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Kernel: Implement some basic stack pointer validation

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VM regions can now be marked as stack regions, which is then validated
on syscall, and on page fault.

If a thread is caught with its stack pointer pointing into anything
that's *not* a Region with its stack bit set, we'll crash the whole
process with SIGSTKFLT.

Userspace must now allocate custom stacks by using mmap() with the new
MAP_STACK flag. This mechanism was first introduced in OpenBSD, and now
we have it too, yay! :^)
This commit is contained in:
Andreas Kling 2019-11-17 12:11:43 +01:00
parent 197ed1bb2a
commit 794758df3a
12 changed files with 101 additions and 5 deletions
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4
Kernel/VM/Region.h
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@ -50,6 +50,9 @@ public:
bool is_shared() const { return m_shared; }
void set_shared(bool shared) { m_shared = shared; }
bool is_stack() const { return m_stack; }
void set_stack(bool stack) { m_stack = stack; }
bool is_user_accessible() const { return m_user_accessible; }
PageFaultResponse handle_fault(const PageFault&);
@ -141,5 +144,6 @@ private:
u8 m_access { 0 };
bool m_shared { false };
bool m_user_accessible { false };
bool m_stack { false };
mutable OwnPtr<Bitmap> m_cow_map;
};