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Kernel: Enable the x86 WP bit to catch invalid memory writes in ring 0

Browse source 
Setting this bit will cause the CPU to generate a page fault when
writing to read-only memory, even if we're executing in the kernel.

Seemingly the only change needed to make this work was to have the
inode-backed page fault handler use a temporary mapping for writing
the read-from-disk data into the newly-allocated physical page.
This commit is contained in:
Andreas Kling 2019-12-21 16:21:13 +01:00
parent 70865e5a5d
commit ae2d72377d
2 changed files with 6 additions and 3 deletions
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2
Kernel/VM/MemoryManager.cpp
View file

@ -174,7 +174,7 @@ void MemoryManager::initialize_paging()
asm volatile("movl %%eax, %%cr3" ::"a"(kernel_page_directory().cr3()));
asm volatile(
"movl %%cr0, %%eax\n"
"orl $0x80000001, %%eax\n"
"orl $0x80010001, %%eax\n"
"movl %%eax, %%cr0\n" ::
: "%eax", "memory");

7
Kernel/VM/Region.cpp
View file

@ -431,8 +431,11 @@ PageFaultResponse Region::handle_inode_fault(size_t page_index_in_region)
kprintf("MM: handle_inode_fault was unable to allocate a physical page\n");
return PageFaultResponse::ShouldCrash;
}
remap_page(page_index_in_region);
u8* dest_ptr = vaddr().offset(page_index_in_region * PAGE_SIZE).as_ptr();
u8* dest_ptr = MM.quickmap_page(*vmobject_physical_page_entry);
memcpy(dest_ptr, page_buffer, PAGE_SIZE);
MM.unquickmap_page();
remap_page(page_index_in_region);
return PageFaultResponse::Continue;
}