Module stack_canary 

Per-Thread Stack Canary Management

Provides stack smashing detection via per-thread random canary values. Each thread receives a unique 64-bit canary generated from an xorshift64 PRNG seeded by architecture-specific entropy. The canary is placed at a known location on the thread’s stack and verified periodically or on context switch.

Design

• CANARY_TABLE: RwLock<BTreeMap<u64, u64>> mapping thread ID to its canary value. Protected by RwLock for concurrent read access during verification with exclusive write access for registration.

• Canary generation: Uses xorshift64 PRNG seeded from hardware entropy (RDRAND/TSC on x86_64, CNTPCT on AArch64, cycle on RISC-V).

• Detection: On canary mismatch, the kernel panics with “stack smashing detected” to prevent exploitation.

Usage

// During thread creation:
let canary = stack_canary::generate_canary();
stack_canary::set_thread_canary(tid, canary);
// Write canary to thread's stack guard location...

// During context switch or verification:
stack_canary::check_canary(tid);  // panics on mismatch

Functions

check_canary

Check a thread’s stack canary.

generate_canary

Generate a new random canary value.

get_stats

Get diagnostic statistics.

get_thread_canary

Get the expected canary value for a thread.

init

Initialize the stack canary subsystem.

is_active

Check if the canary subsystem is initialized.

registered_count

Get the number of threads with registered canaries.

remove_thread_canary

Remove a thread’s canary from the table.

set_thread_canary

Register a canary value for a thread.

verify_stack

Verify a stack canary value against the expected value.