PINSYSCALLS(2) | System Calls Manual | PINSYSCALLS(2)

# NAME

`pinsyscalls` — pin system call entry to precise locations in the address space

# SYNOPSIS

`#include <sys/types.h>`

int
`pinsyscalls`(void *start, size_t len, u_int *pintable, int npins);

# DESCRIPTION

The `pinsyscalls`() system call specifies the start to start + len address space range where the system call entry instructions are found, and a npins-sized array of u_int entries (indexed by the system call number) which are offsets from the start.

This provides the precise location for the system call instruction required for each system call number. Attempting to use a different system call entry instruction to perform a non-corresponding system call operation will fail with signal `SIGABRT`.

`pinsyscalls`() is only called by the shared library linker ld.so(1) to tell the kernel where the text / executable region containing system calls is found in the dynamic library libc.so (the filename is actually /usr/lib/libc.so.major.minor). This has to happen before additional threads are created.

A similar setup operation is done automatically by the kernel for the system calls found in ld.so(1) and in static executables.

# RETURN VALUES

Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

# ERRORS

`pinsyscalls`() will fail if:

[`E2BIG`]
  Implausible number of system calls provided.
[`ENOMEM`]
  Insufficient memory to service the request.
[`EPERM`]
  A static binary tried to call `pinsyscalls`(), or it was called a second time.
[`EPERM`]
  Process is multi-threaded.
[`ERANGE`]
  At least one system call offset is beyond the bounds of len.

# HISTORY

The `pinsyscalls`() system call first appeared in OpenBSD 7.5.

April 6, 2025 | Debian