about summary refs log tree commit diff stats
path: root/termbox
diff options
context:
space:
mode:
authorKartik Agaram <vc@akkartik.com>2018-07-07 23:13:25 -0700
committerKartik Agaram <vc@akkartik.com>2018-07-07 23:13:25 -0700
commitc90fa6534ecbdf3e61f19ce2b7cabbc2957ef202 (patch)
treea841f3e18c9a65ef2dcd22c603b623bcedaa7643 /termbox
parent97a9bd1756d5ea934372847bb9f1dfa8a4ad256d (diff)
downloadmu-c90fa6534ecbdf3e61f19ce2b7cabbc2957ef202.tar.gz
4325
Diffstat (limited to 'termbox')
0 files changed, 0 insertions, 0 deletions
 

generated by cgit-pink 1.4.1-2-gfad0 (git 2.36.2.497.gbbea4dcf42) at 2024-11-20 01:02:00 +0000


 


id='n104' href='#n104'>104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193


//: Loading SubX programs from ELF binaries.
//: This will allow us to run them natively on a Linux kernel.
//: Based on https://github.com/kragen/stoneknifeforth/blob/702d2ebe1b/386.c

:(before "End Main")
assert(argc > 1);
if (is_equal(argv[1], "run")) {
  // Outside of tests, traces must be explicitly requested.
  if (Trace_file.is_open()) Trace_stream = new trace_stream;
  trace(2, "run") << "=== Starting to run" << end();
  if (argc <= 2) {
    raise << "Not enough arguments provided.\n" << die();
  }
  reset();
  cerr << std::hex;
  load_elf(argv[2], argc, argv);
  while (EIP < End_of_program)  // weak final-gasp termination check
    run_one_instruction();
  raise << "executed past end of the world: " << EIP << " vs " << End_of_program << '\n' << end();
  return 1;
}

:(code)
void load_elf(const string& filename, int argc, char* argv[]) {
  int fd = open(filename.c_str(), O_RDONLY);
  if (fd < 0) raise << filename.c_str() << ": open" << perr() << '\n' << die();
  off_t size = lseek(fd, 0, SEEK_END);
  lseek(fd, 0, SEEK_SET);
  uint8_t* elf_contents = static_cast<uint8_t*>(malloc(size));
  if (elf_contents == NULL) raise << "malloc(" << size << ')' << perr() << '\n' << die();
  ssize_t read_size = read(fd, elf_contents, size);
  if (size != read_size) raise << "read → " << size << " (!= " << read_size << ')' << perr() << '\n' << die();
  load_elf_contents(elf_contents, size, argc, argv);
  free(elf_contents);
}

void load_elf_contents(uint8_t* elf_contents, size_t size, int argc, char* argv[]) {
  uint8_t magic[5] = {0};
  memcpy(magic, elf_contents, 4);
  if (memcmp(magic, "\177ELF", 4) != 0)
    raise << "Invalid ELF file; starts with \"" << magic << '"' << die();
  if (elf_contents[4] != 1)
    raise << "Only 32-bit ELF files (4-byte words; virtual addresses up to 4GB) supported.\n" << die();
  if (elf_contents[5] != 1)
    raise << "Only little-endian ELF files supported.\n" << die();
  // unused: remaining 10 bytes of e_ident
  uint32_t e_machine_type = u32_in(&elf_contents[16]);
  if (e_machine_type != 0x00030002)
    raise << "ELF type/machine 0x" << HEXWORD << e_machine_type << " isn't i386 executable\n" << die();
  // unused: e_version. We only support version 1, and later versions will be backwards compatible.
  uint32_t e_entry = u32_in(&elf_contents[24]);
  uint32_t e_phoff = u32_in(&elf_contents[28]);
  // unused: e_shoff
  // unused: e_flags
  uint32_t e_ehsize = u16_in(&elf_contents[40]);
  if (e_ehsize < 52) raise << "Invalid binary; ELF header too small\n" << die();
  uint32_t e_phentsize = u16_in(&elf_contents[42]);
  uint32_t e_phnum = u16_in(&elf_contents[44]);
  trace(90, "load") << e_phnum << " entries in the program header, each " << e_phentsize << " bytes long" << end();
  // unused: e_shentsize
  // unused: e_shnum
  // unused: e_shstrndx

  set<uint32_t> overlap;  // to detect overlapping segments
  for (size_t i = 0;  i < e_phnum;  ++i)
    load_segment_from_program_header(elf_contents, i, size, e_phoff + i*e_phentsize, e_ehsize, overlap);

  // initialize code and stack
  assert(overlap.find(STACK_SEGMENT) == overlap.end());
  Mem.push_back(vma(STACK_SEGMENT));
  assert(overlap.find(AFTER_STACK) == overlap.end());
  // The stack grows downward.
  Reg[ESP].u = AFTER_STACK;
  Reg[EBP].u = 0;
  EIP = e_entry;

