (nand_region_is_secured(chip, to, writelen))
+ return -EIO;
+
column = to & (mtd->writesize - 1);
chipnr = (int)(to >> chip->chip_shift);
@@ -4180,6 +4240,10 @@ int nand_erase_nand(struct nand_chip *chip, struct erase_info *instr,
if (check_offs_len(chip, instr->addr, instr->len))
return -EINVAL;
+ /* Check if the region is secured */
+ if (nand_region_is_secured(chip, instr->addr, instr->len))
+ return -EIO;
+
/* Grab the lock and see if the device is available */
ret = nand_get_device(chip);
if (ret)
@@ -4995,6 +5059,31 @@ static bool of_get_nand_on_flash_bbt(struct device_node *np)
return of_property_read_bool(np, "nand-on-flash-bbt");
}
+static int of_get_nand_secure_regions(struct nand_chip *chip)
+{
+ struct device_node *dn = nand_get_flash_node(chip);
+ int nr_elem, i, j;
+
+ nr_elem = of_property_count_elems_of_size(dn, "secure-regions", sizeof(u64));
+ if (!nr_elem)
+ return 0;
+
+ chip->nr_secure_regions = nr_elem / 2;
+ chip->secure_regions = kcalloc(chip->nr_secure_regions, sizeof(*chip->secure_regions),
+ GFP_KERNEL);
+ if (!chip->secure_regions)
+ return -ENOMEM;
+
+ for (i = 0, j = 0; i < chip->nr_secure_regions; i++, j += 2) {
+ of_property_read_u64_index(dn, "secure-regions", j,
+ &chip->secure_regions[i].offset);
+ of_property_read_u64_index(dn, "secure-regions", j + 1,
+ &chip->secure_regions[i].size);
+ }
+
+ return 0;
+}
+
static int rawnand_dt_init(struct nand_chip *chip)
{
struct nand_device *nand = mtd_to_nanddev(nand_to_mtd(chip));
@@ -5953,6 +6042,16 @@ static int nand_scan_tail(struct nand_chip *chip)
goto err_free_interface_config;
}
+ /*
+ * Look for secure regions in the NAND chip. These regions are supposed
+ * to be protected by a secure element like Trustzone. So the read/write
+ * accesses to these regions will be blocked in the runtime by this
+ * driver.
+ */
+ ret = of_get_nand_secure_regions(chip);
+ if (ret)
+ goto err_free_interface_config;
+
/* Check, if we should skip the bad block table scan */
if (chip->options & NAND_SKIP_BBTSCAN)
return 0;
@@ -5960,10 +6059,13 @@ static int nand_scan_tail(struct nand_chip *chip)
/* Build bad block table */
ret = nand_create_bbt(chip);
if (ret)
- goto err_free_interface_config;
+ goto err_free_secure_regions;
return 0;
+err_free_secure_regions:
+ kfree(chip->secure_regions);
+
err_free_interface_config:
kfree(chip->best_interface_config);
@@ -6051,6 +6153,9 @@ void nand_cleanup(struct nand_chip *chip)
nanddev_cleanup(&chip->base);
+ /* Free secure regions data */
+ kfree(chip->secure_regions);
+
/* Free bad block table memory */
kfree(chip->bbt);
kfree(chip->data_buf);
diff --git a/include/linux/mtd/rawnand.h b/include/linux/mtd/rawnand.h
index 6b3240e44310..17ddc900a1dc 100644
--- a/include/linux/mtd/rawnand.h
+++ b/include/linux/mtd/rawnand.h
@@ -1036,6 +1036,16 @@ struct nand_manufacturer {
void *priv;
};
+/**
+ * struct nand_secure_region - NAND secure region structure
+ * @offset: Offset of the start of the secure region
+ * @size: Size of the secure region
+ */
+struct nand_secure_region {
+ u64 offset;
+ u64 size;
+};
+
/**
* struct nand_chip - NAND Private Flash Chip Data
* @base: Inherit from the generic NAND device
@@ -1086,6 +1096,8 @@ struct nand_manufacturer {
* NAND Controller drivers should not modify this value, but they're
* allowed to read it.
* @read_retries: The number of read retry modes supported
+ * @secure_regions: Structure containing the secure regions info
+ * @nr_secure_regions: Number of secure regions
* @controller: The hardware controller structure which is shared among multiple
* independent devices
* @ecc: The ECC controller structure
@@ -1135,6 +1147,8 @@ struct nand_chip {
unsigned int suspended : 1;
int cur_cs;
int read_retries;
+ struct nand_secure_region *secure_regions;
+ u8 nr_secure_regions;
/* Externals */
struct nand_controller *controller;
--
2.25.1
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