ports/sysdeps/unix/sysv/linux/ia64/nptl/__sigstack_longjmp.c

   1 /* Copyright (C) 2004-2014 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by David Mosberger-Tang <davidm@hpl.hp.com>.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 /* The public __longjmp() implementation is limited to jumping within
  20    the same stack.  That is, in general it is not possible to use this
  21    __longjmp() implementation to cross from one stack to another.
  22    In contrast, the __sigstack_longjmp() implemented here allows
  23    crossing from the alternate signal stack to the normal stack
  24    as a special case.  */
  25
  26 #include <assert.h>
  27 #include <setjmp.h>
  28 #include <signal.h>
  29 #include <stdint.h>
  30 #include <stdlib.h>
  31
  32 #include <sysdep.h>
  33 #include <sys/rse.h>
  34
  35 #define JB_SP   0
  36 #define JB_BSP  17
  37
  38 struct rbs_flush_values
  39   {
  40     unsigned long bsp;
  41     unsigned long rsc;
  42     unsigned long rnat;
  43   };
  44
  45 extern struct rbs_flush_values __ia64_flush_rbs (void);
  46 extern void __ia64_longjmp (__jmp_buf buf, int val, long rnat, long rsc)
  47      __attribute__ ((__noreturn__));
  48
  49 static void
  50 copy_rbs (unsigned long *dst, unsigned long *dst_end, unsigned long dst_rnat,
  51           unsigned long *src, unsigned long *src_end,
  52           unsigned long current_rnat)
  53 {
  54   unsigned long dst_slot, src_rnat = 0, src_slot, *src_rnat_addr, nat_bit;
  55   int first_time = 1;
  56
  57   while (dst < dst_end)
  58     {
  59       dst_slot = ia64_rse_slot_num (dst);
  60       if (dst_slot == 63)
  61         {
  62           *dst++ = dst_rnat;
  63           dst_rnat = 0;
  64         }
  65       else
  66         {
  67           /* read source value, including NaT bit: */
  68           src_slot = ia64_rse_slot_num (src);
  69           if (src_slot == 63)
  70             {
  71               /* skip src RNaT slot */
  72               ++src;
  73               src_slot = 0;
  74             }
  75           if (first_time || src_slot == 0)
  76             {
  77               first_time = 0;
  78               src_rnat_addr = ia64_rse_rnat_addr (src);
  79               if (src_rnat_addr < src_end)
  80                 src_rnat = *src_rnat_addr;
  81               else
  82                 src_rnat = current_rnat;
  83             }
  84           nat_bit = (src_rnat >> src_slot) & 1;
  85
  86           assert (src < src_end);
  87
  88           *dst++ = *src++;
  89           if (nat_bit)
  90             dst_rnat |=  (1UL << dst_slot);
  91           else
  92             dst_rnat &= ~(1UL << dst_slot);
  93         }
  94     }
  95   dst_slot = ia64_rse_slot_num (dst);
  96   if (dst_slot > 0)
  97     *ia64_rse_rnat_addr (dst) = dst_rnat;
  98 }
  99
 100 void
 101 __sigstack_longjmp (__jmp_buf buf, int val)
 102 {
 103   unsigned long *rbs_base, *bsp, *bspstore, *jb_bsp, jb_sp, ss_sp;
 104   unsigned long ndirty, rnat, load_rnat, *jb_rnat_addr;
 105   struct sigcontext *sc;
 106   stack_t stk;
 107   struct rbs_flush_values c;
 108
 109   /* put RSE into enforced-lazy mode and return current bsp/rsc/rnat: */
 110   c = __ia64_flush_rbs ();
 111
 112   jb_sp  = ((unsigned long *)  buf)[JB_SP];
 113   jb_bsp = ((unsigned long **) buf)[JB_BSP];
 114
 115   INTERNAL_SYSCALL_DECL (err);
 116   (void) INTERNAL_SYSCALL (sigaltstack, err, 2, NULL, &stk);
 117
 118   ss_sp = (unsigned long) stk.ss_sp;
 119   jb_rnat_addr = ia64_rse_rnat_addr (jb_bsp);
 120
 121   if ((stk.ss_flags & SS_ONSTACK) == 0 || jb_sp - ss_sp < stk.ss_size)
 122     /* Normal non-stack-crossing longjmp; if the RNaT slot for the bsp
 123        saved in the jump-buffer is the same as the one for the current
 124        BSP, use the current AR.RNAT value, otherwise, load it from the
 125        jump-buffer's RNaT-slot.  */
 126     load_rnat = (ia64_rse_rnat_addr ((unsigned long *) c.bsp) != jb_rnat_addr);
 127   else
 128     {
 129       /* If we are on the alternate signal-stack and the jump-buffer
 130          lies outside the signal-stack, we may need to copy back the
 131          dirty partition which was torn off and saved on the
 132          signal-stack when the signal was delivered.
 133
 134          Caveat: we assume that the top of the alternate signal-stack
 135                  stores the sigcontext structure of the signal that
 136                  caused the switch to the signal-stack.  This should
 137                  be a fairly safe assumption but the kernel _could_
 138                  do things differently.. */
 139       sc = ((struct sigcontext *) ((ss_sp + stk.ss_size) & -16) - 1);
 140
 141       /* As a sanity-check, verify that the register-backing-store base
 142          of the alternate signal-stack is where we expect it.  */
 143       rbs_base = (unsigned long *)
 144         ((ss_sp + sizeof (long) - 1) & -sizeof (long));
 145
 146       assert ((unsigned long) rbs_base == sc->sc_rbs_base);
 147
 148       ndirty = ia64_rse_num_regs (rbs_base, rbs_base + (sc->sc_loadrs >> 19));
 149       bsp = (unsigned long *) sc->sc_ar_bsp;
 150       bspstore = ia64_rse_skip_regs (bsp, -ndirty);
 151
 152       if (bspstore < jb_bsp)
 153         /* AR.BSPSTORE at the time of the signal was below the value
 154            of AR.BSP saved in the jump-buffer => copy the missing
 155            portion from the torn off dirty partition which got saved
 156            on the alternate signal-stack.  */
 157         copy_rbs (bspstore, jb_bsp, sc->sc_ar_rnat,
 158                   rbs_base, (unsigned long *) c.bsp, c.rnat);
 159
 160       load_rnat = 1;
 161     }
 162   if (load_rnat)
 163     rnat = *jb_rnat_addr;
 164   else
 165     rnat = c.rnat;
 166   __ia64_longjmp (buf, val, rnat, c.rsc);
 167 }