fix(x86_64/uefi): unmap stack on drop

[mkroening]

This PR makes the kernel unmap user stacks on drop. In early UEFI times, this was not necessary, since we would never touch the page tables for stacks. This changed in a68db87, but forgot to enable unmapping.

This PR makes the following UB program throw a page fault as expected on UEFI:

use std::thread;

struct Ptr(*mut ());

unsafe impl Send for Ptr {}

fn main() {
	let thread = thread::spawn(move || {
		let rsp: *mut ();
		unsafe {
			core::arch::asm!("mov {}, rsp", out(reg) rsp);
		}
		Ptr(rsp)
	});
	let ptr = thread.join().unwrap().0;
	dbg!(ptr);

	// Yield to drop thread.
	thread::yield_now();

	unsafe {
		ptr.cast::<u8>().write(0);
	}
}

I noticed this while working on #2546.

[github-actions]

Benchmark Results

Details

Benchmark	Current: 72e1efe	Previous: 2e23902	Performance Ratio
startup_benchmark Build Time	82.34 s	80.34 s	1.02 ❗
startup_benchmark File Size	0.76 MB	0.80 MB	0.96 ❗
Startup Time - 1 core	0.75 s (±0.02 s)	0.75 s (±0.02 s)	1.00
Startup Time - 2 cores	0.76 s (±0.03 s)	0.74 s (±0.02 s)	1.03
Startup Time - 4 cores	0.77 s (±0.02 s)	0.74 s (±0.02 s)	1.04
multithreaded_benchmark Build Time	85.95 s	82.11 s	1.05 ❗
multithreaded_benchmark File Size	0.90 MB	0.86 MB	1.05 ❗
Multithreaded Pi Efficiency - 2 Threads	88.45 % (±4.31 %)	85.89 % (±6.61 %)	1.03
Multithreaded Pi Efficiency - 4 Threads	42.96 % (±2.52 %)	43.43 % (±2.56 %)	0.99
Multithreaded Pi Efficiency - 8 Threads	25.51 % (±1.24 %)	25.76 % (±1.53 %)	0.99
micro_benchmarks Build Time	83.33 s	80.40 s	1.04 ❗
micro_benchmarks File Size	0.90 MB	0.86 MB	1.05 ❗
Scheduling time - 1 thread	65.61 ticks (±2.53 ticks)	62.65 ticks (±4.06 ticks)	1.05
Scheduling time - 2 threads	35.16 ticks (±4.19 ticks)	34.08 ticks (±4.10 ticks)	1.03
Micro - Time for syscall (getpid)	4.39 ticks (±0.67 ticks)	3.45 ticks (±0.58 ticks)	1.27 ❗
Memcpy speed - (built_in) block size 4096	85349.81 MByte/s (±58857.17 MByte/s)	82448.38 MByte/s (±56997.13 MByte/s)	1.04
Memcpy speed - (built_in) block size 1048576	30318.36 MByte/s (±24516.13 MByte/s)	30585.98 MByte/s (±24707.84 MByte/s)	0.99
Memcpy speed - (built_in) block size 16777216	25749.61 MByte/s (±21245.64 MByte/s)	26340.06 MByte/s (±21720.96 MByte/s)	0.98
Memset speed - (built_in) block size 4096	85394.45 MByte/s (±58890.27 MByte/s)	82292.76 MByte/s (±56891.50 MByte/s)	1.04
Memset speed - (built_in) block size 1048576	31082.33 MByte/s (±24971.90 MByte/s)	31323.85 MByte/s (±25145.86 MByte/s)	0.99
Memset speed - (built_in) block size 16777216	26529.51 MByte/s (±21769.55 MByte/s)	27104.68 MByte/s (±22209.94 MByte/s)	0.98
Memcpy speed - (rust) block size 4096	76137.56 MByte/s (±52956.16 MByte/s)	74097.96 MByte/s (±51811.44 MByte/s)	1.03
Memcpy speed - (rust) block size 1048576	30296.96 MByte/s (±24508.85 MByte/s)	30361.60 MByte/s (±24602.37 MByte/s)	1.00
Memcpy speed - (rust) block size 16777216	25845.41 MByte/s (±21335.12 MByte/s)	27625.34 MByte/s (±22806.88 MByte/s)	0.94
Memset speed - (rust) block size 4096	76824.44 MByte/s (±53411.16 MByte/s)	74373.47 MByte/s (±51976.48 MByte/s)	1.03
Memset speed - (rust) block size 1048576	31059.74 MByte/s (±24969.87 MByte/s)	31110.89 MByte/s (±25033.24 MByte/s)	1.00
Memset speed - (rust) block size 16777216	26627.72 MByte/s (±21861.40 MByte/s)	28386.93 MByte/s (±23265.03 MByte/s)	0.94
alloc_benchmarks Build Time	81.66 s	74.76 s	1.09 ❗
alloc_benchmarks File Size	0.84 MB	0.87 MB	0.96 ❗
Allocations - Allocation success	91.31 %	91.31 %	1
Allocations - Deallocation success	100.00 %	100.00 %	1
Allocations - Pre-fail Allocations	61.44 %	61.44 %	1
Allocations - Average Allocation time	4349.35 Ticks (±135.04 Ticks)	5860.58 Ticks (±98.43 Ticks)	0.74 ❗
Allocations - Average Allocation time (no fail)	5077.44 Ticks (±134.66 Ticks)	6554.81 Ticks (±92.86 Ticks)	0.77 ❗
Allocations - Average Deallocation time	966.06 Ticks (±199.59 Ticks)	1805.01 Ticks (±250.35 Ticks)	0.54 ❗
mutex_benchmark Build Time	81.23 s	79.82 s	1.02 ❗
mutex_benchmark File Size	0.90 MB	0.86 MB	1.05 ❗
Mutex Stress Test Average Time per Iteration - 1 Threads	12.26 ns (±0.48 ns)	12.10 ns (±0.41 ns)	1.01
Mutex Stress Test Average Time per Iteration - 2 Threads	41.52 ns (±2.58 ns)	40.26 ns (±1.68 ns)	1.03

This comment was automatically generated by workflow using github-action-benchmark.