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      1 /* Copyright (C) 2000-2024 Free Software Foundation, Inc.
      2    Contributed by Richard Henderson <rth (at) cygnus.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 glibc ld.so routines
     26    to avoid register/deregister calls at DSO load/unload.  */
     27 
     28 #ifndef _GNU_SOURCE
     29 #define _GNU_SOURCE 1
     30 #endif
     31 #include "config.h"
     32 #ifndef inhibit_libc
     33 #include <stddef.h>
     34 #include <stdlib.h>
     35 #include <link.h>
     36 #include "unwind-ia64.h"
     37 
     38 #if __GLIBC__ < 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ < 2) \
     39     || (__GLIBC__ == 2 && __GLIBC_MINOR__ == 2 && !defined(DT_CONFIG))
     40 # error You need GLIBC 2.2.4 or later on IA-64 Linux
     41 #endif
     42 
     43 struct unw_ia64_callback_data
     44 {
     45   Elf64_Addr pc;
     46   unsigned long *segment_base;
     47   unsigned long *gp;
     48   struct unw_table_entry *ret;
     49 };
     50 
     51 static int
     52 _Unwind_IteratePhdrCallback (struct dl_phdr_info *info, size_t size, void *ptr)
     53 {
     54   struct unw_ia64_callback_data *data = (struct unw_ia64_callback_data *) ptr;
     55   const Elf64_Phdr *phdr, *p_unwind, *p_dynamic;
     56   long n, match;
     57   Elf64_Addr load_base, seg_base;
     58   struct unw_table_entry *f_base, *f;
     59   size_t lo, hi;
     60 
     61   /* Make sure struct dl_phdr_info is at least as big as we need.  */
     62   if (size < offsetof (struct dl_phdr_info, dlpi_phnum)
     63 	     + sizeof (info->dlpi_phnum))
     64     return -1;
     65 
     66   match = 0;
     67   phdr = info->dlpi_phdr;
     68   load_base = info->dlpi_addr;
     69   p_unwind = NULL;
     70   p_dynamic = NULL;
     71   seg_base = ~(Elf64_Addr) 0;
     72 
     73   /* See if PC falls into one of the loaded segments.  Find the unwind
     74      segment at the same time.  */
     75   for (n = info->dlpi_phnum; --n >= 0; phdr++)
     76     {
     77       if (phdr->p_type == PT_LOAD)
     78 	{
     79 	  Elf64_Addr vaddr = phdr->p_vaddr + load_base;
     80 	  if (data->pc >= vaddr && data->pc < vaddr + phdr->p_memsz)
     81 	    match = 1;
     82 	  if (vaddr < seg_base)
     83 	    seg_base = vaddr;
     84 	}
     85       else if (phdr->p_type == PT_IA_64_UNWIND)
     86 	p_unwind = phdr;
     87       else if (phdr->p_type == PT_DYNAMIC)
     88 	p_dynamic = phdr;
     89     }
     90   if (!match || !p_unwind)
     91     return 0;
     92 
     93   /* Search for the FDE within the unwind segment.  */
     94 
     95   f_base = (struct unw_table_entry *) (p_unwind->p_vaddr + load_base);
     96   lo = 0;
     97   hi = p_unwind->p_memsz / sizeof (struct unw_table_entry);
     98 
     99   while (lo < hi)
    100     {
    101       size_t mid = (lo + hi) / 2;
    102 
    103       f = f_base + mid;
    104       if (data->pc < f->start_offset + seg_base)
    105 	hi = mid;
    106       else if (data->pc >= f->end_offset + seg_base)
    107 	lo = mid + 1;
    108       else
    109         goto found;
    110     }
    111   /* No need to search for further libraries when we know pc is contained
    112      in this library.  */
    113   return 1;
    114 
    115  found:
    116   *data->segment_base = seg_base;
    117   *data->gp = 0;
    118   data->ret = f;
    119 
    120   if (p_dynamic)
    121     {
    122       /* For dynamically linked executables and shared libraries,
    123 	 DT_PLTGOT is the gp value for that object.  */
    124       Elf64_Dyn *dyn = (Elf64_Dyn *)(p_dynamic->p_vaddr + load_base);
    125       for (; dyn->d_tag != DT_NULL ; dyn++)
    126 	if (dyn->d_tag == DT_PLTGOT)
    127 	  {
    128 	    /* On IA-64, _DYNAMIC is writable and GLIBC has relocated it.  */
    129 	    *data->gp = dyn->d_un.d_ptr;
    130 	    break;
    131 	  }
    132     }
    133   else
    134     {
    135       /* Otherwise this is a static executable with no _DYNAMIC.
    136 	 The gp is constant program-wide.  */
    137       register unsigned long gp __asm__("gp");
    138       *data->gp = gp;
    139     }
    140 
    141   return 1;
    142 }
    143 
    144 /* Return a pointer to the unwind table entry for the function
    145    containing PC.  */
    146 
    147 struct unw_table_entry *
    148 _Unwind_FindTableEntry (void *pc, unw_word *segment_base, unw_word *gp,
    149                         struct unw_table_entry *ent ATTRIBUTE_UNUSED)
    150 {
    151   struct unw_ia64_callback_data data;
    152 
    153   data.pc = (Elf64_Addr) pc;
    154   data.segment_base = segment_base;
    155   data.gp = gp;
    156   data.ret = NULL;
    157 
    158   if (dl_iterate_phdr (_Unwind_IteratePhdrCallback, &data) < 0)
    159     return NULL;
    160 
    161   return data.ret;
    162 }
    163 #endif
    164