libgcc/config/ia64/fde-vms.c

   1 /* Copyright (C) 2004-2023 Free Software Foundation, Inc.
   2    Contributed by Douglas B Rupp <rupp@gnat.com>
   3
   4    This file is part of GCC.
   5
   6    GCC is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3, or (at your option)
   9    any later version.
  10
  11    GCC is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    Under Section 7 of GPL version 3, you are granted additional
  17    permissions described in the GCC Runtime Library Exception, version
  18    3.1, as published by the Free Software Foundation.
  19
  20    You should have received a copy of the GNU General Public License and
  21    a copy of the GCC Runtime Library Exception along with this program;
  22    see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23    <http://www.gnu.org/licenses/>.  */
  24
  25 /* Locate the FDE entry for a given address, using VMS Starlet routines
  26    to avoid register/deregister calls at DSO load/unload.  */
  27
  28 #include "tconfig.h"
  29 #include "tsystem.h"
  30 #include "coretypes.h"
  31 #include "tm.h"
  32 #include "libgcc_tm.h"
  33 #include <stddef.h>
  34 #include <stdlib.h>
  35 #include <stdio.h>
  36 #include "unwind-ia64.h"
  37
  38 #include <ossddef.h>
  39 #ifndef SS$_NORMAL
  40 #define SS$_NORMAL 1
  41 #endif
  42
  43 #define UNW_IVMS_MODE(HEADER) (((HEADER) >> 44) & 0x3L)
  44
  45 typedef struct
  46 {
  47   unw_word start_offset;
  48   unw_word end_offset;
  49   unw_word info_offset;
  50   unw_word gp_value;
  51 }  vms_unw_table_entry;
  52
  53 typedef unsigned long long uqword;
  54
  55 /* ENTRY is the unwind table entry found for a PC part of call chain we're
  56    unwinding through.  Return whether we should force the generic unwinder
  57    to resort to "fallback" processing.  */
  58
  59 static int
  60 force_fallback_processing_for (void * pc, vms_unw_table_entry * entry)
  61 {
  62   static int eh_debug = -1;
  63
  64   uqword * unw_info_block = (uqword *)entry->info_offset;
  65   uqword header = *unw_info_block;
  66
  67   /* We need to force fallback processing in two cases:
  68
  69      1/ The exception dispatch frame, since only our fallback
  70         processing knows how to properly unwind through it, and
  71
  72      2/ A bottom of stack frame, since only our fallback processing
  73         will ensure we don't try to unwind further past it, which
  74         would get us into unknown territory and likely cause a severe
  75         crash along the way.
  76
  77      The two cases are indicated by non-default values for specific
  78      bits in the OS Specific Data (OSSD) General Information block
  79      associated with such frames.  */
  80
  81   ossddef * ossd;
  82
  83   if (eh_debug == -1)
  84     {
  85       char * EH_DEBUG = getenv ("EH_DEBUG");
  86       eh_debug = EH_DEBUG ? atoi (EH_DEBUG) : 0;
  87     }
  88
  89   if (eh_debug)
  90     {
  91       printf ("pc @ 0x%p, block @ 0x%p, header = 0x%016llx\n",
  92               pc, unw_info_block, header);
  93       printf ("mode = %d, length = %ld, handler = %d\n",
  94               (int)UNW_IVMS_MODE (header), UNW_LENGTH (header),
  95               UNW_FLAG_EHANDLER (header) || UNW_FLAG_EHANDLER (header));
  96     }
  97
  98   /* An OSSD block is there for IVMS_MODE == 3 only.  */
  99   if (UNW_IVMS_MODE (header) != 3)
 100     return 0;
 101
 102   /* The OSSD block is found past the header, unwind descriptor area
 103      and condition handler pointer, if any.  */
 104   ossd = (ossddef *)
 105     /* Beware: uqword pointer arithmetic below.  */
 106     (unw_info_block
 107      + 1
 108      + UNW_LENGTH (header)
 109      + (UNW_FLAG_EHANDLER (header) || UNW_FLAG_EHANDLER (header)));
 110
 111   /* "A General Information segment may be omitted if all of its fields
 112       would have their default values.  If a General Information segment
 113       is present, it must be the first in the OSSD area."  So ...  */
 114
 115   if (eh_debug)
 116     printf ("ossd @ 0x%p\n", ossd);
 117
 118   if (eh_debug && ossd->ossd$v_type == OSSD$K_GENERAL_INFO)
 119     printf ("exc_frame = %d - bot_frame = %d - base_frame = %d\n",
 120             ossd->ossd$v_exception_frame,
 121             ossd->ossd$v_bottom_of_stack,
 122             ossd->ossd$v_base_frame);
 123
 124   return
 125     ossd->ossd$v_type == OSSD$K_GENERAL_INFO
 126     && (ossd->ossd$v_exception_frame
 127         || ossd->ossd$v_bottom_of_stack || ossd->ossd$v_base_frame);
 128 }
 129
 130 /* Return a pointer to the unwind table entry for the function
 131    containing PC, 0 if we cannot find an entry or if the one we find
 132    calls for fallback processing.  */
 133
 134 struct unw_table_entry *
 135 _Unwind_FindTableEntry (void *pc, unw_word *segment_base,
 136                         unw_word *gp, struct unw_table_entry *ent)
 137 {
 138   vms_unw_table_entry vueblock;
 139
 140   if (SYS$GET_UNWIND_ENTRY_INFO (pc, &vueblock, 0) != SS$_NORMAL)
 141     return 0;
 142
 143   /* If there is no unwind information, use fallback.  */
 144   if (vueblock.info_offset == 0)
 145     return 0;
 146
 147   /* If we need to force fallback processing, just pretend there is
 148      no entry.  */
 149   if (force_fallback_processing_for (pc, &vueblock))
 150     return 0;
 151
 152   *segment_base = 0; /* ??? Fixme. ??? */
 153   *gp = vueblock.gp_value;
 154   ent->start_offset = vueblock.start_offset;
 155   ent->end_offset = vueblock.end_offset;
 156   ent->info_offset = vueblock.info_offset;
 157
 158   return ent;
 159 }