4520 - several syscalls for files

1 files changed, 78 insertions, 0 deletions

diff --git a/subx/020syscalls.cc b/subx/020syscalls.cc
index 177ba6f1..2f6ca994 100644
--- a/subx/020syscalls.cc
+++ b/subx/020syscalls.cc
@@ -21,12 +21,90 @@ void process_int80() {
     exit(/*exit code*/Reg[EBX].u);
     break;
   case 3:
+    trace(91, "run") << "read: " << Reg[EBX].u << ' ' << Reg[ECX].u << '/' << mem_addr_string(Reg[ECX].u) << ' ' << Reg[EDX].u << end();
     Reg[EAX].i = read(/*file descriptor*/Reg[EBX].u, /*memory buffer*/mem_addr_u8(Reg[ECX].u), /*size*/Reg[EDX].u);
+    trace(91, "run") << "result: " << Reg[EAX].i << end();
+    if (Reg[EAX].i == -1) raise << strerror(errno) << '\n' << end();
     break;
   case 4:
+    trace(91, "run") << "write: " << Reg[EBX].u << ' ' << Reg[ECX].u << '/' << mem_addr_string(Reg[ECX].u) << ' ' << Reg[EDX].u << end();
     Reg[EAX].i = write(/*file descriptor*/Reg[EBX].u, /*memory buffer*/mem_addr_u8(Reg[ECX].u), /*size*/Reg[EDX].u);
+    trace(91, "run") << "result: " << Reg[EAX].i << end();
+    if (Reg[EAX].i == -1) raise << strerror(errno) << '\n' << end();
+    break;
+  case 5: {
+    check_flags(ECX);
+    check_mode(EDX);
+    trace(91, "run") << "open: " << Reg[EBX].u << '/' << mem_addr_string(Reg[EBX].u) << ' ' << Reg[ECX].u << end();
+    Reg[EAX].i = open(/*filename*/mem_addr_string(Reg[EBX].u), /*flags*/Reg[ECX].u, /*mode*/0640);
+    trace(91, "run") << "result: " << Reg[EAX].i << end();
+    if (Reg[EAX].i == -1) raise << strerror(errno) << '\n' << end();
+    break;
+  }
+  case 6:
+    trace(91, "run") << "close: " << Reg[EBX].u << end();
+    Reg[EAX].i = close(/*file descriptor*/Reg[EBX].u);
+    trace(91, "run") << "result: " << Reg[EAX].i << end();
+    if (Reg[EAX].i == -1) raise << strerror(errno) << '\n' << end();
+    break;
+  case 8:
+    check_mode(ECX);
+    trace(91, "run") << "creat: " << Reg[EBX].u << '/' << mem_addr_string(Reg[EBX].u) << end();
+    Reg[EAX].i = creat(/*filename*/mem_addr_string(Reg[EBX].u), /*mode*/0640);
+    trace(91, "run") << "result: " << Reg[EAX].i << end();
+    if (Reg[EAX].i == -1) raise << strerror(errno) << '\n' << end();
+    break;
+  case 10:
+    trace(91, "run") << "unlink: " << Reg[EBX].u << '/' << mem_addr_string(Reg[EBX].u) << end();
+    Reg[EAX].i = unlink(/*filename*/mem_addr_string(Reg[EBX].u));
+    trace(91, "run") << "result: " << Reg[EAX].i << end();
+    if (Reg[EAX].i == -1) raise << strerror(errno) << '\n' << end();
+    break;
+  case 38:
+    trace(91, "run") << "rename: " << Reg[EBX].u << '/' << mem_addr_string(Reg[EBX].u) << " -> " << Reg[ECX].u << '/' << mem_addr_string(Reg[ECX].u) << end();
+    Reg[EAX].i = rename(/*old filename*/mem_addr_string(Reg[EBX].u), /*new filename*/mem_addr_string(Reg[ECX].u));
+    trace(91, "run") << "result: " << Reg[EAX].i << end();
+    if (Reg[EAX].i == -1) raise << strerror(errno) << '\n' << end();
+    break;
+  case 45:  // brk: modify size of data segment
+    trace(91, "run") << "grow data segment to " << Reg[EBX].u << end();
+    resize_mem(/*new end address*/Reg[EBX].u);
     break;
   default:
     raise << HEXWORD << EIP << ": unimplemented syscall " << Reg[EAX].u << '\n' << end();
   }
 }
+
+// SubX is oblivious to file permissions, directories, symbolic links, terminals, and much else besides.
+// Also ignoring any concurrency considerations for now.
+void check_flags(int reg) {
+  uint32_t flags = Reg[reg].u;
+  if (flags != ((flags & O_RDONLY) | (flags & O_WRONLY))) {
+    raise << 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" << end();
+    exit(1);
+  }
+  if ((flags & O_RDONLY) && (flags & O_WRONLY)) {
+    raise << 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" << end();
+    exit(1);
+  }
+}
+
+void check_mode(int reg) {
+  if (Reg[reg].u != 0600) {
+    raise << HEXWORD << EIP << ": SubX is oblivious to file permissions; register " << reg << " must be 0.\n" << end();
+    exit(1);
+  }
+}
+
+void resize_mem(uint32_t new_end_address) {
+  if (new_end_address < Mem_offset) {
+    raise << HEXWORD << EIP << ": can't shrink data segment to before code segment\n";
+    return;
+  }
+  int32_t new_size = new_end_address - Mem_offset;
+  if (new_size < SIZE(Mem)) {
+    raise << HEXWORD << EIP << ": shrinking data segment is not supported.\n" << end();
+    return;
+  }
+  Mem.resize(new_size);  // will throw exception on failure
+}