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stack: do not modify pointers unless a valid allocation is possible
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parent
30ccf384e0
commit
190e926903
@ -279,11 +279,12 @@ impl NockStack {
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panic!("Allocation during cleanup phase is prohibited.");
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}
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self.alloc_pointer = self.alloc_pointer.sub(words);
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if self.alloc_pointer > self.stack_pointer {
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self.alloc_pointer
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} else {
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let alloc = self.alloc_pointer.sub(words);
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if alloc < self.stack_pointer {
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ptr::null_mut()
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} else {
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self.alloc_pointer = alloc;
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alloc
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}
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}
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@ -294,11 +295,12 @@ impl NockStack {
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}
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let alloc = self.alloc_pointer;
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self.alloc_pointer = self.alloc_pointer.add(words);
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if self.alloc_pointer < self.stack_pointer {
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alloc
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} else {
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let new_ap = self.alloc_pointer.add(words);
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if new_ap > self.stack_pointer {
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ptr::null_mut()
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} else {
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self.alloc_pointer = new_ap;
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alloc
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}
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}
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@ -343,21 +345,23 @@ impl NockStack {
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unsafe fn raw_alloc_in_previous_frame_west(&mut self, words: usize) -> *mut u64 {
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// note that the allocation is on the east frame, and thus resembles raw_alloc_east
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let alloc = *self.prev_alloc_pointer_pointer();
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*(self.prev_alloc_pointer_pointer()) = (*(self.prev_alloc_pointer_pointer())).add(words);
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if *self.prev_alloc_pointer_pointer() < self.stack_pointer {
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alloc
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} else {
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let new_prev_ap = (*(self.prev_alloc_pointer_pointer())).add(words);
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if new_prev_ap > self.stack_pointer {
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ptr::null_mut()
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} else {
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*(self.prev_alloc_pointer_pointer()) = new_prev_ap;
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alloc
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}
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}
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unsafe fn raw_alloc_in_previous_frame_east(&mut self, words: usize) -> *mut u64 {
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// note that the allocation is on the west frame, and thus resembles raw_alloc_west
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*(self.prev_alloc_pointer_pointer()) = (*(self.prev_alloc_pointer_pointer())).sub(words);
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if *self.prev_alloc_pointer_pointer() > self.stack_pointer {
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*self.prev_alloc_pointer_pointer()
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} else {
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let alloc = (*(self.prev_alloc_pointer_pointer())).sub(words);
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if alloc < self.stack_pointer {
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ptr::null_mut()
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} else {
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*(self.prev_alloc_pointer_pointer()) = alloc;
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alloc
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}
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}
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@ -423,17 +427,27 @@ impl NockStack {
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* or not pre_copy() has been called.*/
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unsafe fn pre_copy(&mut self) {
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if !self.pc {
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*(self.free_slot(FRAME)) = *(self.slot_pointer(FRAME));
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*(self.free_slot(STACK)) = *(self.slot_pointer(STACK));
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*(self.free_slot(ALLOC)) = *(self.slot_pointer(ALLOC));
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let old_stack_pointer = self.stack_pointer;
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self.pc = true;
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// Change polarity of lightweight stack.
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if self.is_west() {
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self.stack_pointer = self.alloc_pointer.sub(RESERVED + 1);
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if self.stack_pointer < old_stack_pointer {
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// OOM
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std::ptr::null::<usize>().read_volatile();
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}
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} else {
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self.stack_pointer = self.alloc_pointer.add(RESERVED);
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if self.stack_pointer > old_stack_pointer {
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// OOM
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std::ptr::null::<usize>().read_volatile();
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}
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}
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self.pc = true;
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*(self.free_slot(FRAME)) = *(self.slot_pointer(FRAME));
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*(self.free_slot(STACK)) = *(self.slot_pointer(STACK));
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*(self.free_slot(ALLOC)) = *(self.slot_pointer(ALLOC));
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}
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}
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@ -630,15 +644,27 @@ impl NockStack {
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/** Push a frame onto the stack with 0 or more local variable slots. */
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pub fn frame_push(&mut self, num_locals: usize) {
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if self.pc {
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panic!("frame_push during cleanup phase is prohibited.");
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}
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let current_frame_pointer = self.frame_pointer;
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let current_stack_pointer = self.stack_pointer;
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let current_alloc_pointer = self.alloc_pointer;
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unsafe {
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self.frame_pointer = if self.is_west() {
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current_alloc_pointer.sub(num_locals + RESERVED)
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if self.is_west() {
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self.frame_pointer = current_alloc_pointer.sub(num_locals + RESERVED);
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if self.frame_pointer <= current_stack_pointer {
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// OOM
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std::ptr::null::<usize>().read_volatile();
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}
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} else {
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current_alloc_pointer.add(num_locals + RESERVED)
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};
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self.frame_pointer = current_alloc_pointer.add(num_locals + RESERVED);
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if self.frame_pointer >= current_stack_pointer {
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// OOM
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std::ptr::null::<usize>().read_volatile();
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}
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}
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self.alloc_pointer = current_stack_pointer;
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self.stack_pointer = self.frame_pointer;
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@ -646,8 +672,6 @@ impl NockStack {
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*(self.slot_pointer(STACK)) = current_stack_pointer as u64;
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*(self.slot_pointer(ALLOC)) = current_alloc_pointer as u64;
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}
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self.pc = false;
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}
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/** Run a closure inside a frame, popping regardless of the value returned by the closure.
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@ -707,11 +731,12 @@ impl NockStack {
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self.alloc_pointer
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};
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let alloc = self.stack_pointer;
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self.stack_pointer = self.stack_pointer.add(word_size_of::<T>());
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if self.stack_pointer < ap {
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alloc as *mut T
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} else {
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let new_sp = self.stack_pointer.add(word_size_of::<T>());
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if new_sp > ap {
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ptr::null_mut()
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} else {
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self.stack_pointer = new_sp;
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alloc as *mut T
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}
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}
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@ -722,11 +747,12 @@ impl NockStack {
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} else {
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self.alloc_pointer
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};
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self.stack_pointer = self.stack_pointer.sub(word_size_of::<T>());
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if self.stack_pointer > ap {
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self.stack_pointer as *mut T
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} else {
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let alloc = self.stack_pointer.sub(word_size_of::<T>());
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if alloc < ap {
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ptr::null_mut()
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} else {
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self.stack_pointer = alloc;
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alloc as *mut T
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}
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}
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