lib/libfdt/fdt_region.c

/*
 * libfdt - Flat Device Tree manipulation
 * Copyright (C) 2013 Google, Inc
 * Written by Simon Glass <sjg@chromium.org>
 * SPDX-License-Identifier:	GPL-2.0+ BSD-2-Clause
 */

#include <libfdt_env.h>

#ifndef USE_HOSTCC
#include <fdt.h>
#include <libfdt.h>
#else
#include "fdt_host.h"
#endif

#include "libfdt_internal.h"

/**
 * fdt_add_region() - Add a new region to our list
 * @info:	State information
 * @offset:	Start offset of region
 * @size:	Size of region
 *
 * The region is added if there is space, but in any case we increment the
 * count. If permitted, and the new region overlaps the last one, we merge
 * them.
 */
static int fdt_add_region(struct fdt_region_state *info, int offset, int size)
{
	struct fdt_region *reg;

	reg = info->region ? &info->region[info->count - 1] : NULL;
	if (info->can_merge && info->count &&
	    info->count <= info->max_regions &&
	    reg && offset <= reg->offset + reg->size) {
		reg->size = offset + size - reg->offset;
	} else if (info->count++ < info->max_regions) {
		if (reg) {
			reg++;
			reg->offset = offset;
			reg->size = size;
		}
	} else {
		return -1;
	}

	return 0;
}

static int region_list_contains_offset(struct fdt_region_state *info,
				       const void *fdt, int target)
{
	struct fdt_region *reg;
	int num;

	target += fdt_off_dt_struct(fdt);
	for (reg = info->region, num = 0; num < info->count; reg++, num++) {
		if (target >= reg->offset && target < reg->offset + reg->size)
			return 1;
	}

	return 0;
}

/**
 * fdt_add_alias_regions() - Add regions covering the aliases that we want
 *
 * The /aliases node is not automatically included by fdtgrep unless the
 * command-line arguments cause to be included (or not excluded). However
 * aliases are special in that we generally want to include those which
 * reference a node that fdtgrep includes.
 *
 * In fact we want to include only aliases for those nodes still included in
 * the fdt, and drop the other aliases since they point to nodes that will not
 * be present.
 *
 * This function scans the aliases and adds regions for those which we want
 * to keep.
 *
 * @fdt: Device tree to scan
 * @region: List of regions
 * @count: Number of regions in the list so far (i.e. starting point for this
 *	function)
 * @max_regions: Maximum number of regions in @region list
 * @info: Place to put the region state
 * @return number of regions after processing, or -FDT_ERR_NOSPACE if we did
 * not have enough room in the regions table for the regions we wanted to add.
 */
int fdt_add_alias_regions(const void *fdt, struct fdt_region *region, int count,
			  int max_regions, struct fdt_region_state *info)
{
	int base = fdt_off_dt_struct(fdt);
	int node, node_end, offset;
	int did_alias_header;

	node = fdt_subnode_offset(fdt, 0, "aliases");
	if (node < 0)
		return -FDT_ERR_NOTFOUND;

	/*
	 * Find the next node so that we know where the /aliases node ends. We
	 * need special handling if /aliases is the last node.
	 */
	node_end = fdt_next_subnode(fdt, node);
	if (node_end == -FDT_ERR_NOTFOUND)
		/* Move back to the FDT_END_NODE tag of '/' */
		node_end = fdt_size_dt_struct(fdt) - sizeof(fdt32_t) * 2;
	else if (node_end < 0) /* other error */
		return node_end;
	node_end -= sizeof(fdt32_t);  /* Move to FDT_END_NODE tag of /aliases */

	did_alias_header = 0;
	info->region = region;
	info->count = count;
	info->can_merge = 0;
	info->max_regions = max_regions;

	for (offset = fdt_first_property_offset(fdt, node);
	     offset >= 0;
	     offset = fdt_next_property_offset(fdt, offset)) {
		const struct fdt_property *prop;
		const char *name;
		int target, next;

		prop = fdt_get_property_by_offset(fdt, offset, NULL);
		name = fdt_string(fdt, fdt32_to_cpu(prop->nameoff));
		target = fdt_path_offset(fdt, name);
		if (!region_list_contains_offset(info, fdt, target))
			continue;
		next = fdt_next_property_offset(fdt, offset);
		if (next < 0)
			next = node_end;

		if (!did_alias_header) {
			fdt_add_region(info, base + node, 12);
			did_alias_header = 1;
		}
		fdt_add_region(info, base + offset, next - offset);
	}

