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of: Add memory limiting function for flattened devicetrees

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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>
This commit is contained in:
Laura Abbott
2014-07-15 10:03:35 -07:00
committed by Grant Likely
parent 4972a74b88
commit 704033cee2
2 changed files with 49 additions and 0 deletions
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48
drivers/of/fdt.c
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@@ -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