kernel/system/do_sigreturn.c

   1 /* The kernel call that is implemented in this file:
   2  *   m_type:    SYS_SIGRETURN
   3  *
   4  * The parameters for this kernel call are:
   5  *     m2_i1:   SIG_ENDPT       # process returning from handler
   6  *     m2_p1:   SIG_CTXT_PTR    # pointer to sigcontext structure
   7  *
   8  */
   9
  10 #include "kernel/system.h"
  11 #include <string.h>
  12 #include <machine/cpu.h>
  13
  14 #if USE_SIGRETURN
  15
  16 /*===========================================================================*
  17  *                            do_sigreturn                                   *
  18  *===========================================================================*/
  19 int do_sigreturn(struct proc * caller, message * m_ptr)
  20 {
  21 /* POSIX style signals require sys_sigreturn to put things in order before
  22  * the signalled process can resume execution
  23  */
  24   struct sigcontext sc;
  25   register struct proc *rp;
  26   int proc_nr, r;
  27
  28   if (! isokendpt(m_ptr->SIG_ENDPT, &proc_nr)) return(EINVAL);
  29   if (iskerneln(proc_nr)) return(EPERM);
  30   rp = proc_addr(proc_nr);
  31
  32   /* Copy in the sigcontext structure. */
  33   if((r=data_copy(m_ptr->SIG_ENDPT, (vir_bytes) m_ptr->SIG_CTXT_PTR,
  34         KERNEL, (vir_bytes) &sc, sizeof(struct sigcontext))) != OK)
  35         return r;
  36
  37   /* Restore user bits of psw from sc, maintain system bits from proc. */
  38   sc.sc_psw  =  (sc.sc_psw & X86_FLAGS_USER) |
  39                 (rp->p_reg.psw & ~X86_FLAGS_USER);
  40
  41 #if defined(__i386__)
  42   /* Don't panic kernel if user gave bad selectors. */
  43   sc.sc_cs = rp->p_reg.cs;
  44   sc.sc_ds = rp->p_reg.ds;
  45   sc.sc_es = rp->p_reg.es;
  46   sc.sc_ss = rp->p_reg.ss;
  47   sc.sc_fs = rp->p_reg.fs;
  48   sc.sc_gs = rp->p_reg.gs;
  49 #endif
  50
  51   /* Restore the registers. */
  52   memcpy(&rp->p_reg, &sc.sc_regs, sizeof(sigregs));
  53 #if defined(__i386__)
  54   if(sc.sc_flags & MF_FPU_INITIALIZED)
  55   {
  56         memcpy(rp->p_seg.fpu_state, &sc.sc_fpu_state, FPU_XFP_SIZE);
  57         rp->p_misc_flags |=  MF_FPU_INITIALIZED; /* Restore math usage flag. */
  58         /* force reloading FPU */
  59         release_fpu(rp);
  60   }
  61 #endif
  62
  63   rp->p_misc_flags |= MF_CONTEXT_SET;
  64
  65   return(OK);
  66 }
  67 #endif /* USE_SIGRETURN */
  68