  // initialize args on stack
  // no envp for now
  // we wastefully use a separate page of memory for argv
  Mem.push_back(vma(ARGV_DATA_SEGMENT));
  uint32_t argv_data = ARGV_DATA_SEGMENT;
  for (int i = argc-1;  i >= /*skip 'subx_bin' and 'run'*/2;  --i) {
    push(argv_data);
    for (size_t j = 0;  j <= strlen(argv[i]);  ++j) {
      assert(overlap.find(argv_data) == overlap.end());  // don't bother comparing ARGV and STACK
      write_mem_u8(argv_data, argv[i][j]);
      argv_data += sizeof(char);
      assert(argv_data < ARGV_DATA_SEGMENT + SEGMENT_ALIGNMENT);
    }
  }
  push(argc-/*skip 'subx_bin' and 'run'*/2);
}

void push(uint32_t val) {
  Reg[ESP].u -= 4;
  if (Reg[ESP].u < STACK_SEGMENT) {
    raise << "The stack overflowed its segment. "
          << "Maybe SPACE_FOR_SEGMENT should be larger? "
          << "Or you need to carve out an exception for the stack segment "
          << "to be larger.\n" << die();
  }
  trace(Callstack_depth+1, "run") << "decrementing ESP to 0x" << HEXWORD << Reg[ESP].u << end();
  trace(Callstack_depth+1, "run") << "pushing value 0x" << HEXWORD << val << end();
  write_mem_u32(Reg[ESP].u, val);
}

void load_segment_from_program_header(uint8_t* elf_contents, int segment_index, size_t size, uint32_t offset, uint32_t e_ehsize, set<uint32_t>& overlap) {
  uint32_t p_type = u32_in(&elf_contents[offset]);
  trace(90, "load") << "program header at offset " << offset << ": type " << p_type << end();
  if (p_type != 1) {
    trace(90, "load") << "ignoring segment at offset " << offset << " of non PT_LOAD type " << p_type << " (see http://refspecs.linuxbase.org/elf/elf.pdf)" << end();
    return;
  }
  uint32_t p_offset = u32_in(&elf_contents[offset + 4]);
  uint32_t p_vaddr = u32_in(&elf_contents[offset + 8]);
  if (e_ehsize > p_vaddr) raise << "Invalid binary; program header overlaps ELF header\n" << die();
  // unused: p_paddr
  uint32_t p_filesz = u32_in(&elf_contents[offset + 16]);
  uint32_t p_memsz = u32_in(&elf_contents[offset + 20]);
  if (p_filesz != p_memsz)
    raise << "Can't yet handle segments where p_filesz != p_memsz (see http://refspecs.linuxbase.org/elf/elf.pdf)\n" << die();

  if (p_offset + p_filesz > size)
    raise << "Invalid binary; segment at offset " << offset << " is too large: wants to end at " << p_offset+p_filesz << " but the file ends at " << size << '\n' << die();
  if (p_memsz >= SEGMENT_ALIGNMENT) {
    raise << "Code segment too small for SubX; for now please manually increase SEGMENT_ALIGNMENT.\n" << end();
    return;
  }
  trace(90, "load") << "blitting file offsets (" << p_offset << ", " << (p_offset+p_filesz) << ") to addresses (" << p_vaddr << ", " << (p_vaddr+p_memsz) << ')' << end();
  if (size > p_memsz) size = p_memsz;
  Mem.push_back(vma(p_vaddr));
  for (size_t i = 0;  i < p_filesz;  ++i) {
    assert(overlap.find(p_vaddr+i) == overlap.end());
    write_mem_u8(p_vaddr+i, elf_contents[p_offset+i]);
    overlap.insert(p_vaddr+i);
  }
  if (segment_index == 0 && End_of_program < p_vaddr+p_memsz)
    End_of_program = p_vaddr+p_memsz;
}

:(before "End Includes")
// Very primitive/fixed/insecure ELF segments for now.
//   --- inaccessible:        0x00000000 -> 0x08047fff
//   code:                    0x09000000 -> 0x09ffffff (specified in ELF binary)
//   data:                    0x0a000000 -> 0x0affffff (specified in ELF binary)
//                      --- heap gets mmap'd somewhere here ---
//   stack:                   0xbdffffff -> 0xbd000000 (downward; not in ELF binary)
//   argv hack:               0xbf000000 -> 0xbfffffff (not in ELF binary)
//   --- reserved for kernel: 0xc0000000 -> ...
const uint32_t START_HEAP        = 0x0b000000;
const uint32_t END_HEAP          = 0xbd000000;
const uint32_t STACK_SEGMENT     = 0xbd000000;
const uint32_t AFTER_STACK       = 0xbe000000;
const uint32_t ARGV_DATA_SEGMENT = 0xbf000000;
// When updating the above memory map, don't forget to update `mmap`'s
// implementation in the 'syscalls' layer.
:(before "End Dump Info for Instruction")
//? dump_stack();  // slow
:(code)
void dump_stack() {
  ostringstream out;
  trace(Callstack_depth+1, "run") << "stack:" << end();
  for (uint32_t a = AFTER_STACK-4;  a > Reg[ESP].u;  a -= 4)
    trace(Callstack_depth+2, "run") << "  0x" << HEXWORD << a << " => 0x" << HEXWORD << read_mem_u32(a) << end();
  trace(Callstack_depth+2, "run") << "  0x" << HEXWORD << Reg[ESP].u << " => 0x" << HEXWORD << read_mem_u32(Reg[ESP].u) << "  <=== ESP" << end();
  for (uint32_t a = Reg[ESP].u-4;  a > Reg[ESP].u-40;  a -= 4)
    trace(Callstack_depth+2, "run") << "  0x" << HEXWORD << a << " => 0x" << HEXWORD << read_mem_u32(a) << end();
}

inline uint32_t u32_in(uint8_t* p) {
  return p[0] | p[1] << 8 | p[2] << 16 | p[3] << 24;
}

inline uint16_t u16_in(uint8_t* p) {
  return p[0] | p[1] << 8;
}

:(before "End Types")
struct perr {};
:(code)
ostream& operator<<(ostream& os, perr /*unused*/) {
  if (errno)
    os << ": " << strerror(errno);
  return os;
}

:(before "End Includes")
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdarg.h>
#include <errno.h>
#include <unistd.h>