127 lines
5.8 KiB
C++
127 lines
5.8 KiB
C++
:(before "End Initialize Op Names")
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put_new(Name, "cd", "software interrupt (int)");
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:(before "End Single-Byte Opcodes")
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case 0xcd: { // int imm8 (software interrupt)
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trace(Callstack_depth+1, "run") << "syscall" << end();
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uint8_t code = next();
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if (code != 0x80) {
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raise << "Unimplemented interrupt code " << HEXBYTE << code << '\n' << end();
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raise << " Only `int 80h` supported for now.\n" << end();
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break;
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}
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process_int80();
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break;
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}
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:(code)
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void process_int80() {
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switch (Reg[EAX].u) {
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case 1:
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exit(/*exit code*/Reg[EBX].u);
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break;
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case 3:
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trace(Callstack_depth+1, "run") << "read: " << Reg[EBX].u << ' ' << Reg[ECX].u << ' ' << Reg[EDX].u << end();
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Reg[EAX].i = read(/*file descriptor*/Reg[EBX].u, /*memory buffer*/mem_addr_u8(Reg[ECX].u), /*size*/Reg[EDX].u);
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trace(Callstack_depth+1, "run") << "result: " << Reg[EAX].i << end();
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if (Reg[EAX].i == -1) raise << "read: " << strerror(errno) << '\n' << end();
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break;
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case 4:
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trace(Callstack_depth+1, "run") << "write: " << Reg[EBX].u << ' ' << Reg[ECX].u << ' ' << Reg[EDX].u << end();
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trace(Callstack_depth+1, "run") << Reg[ECX].u << " => " << mem_addr_string(Reg[ECX].u, Reg[EDX].u) << end();
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Reg[EAX].i = write(/*file descriptor*/Reg[EBX].u, /*memory buffer*/mem_addr_u8(Reg[ECX].u), /*size*/Reg[EDX].u);
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trace(Callstack_depth+1, "run") << "result: " << Reg[EAX].i << end();
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if (Reg[EAX].i == -1) raise << "write: " << strerror(errno) << '\n' << end();
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break;
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case 5: {
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check_flags(ECX);
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check_mode(EDX);
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trace(Callstack_depth+1, "run") << "open: " << Reg[EBX].u << ' ' << Reg[ECX].u << end();
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trace(Callstack_depth+1, "run") << Reg[EBX].u << " => " << mem_addr_kernel_string(Reg[EBX].u) << end();
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Reg[EAX].i = open(/*filename*/mem_addr_kernel_string(Reg[EBX].u), /*flags*/Reg[ECX].u, /*mode*/0640);
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trace(Callstack_depth+1, "run") << "result: " << Reg[EAX].i << end();
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if (Reg[EAX].i == -1) raise << "open: " << strerror(errno) << '\n' << end();
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break;
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}
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case 6:
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trace(Callstack_depth+1, "run") << "close: " << Reg[EBX].u << end();
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Reg[EAX].i = close(/*file descriptor*/Reg[EBX].u);
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trace(Callstack_depth+1, "run") << "result: " << Reg[EAX].i << end();
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if (Reg[EAX].i == -1) raise << "close: " << strerror(errno) << '\n' << end();
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break;
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case 8:
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check_mode(ECX);
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trace(Callstack_depth+1, "run") << "creat: " << Reg[EBX].u << end();
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trace(Callstack_depth+1, "run") << Reg[EBX].u << " => " << mem_addr_kernel_string(Reg[EBX].u) << end();
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Reg[EAX].i = creat(/*filename*/mem_addr_kernel_string(Reg[EBX].u), /*mode*/0640);
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trace(Callstack_depth+1, "run") << "result: " << Reg[EAX].i << end();
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if (Reg[EAX].i == -1) raise << "creat: " << strerror(errno) << '\n' << end();
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break;
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case 10:
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trace(Callstack_depth+1, "run") << "unlink: " << Reg[EBX].u << end();
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trace(Callstack_depth+1, "run") << Reg[EBX].u << " => " << mem_addr_kernel_string(Reg[EBX].u) << end();
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Reg[EAX].i = unlink(/*filename*/mem_addr_kernel_string(Reg[EBX].u));
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trace(Callstack_depth+1, "run") << "result: " << Reg[EAX].i << end();
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if (Reg[EAX].i == -1) raise << "unlink: " << strerror(errno) << '\n' << end();
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break;
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case 38:
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trace(Callstack_depth+1, "run") << "rename: " << Reg[EBX].u << " -> " << Reg[ECX].u << end();
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trace(Callstack_depth+1, "run") << Reg[EBX].u << " => " << mem_addr_kernel_string(Reg[EBX].u) << end();
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trace(Callstack_depth+1, "run") << Reg[ECX].u << " => " << mem_addr_kernel_string(Reg[ECX].u) << end();
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Reg[EAX].i = rename(/*old filename*/mem_addr_kernel_string(Reg[EBX].u), /*new filename*/mem_addr_kernel_string(Reg[ECX].u));
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trace(Callstack_depth+1, "run") << "result: " << Reg[EAX].i << end();
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if (Reg[EAX].i == -1) raise << "rename: " << strerror(errno) << '\n' << end();
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break;
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case 90: // mmap: allocate memory outside existing segment allocations
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trace(Callstack_depth+1, "run") << "mmap: allocate new segment" << end();
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// Ignore most arguments for now: address hint, protection flags, sharing flags, fd, offset.
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// We only support anonymous maps.
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Reg[EAX].u = new_segment(/*length*/read_mem_u32(Reg[EBX].u+0x4));
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trace(Callstack_depth+1, "run") << "result: " << Reg[EAX].u << end();
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break;
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case 0xa2: // nanosleep
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cerr << "not sleeping\n";
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break;
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default:
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raise << HEXWORD << EIP << ": unimplemented syscall " << Reg[EAX].u << '\n' << end();
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}
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}
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// SubX is oblivious to file permissions, directories, symbolic links, terminals, and much else besides.
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// Also ignoring any concurrency considerations for now.
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void check_flags(int reg) {
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uint32_t flags = Reg[reg].u;
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if (flags != ((flags & O_RDONLY) | (flags & O_WRONLY))) {
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cerr << HEXWORD << EIP << ": most POSIX flags to the open() syscall are not supported. Just O_RDONLY and O_WRONLY for now. Zero concurrent access support.\n";
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exit(1);
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}
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if ((flags & O_RDONLY) && (flags & O_WRONLY)) {
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cerr << HEXWORD << EIP << ": can't open a file for both reading and writing at once. See http://man7.org/linux/man-pages/man2/open.2.html.\n";
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exit(1);
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}
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}
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void check_mode(int reg) {
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if (Reg[reg].u != 0600) {
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cerr << HEXWORD << EIP << ": SubX is oblivious to file permissions; register " << reg << " must be 0x180.\n";
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exit(1);
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}
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}
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:(before "End Globals")
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// Very primitive/fixed/insecure mmap segments for now.
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uint32_t Segments_allocated_above = END_HEAP;
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:(code)
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// always allocate multiples of the segment size
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uint32_t new_segment(uint32_t length) {
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assert(length > 0);
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uint32_t result = (Segments_allocated_above - length) & 0xff000000; // same number of zeroes as SEGMENT_ALIGNMENT
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if (result <= START_HEAP) {
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raise << "Allocated too many segments; the VM ran out of memory. "
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<< "Maybe SEGMENT_ALIGNMENT can be smaller?\n" << die();
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}
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Mem.push_back(vma(result, result+length));
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Segments_allocated_above = result;
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return result;
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}
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