	/* Add the FDT_END_NODE tag */
	if (did_alias_header)
		fdt_add_region(info, base + node_end, sizeof(fdt32_t));

	return info->count < max_regions ? info->count : -FDT_ERR_NOSPACE;
}

/**
 * fdt_include_supernodes() - Include supernodes required by this node
 * @info:	State information
 * @depth:	Current stack depth
 *
 * When we decided to include a node or property which is not at the top
 * level, this function forces the inclusion of higher level nodes. For
 * example, given this tree:
 *
 * / {
 *     testing {
 *     }
 * }
 *
 * If we decide to include testing then we need the root node to have a valid
 * tree. This function adds those regions.
 */
static int fdt_include_supernodes(struct fdt_region_state *info, int depth)
{
	int base = fdt_off_dt_struct(info->fdt);
	int start, stop_at;
	int i;

	/*
	 * Work down the stack looking for supernodes that we didn't include.
	 * The algortihm here is actually pretty simple, since we know that
	 * no previous subnode had to include these nodes, or if it did, we
	 * marked them as included (on the stack) already.
	 */
	for (i = 0; i <= depth; i++) {
		if (!info->stack[i].included) {
			start = info->stack[i].offset;

			/* Add the FDT_BEGIN_NODE tag of this supernode */
			fdt_next_tag(info->fdt, start, &stop_at);
			if (fdt_add_region(info, base + start, stop_at - start))
				return -1;

			/* Remember that this supernode is now included */
			info->stack[i].included = 1;
			info->can_merge = 1;
		}

		/* Force (later) generation of the FDT_END_NODE tag */
		if (!info->stack[i].want)
			info->stack[i].want = WANT_NODES_ONLY;
	}

	return 0;
}

enum {
	FDT_DONE_NOTHING,
	FDT_DONE_MEM_RSVMAP,
	FDT_DONE_STRUCT,
	FDT_DONE_END,
	FDT_DONE_STRINGS,
	FDT_DONE_ALL,
};

int fdt_first_region(const void *fdt,
		int (*h_include)(void *priv, const void *fdt, int offset,
				 int type, const char *data, int size),
		void *priv, struct fdt_region *region,
		char *path, int path_len, int flags,
		struct fdt_region_state *info)
{
	struct fdt_region_ptrs *p = &info->ptrs;

	/* Set up our state */
	info->fdt = fdt;
	info->can_merge = 1;
	info->max_regions = 1;
	info->start = -1;
	p->want = WANT_NOTHING;
	p->end = path;
	*p->end = '\0';
	p->nextoffset = 0;
	p->depth = -1;
	p->done = FDT_DONE_NOTHING;

	return fdt_next_region(fdt, h_include, priv, region,
			       path, path_len, flags, info);
}

