Package "psx" provides an API for invoking system calls in a way that
each system call is mirrored on all OS threads of the combined Go/CGo
runtime. Since the Go runtime treats OS threads as interchangeable, a
feature like this is needed to meaningfully change process privilege
(including dropping privilege) in a Go program running on Linux. This
package is required by:

   "kernel.org/pub/linux/libs/security/libcap/cap"

When compiled CGO_ENABLED=0, the functionality requires go1.16+ to
build. That release of Go introduced syscall.AllThreadsSyscall*()
APIs.  When compiled this way, the "psx" package functions
psx.Syscall3() and psx.Syscall6() are aliased to
syscall.AllThreadsSyscall() and syscall.AllThreadsSyscall6()
respectively.

When compiled CGO_ENABLED=1, the functionality is implemented by C
code, [lib]psx, which is distributed with libcap.

The official release announcement site for libcap and libpsx is:

   https://sites.google.com/site/fullycapable/

Like libcap/libpsx itself, the "psx" package is distributed with a
"you choose" License. Specifically: BSD three clause, or GPL2. See the
License file.

Andrew G. Morgan <morgan@kernel.org>