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Kernel: Share the "return to ring 0/3 from signal" trampolines globally.

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Generate a special page containing the "return from signal" trampoline code
on startup and then route signalled threads to it. This avoids a page
allocation in every process that ever receives a signal.
This commit is contained in:
Andreas Kling 2019-07-19 17:01:16 +02:00
parent fdf931cfce
commit f8beb0f665
5 changed files with 36 additions and 21 deletions
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14
Kernel/VM/MemoryManager.cpp
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@ -450,20 +450,28 @@ PageFaultResponse MemoryManager::handle_page_fault(const PageFault& fault)
return PageFaultResponse::ShouldCrash;
}
RefPtr<Region> MemoryManager::allocate_kernel_region(size_t size, String&& name)
RefPtr<Region> MemoryManager::allocate_kernel_region(size_t size, const StringView& name, bool user_accessible)
{
InterruptDisabler disabler;
ASSERT(!(size % PAGE_SIZE));
auto range = kernel_page_directory().range_allocator().allocate_anywhere(size);
ASSERT(range.is_valid());
auto region = Region::create_kernel_only(range, move(name), PROT_READ | PROT_WRITE | PROT_EXEC, false);
RefPtr<Region> region;
if (user_accessible)
region = Region::create_user_accessible(range, name, PROT_READ | PROT_WRITE | PROT_EXEC, false);
else
region = Region::create_kernel_only(range, name, PROT_READ | PROT_WRITE | PROT_EXEC, false);
MM.map_region_at_address(*m_kernel_page_directory, *region, range.base());
// FIXME: It would be cool if these could zero-fill on demand instead.
region->commit();
return region;
}
RefPtr<Region> MemoryManager::allocate_user_accessible_kernel_region(size_t size, const StringView& name)
{
return allocate_kernel_region(size, name, true);
}
void MemoryManager::deallocate_user_physical_page(PhysicalPage&& page)
{
for (auto& region : m_user_physical_regions) {