xref: /external/valgrind/coregrind/m_debuginfo/debuginfo.c

/*--------------------------------------------------------------------*/
/*--- Top level management of symbols and debugging information.   ---*/
/*---                                                  debuginfo.c ---*/
/*--------------------------------------------------------------------*/

/*
   This file is part of Valgrind, a dynamic binary instrumentation
   framework.

   Copyright (C) 2000-2008 Julian Seward
      jseward@acm.org

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   This program is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307, USA.

   The GNU General Public License is contained in the file COPYING.
*/
/*
   Stabs reader greatly improved by Nick Nethercote, Apr 02.
   This module was also extensively hacked on by Jeremy Fitzhardinge
   and Tom Hughes.
*/

#include "pub_core_basics.h"
#include "pub_core_vki.h"
#include "pub_core_threadstate.h"
#include "pub_core_debuginfo.h"  /* self */
#include "pub_core_demangle.h"
#include "pub_core_libcbase.h"
#include "pub_core_libcassert.h"
#include "pub_core_libcprint.h"
#include "pub_core_libcfile.h"
#include "pub_core_options.h"
#include "pub_core_redir.h"      // VG_(redir_notify_{new,delete}_SegInfo)
#include "pub_core_aspacemgr.h"
#include "pub_core_machine.h"    // VG_PLAT_USES_PPCTOC
#include "pub_core_xarray.h"
#include "pub_core_oset.h"
#include "pub_core_stacktrace.h" // VG_(get_StackTrace)

#include "priv_misc.h"           /* dinfo_zalloc/free */
#include "priv_d3basics.h"       /* ML_(pp_GX) */
#include "priv_tytypes.h"
#include "priv_storage.h"
#include "priv_readdwarf.h"
#include "priv_readstabs.h"
#if defined(VGO_linux)
# include "priv_readelf.h"
# include "priv_readdwarf3.h"
#elif defined(VGO_aix5)
# include "pub_core_debuglog.h"
# include "pub_core_libcproc.h"
# include "pub_core_libcfile.h"
# include "priv_readxcoff.h"
#endif


/*------------------------------------------------------------*/
/*--- The _svma / _avma / _image / _bias naming scheme     ---*/
/*------------------------------------------------------------*/

/* JRS 11 Jan 07: I find the different kinds of addresses involved in
   debuginfo reading confusing.  Recently I arrived at some
   terminology which makes it clearer (to me, at least).  There are 3
   kinds of address used in the debuginfo reading process:

   stated VMAs - the address where (eg) a .so says a symbol is, that
                 is, what it tells you if you consider the .so in
                 isolation

   actual VMAs - the address where (eg) said symbol really wound up
                 after the .so was mapped into memory

   image addresses - pointers into the copy of the .so (etc)
                     transiently mmaped aboard whilst we read its info

   Additionally I use the term 'bias' to denote the difference
   between stated and actual VMAs for a given entity.

   This terminology is not used consistently, but a start has been
   made.  readelf.c and the call-frame info reader in readdwarf.c now
   use it.  Specifically, various variables and structure fields have
   been annotated with _avma / _svma / _image / _bias.  In places _img
   is used instead of _image for the sake of brevity.
*/


/*------------------------------------------------------------*/
/*--- Root structure                                       ---*/
/*------------------------------------------------------------*/

/* The root structure for the entire debug info system.  It is a
   linked list of DebugInfos. */
static DebugInfo* debugInfo_list = NULL;


/* Find 'di' in the debugInfo_list and move it one step closer the the
   front of the list, so as to make subsequent searches for it
   cheaper.  When used in a controlled way, makes a major improvement
   in some DebugInfo-search-intensive situations, most notably stack
   unwinding on amd64-linux. */
static void move_DebugInfo_one_step_forward ( DebugInfo* di )
{
   DebugInfo *di0, *di1, *di2;
   if (di == debugInfo_list)
      return; /* already at head of list */
   vg_assert(di != NULL);
   di0 = debugInfo_list;
   di1 = NULL;
   di2 = NULL;
   while (True) {
      if (di0 == NULL || di0 == di) break;
      di2 = di1;
      di1 = di0;
      di0 = di0->next;
   }
   vg_assert(di0 == di);
   if (di0 != NULL && di1 != NULL && di2 != NULL) {
      DebugInfo* tmp;
      /* di0 points to di, di1 to its predecessor, and di2 to di1's
         predecessor.  Swap di0 and di1, that is, move di0 one step
         closer to the start of the list. */
      vg_assert(di2->next == di1);
      vg_assert(di1->next == di0);
      tmp = di0->next;
      di2->next = di0;
      di0->next = di1;
      di1->next = tmp;
   }
   else
   if (di0 != NULL && di1 != NULL && di2 == NULL) {
      /* it's second in the list. */
      vg_assert(debugInfo_list == di1);
      vg_assert(di1->next == di0);
      di1->next = di0->next;
      di0->next = di1;
      debugInfo_list = di0;
   }
}


/*------------------------------------------------------------*/
/*--- Notification (acquire/discard) helpers               ---*/
/*------------------------------------------------------------*/

/* Allocate and zero out a new DebugInfo record. */
static
DebugInfo* alloc_DebugInfo( const UChar* filename,
                            const UChar* memname )
{
   Bool       traceme;
   DebugInfo* di;

   vg_assert(filename);

   di = ML_(dinfo_zalloc)(sizeof(DebugInfo));
   di->filename  = ML_(dinfo_strdup)(filename);
   di->memname   = memname ? ML_(dinfo_strdup)(memname)
                           : NULL;

