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KasperskyOS API  >  POSIX support  >  POSIX support limitations

POSIX support limitations

KasperskyOS uses a limited POSIX interface oriented toward the POSIX.1-2008 standard (without XSI support). These limitations are primarily due to security precautions.

Limitations affect the following:

  • Interaction between processes
  • Interaction between threads via signals
  • Standard input/output
  • Asynchronous input/output
  • Use of robust mutexes
  • Terminal operations
  • Shell usage
  • Management of file handles

Limitations include:

  • Unimplemented interfaces
  • Interfaces that are implemented with deviations from the POSIX.1-2008 standard
  • Stub interfaces that do not perform any operations except assign the ENOSYS value to the errno variable and return the value -1

In KasperskyOS, signals cannot interrupt the Call(), Recv(), and Reply() system calls that support the operation of libraries that implement the POSIX interface.

The KasperskyOS kernel does not transmit signals.

Limitations on interaction between processes

Interface

Purpose

Implementation

Header file based on the POSIX.1-2008 standard

fork()

Create a new (child) process.

Stub

unistd.h

pthread_

atfork()

Register the handlers that are called before and after the child process is created.

Not implemented

pthread.h

wait()

Wait for the child process to stop or complete.

Stub

sys/wait.h

waitid()

Wait for the state of the child process to change.

Not implemented

sys/wait.h

waitpid()

Wait for the child process to stop or complete.

Stub

sys/wait.h

execl()

Run the executable file.

Stub

unistd.h

execle()

Run the executable file.

Stub

unistd.h

execlp()

Run the executable file.

Stub

unistd.h

execv()

Run the executable file.

Stub

unistd.h

execve()

Run the executable file.

Stub

unistd.h

execvp()

Run the executable file.

Stub

unistd.h

fexecve()

Run the executable file.

Stub

unistd.h

setpgid()

Move the process to another group or create a group.

Stub

unistd.h

setsid()

Create a session.

Not implemented

unistd.h

getpgrp()

Get the group ID for the calling process.

Not implemented

unistd.h

getpgid()

Get the group ID.

Stub

unistd.h

getppid()

Get the ID of the parent process.

Not implemented

unistd.h

getsid()

Get the session ID.

Stub

unistd.h

times()

Get the time values for the process and its descendants.

Stub

sys/times.h

kill()

Send a signal to the process or group of processes.

Only the SIGTERM signal can be sent. The pid parameter is ignored.

signal.h

pause()

Wait for a signal.

Not implemented

unistd.h

sigpending()

Check for received blocked signals.

Not implemented

signal.h

sigprocmask()

Get and change the set of blocked signals.

Stub

signal.h

sigsuspend()

Wait for a signal.

Stub

signal.h

sigwait()

Wait for a signal from the defined set of signals.

Stub

signal.h

sigqueue()

Send a signal to the process.

Not implemented

signal.h

sigtimedwait()

Wait for a signal from the defined set of signals.

Not implemented

signal.h

sigwaitinfo()

Wait for a signal from the defined set of signals.

Not implemented

signal.h

sem_init()

Create an unnamed semaphore.

You cannot create an unnamed semaphore for synchronization between processes. If a non-zero value is passed to the function through the pshared parameter, it will only return the value -1 and will assign the ENOTSUP value to the errno variable.

semaphore.h

sem_open()

Create/open a named semaphore.

You cannot open a named semaphore that was created by another process. Named semaphores (like unnamed semaphores) are local, which means that they are accessible only to the process that created them.

semaphore.h

pthread_

mutexattr_

setpshared()

Define the mutex attribute that allows the mutex to be used by multiple processes.

You cannot define the mutex attribute that allows the mutex to be used by multiple processes. If the PTHREAD_PROCESS_SHARED value is passed to the function through the pshared parameter, it will only return the ENOSYS value.

pthread.h

pthread_

barrierattr_

setpshared()

Define the barrier attribute that allows the barrier to be used by multiple processes.

You cannot define the barrier attribute that allows the barrier to be used by multiple processes. If the PTHREAD_PROCESS_SHARED value is passed to the function through the pshared parameter, it will only return the ENOSYS value.

pthread.h

pthread_

condattr_

setpshared()

Define the conditional variable attribute that allows the conditional variable to be used by multiple processes.

You cannot define the conditional variable attribute that allows the conditional variable to be used by multiple processes. If the PTHREAD_PROCESS_SHARED value is passed to the function through the pshared parameter, it will only return the ENOSYS value.

pthread.h

pthread_

rwlockattr_

setpshared()

Define the read/write lock object attribute that allows the read/write lock object attribute to be used by multiple processes.

You cannot define the read/write lock object attribute that allows the read/write lock object attribute to be used by multiple processes. If the PTHREAD_PROCESS_SHARED value is passed to the function through the pshared parameter, it will only return the ENOSYS value.

pthread.h

pthread_

spin_init()

Create a spin lock.

You cannot create a spin lock for synchronization between processes. If the PTHREAD_PROCESS_SHARED value is passed to the function through the pshared parameter, this value will be ignored.

pthread.h

shm_open()

Create or open a shared memory object.

Not implemented

sys/mman.h

mmap()

Map to memory.

You cannot perform memory mapping for interaction between processes. If the MAP_SHARED and PROT_WRITE values are passed to the function through the flags and prot parameters, respectively, the function will return the MAP_FAILED value and will assign the EACCES value to the errno variable. For all other possible values of the prot parameter, the MAP_SHARED value of the flags parameter will be ignored. In addition, you cannot pass combinations of the PROT_WRITE|PROT_EXEC and PROT_READ|PROT_WRITE|PROT_EXEC flags through the prot parameter. In this case, the function will only return the MAP_FAILED value and will assign the ENOMEM value to the errno variable.

sys/mman.h

mprotect()

Define the memory access permissions.

