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Support basic mmap'ing of a file!

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All right, we can now mmap() a file and it gets magically paged in from fs
in response to an NP page fault. This is really cool :^)

I need to refactor this to support sharing of read-only file-backed pages,
but it's cool to just have something working.
This commit is contained in:
Andreas Kling 2018-11-08 12:59:16 +01:00
parent fdbd9f1e27
commit 3c8064a787
8 changed files with 141 additions and 14 deletions
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50
Kernel/MemoryManager.cpp
View file

@ -254,6 +254,31 @@ bool MemoryManager::copy_on_write(Process& process, Region& region, unsigned pag
return true;
}
bool MemoryManager::page_in_from_vnode(Process& process, Region& region, unsigned page_index_in_region)
{
ASSERT(region.physical_pages[page_index_in_region].is_null());
region.physical_pages[page_index_in_region] = allocate_physical_page();
if (region.physical_pages[page_index_in_region].is_null()) {
kprintf("MM: page_in_from_vnode was unable to allocate a physical page\n");
return false;
}
remap_region_page(process.m_page_directory, region, page_index_in_region, true);
byte* dest_ptr = region.linearAddress.offset(page_index_in_region * PAGE_SIZE).asPtr();
dbgprintf("MM: page_in_from_vnode ready to read from vnode, will write to L%x!\n", dest_ptr);
sti(); // Oh god here we go...
auto nread = region.m_vnode->fileSystem()->readInodeBytes(region.m_vnode->inode, region.m_file_offset, PAGE_SIZE, dest_ptr, nullptr);
if (nread < 0) {
kprintf("MM: page_in_form_vnode had error (%d) while reading!\n", nread);
return false;
}
if (nread < PAGE_SIZE) {
// If we read less than a page, zero out the rest to avoid leaking uninitialized data.
memset(dest_ptr + nread, 0, PAGE_SIZE - nread);
}
cli();
return true;
}
PageFaultResponse MemoryManager::handle_page_fault(const PageFault& fault)
{
ASSERT_INTERRUPTS_DISABLED();
@ -264,17 +289,21 @@ PageFaultResponse MemoryManager::handle_page_fault(const PageFault& fault)
ASSERT(region);
auto page_index_in_region = region->page_index_from_address(fault.laddr());
if (fault.is_not_present()) {
kprintf(" >> NP fault in Region{%p}[%u]\n", region, page_index_in_region);
if (region->m_vnode) {
dbgprintf("NP(vnode) fault in Region{%p}[%u]\n", region, page_index_in_region);
page_in_from_vnode(*current, *region, page_index_in_region);
return PageFaultResponse::Continue;
} else {
kprintf("NP(error) fault in Region{%p}[%u]\n", region, page_index_in_region);
}
} else if (fault.is_protection_violation()) {
if (region->cow_map.get(page_index_in_region)) {
#ifdef PAGE_FAULT_DEBUG
dbgprintf(" >> PV (COW) fault in Region{%p}[%u]\n", region, page_index_in_region);
#endif
dbgprintf("PV(cow) fault in Region{%p}[%u]\n", region, page_index_in_region);
bool success = copy_on_write(*current, *region, page_index_in_region);
ASSERT(success);
return PageFaultResponse::Continue;
}
kprintf(" >> PV fault in Region{%p}[%u]\n", region, page_index_in_region);
kprintf("PV(error) fault in Region{%p}[%u]\n", region, page_index_in_region);
} else {
ASSERT_NOT_REACHED();
}
@ -284,6 +313,17 @@ PageFaultResponse MemoryManager::handle_page_fault(const PageFault& fault)
return PageFaultResponse::ShouldCrash;
}
RetainPtr<PhysicalPage> MemoryManager::allocate_physical_page()
{
InterruptDisabler disabler;
if (1 > m_free_physical_pages.size())
return { };
#ifdef MM_DEBUG
dbgprintf("MM: allocate_physical_page vending P%x\n", m_free_physical_pages.last()->paddr().get());
#endif
return m_free_physical_pages.takeLast();
}
Vector<RetainPtr<PhysicalPage>> MemoryManager::allocate_physical_pages(size_t count)
{
InterruptDisabler disabler;