Add drgn tests, man page, and dynamic region list research#4
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- Expand test_drgn.py from 7 to 20 tests covering kernel structure walks (task_struct fields, mm_struct, dentry/inode, per-CPU data, superblocks, network namespaces), filter stats validation, ELF header comparison with /proc/kcore, raw page zeroing verification, sysfs parameter checks, and read consistency - Add kcore_filtered.4 man page documenting all module parameters (Layer 0 page filters, Layer 1 slab lists, Layer 2 audit, Layer 3 rate limits), /proc/kcore_filtered_stats counters, usage examples, permissions, and known limitations - Update Makefile install target to install the man page alongside the module, add uninstall target for cleanup - Add doc/dynamic-region-list.md researching 6 approaches to overcome the static region list limitation (memory hotplug notifier, rebuild on open, lazy re-walk, kallsyms/kprobes, upstream, other notifiers) with recommended solution using register_memory_notifier() combined with lazy rebuild on open https://claude.ai/code/session_01YMjtMS4kfRuUtH5KqzcC2e
Remove the static region list limitation by mirroring the upstream /proc/kcore pattern: register a memory hotplug notifier that sets a dirty flag on MEM_ONLINE/MEM_OFFLINE events, then lazily rebuild the region list on the next kcf_open() call. The rebuild uses atomic_xchg() under write_lock(®ion_lock) to prevent a double-rebuild race when two CPUs open simultaneously. On failure the flag is re-armed so the next open retries. The read path is unchanged (read_lock only). register_memory_notifier() is EXPORT_SYMBOL_GPL and becomes a no-op when CONFIG_MEMORY_HOTPLUG is disabled, so this adds zero overhead on systems without hotplug support. Also removes doc/dynamic-region-list.md (research doc, now implemented) and updates the man page to drop the static region list limitation. https://claude.ai/code/session_01YMjtMS4kfRuUtH5KqzcC2e
Test 35 exercises the hotplug notifier + lazy rebuild path by offlining a memory block via /sys/devices/system/memory/memoryN/state, opening /proc/kcore_filtered to trigger the rebuild, then verifying "region list rebuilt" appears in dmesg. The block is re-onlined immediately after. Gracefully skips when CONFIG_MEMORY_HOTPLUG is not enabled, no sysfs memory blocks exist, or the selected block cannot be offlined (e.g., pinned by kernel allocations). https://claude.ai/code/session_01YMjtMS4kfRuUtH5KqzcC2e
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Expand test_drgn.py from 7 to 20 tests covering kernel structure
walks (task_struct fields, mm_struct, dentry/inode, per-CPU data,
superblocks, network namespaces), filter stats validation, ELF
header comparison with /proc/kcore, raw page zeroing verification,
sysfs parameter checks, and read consistency
Add kcore_filtered.4 man page documenting all module parameters
(Layer 0 page filters, Layer 1 slab lists, Layer 2 audit, Layer 3
rate limits), /proc/kcore_filtered_stats counters, usage examples,
permissions, and known limitations
Update Makefile install target to install the man page alongside the
module, add uninstall target for cleanup
Add doc/dynamic-region-list.md researching 6 approaches to overcome
the static region list limitation (memory hotplug notifier, rebuild
on open, lazy re-walk, kallsyms/kprobes, upstream, other notifiers)
with recommended solution using register_memory_notifier() combined
with lazy rebuild on open
https://claude.ai/code/session_01YMjtMS4kfRuUtH5KqzcC2e