/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (c) 2013 David Chisnall
* All rights reserved.
*
* This software was developed by SRI International and the University of
* Cambridge Computer Laboratory under DARPA/AFRL contract (FA8750-10-C-0237)
* ("CTSRD"), as part of the DARPA CRASH research programme.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*/
#ifndef _DTB_HH_
#define _DTB_HH_
#include <map>
#include <string>
#include <assert.h>
#include "input_buffer.hh"
#include "util.hh"
namespace dtc
{
/**
* The dtb namespace contains code related to the generation of device tree
* blobs, the binary representation of flattened device trees. The abstract
* tree representation calls into this code to generate the output.
*/
namespace dtb
{
/** The token types in the DTB, as defined by §7.4.1 of the ePAPR
* specification. All of these values are written in big-endian format in the
* output.
*/
enum token_type
{
/**
* Marker indicating the start of a node in the tree. This is followed
* by the nul-terminated name. If a unit address is specified, then
* the name also contains the address, with an @ symbol between the end
* of the name and the start of the address.
*
* The name is then padded such that the next token begins on a 4-byte
* boundary. The node may contain properties, other nodes, both, or be
* empty.
*/
FDT_BEGIN_NODE = 0x00000001,
/**
* Marker indicating the end of a node.
*/
FDT_END_NODE = 0x00000002,
/**
* The start of a property. This is followed by two 32-bit big-endian
* values. The first indicates the length of the property value, the
* second its index in the strings table. It is then followed by the
* property value, if the value is of non-zero length.
*/
FDT_PROP = 0x00000003,
/**
* Ignored token. May be used for padding inside DTB nodes.
*/
FDT_NOP = 0x00000004,
/**
* Marker indicating the end of the tree.
*/
FDT_END = 0x00000009
};
/**
* Returns the token as a string. This is used for debugging and for printing
* human-friendly error messages about malformed DTB input.
*/
inline const char *token_type_name(token_type t)
{
switch(t)
{
case FDT_BEGIN_NODE:
return "FDT_BEGIN_NODE";
case FDT_END_NODE:
return "FDT_END_NODE";
case FDT_PROP:
return "FDT_PROP";
case FDT_NOP:
return "FDT_NOP";
case FDT_END:
return "FDT_END";
}
assert(0);
}
/**
* Abstract class for writing a section of the output. We create one
* of these for each section that needs to be written. It is intended to build
* a temporary buffer of the output in memory and then write it to a file
* stream. The size can be returned after all of the data has been written
* into the internal buffer, so the sizes of the three tables can be calculated
* before storing them in the buffer.
*/
struct output_writer
{
/**
* Writes a label into the output stream. This is only applicable for
* assembly output, where the labels become symbols that can be
* resolved at link time.
*/
virtual void write_label(const std::string &name) = 0;
/**
* Writes a comment into the output stream. Useful only when debugging
* the output.
*/
virtual void write_comment(const std::string &name) = 0;
/**
* Writes a string. A nul terminator is implicitly added.
*/
virtual void write_string(const std::string &name) = 0;
/**
* Writes a single 8-bit value.
*/
virtual void write_data(uint8_t) = 0;
/**
* Writes a single 32-bit value. The value is written in big-endian
* format, but should be passed in the host's native endian.
*/
virtual void write_data(uint32_t) = 0;
/**
* Writes a single 64-bit value. The value is written in big-endian
* format, but should be passed in the host's native endian.
*/
virtual void write_data(uint64_t) = 0;
/**
* Writes the collected output to the specified file descriptor.
*/
virtual void write_to_file(int fd) = 0;
/**
* Returns the number of bytes.
*/
virtual uint32_t size() = 0;
/**
* Helper for writing tokens to the output stream. This writes a
* comment above the token describing its value, for easier debugging
* of the output.
*/
inline void write_token(token_type t)
{
write_comment(token_type_name(t));
write_data((uint32_t)t);
}
/**
* Helper function that writes a byte buffer to the output, one byte at
* a time.
*/
void write_data(byte_buffer b);
};
/**
* Binary file writer. This class is responsible for writing the DTB output
* directly in blob format.
*/
class binary_writer : public output_writer
{
/**
* The internal buffer used to store the blob while it is being
* constructed.
*/
byte_buffer buffer;
public:
/**
* The binary format does not support labels, so this method
* does nothing.
*/
void write_label(const std::string &) override {}
/**
* Comments are ignored by the binary writer.
