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Implement stack/heap collision protection for processes - #42
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- Update I/O device handling in io_device.c - Modify system call processing in system_call_proc.c - Enhance process management in process.c - Improve test coverage for process handling in test_process.cpp
Adjust memory allocation logic for improved stack and heap protection.
- Update paging.h to enhance memory management definitions. - Modify memory.c to support new paging features. - Improve paging.c with additional stack-heap protection logic. - Adjust process.c to align with updated memory management. - Expand test coverage in test_paging.cpp and test_process.cpp.
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Implemented stack and heap collision protection so a process's heap and stack can never grow into each other, plus several related correctness fixes discovered and validated while testing this feature under headless QEMU boots.
Stack/heap collision guard (original feature)
HEAP_STACK_GUARD_PAGES, the minimum unmapped gap required between a process's heap and stack.process_add_pagesnow rejects heap growth that would come within the guard gap of the stack;process_grow_stacknow rejects stack growth that would come within the guard gap of the heap. Both check before touching paging structures and use additive comparisons to avoid unsigned underflow.process_add_pages_CollidesWithStack/process_grow_stack_CollidesWithHeap.Bug fixes found via headless-boot testing
SYS_CALL_PROC_PANIChandler had inverted null-checks that silently discarded the real panic message, and a%s/%uformat mismatch on the line number that crashed the kernel while trying to log a panic. Both fixed - process panics now log correctly instead of taking down the kernel.io_device_closehad an inverted success/failure check, logging a spurious "error 0" on every successful close and never logging real failures. Fixed.process_add_pagesandkernel_alloc_page(kmalloc's page source) both had an off-by-one when callingpaging_add_pages, mapping one extra page per call. This silently leaked/orphaned a physical page on every heap growth, and - sinceHEAP_STACK_GUARD_PAGES == 1- could fully erode the new stack/heap guard band in a single call.Range-convention refactor
Rather than patch each call site with a
-1/+1, convertedpaging_add_pages,paging_remove_pages, andpaging_id_map_rangefrom end-inclusive[start, end]to end-exclusive[start, end)ranges (matching common C/iterator conventions), and updated every call site accordingly. This removes the off-by-one bug at its root instead of just patching symptoms, and empty ranges (start == end) are now valid no-ops.Verification
make lintclean.