100 lines
3.4 KiB
C++
100 lines
3.4 KiB
C++
#include "master.hpp"
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namespace factor {
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void factor_vm::dispatch_non_resumable_signal(cell* sp, cell* pc,
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cell handler,
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cell limit) {
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/* Fault came from the VM or foreign code. We don't try to fix the
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call stack from *sp and instead use the last saved "good value"
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which we get from ctx->callstack_top. Then launch the handler
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without going through the resumable subprimitive. */
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signal_resumable = false;
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cell frame_top = ctx->callstack_top;
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cell seg_start = ctx->callstack_seg->start;
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if (frame_top < seg_start) {
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/* The saved callstack pointer is outside the callstack
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segment. That means that we need to carefully cut off one frame
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first which hopefully should put the pointer within the
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callstack's bounds. */
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code_block *block = code->code_block_for_address(*pc);
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cell frame_size = block->stack_frame_size_for_address(*pc);
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frame_top += frame_size;
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}
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/* Cut the callstack down to the shallowest Factor stack
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frame that leaves room for the signal handler to do its thing,
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and launch the handler without going through the resumable
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subprimitive. */
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FACTOR_ASSERT(seg_start <= frame_top);
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while (frame_top < ctx->callstack_bottom && frame_top < limit) {
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frame_top = code->frame_predecessor(frame_top);
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}
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ctx->callstack_top = frame_top;
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*sp = frame_top;
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*pc = handler;
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}
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void factor_vm::dispatch_resumable_signal(cell* sp, cell* pc, cell handler) {
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signal_resumable = true;
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/* Fault came from Factor, and we've got a good callstack. Route the
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signal handler through the resumable signal handler
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subprimitive. */
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cell offset = *sp % 16;
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signal_handler_addr = handler;
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/* True stack frames are always 16-byte aligned. Leaf procedures
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that don't create a stack frame will be out of alignment by
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sizeof(cell) bytes. */
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/* On architectures with a link register we would have to check for
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leafness by matching the PC to a word. We should also use
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FRAME_RETURN_ADDRESS instead of assuming the stack pointer is the
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right place to put the resume address. */
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cell index = 0;
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cell delta = 0;
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if (offset == 0) {
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delta = sizeof(cell);
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index = SIGNAL_HANDLER_WORD;
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} else if (offset == 16 - sizeof(cell)) {
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/* Make a fake frame for the leaf procedure */
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FACTOR_ASSERT(code->code_block_for_address(*pc) != NULL);
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delta = LEAF_FRAME_SIZE;
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index = LEAF_SIGNAL_HANDLER_WORD;
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} else {
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FACTOR_ASSERT(false);
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}
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cell new_sp = *sp - delta;
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*sp = new_sp;
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*(cell*)new_sp = *pc;
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tagged<word> handler_word = tagged<word>(special_objects[index]);
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*pc = (cell)handler_word->entry_point;
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}
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void factor_vm::dispatch_signal_handler(cell* sp, cell* pc, cell handler) {
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bool in_code_seg = code->seg->in_segment_p(*pc);
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cell cs_limit = ctx->callstack_seg->start + stack_reserved;
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bool resumable_p = in_code_seg && *sp >= cs_limit;
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if (resumable_p) {
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dispatch_resumable_signal(sp, pc, handler);
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} else {
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dispatch_non_resumable_signal(sp, pc, handler, cs_limit);
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}
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/* Poking with the stack pointer, which the above code does, means
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that pointers to stack-allocated objects will become
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corrupted. Therefore the root vectors needs to be cleared because
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their pointers to stack variables are now garbage. */
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data_roots.clear();
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code_roots.clear();
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}
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}
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