diff options
Diffstat (limited to 'subx/028translate.cc')
| -rw-r--r-- | subx/028translate.cc | 212 |
1 files changed, 0 insertions, 212 deletions
diff --git a/subx/028translate.cc b/subx/028translate.cc deleted file mode 100644 index d3a6a8ac..00000000 --- a/subx/028translate.cc +++ /dev/null @@ -1,212 +0,0 @@ -//: The bedrock level 1 of abstraction is now done, and we're going to start -//: building levels above it that make programming in x86 machine code a -//: little more ergonomic. -//: -//: All levels will be "pass through by default". Whatever they don't -//: understand they will silently pass through to lower levels. -//: -//: Since raw hex bytes of machine code are always possible to inject, SubX is -//: not a language, and we aren't building a compiler. This is something -//: deliberately leakier. Levels are more for improving auditing, checks and -//: error messages rather than for hiding low-level details. - -//: Translator workflow: read 'source' file. Run a series of transforms on it, -//: each passing through what it doesn't understand. The final program should -//: be just machine code, suitable to write to an ELF binary. -//: -//: Higher levels usually transform code on the basis of metadata. - -:(before "End Main") -if (is_equal(argv[1], "translate")) { - START_TRACING_UNTIL_END_OF_SCOPE; - reset(); - // Begin subx translate - program p; - string output_filename; - for (int i = /*skip 'subx translate'*/2; i < argc; ++i) { - if (is_equal(argv[i], "-o")) { - ++i; - if (i >= argc) { - print_translate_usage(); - cerr << "'-o' must be followed by a filename to write results to\n"; - exit(1); - } - output_filename = argv[i]; - } - else { - trace(2, "parse") << argv[i] << end(); - ifstream fin(argv[i]); - if (!fin) { - cerr << "could not open " << argv[i] << '\n'; - return 1; - } - parse(fin, p); - if (trace_contains_errors()) return 1; - } - } - if (p.segments.empty()) { - print_translate_usage(); - cerr << "nothing to do; must provide at least one file to read\n"; - exit(1); - } - if (output_filename.empty()) { - print_translate_usage(); - cerr << "must provide a filename to write to using '-o'\n"; - exit(1); - } - trace(2, "transform") << "begin" << end(); - transform(p); - if (trace_contains_errors()) return 1; - trace(2, "translate") << "begin" << end(); - save_elf(p, output_filename); - if (trace_contains_errors()) { - unlink(output_filename.c_str()); - return 1; - } - // End subx translate - return 0; -} - -:(code) -void print_translate_usage() { - cerr << "Usage: subx translate file1 file2 ... -o output\n"; -} - -// write out a program to a bare-bones ELF file -void save_elf(const program& p, const string& filename) { - ofstream out(filename.c_str(), ios::binary); - save_elf(p, out); - out.close(); -} - -void save_elf(const program& p, ostream& out) { - // validation: stay consistent with the self-hosted translator - if (p.entry == 0) { - raise << "no 'Entry' label found\n" << end(); - return; - } - if (find(p, "data") == NULL) { - raise << "must include a 'data' segment\n" << end(); - return; - } - // processing - write_elf_header(out, p); - for (size_t i = 0; i < p.segments.size(); ++i) - write_segment(p.segments.at(i), out); -} - -void write_elf_header(ostream& out, const program& p) { - char c = '\0'; -#define O(X) c = (X); out.write(&c, sizeof(c)) -// host is required to be little-endian -#define emit(X) out.write(reinterpret_cast<const char*>(&X), sizeof(X)) - //// ehdr - // e_ident - O(0x7f); O(/*E*/0x45); O(/*L*/0x4c); O(/*F*/0x46); - O(0x1); // 32-bit format - O(0x1); // little-endian - O(0x1); O(0x0); - for (size_t i = 0; i < 8; ++i) { O(0x0); } - // e_type - O(0x02); O(0x00); - // e_machine - O(0x03); O(0x00); - // e_version - O(0x01); O(0x00); O(0x00); O(0x00); - // e_entry - uint32_t e_entry = p.entry; - // Override e_entry - emit(e_entry); - // e_phoff -- immediately after ELF header - uint32_t e_phoff = 0x34; - emit(e_phoff); - // e_shoff; unused - uint32_t dummy32 = 0; - emit(dummy32); - // e_flags; unused - emit(dummy32); - // e_ehsize - uint16_t e_ehsize = 0x34; - emit(e_ehsize); - // e_phentsize - uint16_t e_phentsize = 0x20; - emit(e_phentsize); - // e_phnum - uint16_t e_phnum = SIZE(p.segments); - emit(e_phnum); - // e_shentsize - uint16_t dummy16 = 0x0; - emit(dummy16); - // e_shnum - emit(dummy16); - // e_shstrndx - emit(dummy16); - - uint32_t p_offset = /*size of ehdr*/0x34 + SIZE(p.segments)*0x20/*size of each phdr*/; - for (int i = 0; i < SIZE(p.segments); ++i) { - const segment& curr = p.segments.at(i); - //// phdr - // p_type - uint32_t p_type = 0x1; - emit(p_type); - // p_offset - emit(p_offset); - // p_vaddr - uint32_t p_start = curr.start; - emit(p_start); - // p_paddr - emit(p_start); - // p_filesz - uint32_t size = num_words(curr); - assert(p_offset + size < SEGMENT_ALIGNMENT); - emit(size); - // p_memsz - emit(size); - // p_flags - uint32_t p_flags = (curr.name == "code") ? /*r-x*/0x5 : /*rw-*/0x6; - emit(p_flags); - - // p_align - // "As the system creates or augments a process image, it logically copies - // a file's segment to a virtual memory segment. When—and if— the system - // physically reads the file depends on the program's execution behavior, - // system load, and so on. A process does not require a physical page - // unless it references the logical page during execution, and processes - // commonly leave many pages unreferenced. Therefore delaying physical - // reads frequently obviates them, improving system performance. To obtain - // this efficiency in practice, executable and shared object files must - // have segment images whose file offsets and virtual addresses are - // congruent, modulo the page size." -- http://refspecs.linuxbase.org/elf/elf.pdf (page 95) - uint32_t p_align = 0x1000; // default page size on linux - emit(p_align); - if (p_offset % p_align != p_start % p_align) { - raise << "segment starting at 0x" << HEXWORD << p_start << " is improperly aligned; alignment for p_offset " << p_offset << " should be " << (p_offset % p_align) << " but is " << (p_start % p_align) << '\n' << end(); - return; - } - - // prepare for next segment - p_offset += size; - } -#undef O -#undef emit -} - -void write_segment(const segment& s, ostream& out) { - for (int i = 0; i < SIZE(s.lines); ++i) { - const vector<word>& w = s.lines.at(i).words; - for (int j = 0; j < SIZE(w); ++j) { - uint8_t x = hex_byte(w.at(j).data); // we're done with metadata by this point - out.write(reinterpret_cast<const char*>(&x), /*sizeof(byte)*/1); - } - } -} - -uint32_t num_words(const segment& s) { - uint32_t sum = 0; - for (int i = 0; i < SIZE(s.lines); ++i) - sum += SIZE(s.lines.at(i).words); - return sum; -} - -:(before "End Includes") -using std::ios; |