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Kernel: Implement mprotect for multiple Regions

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Hendiadyoin1 2021-04-01 22:04:04 +02:00 • committed by Andreas Kling
parent 8afaa7f30e
commit ef425a02f7
1 changed files with 61 additions and 1 deletions
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62
Kernel/Syscalls/mmap.cpp
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@ -355,7 +355,67 @@ KResultOr<int> Process::sys$mprotect(Userspace<void*> addr, size_t size, int pro
return 0;
}
// FIXME: We should also support mprotect() across multiple regions. (#175) (#964)
if (const auto& regions = space().find_regions_intersecting(range_to_mprotect); regions.size()) {
size_t full_size_found = 0;
// first check before doing anything
for (const auto* region : regions) {
if (!region->is_mmap())
return EPERM;
if (!validate_mmap_prot(prot, region->is_stack(), region->vmobject().is_anonymous(), region))
return EINVAL;
if (region->access() == prot_to_region_access_flags(prot))
return 0;
if (region->vmobject().is_inode()
&& !validate_inode_mmap_prot(*this, prot, static_cast<const InodeVMObject&>(region->vmobject()).inode(), region->is_shared())) {
return EACCES;
}
full_size_found += region->range().intersect(range_to_mprotect).size();
}
if (full_size_found != range_to_mprotect.size())
return ENOMEM;
// then do all the other stuff
for (auto* old_region : regions) {
const auto intersection_to_mprotect = range_to_mprotect.intersect(old_region->range());
// full sub region
if (intersection_to_mprotect == old_region->range()) {
old_region->set_readable(prot & PROT_READ);
old_region->set_writable(prot & PROT_WRITE);
old_region->set_executable(prot & PROT_EXEC);
old_region->remap();
continue;
}
// Remove the old region from our regions tree, since were going to add another region
// with the exact same start address, but dont deallocate it yet
auto region = space().take_region(*old_region);
VERIFY(region);
// Unmap the old region here, specifying that we *don't* want the VM deallocated.
region->unmap(Region::ShouldDeallocateVirtualMemoryRange::No);
// This vector is the region(s) adjacent to our range.
// We need to allocate a new region for the range we wanted to change permission bits on.
auto adjacent_regions = space().split_region_around_range(*old_region, intersection_to_mprotect);
// there should only be one
VERIFY(adjacent_regions.size() == 1);
size_t new_range_offset_in_vmobject = old_region->offset_in_vmobject() + (intersection_to_mprotect.base().get() - old_region->range().base().get());
auto& new_region = space().allocate_split_region(*region, intersection_to_mprotect, new_range_offset_in_vmobject);
new_region.set_readable(prot & PROT_READ);
new_region.set_writable(prot & PROT_WRITE);
new_region.set_executable(prot & PROT_EXEC);
// Map the new region using our page directory (they were just allocated and don't have one) if any.
if (adjacent_regions.size())
adjacent_regions[0]->map(space().page_directory());
new_region.map(space().page_directory());
}
return 0;
}
return EINVAL;
}