Kernel: Don't treat read faults like CoW exceptions

I'm not sure why we would have a non-readable CoW region, but I suppose we could, so let's not Copy-on-Read in those cases.
fleximus · Aug 6, 2019 · 945f8eb · 945f8eb
1 parent af4cf01
commit 945f8eb
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Showing 2 changed files with 9 additions and 3 deletions.
diff --git a/Kernel/Arch/i386/CPU.h b/Kernel/Arch/i386/CPU.h
@@ -304,14 +304,20 @@ class PageFault {
  }
 
  enum class Type {
- PageNotPresent,
- ProtectionViolation,
+ PageNotPresent = PageFaultFlags::NotPresent,
+ ProtectionViolation = PageFaultFlags::ProtectionViolation,
+ };
+
+ enum class Access {
+ Read = PageFaultFlags::Read,
+ Write = PageFaultFlags::Write,
  };
 
  VirtualAddress vaddr() const { return m_vaddr; }
  u16 code() const { return m_code; }
 
  Type type() const { return (Type)(m_code & 1); }
+ Access access() const { return (Access)(m_code & 2); }
 
  bool is_not_present() const { return (m_code & 1) == PageFaultFlags::NotPresent; }
  bool is_protection_violation() const { return (m_code & 1) == PageFaultFlags::ProtectionViolation; }

diff --git a/Kernel/VM/MemoryManager.cpp b/Kernel/VM/MemoryManager.cpp
@@ -437,7 +437,7 @@ PageFaultResponse MemoryManager::handle_page_fault(const PageFault& fault)
  return PageFaultResponse::Continue;
  }
  ASSERT(fault.type() == PageFault::Type::ProtectionViolation);
- if (region->should_cow(page_index_in_region)) {
+ if (fault.access() == PageFault::Access::Write && region->should_cow(page_index_in_region)) {
 #ifdef PAGE_FAULT_DEBUG
  dbgprintf("PV(cow) fault in Region{%p}[%u]\n", region, page_index_in_region);
 #endif