#include "master.hpp" namespace factor { void factor_vm::dispatch_signal_handler(cell *sp, cell *pc, cell handler) { if (!code->seg->in_segment_p(*pc) || *sp < ctx->callstack_seg->start + stack_reserved) { /* Fault came from foreign code or a callstack overflow, or we don't have enough callstack room to try the resumable handler. Cut the callstack down to the shallowest Factor stack frame that leaves room for the signal handler to do its thing, and launch the handler without going through the resumable subprimitive. */ signal_resumable = false; stack_frame *frame = ctx->bottom_frame(); while((cell)frame >= *sp && frame >= ctx->callstack_top && (cell)frame >= ctx->callstack_seg->start + stack_reserved) { frame = frame_successor(frame); } cell newsp = (cell)(frame+1); *sp = newsp; ctx->callstack_top = (stack_frame*)newsp; *pc = handler; } else { signal_resumable = true; // Fault came from Factor, and we've got a good callstack. Route the signal // handler through the resumable signal handler subprimitive. cell offset = *sp % 16; signal_handler_addr = handler; tagged handler_word = tagged(special_objects[SIGNAL_HANDLER_WORD]); /* True stack frames are always 16-byte aligned. Leaf procedures that don't create a stack frame will be out of alignment by sizeof(cell) bytes. */ /* On architectures with a link register we would have to check for leafness by matching the PC to a word. We should also use FRAME_RETURN_ADDRESS instead of assuming the stack pointer is the right place to put the resume address. */ if (offset == 0) { cell newsp = *sp - sizeof(cell); *sp = newsp; *(cell*)newsp = *pc; } else if (offset == 16 - sizeof(cell)) { // Make a fake frame for the leaf procedure code_block *leaf_block = code->code_block_for_address(*pc); assert(leaf_block != NULL); cell newsp = *sp - 4*sizeof(cell); *(cell*)(newsp + 3*sizeof(cell)) = 4*sizeof(cell); *(cell*)(newsp + 2*sizeof(cell)) = (cell)leaf_block->entry_point(); *(cell*) newsp = *pc; *sp = newsp; handler_word = tagged(special_objects[LEAF_SIGNAL_HANDLER_WORD]); } else assert(false); *pc = (cell)handler_word->entry_point; } } }