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Commit 704033ce authored by Laura Abbott's avatar Laura Abbott Committed by Grant Likely
Browse files

of: Add memory limiting function for flattened devicetrees 



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: default avatarLaura Abbott <lauraa@codeaurora.org>
Tested-by: default avatarAndreas Färber <afaerber@suse.de>
Signed-off-by: default avatarGrant Likely <grant.likely@linaro.org>
parent 4972a74b

drivers/of/fdt.c

+48 −0
Original line number Diff line number Diff line
@@ -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

include/linux/of_fdt.h

+1 −0
Original line number Diff line number Diff line
@@ -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; }