update readme, expand .ci

  needs: ['build-job']

  script:

    - ls -ltrh ${INSTALL_PATH}

    - ${BUILD_PATH}/opendevnull --syscall getpid

    - LD_PRELOAD=${BUILD_PATH}/libeval_intercept.so ${BUILD_PATH}/opendevnull --syscall getpid

    - ${BUILD_PATH}/opendevnull --syscall getpid --reps 1 --verbose

    - LD_PRELOAD=${BUILD_PATH}/libeval_intercept.so ${BUILD_PATH}/opendevnull --syscall getpid --reps 1 --verbose

  artifacts:

    expire_in: 1 week

    when: always

# Syscall Timing Utility

A tool for measuring and analyzing system call execution times on Linux systems.

## Overview

This project provides utilities to measure and analyze the timing of various system calls, helping developers understand performance characteristics and potential bottlenecks in system-level operations.

## Prerequisites

- Linux operating system

- CMake (version 3.13 or higher)

- C++17 compatible compiler

- syscall_intercept library

## Installation

```bash

mkdir build && cd build

cmake ..

make

make install

```

## Usage

The project includes two main components:

- `eval_intercept`: A shared library for syscall interception

- `opendevnull`: An executable for timing syscalls

### Running opendevnull

```bash

./opendevnull --syscall <open|getpid> [options]

Options:

    --reps N           Number of repetitions (default: 100M)

    --always_syscall   Always execute the original syscall (only use with interception and getpid)

    --verbose          Enable debug output

```

## Example

### Native syscall 

```bash

./opendevnull --syscall getpid

Mean time taken: 0.329911 microseconds

```

### Intercepted syscall (syscall interception -> C hook -> native syscall)

```bash

LD_PRELOAD=./libeval_intercept.so ./opendevnull --syscall getpid --always_syscall

Mean time taken: 0.382829 microseconds

```

### Intercepted syscall (syscall interception -> C hook) , no kernel execution

```bash

LD_PRELOAD=./libeval_intercept.so ./opendevnull --syscall getpid 

Mean time taken: 0.0408641 microseconds

```

## License

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

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