xref: /linux/scripts/dtc/libfdt/libfdt_internal.h (revision d0034a7a4ac7fae708146ac0059b9c47a1543f0d)
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 /*
50  * Internal helpers to access tructural elements of the device tree
51  * blob (rather than for exaple reading integers from within property
52  * values).  We assume that we are either given a naturally aligned
53  * address for the platform or if we are not, we are on a platform
54  * where unaligned memory reads will be handled in a graceful manner.
55  * If not the external helpers fdtXX_ld() from libfdt.h can be used
56  * instead.
57  */
fdt32_ld_(const fdt32_t * p)58 static inline uint32_t fdt32_ld_(const fdt32_t *p)
59 {
60 	return fdt32_to_cpu(*p);
61 }
62 
fdt64_ld_(const fdt64_t * p)63 static inline uint64_t fdt64_ld_(const fdt64_t *p)
64 {
65 	return fdt64_to_cpu(*p);
66 }
67 
68 #define FDT_SW_MAGIC		(~FDT_MAGIC)
69 
70 /**********************************************************************/
71 /* Checking controls                                                  */
72 /**********************************************************************/
73 
74 #ifndef FDT_ASSUME_MASK
75 #define FDT_ASSUME_MASK 0
76 #endif
77 
78 /*
79  * Defines assumptions which can be enabled. Each of these can be enabled
80  * individually. For maximum safety, don't enable any assumptions!
81  *
82  * For minimal code size and no safety, use ASSUME_PERFECT at your own risk.
83  * You should have another method of validating the device tree, such as a
84  * signature or hash check before using libfdt.
85  *
86  * For situations where security is not a concern it may be safe to enable
87  * ASSUME_SANE.
88  */
89 enum {
90 	/*
91 	 * This does essentially no checks. Only the latest device-tree
92 	 * version is correctly handled. Inconsistencies or errors in the device
93 	 * tree may cause undefined behaviour or crashes. Invalid parameters
94 	 * passed to libfdt may do the same.
95 	 *
96 	 * If an error occurs when modifying the tree it may leave the tree in
97 	 * an intermediate (but valid) state. As an example, adding a property
98 	 * where there is insufficient space may result in the property name
99 	 * being added to the string table even though the property itself is
100 	 * not added to the struct section.
101 	 *
102 	 * Only use this if you have a fully validated device tree with
103 	 * the latest supported version and wish to minimise code size.
104 	 */
105 	ASSUME_PERFECT		= 0xff,
106 
107 	/*
108 	 * This assumes that the device tree is sane. i.e. header metadata
109 	 * and basic hierarchy are correct.
110 	 *
111 	 * With this assumption enabled, normal device trees produced by libfdt
112 	 * and the compiler should be handled safely. Malicious device trees and
113 	 * complete garbage may cause libfdt to behave badly or crash. Truncated
114 	 * device trees (e.g. those only partially loaded) can also cause
115 	 * problems.
116 	 *
117 	 * Note: Only checks that relate exclusively to the device tree itself
118 	 * (not the parameters passed to libfdt) are disabled by this
119 	 * assumption. This includes checking headers, tags and the like.
120 	 */
121 	ASSUME_VALID_DTB	= 1 << 0,
122 
123 	/*
124 	 * This builds on ASSUME_VALID_DTB and further assumes that libfdt
125 	 * functions are called with valid parameters, i.e. not trigger
126 	 * FDT_ERR_BADOFFSET or offsets that are out of bounds. It disables any
127 	 * extensive checking of parameters and the device tree, making various
128 	 * assumptions about correctness.
129 	 *
130 	 * It doesn't make sense to enable this assumption unless
131 	 * ASSUME_VALID_DTB is also enabled.
132 	 */
133 	ASSUME_VALID_INPUT	= 1 << 1,
134 
135 	/*
136 	 * This disables checks for device-tree version and removes all code
137 	 * which handles older versions.
138 	 *
139 	 * Only enable this if you know you have a device tree with the latest
140 	 * version.
141 	 */
142 	ASSUME_LATEST		= 1 << 2,
143 
144 	/*
145 	 * This assumes that it is OK for a failed addition to the device tree,
146 	 * due to lack of space or some other problem, to skip any rollback
147 	 * steps (such as dropping the property name from the string table).
148 	 * This is safe to enable in most circumstances, even though it may
149 	 * leave the tree in a sub-optimal state.
150 	 */
151 	ASSUME_NO_ROLLBACK	= 1 << 3,
152 
153 	/*
154 	 * This assumes that the device tree components appear in a 'convenient'
155 	 * order, i.e. the memory reservation block first, then the structure
156 	 * block and finally the string block.
157 	 *
158 	 * This order is not specified by the device-tree specification,
159 	 * but is expected by libfdt. The device-tree compiler always created
160 	 * device trees with this order.
161 	 *
162 	 * This assumption disables a check in fdt_open_into() and removes the
163 	 * ability to fix the problem there. This is safe if you know that the
164 	 * device tree is correctly ordered. See fdt_blocks_misordered_().
165 	 */
166 	ASSUME_LIBFDT_ORDER	= 1 << 4,
167 
168 	/*
169 	 * This assumes that libfdt itself does not have any internal bugs. It
170 	 * drops certain checks that should never be needed unless libfdt has an
171 	 * undiscovered bug.
172 	 *
173 	 * This can generally be considered safe to enable.
174 	 */
175 	ASSUME_LIBFDT_FLAWLESS	= 1 << 5,
176 };
177 
178 /**
179  * can_assume_() - check if a particular assumption is enabled
180  *
181  * @mask: Mask to check (ASSUME_...)
182  * @return true if that assumption is enabled, else false
183  */
can_assume_(int mask)184 static inline bool can_assume_(int mask)
185 {
186 	return FDT_ASSUME_MASK & mask;
187 }
188 
189 /** helper macros for checking assumptions */
190 #define can_assume(_assume)	can_assume_(ASSUME_ ## _assume)
191 
192 #endif /* LIBFDT_INTERNAL_H */
193