   /* Everything else -- pointers, sizes, arrays -- is zeroed by calloc.
      Now set up the debugging-output flags. */
   traceme
      = VG_(string_match)( VG_(clo_trace_symtab_patt), filename )
        || (memname && VG_(string_match)( VG_(clo_trace_symtab_patt),
                                          memname ));
   if (traceme) {
      di->trace_symtab = VG_(clo_trace_symtab);
      di->trace_cfi    = VG_(clo_trace_cfi);
      di->ddump_syms   = VG_(clo_debug_dump_syms);
      di->ddump_line   = VG_(clo_debug_dump_line);
      di->ddump_frames = VG_(clo_debug_dump_frames);
   }

   return di;
}


/* Free a DebugInfo, and also all the stuff hanging off it. */
static void free_DebugInfo ( DebugInfo* di )
{
   Word i, j;
   struct strchunk *chunk, *next;
   TyAdmin *admin1, *admin2;
   GExpr *gexpr1, *gexpr2;

   vg_assert(di != NULL);
   if (di->filename)   ML_(dinfo_free)(di->filename);
   if (di->symtab)     ML_(dinfo_free)(di->symtab);
   if (di->loctab)     ML_(dinfo_free)(di->loctab);
   if (di->cfsi)       ML_(dinfo_free)(di->cfsi);
   if (di->cfsi_exprs) VG_(deleteXA)(di->cfsi_exprs);

   for (chunk = di->strchunks; chunk != NULL; chunk = next) {
      next = chunk->next;
      ML_(dinfo_free)(chunk);
   }

   /* Delete the two admin lists.  These lists exist purely so that we
      can visit each object exactly once when we need to delete
      them. */
   for (admin1 = di->admin_tyadmins; admin1; admin1 = admin2) {
      admin2 = admin1->next;
      ML_(delete_TyAdmin_and_payload)(admin1);
   }
   for (gexpr1 = di->admin_gexprs; gexpr1; gexpr1 = gexpr2) {
      gexpr2 = gexpr1->next;
      ML_(dinfo_free)(gexpr1);
   }

   /* Dump the variable info.  This is kinda complex: we must take
      care not to free items which reside in either the admin lists
      (as we have just freed them) or which reside in the DebugInfo's
      string table. */
   if (di->varinfo) {
      for (i = 0; i < VG_(sizeXA)(di->varinfo); i++) {
         OSet* scope = *(OSet**)VG_(indexXA)(di->varinfo, i);
         if (!scope) continue;
         /* iterate over all entries in 'scope' */
         VG_(OSetGen_ResetIter)(scope);
         while (True) {
            DiAddrRange* arange = VG_(OSetGen_Next)(scope);
            if (!arange) break;
            /* for each var in 'arange' */
            vg_assert(arange->vars);
            for (j = 0; j < VG_(sizeXA)( arange->vars ); j++) {
               DiVariable* var = (DiVariable*)VG_(indexXA)(arange->vars,j);
               vg_assert(var);
               /* Nothing to free in var: all the pointer fields refer
                  to stuff either on an admin list, or in
                  .strchunks */
            }
            VG_(deleteXA)(arange->vars);
            /* Don't free arange itself, as OSetGen_Destroy does
               that */
         }
         VG_(OSetGen_Destroy)(scope);
      }
      VG_(deleteXA)(di->varinfo);
   }

   ML_(dinfo_free)(di);
}


/* 'si' is a member of debugInfo_list.  Find it, remove it from the
   list, notify m_redir that this has happened, and free all storage
   reachable from it.
*/
static void discard_DebugInfo ( DebugInfo* di )
{
#  if defined(VGP_ppc32_aix5)
   HChar* reason = "__unload";
#  elif defined(VGP_ppc64_aix5)
   HChar* reason = "kunload64";
#  else
   HChar* reason = "munmap";
#  endif

   DebugInfo** prev_next_ptr = &debugInfo_list;
   DebugInfo*  curr          =  debugInfo_list;

   while (curr) {
      if (curr == di) {
         /* Found it;  remove from list and free it. */
         if (curr->have_dinfo
             && (VG_(clo_verbosity) > 1 || VG_(clo_trace_redir)))
            VG_(message)(Vg_DebugMsg,
                         "Discarding syms at %p-%p in %s due to %s()",
                         di->text_avma,
                         di->text_avma + di->text_size,
                         curr->filename ? curr->filename : (UChar*)"???",
                         reason);
         vg_assert(*prev_next_ptr == curr);
         *prev_next_ptr = curr->next;
         if (curr->have_dinfo)
            VG_(redir_notify_delete_DebugInfo)( curr );
         free_DebugInfo(curr);
         return;
      }
      prev_next_ptr = &curr->next;
      curr          =  curr->next;
   }

   /* Not found. */
}


/* Repeatedly scan debugInfo_list, looking for DebugInfos with text
   AVMAs intersecting [start,start+length), and call discard_DebugInfo
   to get rid of them.  This modifies the list, hence the multiple
   iterations.
*/
static void discard_syms_in_range ( Addr start, SizeT length )
{
   Bool       found;
   DebugInfo* curr;

   while (True) {
      found = False;

      curr = debugInfo_list;
      while (True) {
         if (curr == NULL)
            break;
         if (curr->text_present
             && curr->text_size > 0
             && (start+length - 1 < curr->text_avma
                 || curr->text_avma + curr->text_size - 1 < start)) {
            /* no overlap */
	 } else {
	    found = True;
	    break;
	 }
	 curr = curr->next;
      }

      if (!found) break;
      discard_DebugInfo( curr );
   }
}


/* Does [s1,+len1) overlap [s2,+len2) ?  Note: does not handle
   wraparound at the end of the address space -- just asserts in that
   case. */
static Bool ranges_overlap (Addr s1, SizeT len1, Addr s2, SizeT len2 )
{
   Addr e1, e2;
   if (len1 == 0 || len2 == 0)
      return False;
   e1 = s1 + len1 - 1;
   e2 = s2 + len2 - 1;
   /* Assert that we don't have wraparound.  If we do it would imply
      that file sections are getting mapped around the end of the
      address space, which sounds unlikely. */
   vg_assert(s1 <= e1);
   vg_assert(s2 <= e2);
   if (e1 < s2 || e2 < s1) return False;
   return True;
}


