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-rw-r--r--scripts/dtc/libfdt/libfdt_internal.h122
1 files changed, 122 insertions, 0 deletions
diff --git a/scripts/dtc/libfdt/libfdt_internal.h b/scripts/dtc/libfdt/libfdt_internal.h
index 058c7358d441..d4e0bd49c037 100644
--- a/scripts/dtc/libfdt/libfdt_internal.h
+++ b/scripts/dtc/libfdt/libfdt_internal.h
@@ -48,4 +48,126 @@ static inline struct fdt_reserve_entry *fdt_mem_rsv_w_(void *fdt, int n)
#define FDT_SW_MAGIC (~FDT_MAGIC)
+/**********************************************************************/
+/* Checking controls */
+/**********************************************************************/
+
+#ifndef FDT_ASSUME_MASK
+#define FDT_ASSUME_MASK 0
+#endif
+
+/*
+ * Defines assumptions which can be enabled. Each of these can be enabled
+ * individually. For maximum safety, don't enable any assumptions!
+ *
+ * For minimal code size and no safety, use ASSUME_PERFECT at your own risk.
+ * You should have another method of validating the device tree, such as a
+ * signature or hash check before using libfdt.
+ *
+ * For situations where security is not a concern it may be safe to enable
+ * ASSUME_SANE.
+ */
+enum {
+ /*
+ * This does essentially no checks. Only the latest device-tree
+ * version is correctly handled. Inconsistencies or errors in the device
+ * tree may cause undefined behaviour or crashes. Invalid parameters
+ * passed to libfdt may do the same.
+ *
+ * If an error occurs when modifying the tree it may leave the tree in
+ * an intermediate (but valid) state. As an example, adding a property
+ * where there is insufficient space may result in the property name
+ * being added to the string table even though the property itself is
+ * not added to the struct section.
+ *
+ * Only use this if you have a fully validated device tree with
+ * the latest supported version and wish to minimise code size.
+ */
+ ASSUME_PERFECT = 0xff,
+
+ /*
+ * This assumes that the device tree is sane. i.e. header metadata
+ * and basic hierarchy are correct.
+ *
+ * With this assumption enabled, normal device trees produced by libfdt
+ * and the compiler should be handled safely. Malicious device trees and
+ * complete garbage may cause libfdt to behave badly or crash. Truncated
+ * device trees (e.g. those only partially loaded) can also cause
+ * problems.
+ *
+ * Note: Only checks that relate exclusively to the device tree itself
+ * (not the parameters passed to libfdt) are disabled by this
+ * assumption. This includes checking headers, tags and the like.
+ */
+ ASSUME_VALID_DTB = 1 << 0,
+
+ /*
+ * This builds on ASSUME_VALID_DTB and further assumes that libfdt
+ * functions are called with valid parameters, i.e. not trigger
+ * FDT_ERR_BADOFFSET or offsets that are out of bounds. It disables any
+ * extensive checking of parameters and the device tree, making various
+ * assumptions about correctness.
+ *
+ * It doesn't make sense to enable this assumption unless
+ * ASSUME_VALID_DTB is also enabled.
+ */
+ ASSUME_VALID_INPUT = 1 << 1,
+
+ /*
+ * This disables checks for device-tree version and removes all code
+ * which handles older versions.
+ *
+ * Only enable this if you know you have a device tree with the latest
+ * version.
+ */
+ ASSUME_LATEST = 1 << 2,
+
+ /*
+ * This assumes that it is OK for a failed addition to the device tree,
+ * due to lack of space or some other problem, to skip any rollback
+ * steps (such as dropping the property name from the string table).
+ * This is safe to enable in most circumstances, even though it may
+ * leave the tree in a sub-optimal state.
+ */
+ ASSUME_NO_ROLLBACK = 1 << 3,
+
+ /*
+ * This assumes that the device tree components appear in a 'convenient'
+ * order, i.e. the memory reservation block first, then the structure
+ * block and finally the string block.
+ *
+ * This order is not specified by the device-tree specification,
+ * but is expected by libfdt. The device-tree compiler always created
+ * device trees with this order.
+ *
+ * This assumption disables a check in fdt_open_into() and removes the
+ * ability to fix the problem there. This is safe if you know that the
+ * device tree is correctly ordered. See fdt_blocks_misordered_().
+ */
+ ASSUME_LIBFDT_ORDER = 1 << 4,
+
+ /*
+ * This assumes that libfdt itself does not have any internal bugs. It
+ * drops certain checks that should never be needed unless libfdt has an
+ * undiscovered bug.
+ *
+ * This can generally be considered safe to enable.
+ */
+ ASSUME_LIBFDT_FLAWLESS = 1 << 5,
+};
+
+/**
+ * can_assume_() - check if a particular assumption is enabled
+ *
+ * @mask: Mask to check (ASSUME_...)
+ * @return true if that assumption is enabled, else false
+ */
+static inline bool can_assume_(int mask)
+{
+ return FDT_ASSUME_MASK & mask;
+}
+
+/** helper macros for checking assumptions */
+#define can_assume(_assume) can_assume_(ASSUME_ ## _assume)
+
#endif /* LIBFDT_INTERNAL_H */