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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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2
Kernel/Thread.cpp
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@ -569,6 +569,7 @@ void Thread::make_userspace_stack_for_main_thread(Vector<String> arguments, Vect
{
auto* region = m_process.allocate_region(VirtualAddress(), default_userspace_stack_size, "Stack (Main thread)", PROT_READ | PROT_WRITE, false);
ASSERT(region);
region->set_stack(true);
m_tss.esp = region->vaddr().offset(default_userspace_stack_size).get();
char* stack_base = (char*)region->vaddr().get();
@ -604,6 +605,7 @@ void Thread::make_userspace_stack_for_secondary_thread(void* argument)
{
m_userspace_stack_region = m_process.allocate_region(VirtualAddress(), default_userspace_stack_size, String::format("Stack (Thread %d)", tid()), PROT_READ | PROT_WRITE, false);
ASSERT(m_userspace_stack_region);
m_userspace_stack_region->set_stack(true);
m_tss.esp = m_userspace_stack_region->vaddr().offset(default_userspace_stack_size).get();
// NOTE: The stack needs to be 16-byte aligned.