fdt_overlay.c

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// SPDX-License-Identifier: (GPL-2.0-or-later OR BSD-2-Clause)
/*
 * libfdt - Flat Device Tree manipulation
 * Copyright (C) 2016 Free Electrons
 * Copyright (C) 2016 NextThing Co.
 */
#include "libfdt_env.h"
 
#include <fdt.h>
#include <libfdt.h>
 
#include "libfdt_internal.h"
 
static uint32_t overlay_get_target_phandle(const void *fdto, int fragment)
{
    const fdt32_t *val;
    int len;
 
    val = fdt_getprop(fdto, fragment, "target", &len);
    if (!val)
        return 0;
 
    if ((len != sizeof(*val)) || (fdt32_to_cpu(*val) == (uint32_t)-1))
        return (uint32_t)-1;
 
    return fdt32_to_cpu(*val);
}
 
int fdt_overlay_target_offset(const void *fdt, const void *fdto,
                  int fragment_offset, char const **pathp)
{
    uint32_t phandle;
    const char *path = NULL;
    int path_len = 0, ret;
 
    /* Try first to do a phandle based lookup */
    phandle = overlay_get_target_phandle(fdto, fragment_offset);
    if (phandle == (uint32_t)-1)
        return -FDT_ERR_BADPHANDLE;
 
    /* no phandle, try path */
    if (!phandle) {
        /* And then a path based lookup */
        path = fdt_getprop(fdto, fragment_offset, "target-path", &path_len);
        if (path)
            ret = fdt_path_offset(fdt, path);
        else
            ret = path_len;
    } else
        ret = fdt_node_offset_by_phandle(fdt, phandle);
 
    /*
    * If we haven't found either a target or a
    * target-path property in a node that contains a
    * __overlay__ subnode (we wouldn't be called
    * otherwise), consider it a improperly written
    * overlay
    */
    if (ret < 0 && path_len == -FDT_ERR_NOTFOUND)
        ret = -FDT_ERR_BADOVERLAY;
 
    /* return on error */
    if (ret < 0)
        return ret;
 
    /* return pointer to path (if available) */
    if (pathp)
        *pathp = path ? path : NULL;
 
    return ret;
}
 
static int overlay_phandle_add_offset(void *fdt, int node,
                      const char *name, uint32_t delta)
{
    const fdt32_t *val;
    uint32_t adj_val;
    int len;
 
    val = fdt_getprop(fdt, node, name, &len);
    if (!val)
        return len;
 
    if (len != sizeof(*val))
        return -FDT_ERR_BADPHANDLE;
 
    adj_val = fdt32_to_cpu(*val);
    if ((adj_val + delta) < adj_val)
        return -FDT_ERR_NOPHANDLES;
 
    adj_val += delta;
    if (adj_val == (uint32_t)-1)
        return -FDT_ERR_NOPHANDLES;
 
    return fdt_setprop_inplace_u32(fdt, node, name, adj_val);
}
 
static int overlay_adjust_node_phandles(void *fdto, int node,
                    uint32_t delta)
{
    int child;
    int ret;
 
    ret = overlay_phandle_add_offset(fdto, node, "phandle", delta);
    if (ret && ret != -FDT_ERR_NOTFOUND)
        return ret;
 
    ret = overlay_phandle_add_offset(fdto, node, "linux,phandle", delta);
    if (ret && ret != -FDT_ERR_NOTFOUND)
        return ret;
 
    fdt_for_each_subnode(child, fdto, node) {
        ret = overlay_adjust_node_phandles(fdto, child, delta);
        if (ret)
            return ret;
    }
 
    return 0;
}
 
static int overlay_adjust_local_phandles(void *fdto, uint32_t delta)
{
    /*
     * Start adjusting the phandles from the overlay root
     */
    return overlay_adjust_node_phandles(fdto, 0, delta);
}
 
static int overlay_update_local_node_references(void *fdto,
                        int tree_node,
                        int fixup_node,
                        uint32_t delta)
{
    int fixup_prop;
    int fixup_child;
    int ret;
 
    fdt_for_each_property_offset(fixup_prop, fdto, fixup_node) {
        const fdt32_t *fixup_val;
        const char *tree_val;
        const char *name;
        int fixup_len;
        int tree_len;
        int i;
 
        fixup_val = fdt_getprop_by_offset(fdto, fixup_prop,
                          &name, &fixup_len);
        if (!fixup_val)
            return fixup_len;
 
        if (fixup_len % sizeof(uint32_t))
            return -FDT_ERR_BADOVERLAY;
        fixup_len /= sizeof(uint32_t);
 
        tree_val = fdt_getprop(fdto, tree_node, name, &tree_len);
        if (!tree_val) {
            if (tree_len == -FDT_ERR_NOTFOUND)
                return -FDT_ERR_BADOVERLAY;
 
            return tree_len;
        }
 
        for (i = 0; i < fixup_len; i++) {
            fdt32_t adj_val;
            uint32_t poffset;
 
            poffset = fdt32_to_cpu(fixup_val[i]);
 
