1 /* SPDX-License-Identifier: (GPL-2.0-or-later OR BSD-2-Clause) */
2 #ifndef LIBFDT_INTERNAL_H
3 #define LIBFDT_INTERNAL_H
4 /*
5  * libfdt - Flat Device Tree manipulation
6  * Copyright (C) 2006 David Gibson, IBM Corporation.
7  */
8 #include <fdt.h>
9 
10 #define FDT_ALIGN(x, a)		(((x) + (a) - 1) & ~((a) - 1))
11 #define FDT_TAGALIGN(x)		(FDT_ALIGN((x), FDT_TAGSIZE))
12 
13 int32_t fdt_ro_probe_(const void *fdt);
14 #define FDT_RO_PROBE(fdt)					\
15 	{							\
16 		int32_t totalsize_;				\
17 		if ((totalsize_ = fdt_ro_probe_(fdt)) < 0)	\
18 			return totalsize_;			\
19 	}
20 
21 int fdt_check_node_offset_(const void *fdt, int offset);
22 int fdt_check_prop_offset_(const void *fdt, int offset);
23 const char *fdt_find_string_(const char *strtab, int tabsize, const char *s);
24 int fdt_node_end_offset_(void *fdt, int nodeoffset);
25 
fdt_offset_ptr_(const void * fdt,int offset)26 static inline const void *fdt_offset_ptr_(const void *fdt, int offset)
27 {
28 	return (const char *)fdt + fdt_off_dt_struct(fdt) + offset;
29 }
30 
fdt_offset_ptr_w_(void * fdt,int offset)31 static inline void *fdt_offset_ptr_w_(void *fdt, int offset)
32 {
33 	return (void *)(uintptr_t)fdt_offset_ptr_(fdt, offset);
34 }
35 
fdt_mem_rsv_(const void * fdt,int n)36 static inline const struct fdt_reserve_entry *fdt_mem_rsv_(const void *fdt, int n)
37 {
38 	const struct fdt_reserve_entry *rsv_table =
39 		(const struct fdt_reserve_entry *)
40 		((const char *)fdt + fdt_off_mem_rsvmap(fdt));
41 
42 	return rsv_table + n;
43 }
fdt_mem_rsv_w_(void * fdt,int n)44 static inline struct fdt_reserve_entry *fdt_mem_rsv_w_(void *fdt, int n)
45 {
46 	return (void *)(uintptr_t)fdt_mem_rsv_(fdt, n);
47 }
48 
49 #define FDT_SW_MAGIC		(~FDT_MAGIC)
50 
51 /**********************************************************************/
52 /* Checking controls                                                  */
53 /**********************************************************************/
54 
55 #ifndef FDT_ASSUME_MASK
56 #define FDT_ASSUME_MASK 0
57 #endif
58 
59 /*
60  * Defines assumptions which can be enabled. Each of these can be enabled
61  * individually. For maximum safety, don't enable any assumptions!
62  *
63  * For minimal code size and no safety, use ASSUME_PERFECT at your own risk.
64  * You should have another method of validating the device tree, such as a
65  * signature or hash check before using libfdt.
66  *
67  * For situations where security is not a concern it may be safe to enable
68  * ASSUME_SANE.
69  */
70 enum {
71 	/*
72 	 * This does essentially no checks. Only the latest device-tree
73 	 * version is correctly handled. Inconsistencies or errors in the device
74 	 * tree may cause undefined behaviour or crashes. Invalid parameters
75 	 * passed to libfdt may do the same.
76 	 *
77 	 * If an error occurs when modifying the tree it may leave the tree in
78 	 * an intermediate (but valid) state. As an example, adding a property
79 	 * where there is insufficient space may result in the property name
80 	 * being added to the string table even though the property itself is
81 	 * not added to the struct section.
82 	 *
83 	 * Only use this if you have a fully validated device tree with
84 	 * the latest supported version and wish to minimise code size.
85 	 */
86 	ASSUME_PERFECT		= 0xff,
87 
88 	/*
89 	 * This assumes that the device tree is sane. i.e. header metadata
90 	 * and basic hierarchy are correct.
91 	 *
92 	 * With this assumption enabled, normal device trees produced by libfdt
93 	 * and the compiler should be handled safely. Malicious device trees and
94 	 * complete garbage may cause libfdt to behave badly or crash. Truncated
95 	 * device trees (e.g. those only partially loaded) can also cause
96 	 * problems.
97 	 *
98 	 * Note: Only checks that relate exclusively to the device tree itself
99 	 * (not the parameters passed to libfdt) are disabled by this
100 	 * assumption. This includes checking headers, tags and the like.
101 	 */
102 	ASSUME_VALID_DTB	= 1 << 0,
103 
104 	/*
105 	 * This builds on ASSUME_VALID_DTB and further assumes that libfdt
106 	 * functions are called with valid parameters, i.e. not trigger
107 	 * FDT_ERR_BADOFFSET or offsets that are out of bounds. It disables any
108 	 * extensive checking of parameters and the device tree, making various
109 	 * assumptions about correctness.
110 	 *
111 	 * It doesn't make sense to enable this assumption unless
112 	 * ASSUME_VALID_DTB is also enabled.
113 	 */
114 	ASSUME_VALID_INPUT	= 1 << 1,
115 
116 	/*
117 	 * This disables checks for device-tree version and removes all code
118 	 * which handles older versions.
119 	 *
120 	 * Only enable this if you know you have a device tree with the latest
121 	 * version.
122 	 */
123 	ASSUME_LATEST		= 1 << 2,
124 
125 	/*
126 	 * This assumes that it is OK for a failed addition to the device tree,
127 	 * due to lack of space or some other problem, to skip any rollback
128 	 * steps (such as dropping the property name from the string table).
129 	 * This is safe to enable in most circumstances, even though it may
130 	 * leave the tree in a sub-optimal state.
131 	 */
132 	ASSUME_NO_ROLLBACK	= 1 << 3,
133 
134 	/*
135 	 * This assumes that the device tree components appear in a 'convenient'
136 	 * order, i.e. the memory reservation block first, then the structure
137 	 * block and finally the string block.
138 	 *
139 	 * This order is not specified by the device-tree specification,
140 	 * but is expected by libfdt. The device-tree compiler always created
141 	 * device trees with this order.
142 	 *
143 	 * This assumption disables a check in fdt_open_into() and removes the
144 	 * ability to fix the problem there. This is safe if you know that the
145 	 * device tree is correctly ordered. See fdt_blocks_misordered_().
146 	 */
147 	ASSUME_LIBFDT_ORDER	= 1 << 4,
148 
149 	/*
150 	 * This assumes that libfdt itself does not have any internal bugs. It
151 	 * drops certain checks that should never be needed unless libfdt has an
152 	 * undiscovered bug.
153 	 *
154 	 * This can generally be considered safe to enable.
155 	 */
156 	ASSUME_LIBFDT_FLAWLESS	= 1 << 5,
157 };
158 
159 /**
160  * can_assume_() - check if a particular assumption is enabled
161  *
162  * @mask: Mask to check (ASSUME_...)
163  * @return true if that assumption is enabled, else false
164  */
can_assume_(int mask)165 static inline bool can_assume_(int mask)
166 {
167 	return FDT_ASSUME_MASK & mask;
168 }
169 
170 /** helper macros for checking assumptions */
171 #define can_assume(_assume)	can_assume_(ASSUME_ ## _assume)
172 
173 #endif /* LIBFDT_INTERNAL_H */
174