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authorLaura Abbott <lauraa@codeaurora.org>2014-07-15 10:03:35 -0700
committerGrant Likely <grant.likely@linaro.org>2014-07-29 21:26:45 -0600
commit704033cee2e5b3c1c6eaf5bb398e465a9c3667b5 (patch)
tree4b6e7a5ca961e3b8c82fd82295b53cca550a332a
parent4972a74b888c6b52ca41fae6076786dbbeb746d5 (diff)
downloadlinux-704033cee2e5b3c1c6eaf5bb398e465a9c3667b5.tar.gz
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: Laura Abbott <lauraa@codeaurora.org> Tested-by: Andreas Färber <afaerber@suse.de> Signed-off-by: Grant Likely <grant.likely@linaro.org>
-rw-r--r--drivers/of/fdt.c48
-rw-r--r--include/linux/of_fdt.h1
2 files changed, 49 insertions, 0 deletions
diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index ecc7a02d868..9aa012e6ea0 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 ebb2449082f..0ff360d5b3b 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; }