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Kernel: Allocate page tables for the entire kmalloc VM range up front

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This avoids getting caught with our pants down when heap expansion fails
due to missing page tables. It also avoids a circular dependency on
kmalloc() by way of HashMap::set() in MemoryManager::ensure_pte().
This commit is contained in:
Andreas Kling 2021-12-26 02:42:49 +01:00
parent 8a51f64503
commit f49649645c
Notes: sideshowbarker 2024-07-17 22:10:50 +09:00 
Author: https://github.com/awesomekling
Commit: https://github.com/SerenityOS/serenity/commit/f49649645ca
1 changed files with 22 additions and 15 deletions
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37
Kernel/Heap/kmalloc.cpp
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@ -136,15 +136,8 @@ struct KmallocGlobalData {
for (auto vaddr = new_subheap_base; !physical_pages.is_empty(); vaddr = vaddr.offset(PAGE_SIZE)) {
// FIXME: We currently leak physical memory when mapping it into the kmalloc heap.
auto& page = physical_pages.take_one().leak_ref();
auto* pte = MM.ensure_pte(MM.kernel_page_directory(), vaddr);
if (!pte) {
// FIXME: If ensure_pte() fails due to lazy page directory construction, it returns nullptr
// and we're in trouble. Find a way to avoid getting into that situation.
// Perhaps we could do a dry run through the address range and ensure_pte() for each
// virtual address to ensure that each PTE is available. Not maximally efficient,
// but could work.. Needs more thought.
PANIC("Unable to acquire PTE during heap expansion");
}
auto* pte = MM.pte(MM.kernel_page_directory(), vaddr);
VERIFY(pte);
pte->set_physical_page_base(page.paddr().get());
pte->set_global(true);
pte->set_user_allowed(false);
@ -160,6 +153,25 @@ struct KmallocGlobalData {
return true;
}
void enable_expansion()
{
// FIXME: This range can be much bigger on 64-bit, but we need to figure something out for 32-bit.
auto virtual_range = MM.kernel_page_directory().range_allocator().try_allocate_anywhere(64 * MiB, 1 * MiB);
expansion_data = KmallocGlobalData::ExpansionData {
.virtual_range = virtual_range.value(),
.next_virtual_address = virtual_range.value().base(),
};
// Make sure the entire kmalloc VM range is backed by page tables.
// This avoids having to deal with lazy page table allocation during heap expansion.
SpinlockLocker mm_locker(Memory::s_mm_lock);
SpinlockLocker pd_locker(MM.kernel_page_directory().get_lock());
for (auto vaddr = virtual_range.value().base(); vaddr < virtual_range.value().end(); vaddr = vaddr.offset(PAGE_SIZE)) {
MM.ensure_pte(MM.kernel_page_directory(), vaddr);
}
}
struct ExpansionData {
Memory::VirtualRange virtual_range;
VirtualAddress next_virtual_address;
@ -189,12 +201,7 @@ READONLY_AFTER_INIT static u8* s_end_of_eternal_range;
void kmalloc_enable_expand()
{
// FIXME: This range can be much bigger on 64-bit, but we need to figure something out for 32-bit.
auto virtual_range = MM.kernel_page_directory().range_allocator().try_allocate_anywhere(64 * MiB, 1 * MiB);
g_kmalloc_global->expansion_data = KmallocGlobalData::ExpansionData {
.virtual_range = virtual_range.value(),
.next_virtual_address = virtual_range.value().base(),
};
g_kmalloc_global->enable_expansion();
}
static inline void kmalloc_verify_nospinlock_held()