How can I debug kernel code without using print statements?

Use external tracing tools like QEMU's interrupt logging (-d int), attach GDB for non-intrusive breakpoints, or use atomic counters to record statistics that can be read in non-critical paths.

Are memory allocations allowed during context switches?

No. Memory allocations (Box, Vec, etc.) involve locks and complex logic that are non-deterministic and can lead to deadlocks or timing-related crashes during a context switch.

Why is logging forbidden in interrupt and syscall paths?

Serial output and logging take tens of thousands of cycles, which can exceed the window before the next timer interrupt. This prevents userspace from ever executing, leading to a system freeze.

What is the recommended cycle budget for an interrupt handler?

Interrupt handlers should aim to complete in fewer than 1000 cycles (approx. 500 nanoseconds on modern hardware) to ensure minimal impact on system throughput and responsiveness.

Breenix OS Interrupt & Syscall Development

Name: Breenix OS Interrupt & Syscall Development
Author: ryanbreen

byryanbreen

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Herramientas para Desarrolladores

Enforces strict performance constraints and architectural patterns for OS kernel interrupt and syscall critical paths.

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This skill provides specialized guidance for developing low-level operating system components, specifically focusing on the high-performance paths of interrupts, system calls, and context switches. It enforces a 'pristine path' philosophy, prohibiting logging, memory allocation, and non-deterministic operations that lead to catastrophic timing failures and 'Heisenbugs'. By utilizing these mandatory rules and implementation workflows, developers can ensure userspace forward progress and system stability during x86_64 kernel development.

Características Principales

Strict enforcement of zero-logging and zero-allocation in critical paths
Mandatory cycle-budget constraints (<1000 cycles) for interrupt handlers
Safe patterns for atomic counter increments and register manipulation
Advanced debugging workflows using QEMU tracing and GDB integration
Comprehensive code review checklists for kernel-level transitions
4 GitHub stars

Casos de Uso

Developing x86_64 interrupt service routines and context switching logic
Implementing system call entry and exit points with minimal overhead
Debugging kernel timing issues where traditional logging causes system freezes

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Características Principales

Strict enforcement of zero-logging and zero-allocation in critical paths
Mandatory cycle-budget constraints (<1000 cycles) for interrupt handlers
Safe patterns for atomic counter increments and register manipulation
Advanced debugging workflows using QEMU tracing and GDB integration
Comprehensive code review checklists for kernel-level transitions
4 GitHub stars

Casos de Uso

Developing x86_64 interrupt service routines and context switching logic
Implementing system call entry and exit points with minimal overhead
Debugging kernel timing issues where traditional logging causes system freezes