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

   1 /* Copyright (C) 2004-2024 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 /* The public __longjmp() implementation is limited to jumping within
  19    the same stack.  That is, in general it is not possible to use this
  20    __longjmp() implementation to cross from one stack to another.
  21    In contrast, the __sigstack_longjmp() implemented here allows
  22    crossing from the alternate signal stack to the normal stack
  23    as a special case.  */
  24
  25 #include <assert.h>
  26 #include <setjmp.h>
  27 #include <signal.h>
  28 #include <stdint.h>
  29 #include <stdlib.h>
  30
  31 #include <sysdep.h>
  32 #include <sys/rse.h>
  33
  34 #define JB_SP   0
  35 #define JB_BSP  17
  36
  37 struct rbs_flush_values
  38   {
  39     unsigned long bsp;
  40     unsigned long rsc;
  41     unsigned long rnat;
  42   };
  43
  44 extern struct rbs_flush_values __ia64_flush_rbs (void);
  45 extern void __ia64_longjmp (__jmp_buf buf, int val, long rnat, long rsc)
  46      __attribute__ ((__noreturn__));
  47
  48 static void
  49 copy_rbs (unsigned long *dst, unsigned long *dst_end, unsigned long dst_rnat,
  50           unsigned long *src, unsigned long *src_end,
  51           unsigned long current_rnat)
  52 {
  53   unsigned long dst_slot, src_rnat = 0, src_slot, *src_rnat_addr, nat_bit;
  54   int first_time = 1;
  55
  56   while (dst < dst_end)
  57     {
  58       dst_slot = ia64_rse_slot_num (dst);
  59       if (dst_slot == 63)
  60         {
  61           *dst++ = dst_rnat;
  62           dst_rnat = 0;
  63         }
  64       else
  65         {
  66           /* read source value, including NaT bit: */
  67           src_slot = ia64_rse_slot_num (src);
  68           if (src_slot == 63)
  69             {
  70               /* skip src RNaT slot */
  71               ++src;
  72               src_slot = 0;
  73             }
  74           if (first_time || src_slot == 0)
  75             {
  76               first_time = 0;
  77               src_rnat_addr = ia64_rse_rnat_addr (src);
  78               if (src_rnat_addr < src_end)
  79                 src_rnat = *src_rnat_addr;
  80               else
  81                 src_rnat = current_rnat;
  82             }
  83           nat_bit = (src_rnat >> src_slot) & 1;
  84
  85           assert (src < src_end);
  86
  87           *dst++ = *src++;
  88           if (nat_bit)
  89             dst_rnat |=  (1UL << dst_slot);
  90           else
  91             dst_rnat &= ~(1UL << dst_slot);
  92         }
  93     }
  94   dst_slot = ia64_rse_slot_num (dst);
  95   if (dst_slot > 0)
  96     *ia64_rse_rnat_addr (dst) = dst_rnat;
  97 }
  98
  99 void
 100 __sigstack_longjmp (__jmp_buf buf, int val)
 101 {
 102   unsigned long *rbs_base, *bsp, *bspstore, *jb_bsp, jb_sp, ss_sp;
 103   unsigned long ndirty, rnat, load_rnat, *jb_rnat_addr;
 104   struct sigcontext *sc;
 105   stack_t stk;
 106   struct rbs_flush_values c;
 107
 108   /* put RSE into enforced-lazy mode and return current bsp/rsc/rnat: */
 109   c = __ia64_flush_rbs ();
 110
 111   jb_sp  = ((unsigned long *)  buf)[JB_SP];
 112   jb_bsp = ((unsigned long **) buf)[JB_BSP];
 113
 114   INTERNAL_SYSCALL_CALL (sigaltstack, NULL, &stk);
 115
 116   ss_sp = (unsigned long) stk.ss_sp;
 117   jb_rnat_addr = ia64_rse_rnat_addr (jb_bsp);
 118
 119   if ((stk.ss_flags & SS_ONSTACK) == 0 || jb_sp - ss_sp < stk.ss_size)
 120     /* Normal non-stack-crossing longjmp; if the RNaT slot for the bsp
 121        saved in the jump-buffer is the same as the one for the current
 122        BSP, use the current AR.RNAT value, otherwise, load it from the
 123        jump-buffer's RNaT-slot.  */
 124     load_rnat = (ia64_rse_rnat_addr ((unsigned long *) c.bsp) != jb_rnat_addr);
 125   else
 126     {
 127       /* If we are on the alternate signal-stack and the jump-buffer
 128          lies outside the signal-stack, we may need to copy back the
 129          dirty partition which was torn off and saved on the
 130          signal-stack when the signal was delivered.
 131
 132          Caveat: we assume that the top of the alternate signal-stack
 133                  stores the sigcontext structure of the signal that
 134                  caused the switch to the signal-stack.  This should
 135                  be a fairly safe assumption but the kernel _could_
 136                  do things differently.. */
 137       sc = ((struct sigcontext *) ((ss_sp + stk.ss_size) & -16) - 1);
 138
 139       /* As a sanity-check, verify that the register-backing-store base
 140          of the alternate signal-stack is where we expect it.  */
 141       rbs_base = (unsigned long *)
 142         ((ss_sp + sizeof (long) - 1) & -sizeof (long));
 143
 144       assert ((unsigned long) rbs_base == sc->sc_rbs_base);
 145
 146       ndirty = ia64_rse_num_regs (rbs_base, rbs_base + (sc->sc_loadrs >> 19));
 147       bsp = (unsigned long *) sc->sc_ar_bsp;
 148       bspstore = ia64_rse_skip_regs (bsp, -ndirty);
 149
 150       if (bspstore < jb_bsp)
 151         /* AR.BSPSTORE at the time of the signal was below the value
 152            of AR.BSP saved in the jump-buffer => copy the missing
 153            portion from the torn off dirty partition which got saved
 154            on the alternate signal-stack.  */
 155         copy_rbs (bspstore, jb_bsp, sc->sc_ar_rnat,
 156                   rbs_base, (unsigned long *) c.bsp, c.rnat);
 157
 158       load_rnat = 1;
 159     }
 160   if (load_rnat)
 161     rnat = *jb_rnat_addr;
 162   else
 163     rnat = c.rnat;
 164   __ia64_longjmp (buf, val, rnat, c.rsc);
 165 }