scripts/dtc/libfdt/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
  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
  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
  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
  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 }
  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  */
 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 */