/* Do the basic rx_ and rw_ mappings of the two DebugInfos overlap in
   any way? */
static Bool do_DebugInfos_overlap ( DebugInfo* di1, DebugInfo* di2 )
{
   vg_assert(di1);
   vg_assert(di2);

   if (di1->have_rx_map && di2->have_rx_map
       && ranges_overlap(di1->rx_map_avma, di1->rx_map_size,
                         di2->rx_map_avma, di2->rx_map_size))
      return True;

   if (di1->have_rx_map && di2->have_rw_map
       && ranges_overlap(di1->rx_map_avma, di1->rx_map_size,
                         di2->rw_map_avma, di2->rw_map_size))
      return True;

   if (di1->have_rw_map && di2->have_rx_map
       && ranges_overlap(di1->rw_map_avma, di1->rw_map_size,
                         di2->rx_map_avma, di2->rx_map_size))
      return True;

   if (di1->have_rw_map && di2->have_rw_map
       && ranges_overlap(di1->rw_map_avma, di1->rw_map_size,
                         di2->rw_map_avma, di2->rw_map_size))
      return True;

   return False;
}


/* Discard all elements of debugInfo_list whose .mark bit is set.
*/
static void discard_marked_DebugInfos ( void )
{
   DebugInfo* curr;

   while (True) {

      curr = debugInfo_list;
      while (True) {
         if (!curr)
            break;
         if (curr->mark)
            break;
	 curr = curr->next;
      }

      if (!curr) break;
      discard_DebugInfo( curr );

   }
}


/* Discard any elements of debugInfo_list which overlap with diRef.
   Clearly diRef must have its rx_ and rw_ mapping information set to
   something sane. */
#if defined(VGO_aix5)
__attribute__((unused))
#endif
static void discard_DebugInfos_which_overlap_with ( DebugInfo* diRef )
{
   DebugInfo* di;
   /* Mark all the DebugInfos in debugInfo_list that need to be
      deleted.  First, clear all the mark bits; then set them if they
      overlap with siRef.  Since siRef itself is in this list we at
      least expect its own mark bit to be set. */
   for (di = debugInfo_list; di; di = di->next) {
      di->mark = do_DebugInfos_overlap( di, diRef );
      if (di == diRef) {
         vg_assert(di->mark);
         di->mark = False;
      }
   }
   discard_marked_DebugInfos();
}


/* Find the existing DebugInfo for (memname,filename) or if not found,
   create one.  In the latter case memname and filename are strdup'd
   into VG_AR_DINFO, and the new DebugInfo is added to
   debugInfo_list. */
static
DebugInfo* find_or_create_DebugInfo_for ( UChar* filename, UChar* memname )
{
   DebugInfo* di;
   vg_assert(filename);
   for (di = debugInfo_list; di; di = di->next) {
      vg_assert(di->filename);
      if (0==VG_(strcmp)(di->filename, filename)
          && ( (memname && di->memname)
                  ? 0==VG_(strcmp)(memname, di->memname)
                  : True ))
         break;
   }
   if (!di) {
      di = alloc_DebugInfo(filename, memname);
      vg_assert(di);
      di->next = debugInfo_list;
      debugInfo_list = di;
   }
   return di;
}


/*--------------------------------------------------------------*/
/*---                                                        ---*/
/*--- TOP LEVEL: NOTIFICATION (ACQUIRE/DISCARD INFO) (LINUX) ---*/
/*---                                                        ---*/
/*--------------------------------------------------------------*/

#if defined(VGO_linux)

/* The debug info system is driven by notifications that a text
   segment has been mapped in, or unmapped.  When that happens it
   tries to acquire/discard whatever info is available for the
   corresponding object.  This section contains the notification
   handlers. */

/* Notify the debuginfo system about a new mapping.  This is the way
   new debug information gets loaded.  If allow_SkFileV is True, it
   will try load debug info if the mapping at 'a' belongs to Valgrind;
   whereas normally (False) it will not do that.  This allows us to
   carefully control when the thing will read symbols from the
   Valgrind executable itself. */

void VG_(di_notify_mmap)( Addr a, Bool allow_SkFileV )
{
   NSegment const * seg;
   HChar*     filename;
   Bool       ok, is_rx_map, is_rw_map;
   DebugInfo* di;
   SysRes     fd;
   Int        nread;
   HChar      buf1k[1024];
   Bool       debug = False;

   /* In short, figure out if this mapping is of interest to us, and
      if so, try to guess what ld.so is doing and when/if we should
      read debug info. */
   seg = VG_(am_find_nsegment)(a);
   vg_assert(seg);

   if (debug)
      VG_(printf)("di_notify_mmap-1: %p-%p %c%c%c\n",
                  seg->start, seg->end,
                  seg->hasR ? 'r' : '-',
                  seg->hasW ? 'w' : '-',seg->hasX ? 'x' : '-' );

   /* guaranteed by aspacemgr-linux.c, sane_NSegment() */
   vg_assert(seg->end > seg->start);

   /* Ignore non-file mappings */
   if ( ! (seg->kind == SkFileC
           || (seg->kind == SkFileV && allow_SkFileV)) )
      return;

   /* If the file doesn't have a name, we're hosed.  Give up. */
   filename = VG_(am_get_filename)( (NSegment*)seg );
   if (!filename)
      return;

   if (debug)
      VG_(printf)("di_notify_mmap-2: %s\n", filename);

   /* XXXX begin KLUDGE */
   /* Skip filenames in /dev/.  Don't even bother to try opening them.
      Why?

