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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,103 @@ | ||
| //! Write barrier implementation and testing utilities | ||
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| use crate::memory::{alloc_blob, Memory}; | ||
| use crate::types::*; | ||
| use crate::visitor::visit_pointer_fields; | ||
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| static mut UPDATED_FIELDS: [usize; 1024] = [0usize; 1024]; | ||
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| static mut N_UPDATED_FIELDS: usize = 0; | ||
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| static mut HEAP_COPY: *mut Blob = core::ptr::null_mut(); | ||
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| // loc: updated location (object field) | ||
| // new: value being written | ||
| // | ||
| // Called before writing the value, so `*loc` gives the old (current) value. | ||
| #[no_mangle] | ||
| pub unsafe extern "C" fn write_barrier(loc: usize) { | ||
| // Make sure we unskewed the object when calculating the field | ||
| assert_eq!(loc & 0b1, 0); | ||
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| assert!(N_UPDATED_FIELDS < 1024); | ||
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| // println!(100, "Write barrier recording {:#x}", loc); | ||
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| UPDATED_FIELDS[N_UPDATED_FIELDS] = loc; | ||
| N_UPDATED_FIELDS += 1; | ||
| } | ||
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| /// Copy the current heap, store it in heap as a blob. Update `HEAP_COPY_BLOB` to the location of | ||
| /// the blob. This copy will then be used to check write barrier correctness, by `check_heap_copy`. | ||
| pub unsafe fn copy_heap<M: Memory>(mem: &mut M, heap_base: u32, hp: u32) { | ||
| let blob_size = Bytes(hp - heap_base); | ||
| let blob = alloc_blob(mem, blob_size).unskew() as *mut Blob; | ||
| let mut payload = blob.payload_addr() as *mut u32; | ||
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| let mut p = heap_base; | ||
| while p < hp { | ||
| *payload = *(p as *const u32); | ||
| payload = payload.add(1); | ||
| p += core::mem::size_of::<u32>() as u32; | ||
| } | ||
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| HEAP_COPY = blob; | ||
| N_UPDATED_FIELDS = 0; | ||
| } | ||
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| pub unsafe fn check_heap_copy(heap_base: u32, hp: u32) { | ||
| if HEAP_COPY.is_null() { | ||
| return; | ||
| } | ||
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| assert!((HEAP_COPY as u32) < hp); | ||
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| let mut copy_ptr = HEAP_COPY.payload_addr() as *mut u32; | ||
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| let mut p = heap_base; | ||
| while p < HEAP_COPY as u32 { | ||
| let obj_heap = p as *mut Obj; | ||
| let obj_copy = copy_ptr as *mut Obj; | ||
| let diff = obj_copy as usize - obj_heap as usize; | ||
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| let tag = obj_heap.tag(); | ||
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| assert_eq!(tag, obj_copy.tag()); | ||
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| visit_pointer_fields(obj_heap, tag, heap_base as usize, |obj_field_ptr| { | ||
| let copy_field_ptr = (obj_field_ptr as usize + diff) as *mut SkewedPtr; | ||
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| let obj_field_value = *obj_field_ptr; | ||
| let copy_field_value = *copy_field_ptr; | ||
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| if obj_field_value != copy_field_value { | ||
| // Field was updated, check that we called the write barrier | ||
| let mut found = false; | ||
| for updated_field_idx in 0..N_UPDATED_FIELDS { | ||
| if UPDATED_FIELDS[updated_field_idx] == obj_field_ptr as usize { | ||
| found = true; | ||
| break; | ||
| } | ||
| } | ||
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| if !found { | ||
| panic!( | ||
| "Updated field {:#x} of object {:#x} ({}) not found in \ | ||
| updated fields recorded by write barrier (heap base={:#x}, hp={:#x}, static={})", | ||
| obj_field_ptr as usize, | ||
| obj_heap as usize, | ||
| tag_str(tag), | ||
| heap_base, | ||
| hp, | ||
| (obj_heap as u32) < heap_base, | ||
| ); | ||
| } | ||
| } | ||
| }); | ||
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| let size: Words<u32> = object_size(obj_heap as usize); | ||
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| p += size.to_bytes().0; | ||
| copy_ptr = copy_ptr.add(size.0 as usize); | ||
| } | ||
| } |
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