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Kernel: Make ProcessPagingScope restore CR3 properly

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Instead of restoring CR3 to the current process's paging scope when a
ProcessPagingScope goes out of scope, we now restore exactly whatever
the CR3 value was when we created the ProcessPagingScope.

This fixes breakage in situations where a process ends up with nested
ProcessPagingScopes. This was making profiling very fragile, and with
this change it's now possible to profile g++! :^)
This commit is contained in:
Andreas Kling 2020-01-19 13:44:53 +01:00
parent ad3f931707
commit 6eab7b398d
3 changed files with 16 additions and 7 deletions
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7
Kernel/VM/MemoryManager.cpp
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@ -682,10 +682,15 @@ void MemoryManager::dump_kernel_regions()
ProcessPagingScope::ProcessPagingScope(Process& process)
{
ASSERT(current);
asm("movl %%cr3, %%eax"
: "=a"(m_previous_cr3));
MM.enter_process_paging_scope(process);
}
ProcessPagingScope::~ProcessPagingScope()
{
MM.enter_process_paging_scope(current->process());
InterruptDisabler disabler;
current->tss().cr3 = m_previous_cr3;
asm volatile("movl %%eax, %%cr3" ::"a"(m_previous_cr3)
: "memory");
}