      Suppose the client opens and then mmaps the file specified by
      'filename' and puts some kind of lock on it, so nobody else can
      open it.  If we now try to open it to peer at the ELF header,
      the system can hang, because the VG_(open) call blocks.
      Precisely this happed when running Amarok, which opened and then
      mmap'd /dev/snd/pcmC0D0c.

      A clean(er) solution is to open the file with VKI_O_NONBLOCK, so
      that if it is locked, we simply fail immediately and don't hang
      the whole system.  But "man 2 open" gives only a sketchy
      description of the resulting file semantics.  So for the
      meantime, just skip files in /dev/ as (1) they are likely to be
      subject to wierd-ass locking stuff, and (2) they won't contain
      useful debug info anyway.

      But that's a kludge; in principle the same problem could occur
      with *any* file.
   */
   if (0 == VG_(strncmp)(filename, "/dev/", 5)) {
      if (debug)
         VG_(printf)("di_notify_mmap-2: skipping %s\n", filename);
      return;
   }
   /* XXXX end KLUDGE */

   /* Peer at the first few bytes of the file, to see if it is an ELF
      object file. */
   VG_(memset)(buf1k, 0, sizeof(buf1k));
   fd = VG_(open)( filename, VKI_O_RDONLY, 0 );
   if (fd.isError) {
      DebugInfo fake_di;
      VG_(memset)(&fake_di, 0, sizeof(fake_di));
      fake_di.filename = filename;
      ML_(symerr)(&fake_di, True, "can't open file to inspect ELF header");
      return;
   }
   nread = VG_(read)( fd.res, buf1k, sizeof(buf1k) );
   VG_(close)( fd.res );

   if (nread <= 0) {
      ML_(symerr)(NULL, True, "can't read file to inspect ELF header");
      return;
   }
   vg_assert(nread > 0 && nread <= sizeof(buf1k) );

   /* We're only interested in mappings of ELF object files. */
   if (!ML_(is_elf_object_file)( buf1k, (SizeT)nread ))
      return;

   /* Now we have to guess if this is a text-like mapping, a data-like
      mapping, neither or both.  The rules are:

        text if:   x86-linux    r and x
                   other-linux  r and x and not w

        data if:   x86-linux    r and w
                   other-linux  r and w and not x

      Background: On x86-linux, objects are typically mapped twice:

      1b8fb000-1b8ff000 r-xp 00000000 08:02 4471477 vgpreload_memcheck.so
      1b8ff000-1b900000 rw-p 00004000 08:02 4471477 vgpreload_memcheck.so

      whereas ppc32-linux mysteriously does this:

      118a6000-118ad000 r-xp 00000000 08:05 14209428 vgpreload_memcheck.so
      118ad000-118b6000 ---p 00007000 08:05 14209428 vgpreload_memcheck.so
      118b6000-118bd000 rwxp 00000000 08:05 14209428 vgpreload_memcheck.so

      The third mapping should not be considered to have executable
      code in.  Therefore a test which works for both is: r and x and
      NOT w.  Reading symbols from the rwx segment -- which overlaps
      the r-x segment in the file -- causes the redirection mechanism
      to redirect to addresses in that third segment, which is wrong
      and causes crashes.

      JRS 28 Dec 05: unfortunately icc 8.1 on x86 has been seen to
      produce executables with a single rwx segment rather than a
      (r-x,rw-) pair. That means the rules have to be modified thusly:

      x86-linux:   consider if r and x
      all others:  consider if r and x and not w
   */
   is_rx_map = False;
   is_rw_map = False;
#  if defined(VGP_x86_linux)
   is_rx_map = seg->hasR && seg->hasX;
   is_rw_map = seg->hasR && seg->hasW;
#  elif defined(VGP_amd64_linux) \
        || defined(VGP_ppc32_linux) || defined(VGP_ppc64_linux)
   is_rx_map = seg->hasR && seg->hasX && !seg->hasW;
   is_rw_map = seg->hasR && seg->hasW && !seg->hasX;
#  else
#    error "Unknown platform"
#  endif

   if (debug)
      VG_(printf)("di_notify_mmap-3: is_rx_map %d, is_rw_map %d\n",
                  (Int)is_rx_map, (Int)is_rw_map);

   /* If it is neither text-ish nor data-ish, we're not interested. */
   if (!(is_rx_map || is_rw_map))
      return;

   /* See if we have a DebugInfo for this filename.  If not,
      create one. */
   di = find_or_create_DebugInfo_for( filename, NULL/*membername*/ );
   vg_assert(di);

   if (is_rx_map) {
      /* We have a text-like mapping.  Note the details. */
      if (!di->have_rx_map) {
         di->have_rx_map = True;
         di->rx_map_avma = a;
         di->rx_map_size = seg->end + 1 - seg->start;
         di->rx_map_foff = seg->offset;
      } else {
         /* FIXME: complain about a second text-like mapping */
      }
   }

   if (is_rw_map) {
      /* We have a data-like mapping.  Note the details. */
      if (!di->have_rw_map) {
         di->have_rw_map = True;
         di->rw_map_avma = a;
         di->rw_map_size = seg->end + 1 - seg->start;
         di->rw_map_foff = seg->offset;
      } else {
         /* FIXME: complain about a second data-like mapping */
      }
   }

   if (di->have_rx_map && di->have_rw_map && !di->have_dinfo) {

      vg_assert(di->filename);
      TRACE_SYMTAB("\n");
      TRACE_SYMTAB("------ start ELF OBJECT "
                   "------------------------------\n");
      TRACE_SYMTAB("------ name = %s\n", di->filename);
      TRACE_SYMTAB("\n");