This function works as a stub by default. To use this function, define special settings for the KasperskyOS kernel.

sys/mman.h

pipe()

Create an unnamed channel.

You cannot use an unnamed channel for data transfer between processes. Unnamed channels are local, which means that they are accessible only to the process that created them.

unistd.h

mkfifo()

Create a special FIFO file (named channel).

Stub

sys/stat.h

mkfifoat()

Create a special FIFO file (named channel).

Not implemented

sys/stat.h

Limitations on interaction between threads via signals

Interface

Purpose

Implementation

Header file based on the POSIX.1-2008 standard

pthread_kill()

Send a signal to a thread.

You cannot send a signal to a thread. If a signal number is passed to the function through the sig parameter, it only returns the ENOSYS value.

signal.h

pthread_sigmask()

Get and change the set of blocked signals.

Stub

signal.h

siglongjmp()

Restore the state of the control thread and the signals mask.

Not implemented

setjmp.h

sigsetjmp()

Save the state of the control thread and the signals mask.

Not implemented

setjmp.h

Standard input/output limitations

Interface

Purpose

Implementation

Header file based on the POSIX.1-2008 standard

dprintf()

Formatted print to file.

Not implemented

stdio.h

fmemopen()

Use memory as a data stream.

Not implemented

stdio.h

open_memstream()

Use dynamically allocated memory as a data stream.

Not implemented

stdio.h

vdprintf()

Formatted print to file.

Not implemented

stdio.h

Asynchronous input/output limitations

Interface

Purpose

Implementation

Header file based on the POSIX.1-2008 standard

aio_cancel()

Cancel input/output requests that are waiting to be handled.

Not implemented

aio.h

aio_error()

Receive an error from an asynchronous input/output operation.

Not implemented

aio.h

aio_fsync()

Request the execution of input/output operations.

Not implemented

aio.h

aio_read()

Request a file read operation.

Not implemented

aio.h

aio_return()

Get the status of an asynchronous input/output operation.

Not implemented

aio.h

aio_suspend()

Wait for the completion of asynchronous input/output operations.

Not implemented

aio.h

aio_write()

Request a file write operation.

Not implemented

aio.h

lio_listio()

Request execution of a set of input/output operations.

Not implemented

aio.h

Limitations on the use of robust mutexes

Interface

Purpose

Implementation

Header file based on the POSIX.1-2008 standard

pthread_mutex_consistent()

Return a robust mutex to a consistent state.

Not implemented

pthread.h

pthread_mutexattr_getrobust()

Get a robust mutex attribute.

Not implemented

pthread.h

pthread_mutexattr_setrobust()

Define a robust mutex attribute.

Not implemented

pthread.h

Terminal operation limitations

Interface

Purpose

Implementation

Header file based on the POSIX.1-2008 standard

ctermid()

Get the path to the file of the control terminal.

This function only returns or passes an empty string through the s parameter.

stdio.h

tcsetattr()

Define the terminal settings.

The input speed, output speed, and other settings specific to hardware terminals are ignored.

termios.h

tcdrain()

Wait for output completion.

This function only returns the value -1.

termios.h

tcflow()

Suspend or resume receipt or transmission of data.

Suspending output and resuming suspended output are not supported.

termios.h

tcflush()

Clear the input queue or output queue, or both of these queues.

This function only returns the value -1.

termios.h

tcsendbreak()

Break the connection with the terminal for a set time.

This function only returns the value -1.

termios.h

ttyname()

Get the path to the terminal file.

This function only returns a null pointer.

unistd.h

ttyname_r()

Get the path to the terminal file.

This function only returns an error value.

unistd.h

tcgetpgrp()

Get the ID of a group of processes using the terminal.

This function only returns the value -1.

unistd.h

tcsetpgrp()

Define the ID for a group of processes using the terminal.

This function only returns the value -1.

unistd.h

tcgetsid()

Get the ID of a group of processes for the leader of the session connected to the terminal.

This function only returns the value -1.

termios.h

Shell operation limitations

Interface

Purpose

Implementation

Header file based on the POSIX.1-2008 standard

popen()

Create a child process for command execution and a channel for this process.

This function only assigns the ENOSYS value to the errno variable and returns the value NULL.

stdio.h

pclose()

Close the channel with the child process created by the popen() function, and wait for this child process to terminate.

This function cannot be used because its input parameter is the data stream handle returned by the popen() function, which cannot return anything except the value NULL.

stdio.h

system()

Create a child process for command execution.

Stub

stdlib.h

wordexp()

Perform a shell-like expansion of the string.

Not implemented

wordexp.h

wordfree()

Free up the memory allocated for the results of calling the wordexp() interface.

Not implemented

wordexp.h

Limitations on management of file handles

Interface

Purpose

Implementation

Header file based on the POSIX.1-2008 standard

dup()

Make a copy of the handle of an opened file.

Handles of regular files, standard I/O streams, sockets and channels are supported. There is no guarantee that the lowest available handle will be received.

fcntl.h

dup2()

Make a copy of the handle of an opened file.

Handles of regular files, standard I/O streams, sockets and channels are supported. The handle of an opened file needs to be passed through the fildes2 parameter.

fcntl.h

Article ID: posix_uns_ifaces, Last review: Aug 2, 2023
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