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Kernel: Clean up the page fault handling code a bit

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Not using "else" after "return" unnests the code and makes it easier to
follow. Also use an enum for the two different page fault types.
This commit is contained in:
Andreas Kling 2019-08-06 09:33:35 +02:00
parent f58b0c245d
commit af4cf01560
2 changed files with 22 additions and 19 deletions
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7
Kernel/Arch/i386/CPU.h
View file

@ -303,9 +303,16 @@ public:
{ {
} }
enum class Type {
PageNotPresent,
ProtectionViolation,
};
VirtualAddress vaddr() const { return m_vaddr; } VirtualAddress vaddr() const { return m_vaddr; }
u16 code() const { return m_code; } u16 code() const { return m_code; }
Type type() const { return (Type)(m_code & 1); }
bool is_not_present() const { return (m_code & 1) == PageFaultFlags::NotPresent; } bool is_not_present() const { return (m_code & 1) == PageFaultFlags::NotPresent; }
bool is_protection_violation() const { return (m_code & 1) == PageFaultFlags::ProtectionViolation; } bool is_protection_violation() const { return (m_code & 1) == PageFaultFlags::ProtectionViolation; }
bool is_read() const { return (m_code & 2) == PageFaultFlags::Read; } bool is_read() const { return (m_code & 2) == PageFaultFlags::Read; }

12
Kernel/VM/MemoryManager.cpp
View file

@ -405,7 +405,7 @@ PageFaultResponse MemoryManager::handle_page_fault(const PageFault& fault)
dbgprintf("MM: handle_page_fault(%w) at L%x\n", fault.code(), fault.vaddr().get()); dbgprintf("MM: handle_page_fault(%w) at L%x\n", fault.code(), fault.vaddr().get());
#endif #endif
ASSERT(fault.vaddr() != m_quickmap_addr); ASSERT(fault.vaddr() != m_quickmap_addr);
if (fault.is_not_present() && fault.vaddr().get() >= 0xc0000000) { if (fault.type() == PageFault::Type::PageNotPresent && fault.vaddr().get() >= 0xc0000000) {
u32 page_directory_index = (fault.vaddr().get() >> 22) & 0x3ff; u32 page_directory_index = (fault.vaddr().get() >> 22) & 0x3ff;
auto& kernel_pde = kernel_page_directory().entries()[page_directory_index]; auto& kernel_pde = kernel_page_directory().entries()[page_directory_index];
if (kernel_pde.is_present()) { if (kernel_pde.is_present()) {
@ -422,21 +422,21 @@ PageFaultResponse MemoryManager::handle_page_fault(const PageFault& fault)
return PageFaultResponse::ShouldCrash; return PageFaultResponse::ShouldCrash;
} }
auto page_index_in_region = region->page_index_from_address(fault.vaddr()); auto page_index_in_region = region->page_index_from_address(fault.vaddr());
if (fault.is_not_present()) { if (fault.type() == PageFault::Type::PageNotPresent) {
if (region->vmo().inode()) { if (region->vmo().inode()) {
#ifdef PAGE_FAULT_DEBUG #ifdef PAGE_FAULT_DEBUG
dbgprintf("NP(inode) fault in Region{%p}[%u]\n", region, page_index_in_region); dbgprintf("NP(inode) fault in Region{%p}[%u]\n", region, page_index_in_region);
#endif #endif
page_in_from_inode(*region, page_index_in_region); page_in_from_inode(*region, page_index_in_region);
return PageFaultResponse::Continue; return PageFaultResponse::Continue;
} else { }
#ifdef PAGE_FAULT_DEBUG #ifdef PAGE_FAULT_DEBUG
dbgprintf("NP(zero) fault in Region{%p}[%u]\n", region, page_index_in_region); dbgprintf("NP(zero) fault in Region{%p}[%u]\n", region, page_index_in_region);
#endif #endif
zero_page(*region, page_index_in_region); zero_page(*region, page_index_in_region);
return PageFaultResponse::Continue; return PageFaultResponse::Continue;
} }
} else if (fault.is_protection_violation()) { ASSERT(fault.type() == PageFault::Type::ProtectionViolation);
if (region->should_cow(page_index_in_region)) { if (region->should_cow(page_index_in_region)) {
#ifdef PAGE_FAULT_DEBUG #ifdef PAGE_FAULT_DEBUG
dbgprintf("PV(cow) fault in Region{%p}[%u]\n", region, page_index_in_region); dbgprintf("PV(cow) fault in Region{%p}[%u]\n", region, page_index_in_region);
@ -446,10 +446,6 @@ PageFaultResponse MemoryManager::handle_page_fault(const PageFault& fault)
return PageFaultResponse::Continue; return PageFaultResponse::Continue;
} }
kprintf("PV(error) fault in Region{%p}[%u] at L%x\n", region, page_index_in_region, fault.vaddr().get()); kprintf("PV(error) fault in Region{%p}[%u] at L%x\n", region, page_index_in_region, fault.vaddr().get());
} else {
ASSERT_NOT_REACHED();
}
return PageFaultResponse::ShouldCrash; return PageFaultResponse::ShouldCrash;
} }