When a fixed mapping spans multiple free runs and a later gap cannot be
backed, any earlier host allocations were leaked. Stage all allocations
during the walk and insert MemoryRegions only after every gap has been
backed successfully. On any failure, free all staged allocations.
Fixes#472🤖 Generated with Hermes Agent
A SCE_KERNEL_MAP_FIXED request whose window partially overlaps an
existing allocation was failing outright: AllocateAt reserves the whole
range in one all-or-nothing VirtualAlloc, which returns 0 on partial
overlap. The mapping call then returned NOT_FOUND while leaving the free
tail unmapped, so the guest faulted (0xC0000005) writing into it.
Add IGuestAddressSpace.TryBackFixedRange, which walks the range via the
host Query (VirtualQuery reports contiguous same-state runs) and fills
only the free sub-ranges, leaving already-backed pages untouched. This
matches the fixed-mapping contract on hardware. Route the fixed
reservation path through it via a new backPartialOverlap flag.
Co-authored-by: slick-daddy <slick-daddy@users.noreply.github.com>
kostyaff