kexec: Use fdt_appendprop_addrrange() to add ima buffer to FDT

fdt_appendprop_addrrange() function adds a property, with the given name,
to the device tree at the given node offset, and also sets the address
and size of the property.  This function should be used to add
"linux,ima-kexec-buffer" property to the device tree and set the address
and size of the IMA measurement buffer, instead of using custom function.

Use fdt_appendprop_addrrange() to add  "linux,ima-kexec-buffer" property
to the device tree.  This property holds the address and size of
the IMA measurement buffer that needs to be passed from the current
kernel to the next kernel across kexec system call.

Remove custom code that is used in setup_ima_buffer() to add
"linux,ima-kexec-buffer" property to the device tree.
Co-developed-by: Prakhar Srivastava <prsriva@linux.microsoft.com>
Signed-off-by: Prakhar Srivastava <prsriva@linux.microsoft.com>
Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210221174930.27324-12-nramas@linux.microsoft.com

drivers/of/kexec.c

@@ -216,36 +216,6 @@ static void remove_ima_buffer(void *fdt, int chosen_node)
 }
 
 #ifdef CONFIG_IMA_KEXEC
-/**
- * write_number - Convert number to big-endian format
- *
- * @p:		Buffer to write the number to
- * @value:	Number to convert
- * @cells:	Number of cells
- *
- * Return: 0 on success, or negative errno on error.
- */
-static int write_number(void *p, u64 value, int cells)
-{
-	if (cells == 1) {
-		u32 tmp;
-
-		if (value > U32_MAX)
-			return -EINVAL;
-
-		tmp = cpu_to_be32(value);
-		memcpy(p, &tmp, sizeof(tmp));
-	} else if (cells == 2) {
-		u64 tmp;
-
-		tmp = cpu_to_be64(value);
-		memcpy(p, &tmp, sizeof(tmp));
-	} else
-		return -EINVAL;
-
-	return 0;
-}
-
 /**
  * setup_ima_buffer - add IMA buffer information to the fdt
  * @image:		kexec image being loaded.
@@ -257,32 +227,15 @@ static int write_number(void *p, u64 value, int cells)
 static int setup_ima_buffer(const struct kimage *image, void *fdt,
 			    int chosen_node)
 {
-	int ret, addr_cells, size_cells, entry_size;
-	u8 value[16];
+	int ret;
 
 	if (!image->ima_buffer_size)
 		return 0;
 
-	ret = get_addr_size_cells(&addr_cells, &size_cells);
-	if (ret)
-		return ret;
-
-	entry_size = 4 * (addr_cells + size_cells);
-
-	if (entry_size > sizeof(value))
-		return -EINVAL;
-
-	ret = write_number(value, image->ima_buffer_addr, addr_cells);
-	if (ret)
-		return ret;
-
-	ret = write_number(value + 4 * addr_cells, image->ima_buffer_size,
-			   size_cells);
-	if (ret)
-		return ret;
-
-	ret = fdt_setprop(fdt, chosen_node, "linux,ima-kexec-buffer", value,
-			  entry_size);
+	ret = fdt_appendprop_addrrange(fdt, 0, chosen_node,
+				       "linux,ima-kexec-buffer",
+				       image->ima_buffer_addr,
+				       image->ima_buffer_size);
 	if (ret < 0)
 		return -EINVAL;