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MemGuard - memory allocator for debugging purposes
MemGuard is a simple and small replacement memory allocator designed to
help detect tamper-after-free scenarios. These problems are more and
more common and likely with multithreaded kernels where race conditions
are more prevalent.
Currently, MemGuard can only take over malloc(), realloc() and free() for
a particular malloc type.
To use MemGuard for memory type compiled into the kernel, one has to add
the following line to the /boot/loader.conf:
Where memory_type is a short description of memory type to monitor. The
short description of memory type is the second argument to
MALLOC_DEFINE(9), so one has to find it in the kernel source.
To use MemGuard for memory type defined in a kernel module, one has to
set vm.memguard.desc sysctl(8) variable before loading the module:
The vm.memguard.divisor boot-time tunable is used to scale how much of
kmem_map one wants to allocate for MemGuard. The default is 10, so
kmem_size/10 bytes will be used. The kmem_size value can be obtained via
the vm.kmem_size sysctl(8) variable.
sysctl(8), vmstat(8), contigmalloc(9), malloc(9), redzone(9)
MemGuard first appeared in FreeBSD 6.0.
MemGuard was written by Bosko Milekic 〈bmilekic@FreeBSD.org〉. This
manual page was written by Christian Brueffer 〈brueffer@FreeBSD.org〉.
Currently, it is not possible to override UMA zone(9) allocations.