/***********************************************************************
 *
 *	Theory of operation
 *
 * Note: in this description 'included' means that a node (or other part
 * of the tree) should be included in the region list, i.e. it will have
 * a region which covers its part of the tree.
 *
 * This function maintains some state from the last time it is called.
 * It checks the next part of the tree that it is supposed to look at
 * (p.nextoffset) to see if that should be included or not. When it
 * finds something to include, it sets info->start to its offset. This
 * marks the start of the region we want to include.
 *
 * Once info->start is set to the start (i.e. not -1), we continue
 * scanning until we find something that we don't want included. This
 * will be the end of a region. At this point we can close off the
 * region and add it to the list. So we do so, and reset info->start
 * to -1.
 *
 * One complication here is that we want to merge regions. So when we
 * come to add another region later, we may in fact merge it with the
 * previous one if one ends where the other starts.
 *
 * The function fdt_add_region() will return -1 if it fails to add the
 * region, because we already have a region ready to be returned, and
 * the new one cannot be merged in with it. In this case, we must return
 * the region we found, and wait for another call to this function.
 * When it comes, we will repeat the processing of the tag and again
 * try to add a region. This time it will succeed.
 *
 * The current state of the pointers (stack, offset, etc.) is maintained
 * in a ptrs member. At the start of every loop iteration we make a copy
 * of it.  The copy is then updated as the tag is processed. Only if we
 * get to the end of the loop iteration (and successfully call
 * fdt_add_region() if we need to) can we commit the changes we have
 * made to these pointers. For example, if we see an FDT_END_NODE tag,
 * we will decrement the depth value. But if we need to add a region
 * for this tag (let's say because the previous tag is included and this
 * FDT_END_NODE tag is not included) then we will only commit the result
 * if we were able to add the region. That allows us to retry again next
 * time.
 *
 * We keep track of a variable called 'want' which tells us what we want
 * to include when there is no specific information provided by the
 * h_include function for a particular property. This basically handles
 * the inclusion of properties which are pulled in by virtue of the node
 * they are in. So if you include a node, its properties are also
 * included.  In this case 'want' will be WANT_NODES_AND_PROPS. The
 * FDT_REG_DIRECT_SUBNODES feature also makes use of 'want'. While we
 * are inside the subnode, 'want' will be set to WANT_NODES_ONLY, so
 * that only the subnode's FDT_BEGIN_NODE and FDT_END_NODE tags will be
 * included, and properties will be skipped. If WANT_NOTHING is
 * selected, then we will just rely on what the h_include() function
 * tells us.
 *
 * Using 'want' we work out 'include', which tells us whether this
 * current tag should be included or not. As you can imagine, if the
 * value of 'include' changes, that means we are on a boundary between
 * nodes to include and nodes to exclude. At this point we either close
 * off a previous region and add it to the list, or mark the start of a
 * new region.
 *
 * Apart from the nodes, we have mem_rsvmap, the FDT_END tag and the
 * string list. Each of these dealt with as a whole (i.e. we create a
 * region for each if it is to be included). For mem_rsvmap we don't
 * allow it to merge with the first struct region. For the stringlist,
 * we don't allow it to merge with the last struct region (which
 * contains at minimum the FDT_END tag).
 *
 *********************************************************************/

int fdt_next_region(const void *fdt,
		int (*h_include)(void *priv, const void *fdt, int offset,
				 int type, const char *data, int size),
		void *priv, struct fdt_region *region,
		char *path, int path_len, int flags,
		struct fdt_region_state *info)
{
	int base = fdt_off_dt_struct(fdt);
	int last_node = 0;
	const char *str;

	info->region = region;
	info->count = 0;
	if (info->ptrs.done < FDT_DONE_MEM_RSVMAP &&
	    (flags & FDT_REG_ADD_MEM_RSVMAP)) {
		/* Add the memory reserve map into its own region */
		if (fdt_add_region(info, fdt_off_mem_rsvmap(fdt),
				   fdt_off_dt_struct(fdt) -
				   fdt_off_mem_rsvmap(fdt)))
			return 0;
		info->can_merge = 0;	/* Don't allow merging with this */
		info->ptrs.done = FDT_DONE_MEM_RSVMAP;
	}

	/*
	 * Work through the tags one by one, deciding whether each needs to
	 * be included or not. We set the variable 'include' to indicate our
	 * decision. 'want' is used to track what we want to include - it
	 * allows us to pick up all the properties (and/or subnode tags) of
	 * a node.
	 */
	while (info->ptrs.done < FDT_DONE_STRUCT) {
		const struct fdt_property *prop;
		struct fdt_region_ptrs p;
		const char *name;
		int include = 0;
		int stop_at = 0;
		uint32_t tag;
		int offset;
		int val;
		int len;

		/*
		 * Make a copy of our pointers. If we make it to the end of
		 * this block then we will commit them back to info->ptrs.
		 * Otherwise we can try again from the same starting state
		 * next time we are called.
		 */
		p = info->ptrs;

		/*
		 * Find the tag, and the offset of the next one. If we need to
		 * stop including tags, then by default we stop *after*
		 * including the current tag
		 */
		offset = p.nextoffset;
		tag = fdt_next_tag(fdt, offset, &p.nextoffset);
		stop_at = p.nextoffset;

		switch (tag) {
		case FDT_PROP:
			stop_at = offset;
			prop = fdt_get_property_by_offset(fdt, offset, NULL);
			str = fdt_string(fdt, fdt32_to_cpu(prop->nameoff));
			val = h_include(priv, fdt, last_node, FDT_IS_PROP, str,
					    strlen(str) + 1);
			if (val == -1) {
				include = p.want >= WANT_NODES_AND_PROPS;
			} else {
				include = val;
				/*
				 * Make sure we include the } for this block.
				 * It might be more correct to have this done
				 * by the call to fdt_include_supernodes() in
				 * the case where it adds the node we are
				 * currently in, but this is equivalent.
				 */
				if ((flags & FDT_REG_SUPERNODES) && val &&
				    !p.want)
					p.want = WANT_NODES_ONLY;
			}

