[PATCH v10 3/8] powerpc: Move ima buffer functions to drivers/of/kexec.c

[Lakshmi Ramasubramanian <nramas@linux.microsoft.com>]

The functions do_get_kexec_buffer() and get_addr_size_cells(),
defined in arch/powerpc/kexec/ima.c, retrieve the address and size
of the given property from the device tree blob. These functions do
not have architecture specific code, but are currently limited to
powerpc. do_get_kexec_buffer() correctly handles a device tree property
that is a child node of the root node, but not anything other than
the immediate root child nodes.

Move architecture independent functions get_ima_kexec_buffer() and
get_root_addr_size_cells() to "drivers/of/kexec.c". These functions
retrieve the chosen node "linux,ima-kexec-buffer" from the device tree,
and return the address and size of the buffer used for carrying forward
the IMA measurement log across kexec system call.

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>
---
 drivers/of/kexec.c    | 70 +++++++++++++++++++++++++++++++++++++++++++
 include/linux/kexec.h |  3 ++
 2 files changed, 73 insertions(+)

diff --git a/drivers/of/kexec.c b/drivers/of/kexec.c
index b7d59105fcb8..516b86f7113a 100644
--- a/drivers/of/kexec.c
+++ b/drivers/of/kexec.c
@@ -59,3 +59,73 @@ int delete_fdt_mem_rsv(void *fdt, unsigned long start, unsigned long size)
 
 	return -ENOENT;
 }
+
+/**
+ * get_root_addr_size_cells - Get address and size of root node
+ *
+ * @addr_cells: Return address of the root node
+ * @size_cells: Return size of the root node
+ *
+ * Return: 0 on success, or negative errno on error.
+ */
+int get_root_addr_size_cells(int *addr_cells, int *size_cells)
+{
+	struct device_node *root;
+
+	if (!IS_ENABLED(CONFIG_HAVE_IMA_KEXEC))
+		return -EOPNOTSUPP;
+
+	root = of_find_node_by_path("/");
+	if (!root)
+		return -EINVAL;
+
+	*addr_cells = of_n_addr_cells(root);
+	*size_cells = of_n_size_cells(root);
+
+	of_node_put(root);
+
+	return 0;
+}
+
+/**
+ * get_ima_kexec_buffer - Get address and size of IMA kexec buffer
+ *
+ * @fdt: Flattened Device Tree
+ * @chosen_node: Offset of chosen node in the FDT
+ * @addr: Return address of the node
+ * @size: Return size of the node
+ *
+ * Return: 0 on success, or negative errno on error.
+ */
+int get_ima_kexec_buffer(void *fdt, int chosen_node,
+			 unsigned long *addr, size_t *size)
+{
+	const void *prop;
+	int addr_cells, size_cells, prop_len;
+	int rc;
+
+	if (!IS_ENABLED(CONFIG_HAVE_IMA_KEXEC))
+		return -EOPNOTSUPP;
+
+	rc = get_root_addr_size_cells(&addr_cells, &size_cells);
+	if (rc)
+		return rc;
+
+	if (fdt)
+		prop = fdt_getprop(fdt, chosen_node,
+				   "linux,ima-kexec-buffer", &prop_len);
+	else
+		prop = of_get_property(of_chosen,
+				       "linux,ima-kexec-buffer", &prop_len);
+
+	if (!prop)
+		return -ENOENT;
+
+	if (prop_len < 4 * (addr_cells + size_cells))
+		return -EINVAL;
+
+	*addr = of_read_number(prop, addr_cells);
+	*size = of_read_number(prop + 4 * addr_cells, size_cells);
+
+	return 0;
+}
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index d0234c4815da..10ff704ab670 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -408,6 +408,9 @@ static inline int kexec_crash_loaded(void) { return 0; }
 #endif /* CONFIG_KEXEC_CORE */
 
 #if defined(CONFIG_OF_FLATTREE)
+extern int get_root_addr_size_cells(int *addr_cells, int *size_cells);
+extern int get_ima_kexec_buffer(void *fdt, int chosen_node,
+				unsigned long *addr, size_t *size);
 extern int delete_fdt_mem_rsv(void *fdt, unsigned long start,
 			      unsigned long size);
 #endif /* CONFIG_OF_FLATTREE */
-- 
2.29.2