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Kernel: Add mechanism to make some memory read-only after init finishes

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You can now use the READONLY_AFTER_INIT macro when declaring a variable
and we will put it in a special ".ro_after_init" section in the kernel.

Data in that section remains writable during the boot and init process,
and is then marked read-only just before launching the SystemServer.

This is based on an idea from the Linux kernel. :^)
This commit is contained in:
Andreas Kling 2021-02-14 17:35:07 +01:00
parent 917f7d668c
commit d8013c60bb
5 changed files with 28 additions and 0 deletions
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14
Kernel/VM/MemoryManager.cpp
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@ -46,6 +46,8 @@ extern u8* end_of_kernel_image;
extern FlatPtr start_of_kernel_text;
extern FlatPtr start_of_kernel_data;
extern FlatPtr end_of_kernel_bss;
extern FlatPtr start_of_ro_after_init;
extern FlatPtr end_of_ro_after_init;
extern multiboot_module_entry_t multiboot_copy_boot_modules_array[16];
extern size_t multiboot_copy_boot_modules_count;
@ -121,6 +123,18 @@ void MemoryManager::protect_kernel_image()
}
}
void MemoryManager::protect_readonly_after_init_memory()
{
ScopedSpinLock mm_lock(s_mm_lock);
ScopedSpinLock page_lock(kernel_page_directory().get_lock());
// Disable writing to the .ro_after_init section
for (auto i = (FlatPtr)&start_of_ro_after_init; i < (FlatPtr)&end_of_ro_after_init; i += PAGE_SIZE) {
auto& pte = *ensure_pte(kernel_page_directory(), VirtualAddress(i));
pte.set_writable(false);
flush_tlb(&kernel_page_directory(), VirtualAddress(i));
}
}
void MemoryManager::register_reserved_ranges()
{
ASSERT(!m_physical_memory_ranges.is_empty());