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Implement Context Switch in Assembly

hard13/15

Set Up x86 Page Tables for Virtual Memory Build a Round-Robin Task Scheduler

Language

Compiler

2.0s Limit 256MB

Submit and pass all tests to enable saving to GitHub.

Implementation

Simulate an x86 context switch in C.

Requirements:

Define TASK structure with register state and stack pointer
Implement switch_context() that saves current registers and loads new ones
Show each register being saved and restored
Use a simulated stack (array) for each task
Implement create_task() that initializes a task with entry point
Show two tasks switching back and forth
Track which task is currently running
Print register values before and after switch
Simulate timer interrupt triggering the switch
Show task counter incrementing to prove both tasks run

Test:

Show task A running and saving state
Show task B restoring state and running
Show register values preserved across switches
Show multiple switches between tasks

Why This Matters

The pusha/popa register save-and-restore sequence you're simulating here is exactly what xv6's swtch.S and every real x86 kernel's context switch does to move the CPU from one task's stack to another's. Forgetting to save ESP separately (pusha doesn't cover it) is a classic bug that corrupts a task's entire stack the moment it resumes, wiping out every local variable it had in flight.

Hints

0 / 3 revealed

Validation Suite

main.c

Workspace 1.0

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