476 lines
10 KiB
C++
476 lines
10 KiB
C++
/*
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* \brief ISO 9660 file system support
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* \author Sebastian Sumpf <sebastian.sumpf@genode-labs.com>
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* \date 2010-07-26
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*/
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/*
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* Copyright (C) 2010-2017 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU Affero General Public License version 3.
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*/
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/* Genode includes */
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#include <base/allocator_avl.h>
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#include <base/exception.h>
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#include <base/log.h>
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#include <base/stdint.h>
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#include <util/misc_math.h>
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#include <util/token.h>
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#include "iso9660.h"
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using namespace Genode;
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namespace Iso {
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class Sector;
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class Rock_ridge;
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class Iso_base;
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}
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/*
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* Sector reads one or more packets from the block interface
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*/
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class Iso::Sector {
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public:
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enum {
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MAX_SECTORS = 32, /* max. number sectors that can be read in one
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transaction */
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BLOCK_SIZE = 2048,
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};
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private:
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Block::Session::Tx::Source &_source;
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Block::Packet_descriptor _p { };
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public:
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Sector(Block::Connection &block,
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unsigned long blk_nr, unsigned long count)
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: _source(*block.tx())
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{
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try {
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_p = Block::Packet_descriptor(
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block.alloc_packet(blk_size() * count),
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Block::Packet_descriptor::READ,
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blk_nr * ((float)blk_size() / BLOCK_SIZE),
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count * ((float)blk_size() / BLOCK_SIZE));
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_source.submit_packet(_p);
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_p = _source.get_acked_packet();
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if (!_p.succeeded()) {
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Genode::error("Could not read block ", blk_nr);
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throw Io_error();
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}
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} catch (Block::Session::Tx::Source::Packet_alloc_failed) {
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Genode::error("packet overrun!");
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_p = _source.get_acked_packet();
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throw Io_error();
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}
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}
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~Sector() {
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_source.release_packet(_p);
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}
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/**
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* Return address of packet content
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*/
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template <typename T>
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T addr() { return reinterpret_cast<T>(_source.packet_content(_p)); }
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static size_t blk_size() { return BLOCK_SIZE; }
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static unsigned long to_blk(unsigned long bytes) {
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return ((bytes + blk_size() - 1) & ~(blk_size() - 1)) / blk_size(); }
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};
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/**
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* Rock ridge extension (see IEEE P1282)
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*/
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class Iso::Rock_ridge
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{
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public:
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enum {
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NM = 0x4d4e, /* POSIX name system use entry (little endian) */
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};
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private:
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uint16_t _signature;
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uint8_t _length;
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uint8_t _version;
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uint8_t _flags;
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char _name;
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public:
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char *name() { return &_name; }
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uint8_t length() { return _length - 5; }
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static Rock_ridge* scan_name(uint8_t *ptr, uint8_t size)
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{
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Rock_ridge *rr = (Rock_ridge *)ptr;
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while (rr->_length && ((uint8_t *)rr < ptr + size - 4)) {
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if (rr->_signature == NM)
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return rr;
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rr = rr->next();
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}
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return 0;
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}
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Rock_ridge *next() { return (Rock_ridge *)((uint8_t *)this + _length); }
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};
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/*********************
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** ISO9660 classes **
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*********************/
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/**
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* Access memory using offsets
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*/
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class Iso::Iso_base
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{
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protected:
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template <typename T>
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T value(int offset) { return *((T *)(this + offset)); }
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template <typename T>
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T ptr(int offset) { return (T)(this + offset); }
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};
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/**
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* Class representing a directory descriptions (see ECMA 119)
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*/
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class Directory_record : public Iso::Iso_base
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{
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enum {
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TABLE_LENGTH = 33, /* fixed length of directory record */
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ROOT_DIR = 0x0, /* special names of root and parent directories */
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PARENT_DIR = 0x1,
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DIR_FLAG = 0x2, /* directory flag in attributes */
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};
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public:
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/* total length of this record */
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uint8_t record_length() { return value<uint8_t>(0); }
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/* starting block of extent */
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uint32_t blk_nr() { return value<uint32_t>(2); }
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/* length in bytes of extent */
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uint32_t data_length() { return value<uint32_t>(10); }
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/* attributes */
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uint8_t file_flags() { return value<uint8_t>(25); }
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/* length of file name */
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uint8_t file_name_length() { return value<uint8_t>(32); }
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/* retrieve the file name */
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void file_name(char *buf)
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{
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buf[0] = 0;
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/* try Rock Ridge name */
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Iso::Rock_ridge *rr = Iso::Rock_ridge::scan_name(system_use(),
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system_use_size());
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if (rr) {
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memcpy(buf, rr->name(), rr->length());
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buf[rr->length()] = 0;
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return;
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}
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/* retrieve iso name */
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char *name = ptr<char*>(33);
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/*
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* Check for root and parent directory names and modify them
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* to '.' and '..' respectively.
