How to Use the Command 'ausyscall' (with Examples)

ausyscall is a command-line tool used for mapping syscall names and numbers, providing a crucial bridge between human-readable syscall names and their corresponding numeric codes that are used at the kernel level. Understanding syscalls is particularly important for developers and system administrators involved in debugging or auditing low-level system calls on Linux systems. By translating between syscall names and numbers, ausyscall allows users to gain clarity and insight into system-level operations.

Use Case 1: Display Syscall Number of a Specific System Call

Code:

ausyscall getpid

Motivation:

Using ausyscall to determine the syscall number of a specific system call is useful because developers often need to reference these numbers in low-level programming, auditing, or debugging. Knowing the syscall number is essential when writing code that interacts directly with the kernel using assembly language or when analyzing raw data captured via system monitors or security audits.

Explanation:

• ausyscall: Invokes the command to interface with syscall mappings.
• getpid: Represents a specific system call name. Here, “getpid” is used, which retrieves the process ID of the calling process.

Example Output:

20 (for example, it might vary depending on architecture and system)

This output signifies that the syscall number for getpid is 20, which is a common reference point for interacting with the Linux kernel regarding process identifiers.

Use Case 2: Display Name of a Specific System Call Number

Code:

ausyscall 60

Motivation:

Projects that involve binary analysis or system monitoring often yield raw syscall numbers without context. Using ausyscall to obtain the syscall name from a numeric value helps analysts and developers understand what specific action was invoked by a system binary. This translation aids in debugging, auditing, and enhancing software security.

Explanation:

• ausyscall: Utilizes the command to perform syscall name-number mapping.
• 60: Denotes an example syscall number for which the user seeks the corresponding name.

Example Output:

exit

In this case, ’exit’ correlates to syscall number 60, which is critical information when examining how a program terminates or interacts with process management.

Use Case 3: Display All System Calls for a Specific Architecture

Code:

ausyscall x86_64 --dump

Motivation:

When developing or debugging software that must interact with a specific hardware architecture, it is indispensable to have a comprehensive view of all available syscalls. This understanding of architecture-specific syscall lists is especially significant in cross-platform development or when porting software to different platforms.

Explanation:

• ausyscall: Calls upon the command to fetch syscall data.
• x86_64: Indicates the desired architecture. In this command, it specifies fetching syscall data pertinent to the x86_64 architecture.
• --dump: An argument that instructs the command to output the entire list of syscalls for the specified architecture.

Example Output:

0 read
1 write
2 open
...

This output enumerates every syscall name along with its number for the x86_64 architecture, providing developers and system architects with invaluable data for system-level coding and architecture-specific optimizations.

Conclusion

The ausyscall command serves as a pivotal tool for developers, system administrators, and security professionals who need to map syscall names to their numeric representations and vice versa. Each use case outlined demonstrates a unique scenario where this command proves advantageous, whether it’s understanding low-level operations, analyzing system behavior, or developing cross-platform applications. By mastering ausyscall, users enhance their proficiency in handling Linux systems and achieve greater insights into the kernel’s workings.