5 void factor_vm::dispatch_non_resumable_signal(cell* sp, cell* pc,
9 /* Fault came from the VM or foreign code. We don't try to fix the
10 call stack from *sp and instead use the last saved "good value"
11 which we get from ctx->callstack_top. Then launch the handler
12 without going through the resumable subprimitive. */
13 cell frame_top = ctx->callstack_top;
14 cell seg_start = ctx->callstack_seg->start;
16 if (frame_top < seg_start) {
17 /* The saved callstack pointer is outside the callstack
18 segment. That means that we need to carefully cut off one frame
19 first which hopefully should put the pointer within the
20 callstack's bounds. */
21 code_block *block = code->code_block_for_address(*pc);
22 cell frame_size = block->stack_frame_size_for_address(*pc);
23 frame_top += frame_size;
26 /* Cut the callstack down to the shallowest Factor stack
27 frame that leaves room for the signal handler to do its thing,
28 and launch the handler without going through the resumable
30 FACTOR_ASSERT(seg_start <= frame_top);
31 while (frame_top < ctx->callstack_bottom && frame_top < limit) {
32 frame_top = code->frame_predecessor(frame_top);
34 ctx->callstack_top = frame_top;
39 void factor_vm::dispatch_resumable_signal(cell* sp, cell* pc, cell handler) {
41 /* Fault came from Factor, and we've got a good callstack. Route the
42 signal handler through the resumable signal handler
45 cell offset = *sp % 16;
47 signal_handler_addr = handler;
49 /* True stack frames are always 16-byte aligned. Leaf procedures
50 that don't create a stack frame will be out of alignment by
51 sizeof(cell) bytes. */
52 /* On architectures with a link register we would have to check for
53 leafness by matching the PC to a word. We should also use
54 FRAME_RETURN_ADDRESS instead of assuming the stack pointer is the
55 right place to put the resume address. */
60 index = SIGNAL_HANDLER_WORD;
61 } else if (offset == 16 - sizeof(cell)) {
62 /* Make a fake frame for the leaf procedure */
63 FACTOR_ASSERT(code->code_block_for_address(*pc) != NULL);
64 delta = LEAF_FRAME_SIZE;
65 index = LEAF_SIGNAL_HANDLER_WORD;
69 cell new_sp = *sp - delta;
72 tagged<word> handler_word = tagged<word>(special_objects[index]);
73 *pc = (cell)handler_word->entry_point;
76 void factor_vm::dispatch_signal_handler(cell* sp, cell* pc, cell handler) {
78 bool in_code_seg = code->seg->in_segment_p(*pc);
79 cell cs_limit = ctx->callstack_seg->start + stack_reserved;
80 signal_resumable = in_code_seg && *sp >= cs_limit;
82 if (signal_resumable) {
83 dispatch_resumable_signal(sp, pc, handler);
85 dispatch_non_resumable_signal(sp, pc, handler, cs_limit);
88 /* Poking with the stack pointer, which the above code does, means
89 that pointers to stack-allocated objects will become
90 corrupted. Therefore the root vectors needs to be cleared because
91 their pointers to stack variables are now garbage. */