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clarify wording

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Daniel Micay 2018-11-19 08:04:37 -05:00
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@ -17,16 +17,16 @@ This allocator is intended as a successor to a previous implementation based on
extending OpenBSD malloc with various additional security features. It's still
heavily based on the OpenBSD malloc design, albeit not on the existing code
other than reusing the hash table implementation for the time being. The main
differences in the design are that it's solely focused on hardening rather than
finding bugs, uses finer-grained size classes based on jemalloc with slab sizes
going beyond 4k, it doesn't rely on the kernel having fine-grained mmap
randomization and it only targets 64-bit to make aggressive use of the large
address space. There are lots of smaller differences in the implementation
approach. It incorporates the previous extensions made to OpenBSD malloc
including adding padding to allocations for canaries (distinct from the current
OpenBSD malloc canaries), write-after-free detection tied to the existing
clearing on free, queues alongside the existing randomized arrays for
quarantining allocations and proper double-free detection for quarantined
differences in the design are that it is solely focused on hardening rather
than finding bugs, uses finer-grained size classes along with slab sizes going
beyond 4k to reduce internal fragmentation, doesn't rely on the kernel having
fine-grained mmap randomization and only targets 64-bit to make aggressive use
of the large address space. There are lots of smaller differences in the
implementation approach. It incorporates the previous extensions made to
OpenBSD malloc including adding padding to allocations for canaries (distinct
from the current OpenBSD malloc canaries), write-after-free detection tied to
the existing clearing on free, queues alongside the existing randomized arrays
for quarantining allocations and proper double-free detection for quarantined
allocations. The per-size-class memory regions with their own random bases were
loosely inspired by the size and type-based partitioning in PartitionAlloc. The
planned changes to OpenBSD malloc ended up being too extensive and invasive so