src/os_cpu/linux_ppc/vm/os_linux_ppc.cpp

rev 7905 : 8074552:  SafeFetch32 and SafeFetchN do not work in error handling
Summary: handle SafeFetch faults in secondary signal handlers
Contributed-by: Thomas Stuefe

*** 111,120 ****
--- 111,128 ----
    //   Hopefully it was zero'd out beforehand.
    guarantee(uc->uc_mcontext.regs != NULL, "only use ucontext_get_pc in sigaction context");
    return (address)uc->uc_mcontext.regs->nip;
  }
  
+ // modify PC in ucontext.
+ // Note: Only use this for an ucontext handed down to a signal handler. See comment
+ // in ucontext_get_pc.
+ void os::Linux::ucontext_set_pc(ucontext_t * uc, address pc) {
+   guarantee(uc->uc_mcontext.regs != NULL, "only use ucontext_set_pc in sigaction context");
+   uc->uc_mcontext.regs->nip = (unsigned long)pc;
+ }
+ 
  intptr_t* os::Linux::ucontext_get_sp(ucontext_t * uc) {
    return (intptr_t*)uc->uc_mcontext.regs->gpr[1/*REG_SP*/];
  }
  
  intptr_t* os::Linux::ucontext_get_fp(ucontext_t * uc) {
*** 211,221 ****
    // Moved SafeFetch32 handling outside thread!=NULL conditional block to make
    // it work if no associated JavaThread object exists.
    if (uc) {
      address const pc = os::Linux::ucontext_get_pc(uc);
      if (pc && StubRoutines::is_safefetch_fault(pc)) {
!       uc->uc_mcontext.regs->nip = (unsigned long)StubRoutines::continuation_for_safefetch_fault(pc);
        return true;
      }
    }
  
    // decide if this trap can be handled by a stub
--- 219,229 ----
    // Moved SafeFetch32 handling outside thread!=NULL conditional block to make
    // it work if no associated JavaThread object exists.
    if (uc) {
      address const pc = os::Linux::ucontext_get_pc(uc);
      if (pc && StubRoutines::is_safefetch_fault(pc)) {
!       os::Linux::ucontext_set_pc(uc, StubRoutines::continuation_for_safefetch_fault(pc));
        return true;
      }
    }
  
    // decide if this trap can be handled by a stub
*** 358,368 ****
          if (nm != NULL && nm->has_unsafe_access()) {
            // We don't really need a stub here! Just set the pending exeption and
            // continue at the next instruction after the faulting read. Returning
            // garbage from this read is ok.
            thread->set_pending_unsafe_access_error();
!           uc->uc_mcontext.regs->nip = ((unsigned long)pc) + 4;
            return true;
          }
        }
      }
  
--- 366,376 ----
          if (nm != NULL && nm->has_unsafe_access()) {
            // We don't really need a stub here! Just set the pending exeption and
            // continue at the next instruction after the faulting read. Returning
            // garbage from this read is ok.
            thread->set_pending_unsafe_access_error();
!           os::Linux::ucontext_set_pc(uc, pc + 4);
            return true;
          }
        }
      }
  
*** 377,387 ****
                 sig == SIGBUS && thread->doing_unsafe_access()) {
          // We don't really need a stub here! Just set the pending exeption and
          // continue at the next instruction after the faulting read. Returning
          // garbage from this read is ok.
          thread->set_pending_unsafe_access_error();
!         uc->uc_mcontext.regs->nip = ((unsigned long)pc) + 4;
          return true;
        }
      }
  
      // Check to see if we caught the safepoint code in the
--- 385,395 ----
                 sig == SIGBUS && thread->doing_unsafe_access()) {
          // We don't really need a stub here! Just set the pending exeption and
          // continue at the next instruction after the faulting read. Returning
          // garbage from this read is ok.
          thread->set_pending_unsafe_access_error();
!         os::Linux::ucontext_set_pc(uc, pc + 4);
          return true;
        }
      }
  
      // Check to see if we caught the safepoint code in the
*** 400,410 ****
    }
  
    if (stub != NULL) {
      // Save all thread context in case we need to restore it.
      if (thread != NULL) thread->set_saved_exception_pc(pc);
!     uc->uc_mcontext.regs->nip = (unsigned long)stub;
      return true;
    }
  
    // signal-chaining
    if (os::Linux::chained_handler(sig, info, ucVoid)) {
--- 408,418 ----
    }
  
    if (stub != NULL) {
      // Save all thread context in case we need to restore it.
      if (thread != NULL) thread->set_saved_exception_pc(pc);
!     os::Linux::ucontext_set_pc(uc, stub);
      return true;
    }
  
    // signal-chaining
    if (os::Linux::chained_handler(sig, info, ucVoid)) {