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