            /*
             * phandles to fixup can be unaligned.
             *
             * Use a memcpy for the architectures that do
             * not support unaligned accesses.
             */
            memcpy(&adj_val, tree_val + poffset, sizeof(adj_val));
 
            adj_val = cpu_to_fdt32(fdt32_to_cpu(adj_val) + delta);
 
            ret = fdt_setprop_inplace_namelen_partial(fdto,
                                  tree_node,
                                  name,
                                  strlen(name),
                                  poffset,
                                  &adj_val,
                                  sizeof(adj_val));
            if (ret == -FDT_ERR_NOSPACE)
                return -FDT_ERR_BADOVERLAY;
 
            if (ret)
                return ret;
        }
    }
 
    fdt_for_each_subnode(fixup_child, fdto, fixup_node) {
        const char *fixup_child_name = fdt_get_name(fdto, fixup_child,
                                NULL);
        int tree_child;
 
        tree_child = fdt_subnode_offset(fdto, tree_node,
                        fixup_child_name);
        if (tree_child == -FDT_ERR_NOTFOUND)
            return -FDT_ERR_BADOVERLAY;
        if (tree_child < 0)
            return tree_child;
 
        ret = overlay_update_local_node_references(fdto,
                               tree_child,
                               fixup_child,
                               delta);
        if (ret)
            return ret;
    }
 
    return 0;
}
 
static int overlay_update_local_references(void *fdto, uint32_t delta)
{
    int fixups;
 
    fixups = fdt_path_offset(fdto, "/__local_fixups__");
    if (fixups < 0) {
        /* There's no local phandles to adjust, bail out */
        if (fixups == -FDT_ERR_NOTFOUND)
            return 0;
 
        return fixups;
    }
 
    /*
     * Update our local references from the root of the tree
     */
    return overlay_update_local_node_references(fdto, 0, fixups,
                            delta);
}
 
static int overlay_fixup_one_phandle(void *fdt, void *fdto,
                     int symbols_off,
                     const char *path, uint32_t path_len,
                     const char *name, uint32_t name_len,
                     int poffset, const char *label)
{
    const char *symbol_path;
    uint32_t phandle;
    fdt32_t phandle_prop;
    int symbol_off, fixup_off;
    int prop_len;
 
    if (symbols_off < 0)
        return symbols_off;
 
    symbol_path = fdt_getprop(fdt, symbols_off, label,
                  &prop_len);
    if (!symbol_path)
        return prop_len;
 
    symbol_off = fdt_path_offset(fdt, symbol_path);
    if (symbol_off < 0)
        return symbol_off;
 
    phandle = fdt_get_phandle(fdt, symbol_off);
    if (!phandle)
        return -FDT_ERR_NOTFOUND;
 
    fixup_off = fdt_path_offset_namelen(fdto, path, path_len);
    if (fixup_off == -FDT_ERR_NOTFOUND)
        return -FDT_ERR_BADOVERLAY;
    if (fixup_off < 0)
        return fixup_off;
 
    phandle_prop = cpu_to_fdt32(phandle);
    return fdt_setprop_inplace_namelen_partial(fdto, fixup_off,
                           name, name_len, poffset,
                           &phandle_prop,
                           sizeof(phandle_prop));
}
 
static int overlay_fixup_phandle(void *fdt, void *fdto, int symbols_off,
                 int property)
{
    const char *value;
    const char *label;
    int len;
 
    value = fdt_getprop_by_offset(fdto, property,
                      &label, &len);
    if (!value) {
        if (len == -FDT_ERR_NOTFOUND)
            return -FDT_ERR_INTERNAL;
 
        return len;
    }
 
    do {
        const char *path, *name, *fixup_end;
        const char *fixup_str = value;
        uint32_t path_len, name_len;
        uint32_t fixup_len;
        char *sep, *endptr;
        int poffset, ret;
 
        fixup_end = memchr(value, '\0', len);
        if (!fixup_end)
            return -FDT_ERR_BADOVERLAY;
        fixup_len = fixup_end - fixup_str;
 
        len -= fixup_len + 1;
        value += fixup_len + 1;
 
        path = fixup_str;
        sep = memchr(fixup_str, ':', fixup_len);
        if (!sep || *sep != ':')
            return -FDT_ERR_BADOVERLAY;
 
        path_len = sep - path;
        if (path_len == (fixup_len - 1))
            return -FDT_ERR_BADOVERLAY;
 
        fixup_len -= path_len + 1;
        name = sep + 1;
        sep = memchr(name, ':', fixup_len);
        if (!sep || *sep != ':')
            return -FDT_ERR_BADOVERLAY;
 
        name_len = sep - name;
        if (!name_len)
            return -FDT_ERR_BADOVERLAY;
 
        poffset = strtoul(sep + 1, &endptr, 10);
        if ((*endptr != '\0') || (endptr <= (sep + 1)))
            return -FDT_ERR_BADOVERLAY;
 
        ret = overlay_fixup_one_phandle(fdt, fdto, symbols_off,
                        path, path_len, name, name_len,
                        poffset, label);
        if (ret)
            return ret;
    } while (len > 0);
 
    return 0;
}
 
static int overlay_fixup_phandles(void *fdt, void *fdto)
{
    int fixups_off, symbols_off;
    int property;
 
