// TODO: restructure this function
// For example posix_spawn from chromium seems to have a
// maintainable flow: https://chromium.googlesource.com/native_client/nacl-newlib/+/bf66148d14c7fca26b9198dd5dc81e743893bb66/newlib/libc/posix/posix_spawn.c
private static unsafe int ForkAndExec(
string filename, string[] argv, string[] envp,
string cwd, bool useTty, bool redirectStdin,
bool redirectStdout, bool redirectStderr,
out int stdin, out int stdout, out int stderr
)
{
byte **argvPtr = null;
byte **envpPtr = null;
bool success = true;
ArrayHelpers.AllocNullTerminatedArray(argv, ref argvPtr);
ArrayHelpers.AllocNullTerminatedArray(envp, ref envpPtr);
int[] stdInFds = new[] { -1, -1 };
int[] stdOutFds = new[] { -1, -1 };
int[] stdErrFds = new[] { -1, -1 };
int masterFd = -1;
int slaveFd = -1;
try
{
int inFd, outFd, errFd;
if (filename == null || argv == null || envp == null)
{
success = false;
throw new ArgumentException("Provide the correct arguments");
}
if (Libc.access(filename, Libc.X_OK) != 0)
{
success = false;
throw new Exception("The given file is not accessible");
}
if (useTty)
{
var size = new winsize
{
ws_col = DEFAULT_WIDTH,
ws_row = DEFAULT_HEIGHT
};
if (Libc.openpty(out masterFd, out slaveFd, IntPtr.Zero, IntPtr.Zero, ref size) == -1)
{
success = false;
throw new Exception("Could not open a new pty");
}
}
else
{
try
{
if (redirectStdin)
{
CreateCloseOnExecPipe(stdInFds);
}
if (redirectStdout)
{
CreateCloseOnExecPipe(stdOutFds);
}
if (redirectStderr)
{
CreateCloseOnExecPipe(stdErrFds);
}
}
catch (Exception ex)
{
success = false;
throw ex;
}
}
var pid = Libc.fork();
if (pid < 0)
{
success = false;
Error.ThrowExceptionForLastError();
}
if (pid == 0)
{
if (useTty)
{
Libc.close(masterFd);
Libc.setsid();
if (Libc.ioctl(slaveFd, Libc.TIOCSCTTY) == -1)
{
success = false;
Error.ThrowExceptionForLastError();
}
inFd = outFd = errFd = slaveFd;
}
else
{
inFd = stdInFds[READ_END_OF_PIPE];
outFd = stdOutFds[WRITE_END_OF_PIPE];
errFd = stdErrFds[WRITE_END_OF_PIPE];
}
// TODO: this code is just horrible and the likely hood introducing bugs here is quite high.
// I should refactor this asap. But first I would love to get some more tests in place that
// could catch any regressions..
if (redirectStdin)
{
while (Error.ShouldRetrySyscall(Libc.dup2(inFd, Libc.STDIN_FILENO)) && Libc.errno == Libc.EBUSY)
{
;
}
}
if (redirectStdout)
{
while (Error.ShouldRetrySyscall(Libc.dup2(outFd, Libc.STDOUT_FILENO)) && Libc.errno == Libc.EBUSY)
{
;
}
}
if (redirectStderr)
{
while (Error.ShouldRetrySyscall(Libc.dup2(errFd, Libc.STDERR_FILENO)) && Libc.errno == Libc.EBUSY)
{
;
}
}
if (!string.IsNullOrEmpty(cwd))
{
var ret = Libc.chdir(cwd);
if (ret == -1)
{
success = false;
Error.ThrowExceptionForLastError();
}
}
Libc.execve(filename, argvPtr, envpPtr);
// Exec syscall should never return, and thus we should never get here, if we do then exit immediately
Libc._exit(Libc.errno != 0 ? Libc.errno : -1);
}
Libc.close(slaveFd);
if (useTty)
{
stdin = masterFd;
stdout = masterFd;
stderr = masterFd;
}
else
{
stdin = stdInFds[WRITE_END_OF_PIPE];
stdout = stdOutFds[READ_END_OF_PIPE];
stderr = stdErrFds[READ_END_OF_PIPE];
}
return(pid);
}
finally
{
// Regardless of success or failure, close the parent's copy of the child's end of
// any opened pipes. The parent doesn't need them anymore.
CloseIfOpen(stdInFds[READ_END_OF_PIPE]);
CloseIfOpen(stdOutFds[WRITE_END_OF_PIPE]);
CloseIfOpen(stdErrFds[WRITE_END_OF_PIPE]);
if (!success)
{
// Cleanup all open fd
CloseIfOpen(masterFd);
CloseIfOpen(slaveFd);
CloseIfOpen(stdInFds[WRITE_END_OF_PIPE]);
CloseIfOpen(stdOutFds[READ_END_OF_PIPE]);
CloseIfOpen(stdErrFds[READ_END_OF_PIPE]);
}
ArrayHelpers.FreeArray(argvPtr, argv.Length);
ArrayHelpers.FreeArray(envpPtr, envp.Length);
}
}