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Kernel: Replace intersecting ranges in mmap when MAP_FIXED is specified

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This behavior is mandated by POSIX and is used by software like Wine
after reserving large chunks of the address range.
This commit is contained in:
Daniel Bertalan 2021-12-19 01:01:11 +01:00 • committed by Brian Gianforcaro
parent fd3be7ffcc
commit ce1bf3724e
1 changed files with 5 additions and 0 deletions
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5
Kernel/Syscalls/mmap.cpp
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@ -189,11 +189,16 @@ ErrorOr<FlatPtr> Process::sys$mmap(Userspace<const Syscall::SC_mmap_params*> use
if (map_randomized) {
return address_space().page_directory().range_allocator().try_allocate_randomized(Memory::page_round_up(size), alignment);
}
auto range = address_space().try_allocate_range(VirtualAddress(addr), size, alignment);
if (range.is_error()) {
if (addr && !map_fixed) {
// If there's an address but MAP_FIXED wasn't specified, the address is just a hint.
range = address_space().try_allocate_range({}, size, alignment);
} else if (map_fixed) {
// If MAP_FIXED is specified, existing mappings that intersect the requested range are removed.
TRY(address_space().unmap_mmap_range(VirtualAddress(addr), size));
range = address_space().try_allocate_range(VirtualAddress(addr), size, alignment);
}
}
return range;