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@codeaurora.org --- 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; }