libfdt_internal.h

/* SPDX-License-Identifier: (GPL-2.0-or-later OR BSD-2-Clause) */
#ifndef LIBFDT_INTERNAL_H
#define LIBFDT_INTERNAL_H
/*
 * libfdt - Flat Device Tree manipulation
 * Copyright (C) 2006 David Gibson, IBM Corporation.
 */
#include <fdt.h>

#define FDT_ALIGN(x, a)     (((x) + (a) - 1) & ~((a) - 1))
#define FDT_TAGALIGN(x)     (FDT_ALIGN((x), FDT_TAGSIZE))

int32_t fdt_ro_probe_(const void *fdt);
#define FDT_RO_PROBE(fdt)                   \
    {                           \
        int32_t totalsize_;             \
        if ((totalsize_ = fdt_ro_probe_(fdt)) < 0)  \
            return totalsize_;          \
    }

int fdt_check_node_offset_(const void *fdt, int offset);
int fdt_check_prop_offset_(const void *fdt, int offset);
const char *fdt_find_string_(const char *strtab, int tabsize, const char *s);
int fdt_node_end_offset_(void *fdt, int nodeoffset);

static inline const void *fdt_offset_ptr_(const void *fdt, int offset)
{
    return (const char *)fdt + fdt_off_dt_struct(fdt) + offset;
}

static inline void *fdt_offset_ptr_w_(void *fdt, int offset)
{
    return (void *)(uintptr_t)fdt_offset_ptr_(fdt, offset);
}

static inline const struct fdt_reserve_entry *fdt_mem_rsv_(const void *fdt, int n)
{
    const struct fdt_reserve_entry *rsv_table =
        (const struct fdt_reserve_entry *)
        ((const char *)fdt + fdt_off_mem_rsvmap(fdt));

    return rsv_table + n;
}
static inline struct fdt_reserve_entry *fdt_mem_rsv_w_(void *fdt, int n)
{
    return (void *)(uintptr_t)fdt_mem_rsv_(fdt, n);
}

#define FDT_SW_MAGIC        (~FDT_MAGIC)

/**********************************************************************/
/* Checking controls                                                  */
/**********************************************************************/

#ifndef FDT_ASSUME_MASK
#define FDT_ASSUME_MASK 0
#endif

/*
 * Defines assumptions which can be enabled. Each of these can be enabled
 * individually. For maximum saftey, don't enable any assumptions!
 *
 * For minimal code size and no safety, use ASSUME_PERFECT at your own risk.
 * You should have another method of validating the device tree, such as a
 * signature or hash check before using libfdt.
 *
 * For situations where security is not a concern it may be safe to enable
 * ASSUME_SANE.
 */
enum {
    /*
     * This does essentially no checks. Only the latest device-tree
     * version is correctly handled. Inconsistencies or errors in the device
     * tree may cause undefined behaviour or crashes. Invalid parameters
     * passed to libfdt may do the same.
     *
     * If an error occurs when modifying the tree it may leave the tree in
     * an intermediate (but valid) state. As an example, adding a property
     * where there is insufficient space may result in the property name
     * being added to the string table even though the property itself is
     * not added to the struct section.
     *
     * Only use this if you have a fully validated device tree with
     * the latest supported version and wish to minimise code size.
     */
    ASSUME_PERFECT      = 0xff,

    /*
     * This assumes that the device tree is sane. i.e. header metadata
     * and basic hierarchy are correct.
     *
     * With this assumption enabled, normal device trees produced by libfdt
     * and the compiler should be handled safely. Malicious device trees and
     * complete garbage may cause libfdt to behave badly or crash.
     *
     * Note: Only checks that relate exclusively to the device tree itself
     * (not the parameters passed to libfdt) are disabled by this
     * assumption. This includes checking headers, tags and the like.
     */
    ASSUME_VALID_DTB    = 1 << 0,

    /*
     * This builds on ASSUME_VALID_DTB and further assumes that libfdt
     * functions are called with valid parameters, i.e. not trigger
     * FDT_ERR_BADOFFSET or offsets that are out of bounds. It disables any
     * extensive checking of parameters and the device tree, making various
     * assumptions about correctness.
     *
     * It doesn't make sense to enable this assumption unless
     * ASSUME_VALID_DTB is also enabled.
     */
    ASSUME_VALID_INPUT  = 1 << 1,

    /*
     * This disables checks for device-tree version and removes all code
     * which handles older versions.
     *
     * Only enable this if you know you have a device tree with the latest
     * version.
     */
    ASSUME_LATEST       = 1 << 2,

    /*
     * This assume that it is OK for a failed additional to the device tree
     * due to lack of space or some other problem can skip any rollback
     * steps (such as dropping the property name from the string table).
     * This is safe to enable in most circumstances, even though it may
     * leave the tree in a sub-optimal state.
     */
    ASSUME_NO_ROLLBACK  = 1 << 3,

    /*
     * This assumes that the device tree components appear in the correct
     * order. As such it disables a check in fdt_open_into() and removes the
     * ability to fix the problem there. This is safe if you know that the
     * device tree is correctly ordered. See fdt_blocks_misordered_().
     */
    ASSUME_LIBFDT_ORDER = 1 << 4,
};

static inline bool can_assume_(int mask)
{
    return FDT_ASSUME_MASK & mask;
}

#define can_assume(_assume) can_assume_(ASSUME_ ## _assume)

#endif /* LIBFDT_INTERNAL_H */