libfdt_internal.h

  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
 13int32_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
 21int fdt_check_node_offset_(const void *fdt, int offset);
 22int fdt_check_prop_offset_(const void *fdt, int offset);
 23
 24const char *fdt_find_string_len_(const char *strtab, int tabsize, const char *s,
 25				 int s_len);
 26static inline const char *fdt_find_string_(const char *strtab, int tabsize,
 27					   const char *s)
 28{
 29	return fdt_find_string_len_(strtab, tabsize, s, strlen(s));
 30}
 31
 32int fdt_node_end_offset_(void *fdt, int nodeoffset);
 33
 34static inline const void *fdt_offset_ptr_(const void *fdt, int offset)
 35{
 36	return (const char *)fdt + fdt_off_dt_struct(fdt) + offset;
 37}
 38
 39static inline void *fdt_offset_ptr_w_(void *fdt, int offset)
 40{
 41	return (void *)(uintptr_t)fdt_offset_ptr_(fdt, offset);
 42}
 43
 44static inline const struct fdt_reserve_entry *fdt_mem_rsv_(const void *fdt, int n)
 45{
 46	const struct fdt_reserve_entry *rsv_table =
 47		(const struct fdt_reserve_entry *)
 48		((const char *)fdt + fdt_off_mem_rsvmap(fdt));
 49
 50	return rsv_table + n;
 51}
 52static inline struct fdt_reserve_entry *fdt_mem_rsv_w_(void *fdt, int n)
 53{
 54	return (void *)(uintptr_t)fdt_mem_rsv_(fdt, n);
 55}
 56
 57/*
 58 * Internal helpers to access structural elements of the device tree
 59 * blob (rather than for example reading integers from within property
 60 * values).  We assume that we are either given a naturally aligned
 61 * address for the platform or if we are not, we are on a platform
 62 * where unaligned memory reads will be handled in a graceful manner.
 63 * If not the external helpers fdtXX_ld() from libfdt.h can be used
 64 * instead.
 65 */
 66static inline uint32_t fdt32_ld_(const fdt32_t *p)
 67{
 68	return fdt32_to_cpu(*p);
 69}
 70
 71static inline uint64_t fdt64_ld_(const fdt64_t *p)
 72{
 73	return fdt64_to_cpu(*p);
 74}
 75
 76#define FDT_SW_MAGIC		(~FDT_MAGIC)
 77
 78/**********************************************************************/
 79/* Checking controls                                                  */
 80/**********************************************************************/
 81
 82#ifndef FDT_ASSUME_MASK
 83#define FDT_ASSUME_MASK 0
 84#endif
 85
 86/*
 87 * Defines assumptions which can be enabled. Each of these can be enabled
 88 * individually. For maximum safety, don't enable any assumptions!
 89 *
 90 * For minimal code size and no safety, use ASSUME_PERFECT at your own risk.
 91 * You should have another method of validating the device tree, such as a
 92 * signature or hash check before using libfdt.
 93 *
 94 * For situations where security is not a concern it may be safe to enable
 95 * ASSUME_SANE.
 96 */
 97enum {
 98	/*
 99	 * This does essentially no checks. Only the latest device-tree
100	 * version is correctly handled. Inconsistencies or errors in the device
101	 * tree may cause undefined behaviour or crashes. Invalid parameters
102	 * passed to libfdt may do the same.
103	 *
104	 * If an error occurs when modifying the tree it may leave the tree in
105	 * an intermediate (but valid) state. As an example, adding a property
106	 * where there is insufficient space may result in the property name
107	 * being added to the string table even though the property itself is
108	 * not added to the struct section.
109	 *
110	 * Only use this if you have a fully validated device tree with
111	 * the latest supported version and wish to minimise code size.
112	 */
113	ASSUME_PERFECT		= 0xff,
114
115	/*
116	 * This assumes that the device tree is sane. i.e. header metadata
117	 * and basic hierarchy are correct.
118	 *
119	 * With this assumption enabled, normal device trees produced by libfdt
120	 * and the compiler should be handled safely. Malicious device trees and
121	 * complete garbage may cause libfdt to behave badly or crash. Truncated
122	 * device trees (e.g. those only partially loaded) can also cause
123	 * problems.
124	 *
125	 * Note: Only checks that relate exclusively to the device tree itself
126	 * (not the parameters passed to libfdt) are disabled by this
127	 * assumption. This includes checking headers, tags and the like.
128	 */
129	ASSUME_VALID_DTB	= 1 << 0,
130
131	/*
132	 * This builds on ASSUME_VALID_DTB and further assumes that libfdt
133	 * functions are called with valid parameters, i.e. not trigger
134	 * FDT_ERR_BADOFFSET or offsets that are out of bounds. It disables any
135	 * extensive checking of parameters and the device tree, making various
136	 * assumptions about correctness.
137	 *
138	 * It doesn't make sense to enable this assumption unless
139	 * ASSUME_VALID_DTB is also enabled.
140	 */
141	ASSUME_VALID_INPUT	= 1 << 1,
142
143	/*
144	 * This disables checks for device-tree version and removes all code
145	 * which handles older versions.
146	 *
147	 * Only enable this if you know you have a device tree with the latest
148	 * version.
149	 */
150	ASSUME_LATEST		= 1 << 2,
151
152	/*
153	 * This assumes that it is OK for a failed addition to the device tree,
154	 * due to lack of space or some other problem, to skip any rollback
155	 * steps (such as dropping the property name from the string table).
156	 * This is safe to enable in most circumstances, even though it may
157	 * leave the tree in a sub-optimal state.
158	 */
159	ASSUME_NO_ROLLBACK	= 1 << 3,
160
161	/*
162	 * This assumes that the device tree components appear in a 'convenient'
163	 * order, i.e. the memory reservation block first, then the structure
164	 * block and finally the string block.
165	 *
166	 * This order is not specified by the device-tree specification,
167	 * but is expected by libfdt. The device-tree compiler always created
168	 * device trees with this order.
169	 *
170	 * This assumption disables a check in fdt_open_into() and removes the
171	 * ability to fix the problem there. This is safe if you know that the
172	 * device tree is correctly ordered. See fdt_blocks_misordered_().
173	 */
174	ASSUME_LIBFDT_ORDER	= 1 << 4,
175
176	/*
177	 * This assumes that libfdt itself does not have any internal bugs. It
178	 * drops certain checks that should never be needed unless libfdt has an
179	 * undiscovered bug.
180	 *
181	 * This can generally be considered safe to enable.
182	 */
183	ASSUME_LIBFDT_FLAWLESS	= 1 << 5,
184};
185
186/**
187 * can_assume_() - check if a particular assumption is enabled
188 *
189 * @mask: Mask to check (ASSUME_...)
190 * @return true if that assumption is enabled, else false
191 */
192static inline bool can_assume_(int mask)
193{
194	return FDT_ASSUME_MASK & mask;
195}
196
197/** helper macros for checking assumptions */
198#define can_assume(_assume)	can_assume_(ASSUME_ ## _assume)
199
200#endif /* LIBFDT_INTERNAL_H */