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);
}
 
/*
 * Internal helpers to access tructural elements of the device tree
 * blob (rather than for exaple reading integers from within property
 * values).  We assume that we are either given a naturally aligned
 * address for the platform or if we are not, we are on a platform
 * where unaligned memory reads will be handled in a graceful manner.
 * If not the external helpers fdtXX_ld() from libfdt.h can be used
 * instead.
 */
static inline uint32_t fdt32_ld_(const fdt32_t *p)
{
    return fdt32_to_cpu(*p);
}
 
static inline uint64_t fdt64_ld_(const fdt64_t *p)
{
    return fdt64_to_cpu(*p);
}
 
#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 safety, 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. Truncated
     * device trees (e.g. those only partially loaded) can also cause
     * problems.
     *
     * 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 assumes that it is OK for a failed addition to the device tree,
     * due to lack of space or some other problem, to 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 a 'convenient'
     * order, i.e. the memory reservation block first, then the structure
     * block and finally the string block.
     *
     * This order is not specified by the device-tree specification,
     * but is expected by libfdt. The device-tree compiler always created
     * device trees with this order.
     *
     * This assumption 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,
 
    /*
     * This assumes that libfdt itself does not have any internal bugs. It
     * drops certain checks that should never be needed unless libfdt has an
     * undiscovered bug.
     *
     * This can generally be considered safe to enable.
     */
    ASSUME_LIBFDT_FLAWLESS  = 1 << 5,
};

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

#define can_assume(_assume) can_assume_(ASSUME_ ## _assume)
 
#endif /* LIBFDT_INTERNAL_H */