btrfs-progs/kernel-shared/accessors.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 */

#include "kerncompat.h"
#include <stdbool.h>
#include "kernel-shared/extent_io.h"
#include "kernel-shared/uapi/btrfs_tree.h"
#include "kernel-shared/messages.h"
#include "kernel-shared/accessors.h"

static bool check_setget_bounds(const struct extent_buffer *eb,
				const void *ptr, unsigned off, int size)
{
	const unsigned long member_offset = (unsigned long)ptr + off;

	if (unlikely(member_offset + size > eb->len)) {
		btrfs_warn(eb->fs_info,
		"bad eb member %s: ptr 0x%lx start %llu member offset %lu size %d",
			(member_offset > eb->len ? "start" : "end"),
			(unsigned long)ptr, eb->start, member_offset, size);
		return false;
	}

	return true;
}

/*
 * MODIFIED:
 *  - We don't have eb->pages.
 */
void btrfs_init_map_token(struct btrfs_map_token *token, struct extent_buffer *eb)
{
	token->eb = eb;
	token->kaddr = eb->data;
	token->offset = 0;
}

/*
 * MODIFIED:
 *  - We don't have eb->pages, simply wrap the set/get helpers.
 */

/*
 * Macro templates that define helpers to read/write extent buffer data of a
 * given size, that are also used via ctree.h for access to item members by
 * specialized helpers.
 *
 * Generic helpers:
 * - btrfs_set_8 (for 8/16/32/64)
 * - btrfs_get_8 (for 8/16/32/64)
 *
 * Generic helpers with a token (cached address of the most recently accessed
 * page):
 * - btrfs_set_token_8 (for 8/16/32/64)
 * - btrfs_get_token_8 (for 8/16/32/64)
 *
 * The set/get functions handle data spanning two pages transparently, in case
 * metadata block size is larger than page.  Every pointer to metadata items is
 * an offset into the extent buffer page array, cast to a specific type.  This
 * gives us all the type checking.
 *
 * The extent buffer pages stored in the array pages do not form a contiguous
 * phyusical range, but the API functions assume the linear offset to the range
 * from 0 to metadata node size.
 */

#define DEFINE_BTRFS_SETGET_BITS(bits)					\
u##bits btrfs_get_token_##bits(struct btrfs_map_token *token,		\
			       const void *ptr, unsigned long off)	\
{									\
	const unsigned long member_offset = (unsigned long)ptr + off;	\
	const int size = sizeof(u##bits);				\
	ASSERT(token);							\
	ASSERT(token->kaddr);						\
	ASSERT(check_setget_bounds(token->eb, ptr, off, size));		\
	return get_unaligned_le##bits(token->kaddr + member_offset);	\
}									\
u##bits btrfs_get_##bits(const struct extent_buffer *eb,		\
			 const void *ptr, unsigned long off)		\
{									\
	const unsigned long member_offset = (unsigned long)ptr + off;	\
	const int size = sizeof(u##bits);				\
	ASSERT(check_setget_bounds(eb, ptr, off, size));		\
	return get_unaligned_le##bits(eb->data + member_offset);	\
}									\
void btrfs_set_token_##bits(struct btrfs_map_token *token,		\
			    const void *ptr, unsigned long off,		\
			    u##bits val)				\
{									\
	unsigned long member_offset = (unsigned long)ptr + off;		\
	const int size = sizeof(u##bits);				\
	ASSERT(token);							\
	ASSERT(token->kaddr);						\
	ASSERT(check_setget_bounds(token->eb, ptr, off, size));		\
	put_unaligned_le##bits(val, token->kaddr + member_offset);	\
}									\
void btrfs_set_##bits(const struct extent_buffer *eb, void *ptr,	\
		      unsigned long off, u##bits val)			\
{									\
	unsigned long member_offset = (unsigned long)ptr + off;		\
	const int size = sizeof(u##bits);				\
	ASSERT(check_setget_bounds(eb, ptr, off, size));		\
	put_unaligned_le##bits(val, (void *)eb->data + member_offset);	\
}

DEFINE_BTRFS_SETGET_BITS(8)
DEFINE_BTRFS_SETGET_BITS(16)
DEFINE_BTRFS_SETGET_BITS(32)
DEFINE_BTRFS_SETGET_BITS(64)

void btrfs_node_key(const struct extent_buffer *eb,
		    struct btrfs_disk_key *disk_key, int nr)
{
	unsigned long ptr = btrfs_node_key_ptr_offset(eb, nr);
	read_eb_member(eb, (struct btrfs_key_ptr *)ptr,
		       struct btrfs_key_ptr, key, disk_key);
}