      /* We're going to read symbols and debug info for the avma
         ranges [rx_map_avma, +rx_map_size) and [rw_map_avma,
         +rw_map_size).  First get rid of any other DebugInfos which
         overlap either of those ranges (to avoid total confusion). */
      discard_DebugInfos_which_overlap_with( di );

      /* .. and acquire new info. */
      ok = ML_(read_elf_debug_info)( di );

      if (ok) {
         TRACE_SYMTAB("\n------ Canonicalising the "
                      "acquired info ------\n");
         /* prepare read data for use */
         ML_(canonicaliseTables)( di );
         /* notify m_redir about it */
         TRACE_SYMTAB("\n------ Notifying m_redir ------\n");
         VG_(redir_notify_new_DebugInfo)( di );
         /* Note that we succeeded */
         di->have_dinfo = True;
      } else {
         TRACE_SYMTAB("\n------ ELF reading failed ------\n");
         /* Something went wrong (eg. bad ELF file).  Should we delete
            this DebugInfo?  No - it contains info on the rw/rx
            mappings, at least. */
      }

      TRACE_SYMTAB("\n");
      TRACE_SYMTAB("------ name = %s\n", di->filename);
      TRACE_SYMTAB("------ end ELF OBJECT "
                   "------------------------------\n");
      TRACE_SYMTAB("\n");

   }
}


/* Unmap is simpler - throw away any SegInfos intersecting
   [a, a+len).  */
void VG_(di_notify_munmap)( Addr a, SizeT len )
{
   if (0) VG_(printf)("DISCARD %p %p\n", a, a+len);
   discard_syms_in_range(a, len);
}


/* Uh, this doesn't do anything at all.  IIRC glibc (or ld.so, I don't
   remember) does a bunch of mprotects on itself, and if we follow
   through here, it causes the debug info for that object to get
   discarded. */
void VG_(di_notify_mprotect)( Addr a, SizeT len, UInt prot )
{
   Bool exe_ok = toBool(prot & VKI_PROT_EXEC);
#  if defined(VGP_x86_linux)
   exe_ok = exe_ok || toBool(prot & VKI_PROT_READ);
#  endif
   if (0 && !exe_ok)
      discard_syms_in_range(a, len);
}

#endif /* defined(VGO_linux) */


/*-------------------------------------------------------------*/
/*---                                                       ---*/
/*--- TOP LEVEL: NOTIFICATION (ACQUIRE/DISCARD INFO) (AIX5) ---*/
/*---                                                       ---*/
/*-------------------------------------------------------------*/

#if defined(VGO_aix5)

/* The supplied parameters describe a code segment and its associated
   data segment, that have recently been mapped in -- so we need to
   read debug info for it -- or conversely, have recently been dumped,
   in which case the relevant debug info has to be unloaded. */

void VG_(di_aix5_notify_segchange)(
               Addr   code_start,
               Word   code_len,
               Addr   data_start,
               Word   data_len,
               UChar* file_name,
               UChar* mem_name,
               Bool   is_mainexe,
               Bool   acquire )
{
   if (acquire) {

      Bool       ok;
      DebugInfo* di;
      di = find_or_create_DebugInfo_for( file_name, mem_name );
      vg_assert(di);

      if (code_len > 0) {
         di->text_present = True;
         di->text_svma = 0; /* don't know yet */
         di->text_bias = 0; /* don't know yet */
         di->text_avma = code_start;
         di->text_size = code_len;
      }
      if (data_len > 0) {
         di->data_present = True;
         di->data_svma = 0; /* don't know yet */
         di->data_bias = 0; /* don't know yet */
         di->data_avma = data_start;
         di->data_size = data_len;
      }

      /* These need to be filled in in order to keep various
         assertions in storage.c happy.  In particular see
         "Comment_Regarding_Text_Range_Checks" in that file. */
      di->have_rx_map = True;
      di->rx_map_avma = code_start;
      di->rx_map_size = code_len;
      di->have_rw_map = True;
      di->rw_map_avma = data_start;
      di->rw_map_size = data_len;

      ok = ML_(read_xcoff_debug_info) ( di, is_mainexe );

      if (ok) {
         /* prepare read data for use */
         ML_(canonicaliseTables)( di );
         /* notify m_redir about it */
         VG_(redir_notify_new_DebugInfo)( di );
         /* Note that we succeeded */
         di->have_dinfo = True;
      } else {
         /*  Something went wrong (eg. bad XCOFF file). */
         discard_DebugInfo( di );
         di = NULL;
      }

   } else {

      /* Dump all the debugInfos whose text segments intersect
         code_start/code_len. */
      if (code_len > 0)
         discard_syms_in_range( code_start, code_len );

   }
}


#endif /* defined(VGO_aix5) */


/*------------------------------------------------------------*/
/*---                                                      ---*/
/*--- TOP LEVEL: QUERYING EXISTING DEBUG INFO              ---*/
/*---                                                      ---*/
/*------------------------------------------------------------*/

/*------------------------------------------------------------*/
/*--- Use of symbol table & location info to create        ---*/
/*--- plausible-looking stack dumps.                       ---*/
/*------------------------------------------------------------*/

