fdt/wrappers: Replace fdtw_read_cells() implementation

Our fdtw_read_cells() implementation goes to great lengths to
sanity-check every parameter and result, but leaves a big hole open:
The size of the storage the value pointer points at needs to match the
number of cells given. This can't be easily checked at compile time,
since we lose the size information by using a void pointer.
Regardless the current usage of this function is somewhat wrong anyways,
since we use it on single-element, fixed-length properties only, for
which the DT binding specifies the size.
Typically we use those functions dealing with a number of cells in DT
context to deal with *dynamically* sized properties, which depend on
other properties (#size-cells, #clock-cells, ...), to specify the number
of cells needed.

Another problem with the current implementation is the use of
ambiguously sized types (uintptr_t, size_t) together with a certain
expectation about their size. In general there is no relation between
the length of a DT property and the bitness of the code that parses the
DTB: AArch64 code could encounter 32-bit addresses (where the physical
address space is limited to 4GB [1]), while AArch32 code could read
64-bit sized properties (/memory nodes on LPAE systems, [2]).

To make this more clear, fix the potential issues and also align more
with other DT users (Linux and U-Boot), introduce functions to explicitly
read uint32 and uint64 properties. As the other DT consumers, we do this
based on the generic "read array" function.
Convert all users to use either of those two new functions, and make
sure we never use a pointer to anything other than uint32_t or uint64_t
variables directly.

This reveals (and fixes) a bug in plat_spmd_manifest.c, where we write
4 bytes into a uint16_t variable (passed via a void pointer).

Also we change the implementation of the function to better align with
other libfdt users, by using the right types (fdt32_t) and common
variable names (*prop, prop_names).

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi#n874
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/ecx-2000.dts

Change-Id: I718de960515117ac7a3331a1b177d2ec224a3890
Signed-off-by: Andre Przywara <andre.przywara@arm.com>

1 files changed, 21 insertions, 49 deletions

diff --git a/common/fdt_wrappers.c b/common/fdt_wrappers.c
index 5afa14271..394f3b0ca 100644
--- a/common/fdt_wrappers.c
+++ b/common/fdt_wrappers.c
@@ -15,55 +15,6 @@
 #include <common/fdt_wrappers.h>
 
 /*
- * Read cells from a given property of the given node. At most 2 cells of the
- * property are read, and pointer is updated. Returns 0 on success, and -1 upon
- * error
- */
-int fdtw_read_cells(const void *dtb, int node, const char *prop,
-		unsigned int cells, void *value)
-{
-	const uint32_t *value_ptr;
-	uint32_t hi = 0, lo;
-	int value_len;
-
-	assert(dtb != NULL);
-	assert(prop != NULL);
-	assert(value != NULL);
-	assert(node >= 0);
-
-	/* We expect either 1 or 2 cell property */
-	assert(cells <= 2U);
-
-	/* Access property and obtain its length (in bytes) */
-	value_ptr = fdt_getprop_namelen(dtb, node, prop, (int)strlen(prop),
-			&value_len);
-	if (value_ptr == NULL) {
-		WARN("Couldn't find property %s in dtb\n", prop);
-		return -1;
-	}
-
-	/* Verify that property length accords with cell length */
-	if (NCELLS((unsigned int)value_len) != cells) {
-		WARN("Property length mismatch\n");
-		return -1;
-	}
-
-	if (cells == 2U) {
-		hi = fdt32_to_cpu(*value_ptr);
-		value_ptr++;
-	}
-
-	lo = fdt32_to_cpu(*value_ptr);
-
-	if (cells == 2U)
-		*((uint64_t *) value) = ((uint64_t) hi << 32) | lo;
-	else
-		*((uint32_t *) value) = lo;
-
-	return 0;
-}
-
-/*
  * Read cells from a given property of the given node. Any number of 32-bit
  * cells of the property can be read. Returns 0 on success, or a negative
  * FDT error value otherwise.
@@ -99,6 +50,27 @@ int fdt_read_uint32_array(const void *dtb, int node, const char *prop_name,
 	return 0;
 }
 
+int fdt_read_uint32(const void *dtb, int node, const char *prop_name,
+		    uint32_t *value)
+{
+	return fdt_read_uint32_array(dtb, node, prop_name, 1, value);
+}
+
+int fdt_read_uint64(const void *dtb, int node, const char *prop_name,
+		    uint64_t *value)
+{
+	uint32_t array[2] = {0, 0};
+	int ret;
+
+	ret = fdt_read_uint32_array(dtb, node, prop_name, 2, array);
+	if (ret < 0) {
+		return ret;
+	}
+
+	*value = ((uint64_t)array[0] << 32) | array[1];
+	return 0;
+}
+
 /*
  * Read bytes from a given property of the given node. Any number of
  * bytes of the property can be read. The fdt pointer is updated.