			/* Value grepping is not yet supported */
			break;

		case FDT_NOP:
			include = p.want >= WANT_NODES_AND_PROPS;
			stop_at = offset;
			break;

		case FDT_BEGIN_NODE:
			last_node = offset;
			p.depth++;
			if (p.depth == FDT_MAX_DEPTH)
				return -FDT_ERR_TOODEEP;
			name = fdt_get_name(fdt, offset, &len);
			if (p.end - path + 2 + len >= path_len)
				return -FDT_ERR_NOSPACE;

			/* Build the full path of this node */
			if (p.end != path + 1)
				*p.end++ = '/';
			strcpy(p.end, name);
			p.end += len;
			info->stack[p.depth].want = p.want;
			info->stack[p.depth].offset = offset;

			/*
			 * If we are not intending to include this node unless
			 * it matches, make sure we stop *before* its tag.
			 */
			if (p.want == WANT_NODES_ONLY ||
			    !(flags & (FDT_REG_DIRECT_SUBNODES |
				       FDT_REG_ALL_SUBNODES))) {
				stop_at = offset;
				p.want = WANT_NOTHING;
			}
			val = h_include(priv, fdt, offset, FDT_IS_NODE, path,
					p.end - path + 1);

			/* Include this if requested */
			if (val) {
				p.want = (flags & FDT_REG_ALL_SUBNODES) ?
					WANT_ALL_NODES_AND_PROPS :
					WANT_NODES_AND_PROPS;
			}

			/* If not requested, decay our 'p.want' value */
			else if (p.want) {
				if (p.want != WANT_ALL_NODES_AND_PROPS)
					p.want--;

			/* Not including this tag, so stop now */
			} else {
				stop_at = offset;
			}

			/*
			 * Decide whether to include this tag, and update our
			 * stack with the state for this node
			 */
			include = p.want;
			info->stack[p.depth].included = include;
			break;

		case FDT_END_NODE:
			include = p.want;
			if (p.depth < 0)
				return -FDT_ERR_BADSTRUCTURE;

			/*
			 * If we don't want this node, stop right away, unless
			 * we are including subnodes
			 */
			if (!p.want && !(flags & FDT_REG_DIRECT_SUBNODES))
				stop_at = offset;
			p.want = info->stack[p.depth].want;
			p.depth--;
			while (p.end > path && *--p.end != '/')
				;
			*p.end = '\0';
			break;

		case FDT_END:
			/* We always include the end tag */
			include = 1;
			p.done = FDT_DONE_STRUCT;
			break;
		}

		/* If this tag is to be included, mark it as region start */
		if (include && info->start == -1) {
			/* Include any supernodes required by this one */
			if (flags & FDT_REG_SUPERNODES) {
				if (fdt_include_supernodes(info, p.depth))
					return 0;
			}
			info->start = offset;
		}

		/*
		 * If this tag is not to be included, finish up the current
		 * region.
		 */
		if (!include && info->start != -1) {
			if (fdt_add_region(info, base + info->start,
					   stop_at - info->start))
				return 0;
			info->start = -1;
			info->can_merge = 1;
		}

		/* If we have made it this far, we can commit our pointers */
		info->ptrs = p;
	}

	/* Add a region for the END tag and a separate one for string table */
	if (info->ptrs.done < FDT_DONE_END) {
		if (info->ptrs.nextoffset != fdt_size_dt_struct(fdt))
			return -FDT_ERR_BADSTRUCTURE;

		if (fdt_add_region(info, base + info->start,
				   info->ptrs.nextoffset - info->start))
			return 0;
		info->ptrs.done++;
	}
	if (info->ptrs.done < FDT_DONE_STRINGS) {
		if (flags & FDT_REG_ADD_STRING_TAB) {
			info->can_merge = 0;
			if (fdt_off_dt_strings(fdt) <
			    base + info->ptrs.nextoffset)
				return -FDT_ERR_BADLAYOUT;
			if (fdt_add_region(info, fdt_off_dt_strings(fdt),
					   fdt_size_dt_strings(fdt)))
				return 0;
		}
		info->ptrs.done++;
	}

	return info->count > 0 ? 0 : -FDT_ERR_NOTFOUND;
}