/* Search all symtabs that we know about to locate ptr.  If found, set
   *pdi to the relevant DebugInfo, and *symno to the symtab entry
   *number within that.  If not found, *psi is set to NULL.
   If findText==True,  only text symbols are searched for.
   If findText==False, only data symbols are searched for.
*/
static void search_all_symtabs ( Addr ptr, /*OUT*/DebugInfo** pdi,
                                           /*OUT*/Int* symno,
                                 Bool match_anywhere_in_sym,
                                 Bool findText )
{
   Int        sno;
   DebugInfo* di;
   Bool       inRange;

   for (di = debugInfo_list; di != NULL; di = di->next) {

      if (findText) {
         inRange = di->text_present
                   && di->text_size > 0
                   && di->text_avma <= ptr
                   && ptr < di->text_avma + di->text_size;
      } else {
         inRange = (di->data_present
                    && di->data_size > 0
                    && di->data_avma <= ptr
                    && ptr < di->data_avma + di->data_size)
                   ||
                   (di->sdata_present
                    && di->sdata_size > 0
                    && di->sdata_avma <= ptr
                    && ptr < di->sdata_avma + di->sdata_size)
                   ||
                   (di->bss_present
                    && di->bss_size > 0
                    && di->bss_avma <= ptr
                    && ptr < di->bss_avma + di->bss_size);
      }

      if (!inRange) continue;

      sno = ML_(search_one_symtab) (
               di, ptr, match_anywhere_in_sym, findText );
      if (sno == -1) goto not_found;
      *symno = sno;
      *pdi = di;
      return;

   }
  not_found:
   *pdi = NULL;
}


/* Search all loctabs that we know about to locate ptr.  If found, set
   *pdi to the relevant DebugInfo, and *locno to the loctab entry
   *number within that.  If not found, *pdi is set to NULL. */
static void search_all_loctabs ( Addr ptr, /*OUT*/DebugInfo** pdi,
                                           /*OUT*/Int* locno )
{
   Int        lno;
   DebugInfo* di;
   for (di = debugInfo_list; di != NULL; di = di->next) {
      if (di->text_present
          && di->text_avma <= ptr
          && ptr < di->text_avma + di->text_size) {
         lno = ML_(search_one_loctab) ( di, ptr );
         if (lno == -1) goto not_found;
         *locno = lno;
         *pdi = di;
         return;
      }
   }
  not_found:
   *pdi = NULL;
}


/* The whole point of this whole big deal: map a code address to a
   plausible symbol name.  Returns False if no idea; otherwise True.
   Caller supplies buf and nbuf.  If demangle is False, don't do
   demangling, regardless of VG_(clo_demangle) -- probably because the
   call has come from VG_(get_fnname_nodemangle)().  findText
   indicates whether we're looking for a text symbol or a data symbol
   -- caller must choose one kind or the other. */
static
Bool get_sym_name ( Bool demangle, Addr a, Char* buf, Int nbuf,
                    Bool match_anywhere_in_sym, Bool show_offset,
                    Bool findText, /*OUT*/OffT* offsetP )
{
   DebugInfo* di;
   Int        sno;
   Int        offset;

   search_all_symtabs ( a, &di, &sno, match_anywhere_in_sym, findText );
   if (di == NULL)
      return False;
   if (demangle) {
      VG_(demangle) ( True/*do C++ demangle*/,
                      di->symtab[sno].name, buf, nbuf );
   } else {
      VG_(strncpy_safely) ( buf, di->symtab[sno].name, nbuf );
   }

   offset = a - di->symtab[sno].addr;
   if (offsetP) *offsetP = (OffT)offset;

   if (show_offset && offset != 0) {
      Char     buf2[12];
      Char*    symend = buf + VG_(strlen)(buf);
      Char*    end = buf + nbuf;
      Int      len;

      len = VG_(sprintf)(buf2, "%c%d",
			 offset < 0 ? '-' : '+',
			 offset < 0 ? -offset : offset);
      vg_assert(len < (Int)sizeof(buf2));

      if (len < (end - symend)) {
	 Char *cp = buf2;
	 VG_(memcpy)(symend, cp, len+1);
      }
   }

   return True;
}

/* ppc64-linux only: find the TOC pointer (R2 value) that should be in
   force at the entry point address of the function containing
   guest_code_addr.  Returns 0 if not known. */
Addr VG_(get_tocptr) ( Addr guest_code_addr )
{
   DebugInfo* si;
   Int        sno;
   search_all_symtabs ( guest_code_addr,
                        &si, &sno,
                        True/*match_anywhere_in_fun*/,
                        True/*consider text symbols only*/ );
   if (si == NULL)
      return 0;
   else
      return si->symtab[sno].tocptr;
}

/* This is available to tools... always demangle C++ names,
   match anywhere in function, but don't show offsets. */
Bool VG_(get_fnname) ( Addr a, Char* buf, Int nbuf )
{
   return get_sym_name ( /*demangle*/True, a, buf, nbuf,
                         /*match_anywhere_in_fun*/True,
                         /*show offset?*/False,
                         /*text syms only*/True,
                         /*offsetP*/NULL );
}

/* This is available to tools... always demangle C++ names,
   match anywhere in function, and show offset if nonzero. */
Bool VG_(get_fnname_w_offset) ( Addr a, Char* buf, Int nbuf )
{
   return get_sym_name ( /*demangle*/True, a, buf, nbuf,
                         /*match_anywhere_in_fun*/True,
                         /*show offset?*/True,
                         /*text syms only*/True,
                         /*offsetP*/NULL );
}

/* This is available to tools... always demangle C++ names,
   only succeed if 'a' matches first instruction of function,
   and don't show offsets. */
Bool VG_(get_fnname_if_entry) ( Addr a, Char* buf, Int nbuf )
{
   return get_sym_name ( /*demangle*/True, a, buf, nbuf,
                         /*match_anywhere_in_fun*/False,
                         /*show offset?*/False,
                         /*text syms only*/True,
                         /*offsetP*/NULL );
}

/* This is only available to core... don't demangle C++ names,
   match anywhere in function, and don't show offsets. */
Bool VG_(get_fnname_nodemangle) ( Addr a, Char* buf, Int nbuf )
{
   return get_sym_name ( /*demangle*/False, a, buf, nbuf,
                         /*match_anywhere_in_fun*/True,
                         /*show offset?*/False,
                         /*text syms only*/True,
                         /*offsetP*/NULL );
}

