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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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8
Kernel/Process.cpp
View file

@ -734,7 +734,8 @@ int Process::do_exec(NonnullRefPtr<FileDescription> main_program_description, Ve
#ifdef MM_DEBUG #ifdef MM_DEBUG
dbgprintf("Process %u exec: PD=%x created\n", pid(), m_page_directory.ptr()); dbgprintf("Process %u exec: PD=%x created\n", pid(), m_page_directory.ptr());
#endif #endif
ProcessPagingScope paging_scope(*this);
MM.enter_process_paging_scope(*this);
Region* region { nullptr }; Region* region { nullptr };
@ -775,11 +776,10 @@ int Process::do_exec(NonnullRefPtr<FileDescription> main_program_description, Ve
m_regions.append(move(executable_region)); m_regions.append(move(executable_region));
ArmedScopeGuard rollback_regions_guard([&]() { ArmedScopeGuard rollback_regions_guard([&]() {
m_page_directory = move(old_page_directory);
ASSERT(&current->process() == this); ASSERT(&current->process() == this);
MM.enter_process_paging_scope(*this); m_page_directory = move(old_page_directory);
executable_region = m_regions.take_first();
m_regions = move(old_regions); m_regions = move(old_regions);
MM.enter_process_paging_scope(*this);
}); });
loader = make<ELFLoader>(region->vaddr().as_ptr(), loader_metadata.size); loader = make<ELFLoader>(region->vaddr().as_ptr(), loader_metadata.size);

7
Kernel/VM/MemoryManager.cpp
View file

@ -682,10 +682,15 @@ void MemoryManager::dump_kernel_regions()
ProcessPagingScope::ProcessPagingScope(Process& process) ProcessPagingScope::ProcessPagingScope(Process& process)
{ {
ASSERT(current); ASSERT(current);
asm("movl %%cr3, %%eax"
: "=a"(m_previous_cr3));
MM.enter_process_paging_scope(process); MM.enter_process_paging_scope(process);
} }
ProcessPagingScope::~ProcessPagingScope() 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");
} }

8
Kernel/VM/MemoryManager.h
View file

@ -190,9 +190,13 @@ private:
bool m_quickmap_in_use { false }; bool m_quickmap_in_use { false };
}; };
struct ProcessPagingScope { class ProcessPagingScope {
ProcessPagingScope(Process&); public:
explicit ProcessPagingScope(Process&);
~ProcessPagingScope(); ~ProcessPagingScope();
private:
u32 m_previous_cr3 { 0 };
}; };
template<typename Callback> template<typename Callback>