default or selected kernelversion does not have config value CONFIG_ASHMEM.
Result is shown for kernelversion 6.9.5

Enable the Anonymous Shared Memory Subsystem

modulename: ashmem.ko

configname: CONFIG_ASHMEM

Linux Kernel Configuration
└─>Device Drivers
└─>Staging drivers
└─>Enable the Anonymous Shared Memory Subsystem
In linux kernel since version 3.1 (release Date: 2011-10-24)  
The ashmem subsystem is a new shared memory allocator, similar to
POSIX SHM but with different behavior and sporting a simpler
file-based API.

It is, in theory, a good memory allocator for low-memory devices,
because it can discard shared memory units when under memory pressure.

source code: