Mu - 030translate.cc

From fcc161e70502caf34bc0206d2c428e8341e97fa6 Mon Sep 17 00:00:00 2001 From: Kartik Agaram Date: Sun, 24 May 2020 22:43:18 -0700 Subject: 6397 Drop '---' section boundaries from filenames. I noticed them confusing tab-completion for certain advanced shell setups. --- html/030translate.cc.html | 271 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 271 insertions(+) create mode 100644 html/030translate.cc.html (limited to 'html/030translate.cc.html') diff --git a/html/030translate.cc.html b/html/030translate.cc.html new file mode 100644 index 00000000..52de2c83 --- /dev/null +++ b/html/030translate.cc.html @@ -0,0 +1,271 @@ + + + + +Mu - 030translate.cc + + + + + + + + + + +https://github.com/akkartik/mu/blob/master/030translate.cc +
+  1 //: After that lengthy prelude to define an x86 emulator, we are now ready to
+  2 //: start translating SubX notation.
+  3 
+  4 //: Translator workflow: read 'source' file. Run a series of transforms on it,
+  5 //: each passing through what it doesn't understand. The final program should
+  6 //: be just machine code, suitable to emulate, or to write to an ELF binary.
+  7 
+  8 :(before "End Main")
+  9 if (is_equal(argv[1], "translate")) {
+ 10   // Outside of tests, traces must be explicitly requested.
+ 11   if (Trace_file.is_open()) Trace_stream = new trace_stream;
+ 12   reset();
+ 13   // Begin bootstrap translate
+ 14   program p;
+ 15   string output_filename;
+ 16   for (int i = /*skip 'bootstrap translate'*/2;  i < argc;  ++i) {
+ 17     if (is_equal(argv[i], "-o")) {
+ 18       ++i;
+ 19       if (i >= argc) {
+ 20         print_translate_usage();
+ 21         cerr << "'-o' must be followed by a filename to write results to\n";
+ 22         exit(1);
+ 23       }
+ 24       output_filename = argv[i];
+ 25     }
+ 26     else {
+ 27       trace(2, "parse") << argv[i] << end();
+ 28       ifstream fin(argv[i]);
+ 29       if (!fin) {
+ 30         cerr << "could not open " << argv[i] << '\n';
+ 31         return 1;
+ 32       }
+ 33       parse(fin, p);
+ 34       if (trace_contains_errors()) return 1;
+ 35     }
+ 36   }
+ 37   if (p.segments.empty()) {
+ 38     print_translate_usage();
+ 39     cerr << "nothing to do; must provide at least one file to read\n";
+ 40     exit(1);
+ 41   }
+ 42   if (output_filename.empty()) {
+ 43     print_translate_usage();
+ 44     cerr << "must provide a filename to write to using '-o'\n";
+ 45     exit(1);
+ 46   }
+ 47   trace(2, "transform") << "begin" << end();
+ 48   transform(p);
+ 49   if (trace_contains_errors()) return 1;
+ 50   trace(2, "translate") << "begin" << end();
+ 51   save_elf(p, output_filename);
+ 52   if (trace_contains_errors()) {
+ 53     unlink(output_filename.c_str());
+ 54     return 1;
+ 55   }
+ 56   // End bootstrap translate
+ 57   return 0;
+ 58 }
+ 59 
+ 60 :(code)
+ 61 void transform(program& p) {
+ 62   // End transform(program& p)
+ 63 }
+ 64 
+ 65 void print_translate_usage() {
+ 66   cerr << "Usage: bootstrap translate file1 file2 ... -o output\n";
+ 67 }
+ 68 
+ 69 // write out a program to a bare-bones ELF file
+ 70 void save_elf(const program& p, const string& filename) {
+ 71   ofstream out(filename.c_str(), ios::binary);
+ 72   save_elf(p, out);
+ 73   out.close();
+ 74 }
+ 75 
+ 76 void save_elf(const program& p, ostream& out) {
+ 77   // validation: stay consistent with the self-hosted translator
+ 78   if (p.entry == 0) {
+ 79     raise << "no 'Entry' label found\n" << end();
+ 80     return;
+ 81   }
+ 82   if (find(p, "data") == NULL) {
+ 83     raise << "must include a 'data' segment\n" << end();
+ 84     return;
+ 85   }
+ 86   // processing
+ 87   write_elf_header(out, p);
+ 88   for (size_t i = 0;  i < p.segments.size();  ++i)
+ 89     write_segment(p.segments.at(i), out);
+ 90 }
+ 91 
+ 92 void write_elf_header(ostream& out, const program& p) {
+ 93   char c = '\0';
+ 94 #define O(X)  c = (X); out.write(&c, sizeof(c))