/* This is only available to core... don't demangle C++ names, but do
   do Z-demangling, match anywhere in function, and don't show
   offsets. */
Bool VG_(get_fnname_Z_demangle_only) ( Addr a, Char* buf, Int nbuf )
{
#  define N_TMPBUF 4096 /* arbitrary, 4096 == ERRTXT_LEN */
   Char tmpbuf[N_TMPBUF];
   Bool ok;
   vg_assert(nbuf > 0);
   ok = get_sym_name ( /*demangle*/False, a, tmpbuf, N_TMPBUF,
                       /*match_anywhere_in_fun*/True,
                       /*show offset?*/False,
                       /*text syms only*/True,
                       /*offsetP*/NULL );
   tmpbuf[N_TMPBUF-1] = 0; /* paranoia */
   if (!ok)
      return False;

   /* We have something, at least.  Try to Z-demangle it. */
   VG_(demangle)( False/*don't do C++ demangling*/, tmpbuf, buf, nbuf);

   buf[nbuf-1] = 0; /* paranoia */
   return True;
#  undef N_TMPBUF
}

/* Looks up data_addr in the collection of data symbols, and if found
   puts its name (or as much as will fit) into dname[0 .. n_dname-1],
   which is guaranteed to be zero terminated.  Also data_addr's offset
   from the symbol start is put into *offset. */
Bool VG_(get_datasym_and_offset)( Addr data_addr,
                                  /*OUT*/Char* dname, Int n_dname,
                                  /*OUT*/OffT* offset )
{
   Bool ok;
   vg_assert(n_dname > 1);
   ok = get_sym_name ( /*demangle*/False, data_addr, dname, n_dname,
                       /*match_anywhere_in_sym*/True,
                       /*show offset?*/False,
                       /*data syms only please*/False,
                       offset );
   if (!ok)
      return False;
   dname[n_dname-1] = 0;
   return True;
}

/* Map a code address to the name of a shared object file or the
   executable.  Returns False if no idea; otherwise True.  Doesn't
   require debug info.  Caller supplies buf and nbuf. */
Bool VG_(get_objname) ( Addr a, Char* buf, Int nbuf )
{
   Int used;
   DebugInfo* di;
   const NSegment *seg;
   HChar* filename;
   vg_assert(nbuf > 0);
   for (di = debugInfo_list; di != NULL; di = di->next) {
      if (di->text_present
          && di->text_avma <= a
          && a < di->text_avma + di->text_size) {
         VG_(strncpy_safely)(buf, di->filename, nbuf);
         if (di->memname) {
            used = VG_(strlen)(buf);
            if (used < nbuf)
               VG_(strncpy_safely)(&buf[used], "(", nbuf-used);
            used = VG_(strlen)(buf);
            if (used < nbuf)
               VG_(strncpy_safely)(&buf[used], di->memname, nbuf-used);
            used = VG_(strlen)(buf);
            if (used < nbuf)
               VG_(strncpy_safely)(&buf[used], ")", nbuf-used);
         }
         buf[nbuf-1] = 0;
         return True;
      }
   }
   if ((seg = VG_(am_find_nsegment(a))) != NULL &&
       (filename = VG_(am_get_filename)(seg)) != NULL)
   {
      VG_(strncpy_safely)(buf, filename, nbuf);
      return True;
   }
   return False;
}

/* Map a code address to its DebugInfo.  Returns NULL if not found.  Doesn't
   require debug info. */
DebugInfo* VG_(find_seginfo) ( Addr a )
{
   DebugInfo* di;
   for (di = debugInfo_list; di != NULL; di = di->next) {
      if (di->text_present
          && di->text_avma <= a
          && a < di->text_avma + di->text_size) {
         return di;
      }
   }
   return NULL;
}

/* Map a code address to a filename.  Returns True if successful.  */
Bool VG_(get_filename)( Addr a, Char* filename, Int n_filename )
{
   DebugInfo* si;
   Int      locno;
   search_all_loctabs ( a, &si, &locno );
   if (si == NULL)
      return False;
   VG_(strncpy_safely)(filename, si->loctab[locno].filename, n_filename);
   return True;
}

/* Map a code address to a line number.  Returns True if successful. */
Bool VG_(get_linenum)( Addr a, UInt* lineno )
{
   DebugInfo* si;
   Int      locno;
   search_all_loctabs ( a, &si, &locno );
   if (si == NULL)
      return False;
   *lineno = si->loctab[locno].lineno;

   return True;
}

/* Map a code address to a filename/line number/dir name info.
   See prototype for detailed description of behaviour.
*/
Bool VG_(get_filename_linenum) ( Addr a,
                                 /*OUT*/Char* filename, Int n_filename,
                                 /*OUT*/Char* dirname,  Int n_dirname,
                                 /*OUT*/Bool* dirname_available,
                                 /*OUT*/UInt* lineno )
{
   DebugInfo* si;
   Int      locno;

   vg_assert( (dirname == NULL && dirname_available == NULL)
              ||
              (dirname != NULL && dirname_available != NULL) );

   search_all_loctabs ( a, &si, &locno );
   if (si == NULL) {
      if (dirname_available) {
         *dirname_available = False;
         *dirname = 0;
      }
      return False;
   }

