Module layout

Constants§

GLOBAL_SIDE_METADATA_BASE_OFFSET 🔒: The compile-time base offset for global side metadata layout. We treat offsets as relative (starting from zero) and add the runtime base address when computing actual addresses.
GLOBAL_SIDE_METADATA_VM_BASE_OFFSET: The base offset for the global side metadata available to VM bindings.
LOCAL_SIDE_METADATA_BASE_OFFSET_FOR_LAYOUT 🔒
LOCAL_SIDE_METADATA_VM_BASE_OFFSET: The base address for the local side metadata space available to VM bindings, to be used for the per-object metadata. VM bindings must use this to avoid overlap with core internal local side metadata.
LOG_GLOBAL_SIDE_METADATA_WORST_CASE_RATIO 🔒
LOG_LOCAL_SIDE_METADATA_WORST_CASE_RATIO 🔒

SIDE_METADATA_BASE_ADDRESS 🔒: The run-time base address for side metadata. This is initialized at startup by mmapping necessary memory address for side metadata, and should be used as the base when computing actual side metadata addresses. We use OnceLock to ensure it is only initialized once. To eliminate the cost of accessing OnceLock after initialization, we can use get().unwrap_unchecked(). TODO: use OncLock::get_unchecked() once it is stabilized.
VM_SIDE_METADATA_UPPER_BOUND_OFFSET 🔒: The upper bound for VM side metadata layout. We need to list all the VM side metadata specs, compute the upper bound, and store it here.

global_side_metadata_base_address: Get the runtime side metadata base address.
global_side_metadata_bytes 🔒: Total global side metadata bytes (independent of the runtime base address).
global_side_metadata_vm_base_address: The base address for the global side metadata space available to VM bindings, to be used for the per-object metadata. VM bindings must use this to avoid overlap with core internal global side metadata.
initialize_side_metadata_base 🔒: Initialize the side metadata base address by reserving address space with quarantine mmap.
local_side_metadata_base_address 🔒
rc_table_start_address: Base address of the LXR reference-counting table, public to VM bindings which may need to use this.
set_vm_side_metadata_specs 🔒: Record VM side metadata layout so startup reservation can cover VM specs. This must be called before initialize_side_metadata_base().
side_metadata_reserved_bytes 🔒: Total side metadata bytes that should be reserved at startup (independent of runtime base, with alignment).
total_side_metadata_bytes 🔒: Total side metadata bytes that should be reserved at startup (independent of runtime base, without alignment).
vo_bit_side_metadata_addr: Base address of VO bit, public to VM bindings which may need to use this.