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*/
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if (file_name_length() == 1)
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switch (name[0]) {
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case PARENT_DIR:
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buf[2] = 0;
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buf[1] = '.';
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buf[0] = '.';
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return;
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case ROOT_DIR:
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buf[1] = 0;
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buf[0] = '.';
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return;
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}
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memcpy(buf, name, file_name_length());
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buf[file_name_length()] = 0;
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}
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/* pad byte after file name (if file name length is even, only) */
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uint8_t pad_byte() { return !(file_name_length() % 2) ? 1 : 0; }
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/* system use area */
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uint8_t *system_use()
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{
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return (uint8_t*)this + TABLE_LENGTH
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+ file_name_length() + pad_byte();
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}
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/* length in bytes of system use area */
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uint8_t system_use_size()
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{
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return record_length() - file_name_length()
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- TABLE_LENGTH - pad_byte();
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}
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/* retrieve next record */
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Directory_record *next()
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{
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Directory_record *_next = this + record_length();
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if (_next->record_length())
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return _next;
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return 0;
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}
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/* find a directory record with file name matching 'level' */
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Directory_record *locate(char const *level)
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{
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Directory_record *dir = this;
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while (dir) {
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char name[Iso::LEVEL_LENGTH];
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dir->file_name(name);
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if (!strcmp(name, level))
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return dir;
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dir = dir->next();
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}
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return 0;
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}
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/* describes this record a directory */
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bool directory() { return file_flags() & DIR_FLAG; }
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};
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/**
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* Volume descriptor (see ECMA 119)
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*/
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class Volume_descriptor : public Iso::Iso_base
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{
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enum {
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/* volume types */
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PRIMARY = 0x01, /* type of primary volume descriptor */
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TERMINATOR = 0xff, /* type of terminating descriptor */
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/* constants */
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ROOT_SIZE = 34, /* the root directory record has a fixed length */
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};
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public:
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/* descriptor type */
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uint8_t type() { return value<uint8_t>(0); }
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/* root directory record */
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Directory_record * root_record() { return ptr<Directory_record *>(156); }
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/* check for primary descriptor */
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bool primary() { return type() == PRIMARY; }
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/* check for terminating descriptor */
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bool terminator() { return type() == TERMINATOR; }
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/* copy the root record */
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Directory_record *copy_root_record(Genode::Allocator &alloc)
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{
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Directory_record *buf;
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if (!(alloc.alloc(ROOT_SIZE, &buf)))
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throw Insufficient_ram_quota();
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memcpy(buf, root_record(), ROOT_SIZE);
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return buf;
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}
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};
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/**
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* Locate the root-directory record in the primary volume descriptor
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*/
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static Directory_record *locate_root(Genode::Allocator &alloc,
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Block::Connection &block)
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{
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/* volume descriptors in ISO9660 start at block 16 */
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for (unsigned long blk_nr = 16;; blk_nr++) {
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Iso::Sector sec(block, blk_nr, 1);
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Volume_descriptor *vol = sec.addr<Volume_descriptor *>();
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if (vol->primary())
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return vol->copy_root_record(alloc);
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if (vol->terminator())
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return nullptr;
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}
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}
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/**
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* Return root directory record
