96 lines
2.4 KiB
Rust
96 lines
2.4 KiB
Rust
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//! Address space layout randomization for MMTk.
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use mmtk::util::{
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conversions::raw_align_down, heap::vm_layout::{VMLayout, BYTES_IN_CHUNK}, options::{GCTriggerSelector, Options}, Address
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};
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use rand::Rng;
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use crate::options::OPTIONS;
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fn get_random_mmap_addr() -> Address {
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let mut rng = rand::rng();
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let uniform = rand::distr::Uniform::new(0, usize::MAX).unwrap();
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let mut raw_addr = rng.sample(uniform);
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raw_addr = raw_align_down(raw_addr, BYTES_IN_CHUNK);
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raw_addr &= 0x3FFFFFFFF000;
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unsafe { Address::from_usize(raw_addr) }
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}
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fn is_address_maybe_unmapped(addr: Address, size: usize) -> bool {
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#[cfg(unix)]
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{
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unsafe {
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let res = libc::msync(addr.to_mut_ptr(), size, libc::MS_ASYNC);
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if res == -1 && errno::errno().0 == libc::ENOMEM {
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return true;
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}
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}
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}
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false
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}
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pub fn aslr_vm_layout(mmtk_options: &mut Options) -> VMLayout {
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let mut vm_layout = VMLayout::default();
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let options = &*OPTIONS;
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if options.compressed_pointers {
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vm_layout.heap_start = unsafe { Address::from_usize(0x4000_0000) };
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vm_layout.heap_end = vm_layout.heap_start + 32usize * 1024 * 1024
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}
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let size = if options.compressed_pointers {
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if options.tag_compressed_pointers {
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32 * 1024 * 1024
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} else {
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16 * 1024 * 1024
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}
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} else {
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options.max_heap_size
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};
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if options.aslr {
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vm_layout.force_use_contiguous_spaces = false;
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loop {
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let start = get_random_mmap_addr().align_down(BYTES_IN_CHUNK);
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if !is_address_maybe_unmapped(start, size) {
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continue;
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}
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let end = (start + size).align_up(BYTES_IN_CHUNK);
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vm_layout.heap_start = start;
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vm_layout.heap_end = end;
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if !options.compressed_pointers {
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vm_layout.log_address_space = if cfg!(target_pointer_width = "32") {
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31
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} else {
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47
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};
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vm_layout.log_space_extent = size.trailing_zeros() as usize - 1;
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}
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break;
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}
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}
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if options.compressed_pointers {
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vm_layout.log_address_space = 36;
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vm_layout.log_space_extent = 31;
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}
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mmtk_options.gc_trigger.set(GCTriggerSelector::DynamicHeapSize(
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options.min_heap_size,
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options.max_heap_size,
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));
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vm_layout
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}
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