*/
void write_comment(const std::string&) override {}
void write_string(const std::string &name) override;
void write_data(uint8_t v) override;
void write_data(uint32_t v) override;
void write_data(uint64_t v) override;
void write_to_file(int fd) override;
uint32_t size() override;
};
/**
* Assembly writer. This class is responsible for writing the output in an
* assembly format that is suitable for linking into a kernel, loader, and so
* on.
*/
class asm_writer : public output_writer
{
/**
* The internal buffer for temporary values. Note that this actually
* contains ASCII text, but it is a byte buffer so that we can just
* copy strings across as-is.
*/
byte_buffer buffer;
/**
* The number of bytes written to the current line. This is used to
* allow line wrapping, where we aim to write four .byte directives to
* make the alignment clearer.
*/
int byte_count;
/**
* The current number of bytes written. This is the number in binary
* format, not the number of bytes in the buffer.
*/
uint32_t bytes_written;
/**
* Writes a string directly to the output as-is. This is the function that
* performs the real output.
*/
void write_string(const char *c);
/**
* Write a string to the output.
*/
void write_string(const std::string &c) override;
/**
* Writes the string, starting on a new line.
*/
void write_line(const char *c);
/**
* Writes a byte in binary format. This will emit a single .byte
* directive, with up to four per line.
*/
void write_byte(uint8_t b);
public:
asm_writer() : byte_count(0), bytes_written(0) {}
void write_label(const std::string &name) override;
void write_comment(const std::string &name) override;
void write_data(uint8_t v) override;
void write_data(uint32_t v) override;
void write_data(uint64_t v) override;
void write_to_file(int fd) override;
uint32_t size() override;
};
/**
* Class encapsulating the device tree blob header. This class stores all of
* the values found in the header and is responsible for writing them to the
* output.
*/
struct header
{
/**
* Magic value, used to validate that this really is a device tree
* blob. Should always be set to 0xd00dfeed.
*/
uint32_t magic;
/**
* The total size of the blob, including header, reservations, strings
* table, and padding.
*/
uint32_t totalsize;
/**
* The offset from the start of the blob of the struct table (i.e. the
* part of the blob containing the entire device tree).
*/
uint32_t off_dt_struct;
/**
* The offset from the start of the blob of the strings table.
*/
uint32_t off_dt_strings;
/**
* The offset of the reservation map from the start of the blob.
*/
uint32_t off_mem_rsvmap;
/**
* The version of the blob. This should always be 17.
*/
uint32_t version;
/**
* The earliest version of the DTB specification with which this blob
* is backwards compatible. This should always be 16.
*/
uint32_t last_comp_version;
/**
* The ID of the CPU where this boots.
*/
uint32_t boot_cpuid_phys;
/**
* The size of the strings table.
*/
uint32_t size_dt_strings;
/**
* The size of the struct table.
*/
uint32_t size_dt_struct;
/**
* Writes the entire header to the specified output buffer.
*/
void write(output_writer &out);
/**
* Reads the header from bits binary representation in a blob.
*/
bool read_dtb(input_buffer &input);
/**
* Default constructor. Initialises the values that have sensible
* defaults, leaves the others blank.
*/
header() : magic(0xd00dfeed), version(17), last_comp_version(16),
boot_cpuid_phys(0) {}
};
/**
* Class encapsulating the string table. FDT strings are stored in a string
* section. This maintains a map from strings to their offsets in the strings
* section.
*
* Note: We don't currently do suffix matching, which may save a small amount
* of space.
*/
class string_table {
/**
* Map from strings to their offset.
*/
std::map<std::string, uint32_t> string_offsets;
/**
* The strings, in the order in which they should be written to the
* output. The order must be stable - adding another string must not
* change the offset of any that we have already referenced - and so we
* simply write the strings in the order that they are passed.
*/
std::vector<std::string> strings;
/**
* The current size of the strings section.
*/
uint32_t size;
public:
/**
* Default constructor, creates an empty strings table.
*/
string_table() : size(0) {}
/**
* Adds a string to the table, returning the offset from the start
* where it will be written. If the string is already present, this
* will return its existing offset, otherwise it will return a new
* offset.
*/
uint32_t add_string(const std::string &str);
/**
* Writes the strings table to the specified output.
*/
void write(dtb::output_writer &writer);
};
} // namespace dtb
} // namespace dtc
#endif // !_DTB_HH_
