15. Detailed Example of Returning to User Space

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15. Detailed Example of Returning to User Space

Walk through a detailed example of the steps involved in returning to user space after a `fork()` system call, from setting return values to continuing execution in user mode.

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Here's a detailed walkthrough of the steps involved in fork:-

Firstly, the fork system call is invoked, which triggers a system call and switches the CPU from user mode to kernel mode.
The kernel performs the necessary operations for creating the child process, including duplicating the address space and file descriptors.
The kernel sets up the task_struct for the child process and marks it as TASK_RUNNING.
Then the kernel sets up the return values of fork in the respective CPU contexts of both parent and child process.
The kernel prepares the CPU state for both the parent and child process which includes setting the program counter and stack pointer.
The kernel then switches the CPU back to user mode, ensuring that both processes run with user-level privileges.
After the CPU is in user mode, both the parent and child processes continue execution from the point immediately following the fork system call.

15. Detailed Example of Returning to User Space

15. Detailed Example of Returning to User Space

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