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Kernel: Add a way to specify which memory regions can make syscalls

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This patch adds sys$msyscall() which is loosely based on an OpenBSD
mechanism for preventing syscalls from non-blessed memory regions.

It works similarly to pledge and unveil, you can call it as many
times as you like, and when you're finished, you call it with a null
pointer and it will stop accepting new regions from then on.

If a syscall later happens and doesn't originate from one of the
previously blessed regions, the kernel will simply crash the process.
This commit is contained in:
Andreas Kling 2021-02-02 19:56:11 +01:00
parent d57b4128a1
commit 823186031d
10 changed files with 43 additions and 1 deletions
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2
Kernel/Process.cpp
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@ -129,6 +129,7 @@ Region& Process::allocate_split_region(const Region& source_region, const Range&
{
auto& region = add_region(
Region::create_user_accessible(this, range, source_region.vmobject(), offset_in_vmobject, source_region.name(), source_region.access(), source_region.is_cacheable(), source_region.is_shared()));
region.set_syscall_region(source_region.is_syscall_region());
region.set_mmap(source_region.is_mmap());
region.set_stack(source_region.is_stack());
size_t page_offset_in_source_region = (offset_in_vmobject - source_region.offset_in_vmobject()) / PAGE_SIZE;
@ -423,6 +424,7 @@ void create_signal_trampolines()
InterruptDisabler disabler;
// NOTE: We leak this region.
auto* trampoline_region = MM.allocate_user_accessible_kernel_region(PAGE_SIZE, "Signal trampolines", Region::Access::Read | Region::Access::Write | Region::Access::Execute, false).leak_ptr();
trampoline_region->set_syscall_region(true);
g_return_to_ring3_from_signal_trampoline = trampoline_region->vaddr();
u8* trampoline = (u8*)asm_signal_trampoline;