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*/
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static Directory_record *root_dir(Genode::Allocator &alloc,
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Block::Connection &block)
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{
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Directory_record *root = locate_root(alloc, block);
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if (!root) { throw Iso::Non_data_disc(); }
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return root;
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}
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/*******************
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** Iso interface **
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*******************/
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static Directory_record *_root_dir;
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Iso::File_info *Iso::file_info(Genode::Allocator &alloc, Block::Connection &block,
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char const *path)
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{
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char level[PATH_LENGTH];
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struct Scanner_policy_file
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{
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static bool identifier_char(char c, unsigned /* i */)
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{
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return c != '/' && c != 0;
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}
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};
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typedef ::Genode::Token<Scanner_policy_file> Token;
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Token t(path);
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if (!_root_dir) {
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_root_dir = root_dir(alloc, block);
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}
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Directory_record *dir = _root_dir;
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uint32_t blk_nr = 0, data_length = 0;
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/* determine block nr and file length on disk, parse directory records */
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while (t) {
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if (t.type() != Token::IDENT) {
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t = t.next();
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continue;
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}
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t.string(level, PATH_LENGTH);
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/*
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* Save current block number in a variable because successive
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* iterations might override the memory location where dir points
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* to when a directory entry spans several sectors.
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*/
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uint32_t current_blk_nr = dir->blk_nr();
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/* load extent of directory record and search for level */
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for (unsigned long i = 0; i < Sector::to_blk(dir->data_length()); i++) {
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Sector sec(block, current_blk_nr + i, 1);
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Directory_record *tmp = sec.addr<Directory_record *>()->locate(level);
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if (!tmp && i == Sector::to_blk(dir->data_length()) - 1) {
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Genode::error("file not found: ", Genode::Cstring(path));
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throw File_not_found();
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}
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if (!tmp) continue;
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dir = tmp;
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current_blk_nr = dir->blk_nr();
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if (!dir->directory()) {
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blk_nr = current_blk_nr;
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data_length = dir->data_length();
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}
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break;
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}
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t = t.next();
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}
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/* Warning: Don't access 'dir' after this point, since the sector is gone */
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if (!blk_nr && !data_length) {
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Genode::error("file not found: ", Genode::Cstring(path));
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throw File_not_found();
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}
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return new (alloc) File_info(blk_nr, data_length);
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}
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unsigned long Iso::read_file(Block::Connection &block, File_info *info,
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off_t file_offset, uint32_t length, void *buf_ptr)
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{
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uint8_t *buf = (uint8_t *)buf_ptr;
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if (info->size() <= (size_t)(length + file_offset))
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length = info->size() - file_offset - 1;
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unsigned long total_blk_count = ((length + (Sector::blk_size() - 1)) &
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~((Sector::blk_size()) - 1)) / Sector::blk_size();
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unsigned long ret = total_blk_count;
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unsigned long blk_count;
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unsigned long blk_nr = info->blk_nr() + (file_offset / Sector::blk_size());
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while ((blk_count = min<unsigned long>(Sector::MAX_SECTORS, total_blk_count))) {
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Sector sec(block, blk_nr, blk_count);
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total_blk_count -= blk_count;
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blk_nr += blk_count;
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unsigned long copy_length = blk_count * Sector::blk_size();
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memcpy(buf, sec.addr<void *>(), copy_length);
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length -= copy_length;
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buf += copy_length;
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/* zero out rest of page */
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if (!total_blk_count && (blk_count % 2))
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memset(buf, 0, Sector::blk_size());
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}
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return ret * Sector::blk_size();
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}
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