Analyzing Process Memory Maps

Differentiate between private, shared, and mapped memory segments for a given process.

In this lesson, you will learn how to distinguish between private, shared, and mapped memory segments by inspecting a process’s memory layout.

When you look at a process’s memory map—typically found in /proc/[pid]/maps—you aren't just seeing a list of numbers; you are seeing how the Linux kernel organizes the resources that process uses. Every process has a unique memory "fingerprint" composed of three primary types of segments.

Understanding the Map

To see this in action, run cat /proc/self/maps in your terminal. You will see columns representing the memory address range, permissions, offset, device, and the associated file.

Private Memory (Anonymous): These segments are specific to the process. If you modify data here, the kernel uses "copy-on-write" to ensure these changes stay local to this process and are not visible to others. These often appear without a file path (or labeled as [anon]). This is where your process stores its stack and heap.
Shared Memory: These segments allow multiple processes to access the same physical RAM. If one process changes data in a shared segment, all other processes attached to it see the update immediately. These are often used for Inter-Process Communication (IPC). In the map, these are typically marked with an s flag in the permissions field (e.g., rw-s).
Mapped Files: This is how Linux handles libraries and executables. Instead of loading an entire large library into RAM at once, the kernel "maps" the file directly into the process's address space. This allows the process to access file contents as if they were memory. You will see these lines ending with the path to a file, such as libc.so.6.

Visualizing the Distinction

If you observe a map entry, look at the flags and the file path:

55d8c3e00000-55d8c3e21000 rw-p 00000000 00:00 0   [heap]    <-- Private Anonymous
7f9a1b000000-7f9a1b200000 rw-s 00000000 00:05 1234 /dev/shm/data <-- Shared
7f9a1b400000-7f9a1b600000 r-xp 00000000 08:01 5500 /usr/lib/libc.so.6 <-- Mapped File

The rw-p indicates private access, while rw-s clearly denotes shared memory.

Key Takeaway: Private segments are unique to the process, shared segments provide a bridge for data exchange between processes, and mapped files efficiently link physical disk data into virtual memory addresses.