+ 95 // host is required to be little-endian
+ 96 #define emit(X)  out.write(reinterpret_cast<const char*>(&X), sizeof(X))
+ 97   //// ehdr
+ 98   // e_ident
+ 99   O(0x7f); O(/*E*/0x45); O(/*L*/0x4c); O(/*F*/0x46);
+100     O(0x1);  // 32-bit format
+101     O(0x1);  // little-endian
+102     O(0x1); O(0x0);
+103   for (size_t i = 0;  i < 8;  ++i) { O(0x0); }
+104   // e_type
+105   O(0x02); O(0x00);
+106   // e_machine
+107   O(0x03); O(0x00);
+108   // e_version
+109   O(0x01); O(0x00); O(0x00); O(0x00);
+110   // e_entry
+111   uint32_t e_entry = p.entry;
+112   // Override e_entry
+113   emit(e_entry);
+114   // e_phoff -- immediately after ELF header
+115   uint32_t e_phoff = 0x34;
+116   emit(e_phoff);
+117   // e_shoff; unused
+118   uint32_t dummy32 = 0;
+119   emit(dummy32);
+120   // e_flags; unused
+121   emit(dummy32);
+122   // e_ehsize
+123   uint16_t e_ehsize = 0x34;
+124   emit(e_ehsize);
+125   // e_phentsize
+126   uint16_t e_phentsize = 0x20;
+127   emit(e_phentsize);
+128   // e_phnum
+129   uint16_t e_phnum = SIZE(p.segments);
+130   emit(e_phnum);
+131   // e_shentsize
+132   uint16_t dummy16 = 0x0;
+133   emit(dummy16);
+134   // e_shnum
+135   emit(dummy16);
+136   // e_shstrndx
+137   emit(dummy16);
+138 
+139   uint32_t p_offset = /*size of ehdr*/0x34 + SIZE(p.segments)*0x20/*size of each phdr*/;
+140   for (int i = 0;  i < SIZE(p.segments);  ++i) {
+141     const segment& curr = p.segments.at(i);
+142     //// phdr
+143     // p_type
+144     uint32_t p_type = 0x1;
+145     emit(p_type);
+146     // p_offset
+147     emit(p_offset);
+148     // p_vaddr
+149     uint32_t p_start = curr.start;
+150     emit(p_start);
+151     // p_paddr
+152     emit(p_start);
+153     // p_filesz
+154     uint32_t size = num_words(curr);
+155     assert(p_offset + size < SEGMENT_ALIGNMENT);
+156     emit(size);
+157     // p_memsz
+158     emit(size);
+159     // p_flags
+160     uint32_t p_flags = (curr.name == "code") ? /*r-x*/0x5 : /*rw-*/0x6;
+161     emit(p_flags);
+162 
+163     // p_align
+164     // "As the system creates or augments a process image, it logically copies
+165     // a file's segment to a virtual memory segment.  When—and if— the system
+166     // physically reads the file depends on the program's execution behavior,
+167     // system load, and so on.  A process does not require a physical page
+168     // unless it references the logical page during execution, and processes
+169     // commonly leave many pages unreferenced. Therefore delaying physical
+170     // reads frequently obviates them, improving system performance. To obtain
+171     // this efficiency in practice, executable and shared object files must
+172     // have segment images whose file offsets and virtual addresses are
+173     // congruent, modulo the page size." -- http://refspecs.linuxbase.org/elf/elf.pdf (page 95)
+174     uint32_t p_align = 0x1000;  // default page size on linux
+175     emit(p_align);
+176     if (p_offset % p_align != p_start % p_align) {
+177       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();
+178       return;
+179     }
+180 
+181     // prepare for next segment
+182     p_offset += size;
+183   }
+184 #undef O
+185 #undef emit
+186 }
+187 
+188 void write_segment(const segment& s, ostream& out) {
+189   for (int i = 0;  i < SIZE(s.lines);  ++i) {
+190     const vector<word>& w = s.lines.at(i).words;
+191     for (int j = 0;  j < SIZE(w);  ++j) {
+192       uint8_t x = hex_byte(w.at(j).data);  // we're done with metadata by this point
+193       out.write(reinterpret_cast<const char*>(&x), /*sizeof(byte)*/1);
+194     }
+195   }
+196 }
+197 
+198 uint32_t num_words(const segment& s) {
+199   uint32_t sum = 0;
+200   for (int i = 0;  i < SIZE(s.lines);  ++i)
+201     sum += SIZE(s.lines.at(i).words);
+202   return sum;
+203 }
+204 
+205 :(before "End Includes")
+206 using std::ios;
+
+ + + -- cgit 1.4.1-2-gfad0