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Kernel: Fix GDT and segment selectors to make userland work on x86_64

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Userland faulted on the very first instruction before because the
PML4T/PDPT/etc. weren't marked as user-accessible. For some reason
x86 doesn't care about that.

Also, we need to provide an appropriate userspace stack segment
selector to iretq.
This commit is contained in:
Gunnar Beutner 2021-06-28 17:03:08 +02:00 • committed by Andreas Kling
parent 04fc7d708c
commit b5aad1c81d
4 changed files with 16 additions and 9 deletions
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9
Kernel/Arch/x86/x86_64/Processor.cpp
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@ -115,8 +115,13 @@ u32 Processor::init_context(Thread& thread, bool leave_crit)
iretframe.rflags = regs.rflags;
iretframe.rip = regs.rip;
iretframe.cs = regs.cs;
iretframe.userspace_rsp = kernel_stack_top;
iretframe.userspace_ss = 0;
if (return_to_user) {
iretframe.userspace_rsp = regs.rsp;
iretframe.userspace_ss = GDT_SELECTOR_DATA3 | 3;
} else {
iretframe.userspace_rsp = kernel_stack_top;
iretframe.userspace_ss = 0;
}
// make space for a trap frame
stack_top -= sizeof(TrapFrame);