This tunable namespace supports operations that affect the way the GNU C Library and the process manage memory.
If the hardware supports memory tagging, this tunable can be used to control the way the GNU C Library uses this feature. At present this is only supported on AArch64 systems with the MTE extension; it is ignored for all other systems.
This tunable takes a value between 0 and 255 and acts as a bitmask that enables various capabilities.
Bit 0 (the least significant bit) causes the malloc
subsystem to allocate
tagged memory, with each allocation being assigned a random tag.
Bit 1 enables precise faulting mode for tag violations on systems that support deferred tag violation reporting. This may cause programs to run more slowly.
Bit 2 enables either precise or deferred faulting mode for tag violations whichever is preferred by the system.
Other bits are currently reserved.
The GNU C Library startup code will automatically enable memory tagging support in the kernel if this tunable has any non-zero value.
The default value is ‘0’, which disables all memory tagging.
If the kernel supports naming anonymous virtual memory areas (since
Linux version 5.17, although not always enabled by some kernel
configurations), this tunable can be used to control whether
the GNU C Library decorates the underlying memory obtained from operating
system with a string describing its usage (for instance, on the thread
stack created by ptthread_create or memory allocated by
malloc).
The process mappings can be obtained by reading the /proc/<pid>maps
(with pid being either the process ID or self for the
process own mapping).
This tunable takes a value of 0 and 1, where 1 enables the feature. The default value is ‘0’, which disables the decoration.