/*- * SPDX-License-Identifier: BSD-2-Clause * * 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. */ #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 ยง7.4.1 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); // Not reached. return nullptr; } /** * 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_
