Buggy bootloaders may pass bogus memory entries in the devicetree.
Add of_fdt_limit_memory to add an upper bound on the number of
entries that can be present in the devicetree.
Signed-off-by: Laura Abbott <lauraa@xxxxxxxxxxxxxx>
---
drivers/of/fdt.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/of_fdt.h | 1 +
2 files changed, 49 insertions(+)
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 55bfca9..fd5db5a 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -26,6 +26,54 @@
#include <asm/setup.h> /* for COMMAND_LINE_SIZE */
#include <asm/page.h>
+/*
+ * of_fdt_limit_memory - limit the number of regions in the /memory node
+ * @limit: maximum entries
+ *
+ * Adjust the flattened device tree to have at most 'limit' number of
+ * memory entries in the /memory node. This function may be called
+ * any time after initial_boot_param is set.
+ */
+void of_fdt_limit_memory(int limit)
+{
+ int memory;
+ int len;
+ const void *val;
+ int nr_address_cells = OF_ROOT_NODE_ADDR_CELLS_DEFAULT;
+ int nr_size_cells = OF_ROOT_NODE_SIZE_CELLS_DEFAULT;
+ const uint32_t *addr_prop;
+ const uint32_t *size_prop;
+ int root_offset;
+ int cell_size;
+
+ root_offset = fdt_path_offset(initial_boot_params, "/");
+ if (root_offset < 0)
+ return;
+
+ addr_prop = fdt_getprop(initial_boot_params, root_offset,
+ "#address-cells", NULL);
+ if (addr_prop)
+ nr_address_cells = fdt32_to_cpu(*addr_prop);
+
+ size_prop = fdt_getprop(initial_boot_params, root_offset,
+ "#size-cells", NULL);
+ if (size_prop)
+ nr_size_cells = fdt32_to_cpu(*size_prop);
+
+ cell_size = sizeof(uint32_t)*(nr_address_cells + nr_size_cells);
+
+ memory = fdt_path_offset(initial_boot_params, "/memory");
+ if (memory > 0) {
+ val = fdt_getprop(initial_boot_params, memory, "reg", &len);
+ if (len > limit*cell_size) {
+ len = limit*cell_size;
+ pr_debug("Limiting number of entries to %d\n", limit);
+ fdt_setprop(initial_boot_params, memory, "reg", val,
+ len);
+ }
+ }
+}
+
/**
* of_fdt_is_compatible - Return true if given node from the given blob has
* compat in its compatible list
diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
index d600993..1aea25c 100644
--- a/include/linux/of_fdt.h
+++ b/include/linux/of_fdt.h
@@ -86,6 +86,7 @@ extern void unflatten_and_copy_device_tree(void);
extern void early_init_devtree(void *);
extern void early_get_first_memblock_info(void *, phys_addr_t *);
extern u64 fdt_translate_address(const void *blob, int node_offset);
+extern void of_fdt_limit_memory(int limit);
#else /* CONFIG_OF_FLATTREE */
static inline void early_init_fdt_scan_reserved_mem(void) {}
static inline const char *of_flat_dt_get_machine_name(void) { return NULL; }
--
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