vm/cpu-x86.cpp

   1 #include "master.hpp"
   2
   3 namespace factor
   4 {
   5
   6 void factor_vm::dispatch_signal_handler(cell *sp, cell *pc, cell handler)
   7 {
   8         if (!code->seg->in_segment_p(*pc) || *sp < ctx->callstack_seg->start + stack_reserved)
   9         {
  10                 /* Fault came from foreign code or a callstack overflow, or we don't
  11                 have enough callstack room to try the resumable handler. Cut the
  12                 callstack down to the shallowest Factor stack frame that leaves room for
  13                 the signal handler to do its thing, and launch the handler without going
  14                 through the resumable subprimitive. */
  15                 signal_resumable = false;
  16                 void *frame_top = (void*)ctx->callstack_top;
  17
  18                 while(frame_top < ctx->callstack_bottom
  19                         && (cell)frame_top < ctx->callstack_seg->start + stack_reserved)
  20                 {
  21                         frame_top = frame_predecessor(frame_top);
  22                 }
  23
  24                 *sp = (cell)frame_top;
  25                 ctx->callstack_top = frame_top;
  26                 *pc = handler;
  27         } else {
  28                 signal_resumable = true;
  29                 // Fault came from Factor, and we've got a good callstack. Route the signal
  30                 // handler through the resumable signal handler subprimitive.
  31                 cell offset = *sp % 16;
  32
  33                 signal_handler_addr = handler;
  34                 tagged<word> handler_word = tagged<word>(special_objects[SIGNAL_HANDLER_WORD]);
  35
  36                 /* True stack frames are always 16-byte aligned. Leaf procedures
  37                 that don't create a stack frame will be out of alignment by sizeof(cell)
  38                 bytes. */
  39                 /* On architectures with a link register we would have to check for leafness
  40                 by matching the PC to a word. We should also use FRAME_RETURN_ADDRESS instead
  41                 of assuming the stack pointer is the right place to put the resume address. */
  42                 if (offset == 0)
  43                 {
  44                         cell newsp = *sp - sizeof(cell);
  45                         *sp = newsp;
  46                         *(cell*)newsp = *pc;
  47                 }
  48                 else if (offset == 16 - sizeof(cell))
  49                 {
  50                         // Make a fake frame for the leaf procedure
  51                         code_block *leaf_block = code->code_block_for_address(*pc);
  52                         FACTOR_ASSERT(leaf_block != NULL);
  53
  54                         cell newsp = *sp - LEAF_FRAME_SIZE;
  55                         *(cell*)(newsp + 3*sizeof(cell)) = 4*sizeof(cell);
  56                         *(cell*)(newsp + 2*sizeof(cell)) = (cell)leaf_block->entry_point();
  57                         *(cell*) newsp                   = *pc;
  58                         *sp = newsp;
  59                         handler_word = tagged<word>(special_objects[LEAF_SIGNAL_HANDLER_WORD]);
  60                 }
  61                 else
  62                         FACTOR_ASSERT(false);
  63
  64                 *pc = (cell)handler_word->entry_point;
  65         }
  66 }
  67
  68 }