text: /* The kernel call that is implemented in this file:
   *   m_type:	SYS_SIGRETURN
   *
   * The parameters for this kernel call are:
   *     m2_i1:	SIG_PROC  	# process returning from handler
   *     m2_p1:	SIG_CTXT_PTR 	# pointer to sigcontext structure
   *
   */
  
  #include "../system.h"
  #include <string.h>
  #include <signal.h>
  #include <sys/sigcontext.h>
  
  #if USE_SIGRETURN 
  
  /*===========================================================================*
   *			      do_sigreturn				     *
   *===========================================================================*/
  PUBLIC int do_sigreturn(m_ptr)
  message *m_ptr;			/* pointer to request message */
  {
  /* POSIX style signals require sys_sigreturn to put things in order before 
   * the signalled process can resume execution
   */
    struct sigcontext sc;
    register struct proc *rp;
    phys_bytes src_phys;
  
    if (! isokprocn(m_ptr->SIG_PROC)) return(EINVAL);
    if (iskerneln(m_ptr->SIG_PROC)) return(EPERM);
    rp = proc_addr(m_ptr->SIG_PROC);
  
    /* Copy in the sigcontext structure. */
    src_phys = umap_local(rp, D, (vir_bytes) m_ptr->SIG_CTXT_PTR,
        (vir_bytes) sizeof(struct sigcontext));
    if (src_phys == 0) return(EFAULT);
    phys_copy(src_phys, vir2phys(&sc), (phys_bytes) sizeof(struct sigcontext));
  
    /* Make sure that this is not just a jump buffer. */
    if ((sc.sc_flags & SC_SIGCONTEXT) == 0) return(EINVAL);
  
    /* Fix up only certain key registers if the compiler doesn't use
     * register variables within functions containing setjmp.
     */
    if (sc.sc_flags & SC_NOREGLOCALS) {
        rp->p_reg.retreg = sc.sc_retreg;
        rp->p_reg.fp = sc.sc_fp;
        rp->p_reg.pc = sc.sc_pc;
        rp->p_reg.sp = sc.sc_sp;
        return(OK);
    }
    sc.sc_psw  = rp->p_reg.psw;
  
  #if (CHIP == INTEL)
    /* Don't panic kernel if user gave bad selectors. */
    sc.sc_cs = rp->p_reg.cs;
    sc.sc_ds = rp->p_reg.ds;
    sc.sc_es = rp->p_reg.es;
  #if _WORD_SIZE == 4
    sc.sc_fs = rp->p_reg.fs;
    sc.sc_gs = rp->p_reg.gs;
  #endif
  #endif
  
    /* Restore the registers. */
    memcpy(&rp->p_reg, &sc.sc_regs, sizeof(struct sigregs));
    return(OK);
  }
  #endif /* USE_SIGRETURN */
  
  