libksmforce

libksmforce is a shared library designed to force all memory allocated by programs to be KSM-mergeable. It leverages the prctl system call to enable Kernel Same-page Merging (KSM) for the entire process.

Table of Contents

• Introduction
• Requirements
• Installation
• Usage
• Functions
• License

Introduction

Kernel Same-page Merging (KSM) is a memory-saving de-duplication feature in the Linux kernel. It allows the kernel to share identical memory pages between different processes. This library intercepts memory allocation functions (malloc, calloc, realloc, mmap, mremap) and marks the allocated memory as mergeable using the prctl system call.

Requirements

• Linux operating system with KSM support
• GCC (GNU Compiler Collection)
• Development libraries: libdl

Installation

1. Compile the library:

   gcc -ggdb3 libksmforce.c -ldl -shared -fno-builtin-malloc -fPIC -o libksmforce.so

2. Set the environment variable LD_PRELOAD to load the library before running a program:

   LD_PRELOAD=./libksmforce.so ./program

Usage

To use libksmforce, compile it as a shared library and preload it before running your target program. This ensures that all memory allocations done by the target program are marked as KSM-mergeable.

Example

1. Compile the library:

   gcc -ggdb3 libksmforce.c -ldl -shared -fno-builtin-malloc -fPIC -o libksmforce.so

2. Run your program with LD_PRELOAD:

   LD_PRELOAD=./libksmforce.so ./your_program

Functions

libksmforce intercepts and overrides the following standard library functions:

• malloc(size_t size)
• free(void *ptr)
• calloc(size_t nmemb, size_t size)
• realloc(void *ptr, size_t size)
• mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset)
• munmap(void *addr, size_t length)
• mremap(void *old_address, size_t old_size, size_t new_size, int flags, ...)

Internal Functions

• libksmforce_init: Initializes the library by resolving the original memory allocation functions using dlsym.
• ksmforce: Enables KSM merging for the allocated memory using prctl.

License

This project is licensed under the MIT License. See the LICENSE file for details.