    /* We can have overlays without any fixups */
    fixups_off = fdt_path_offset(fdto, "/__fixups__");
    if (fixups_off == -FDT_ERR_NOTFOUND)
        return 0; /* nothing to do */
    if (fixups_off < 0)
        return fixups_off;
 
    /* And base DTs without symbols */
    symbols_off = fdt_path_offset(fdt, "/__symbols__");
    if ((symbols_off < 0 && (symbols_off != -FDT_ERR_NOTFOUND)))
        return symbols_off;
 
    fdt_for_each_property_offset(property, fdto, fixups_off) {
        int ret;
 
        ret = overlay_fixup_phandle(fdt, fdto, symbols_off, property);
        if (ret)
            return ret;
    }
 
    return 0;
}
 
static int overlay_apply_node(void *fdt, int target,
                  void *fdto, int node)
{
    int property;
    int subnode;
 
    fdt_for_each_property_offset(property, fdto, node) {
        const char *name;
        const void *prop;
        int prop_len;
        int ret;
 
        prop = fdt_getprop_by_offset(fdto, property, &name,
                         &prop_len);
        if (prop_len == -FDT_ERR_NOTFOUND)
            return -FDT_ERR_INTERNAL;
        if (prop_len < 0)
            return prop_len;
 
        ret = fdt_setprop(fdt, target, name, prop, prop_len);
        if (ret)
            return ret;
    }
 
    fdt_for_each_subnode(subnode, fdto, node) {
        const char *name = fdt_get_name(fdto, subnode, NULL);
        int nnode;
        int ret;
 
        nnode = fdt_add_subnode(fdt, target, name);
        if (nnode == -FDT_ERR_EXISTS) {
            nnode = fdt_subnode_offset(fdt, target, name);
            if (nnode == -FDT_ERR_NOTFOUND)
                return -FDT_ERR_INTERNAL;
        }
 
        if (nnode < 0)
            return nnode;
 
        ret = overlay_apply_node(fdt, nnode, fdto, subnode);
        if (ret)
            return ret;
    }
 
    return 0;
}
 
static int overlay_merge(void *fdt, void *fdto)
{
    int fragment;
 
    fdt_for_each_subnode(fragment, fdto, 0) {
        int overlay;
        int target;
        int ret;
 
        /*
         * Each fragments will have an __overlay__ node. If
         * they don't, it's not supposed to be merged
         */
        overlay = fdt_subnode_offset(fdto, fragment, "__overlay__");
        if (overlay == -FDT_ERR_NOTFOUND)
            continue;
 
        if (overlay < 0)
            return overlay;
 
        target = fdt_overlay_target_offset(fdt, fdto, fragment, NULL);
        if (target < 0)
            return target;
 
        ret = overlay_apply_node(fdt, target, fdto, overlay);
        if (ret)
            return ret;
    }
 
    return 0;
}
 
static int get_path_len(const void *fdt, int nodeoffset)
{
    int len = 0, namelen;
    const char *name;
 
    FDT_RO_PROBE(fdt);
 
    for (;;) {
        name = fdt_get_name(fdt, nodeoffset, &namelen);
        if (!name)
            return namelen;
 
        /* root? we're done */
        if (namelen == 0)
            break;
 
        nodeoffset = fdt_parent_offset(fdt, nodeoffset);
        if (nodeoffset < 0)
            return nodeoffset;
        len += namelen + 1;
    }
 
    /* in case of root pretend it's "/" */
    if (len == 0)
        len++;
    return len;
}
 
static int overlay_symbol_update(void *fdt, void *fdto)
{
    int root_sym, ov_sym, prop, path_len, fragment, target;
    int len, frag_name_len, ret, rel_path_len;
    const char *s, *e;
    const char *path;
    const char *name;
    const char *frag_name;
    const char *rel_path;
    const char *target_path;
    char *buf;
    void *p;
 
    ov_sym = fdt_subnode_offset(fdto, 0, "__symbols__");
 
    /* if no overlay symbols exist no problem */
    if (ov_sym < 0)
        return 0;
 
    root_sym = fdt_subnode_offset(fdt, 0, "__symbols__");
 
    /* it no root symbols exist we should create them */
    if (root_sym == -FDT_ERR_NOTFOUND)
        root_sym = fdt_add_subnode(fdt, 0, "__symbols__");
 
    /* any error is fatal now */
    if (root_sym < 0)
        return root_sym;
 
    /* iterate over each overlay symbol */
    fdt_for_each_property_offset(prop, fdto, ov_sym) {
        path = fdt_getprop_by_offset(fdto, prop, &name, &path_len);
        if (!path)
            return path_len;
 
        /* verify it's a string property (terminated by a single \0) */
        if (path_len < 1 || memchr(path, '\0', path_len) != &path[path_len - 1])
            return -FDT_ERR_BADVALUE;
 
        /* keep end marker to avoid strlen() */
        e = path + path_len;
 
        if (*path != '/')
            return -FDT_ERR_BADVALUE;
 
        /* get fragment name first */
        s = strchr(path + 1, '/');
        if (!s) {
            /* Symbol refers to something that won't end
             * up in the target tree */
            continue;
        }
 
        frag_name = path + 1;
        frag_name_len = s - path - 1;
 
        /* verify format; safe since "s" lies in \0 terminated prop */
        len = sizeof("/__overlay__/") - 1;
        if ((e - s) > len && (memcmp(s, "/__overlay__/", len) == 0)) {
            /* /<fragment-name>/__overlay__/<relative-subnode-path> */
            rel_path = s + len;
            rel_path_len = e - rel_path - 1;
        } else if ((e - s) == len
               && (memcmp(s, "/__overlay__", len - 1) == 0)) {
            /* /<fragment-name>/__overlay__ */
            rel_path = "";
            rel_path_len = 0;
        } else {
            /* Symbol refers to something that won't end
             * up in the target tree */
            continue;
        }
 
        /* find the fragment index in which the symbol lies */
        ret = fdt_subnode_offset_namelen(fdto, 0, frag_name,
                           frag_name_len);
        /* not found? */
        if (ret < 0)
            return -FDT_ERR_BADOVERLAY;
        fragment = ret;
 
        /* an __overlay__ subnode must exist */
        ret = fdt_subnode_offset(fdto, fragment, "__overlay__");
        if (ret < 0)
            return -FDT_ERR_BADOVERLAY;
 
        /* get the target of the fragment */
        ret = fdt_overlay_target_offset(fdt, fdto, fragment, &target_path);
        if (ret < 0)
            return ret;
        target = ret;
 
        /* if we have a target path use */
        if (!target_path) {
            ret = get_path_len(fdt, target);
            if (ret < 0)
                return ret;
            len = ret;
        } else {
            len = strlen(target_path);
        }
 
        ret = fdt_setprop_placeholder(fdt, root_sym, name,
                len + (len > 1) + rel_path_len + 1, &p);
        if (ret < 0)
            return ret;
 
        if (!target_path) {
            /* again in case setprop_placeholder changed it */
            ret = fdt_overlay_target_offset(fdt, fdto, fragment, &target_path);
            if (ret < 0)
                return ret;
            target = ret;
        }
 
        buf = p;
        if (len > 1) { /* target is not root */
            if (!target_path) {
                ret = fdt_get_path(fdt, target, buf, len + 1);
                if (ret < 0)
                    return ret;
            } else
                memcpy(buf, target_path, len + 1);
 
        } else
            len--;
 
        buf[len] = '/';
        memcpy(buf + len + 1, rel_path, rel_path_len);
        buf[len + 1 + rel_path_len] = '\0';
    }
 
    return 0;
}
 
int fdt_overlay_apply(void *fdt, void *fdto)
{
    uint32_t delta;
    int ret;
 
    FDT_RO_PROBE(fdt);
    FDT_RO_PROBE(fdto);
 
    ret = fdt_find_max_phandle(fdt, &delta);
    if (ret)
        goto err;
 
    ret = overlay_adjust_local_phandles(fdto, delta);
    if (ret)
        goto err;
 
    ret = overlay_update_local_references(fdto, delta);
    if (ret)
        goto err;
 
    ret = overlay_fixup_phandles(fdt, fdto);
    if (ret)
        goto err;
 
    ret = overlay_merge(fdt, fdto);
    if (ret)
        goto err;
 
    ret = overlay_symbol_update(fdt, fdto);
    if (ret)
        goto err;
 
    /*
     * The overlay has been damaged, erase its magic.
     */
    fdt_set_magic(fdto, ~0);
 
    return 0;
 
err:
    /*
     * The overlay might have been damaged, erase its magic.
     */
    fdt_set_magic(fdto, ~0);
 
    /*
     * The base device tree might have been damaged, erase its
     * magic.
     */
    fdt_set_magic(fdt, ~0);
 
    return ret;
}