   VG_(strncpy_safely)(filename, si->loctab[locno].filename, n_filename);
   *lineno = si->loctab[locno].lineno;

   if (dirname) {
      /* caller wants directory info too .. */
      vg_assert(n_dirname > 0);
      if (si->loctab[locno].dirname) {
         /* .. and we have some */
         *dirname_available = True;
         VG_(strncpy_safely)(dirname, si->loctab[locno].dirname,
                                      n_dirname);
      } else {
         /* .. but we don't have any */
         *dirname_available = False;
         *dirname = 0;
      }
   }

   return True;
}


/* Map a function name to its entry point and toc pointer.  Is done by
   sequential search of all symbol tables, so is very slow.  To
   mitigate the worst performance effects, you may specify a soname
   pattern, and only objects matching that pattern are searched.
   Therefore specify "*" to search all the objects.  On TOC-afflicted
   platforms, a symbol is deemed to be found only if it has a nonzero
   TOC pointer.  */
Bool VG_(lookup_symbol_SLOW)(UChar* sopatt, UChar* name,
                             Addr* pEnt, Addr* pToc)
{
   Bool     require_pToc = False;
   Int      i;
   DebugInfo* si;
   Bool     debug = False;
#  if defined(VG_PLAT_USES_PPCTOC)
   require_pToc = True;
#  endif
   for (si = debugInfo_list; si; si = si->next) {
      if (debug)
         VG_(printf)("lookup_symbol_SLOW: considering %s\n", si->soname);
      if (!VG_(string_match)(sopatt, si->soname)) {
         if (debug)
            VG_(printf)(" ... skip\n");
         continue;
      }
      for (i = 0; i < si->symtab_used; i++) {
         if (0==VG_(strcmp)(name, si->symtab[i].name)
             && (require_pToc ? si->symtab[i].tocptr : True)) {
            *pEnt = si->symtab[i].addr;
            *pToc = si->symtab[i].tocptr;
            return True;
         }
      }
   }
   return False;
}


/* VG_(describe_IP): print into buf info on code address, function
   name and filename. */

/* Copy str into buf starting at n, but not going past buf[n_buf-1]
   and always ensuring that buf is zero-terminated. */

static Int putStr ( Int n, Int n_buf, Char* buf, Char* str )
{
   vg_assert(n_buf > 0);
   vg_assert(n >= 0 && n < n_buf);
   for (; n < n_buf-1 && *str != 0; n++,str++)
      buf[n] = *str;
   vg_assert(n >= 0 && n < n_buf);
   buf[n] = '\0';
   return n;
}

/* Same as putStr, but escaping chars for XML output, and
   also not adding more than count chars to n_buf. */

static Int putStrEsc ( Int n, Int n_buf, Int count, Char* buf, Char* str )
{
   Char alt[2];
   vg_assert(n_buf > 0);
   vg_assert(count >= 0 && count < n_buf);
   vg_assert(n >= 0 && n < n_buf);
   for (; *str != 0; str++) {
      vg_assert(count >= 0);
      if (count <= 0)
         goto done;
      switch (*str) {
         case '&':
            if (count < 5) goto done;
            n = putStr( n, n_buf, buf, "&amp;");
            count -= 5;
            break;
         case '<':
            if (count < 4) goto done;
            n = putStr( n, n_buf, buf, "&lt;");
            count -= 4;
            break;
         case '>':
            if (count < 4) goto done;
            n = putStr( n, n_buf, buf, "&gt;");
            count -= 4;
            break;
         default:
            if (count < 1) goto done;
            alt[0] = *str;
            alt[1] = 0;
            n = putStr( n, n_buf, buf, alt );
            count -= 1;
            break;
      }
   }
  done:
   vg_assert(count >= 0); /* should not go -ve in loop */
   vg_assert(n >= 0 && n < n_buf);
   return n;
}

Char* VG_(describe_IP)(Addr eip, Char* buf, Int n_buf)
{
#  define APPEND(_str) \
      n = putStr(n, n_buf, buf, _str)
#  define APPEND_ESC(_count,_str) \
      n = putStrEsc(n, n_buf, (_count), buf, (_str))
#  define BUF_LEN    4096

   UInt  lineno;
   UChar ibuf[50];
   Int   n = 0;
   static UChar buf_fn[BUF_LEN];
   static UChar buf_obj[BUF_LEN];
   static UChar buf_srcloc[BUF_LEN];
   static UChar buf_dirname[BUF_LEN];
   Bool  know_dirinfo = False;
   Bool  know_fnname  = VG_(clo_sym_offsets)
                        ? VG_(get_fnname_w_offset) (eip, buf_fn, BUF_LEN)
                        : VG_(get_fnname) (eip, buf_fn, BUF_LEN);
   Bool  know_objname = VG_(get_objname)(eip, buf_obj, BUF_LEN);
   Bool  know_srcloc  = VG_(get_filename_linenum)(
                           eip,
                           buf_srcloc,  BUF_LEN,
                           buf_dirname, BUF_LEN, &know_dirinfo,
                           &lineno
                        );
   if (VG_(clo_xml)) {

      Bool   human_readable = True;
      HChar* maybe_newline  = human_readable ? "\n      " : "";
      HChar* maybe_newline2 = human_readable ? "\n    "   : "";

      /* Print in XML format, dumping in as much info as we know.
         Ensure all tags are balanced even if the individual strings
         are too long.  Allocate 1/10 of BUF_LEN to the object name,
         6/10s to the function name, 1/10 to the directory name and
         1/10 to the file name, leaving 1/10 for all the fixed-length
         stuff. */
      APPEND("<frame>");
      VG_(sprintf)(ibuf,"<ip>0x%llX</ip>", (ULong)eip);
      APPEND(maybe_newline);
      APPEND(ibuf);
      if (know_objname) {
         APPEND(maybe_newline);
         APPEND("<obj>");
         APPEND_ESC(1*BUF_LEN/10, buf_obj);
         APPEND("</obj>");
      }
      if (know_fnname) {
         APPEND(maybe_newline);
         APPEND("<fn>");
         APPEND_ESC(6*BUF_LEN/10, buf_fn);
         APPEND("</fn>");
      }
      if (know_srcloc) {
         if (know_dirinfo) {
            APPEND(maybe_newline);
            APPEND("<dir>");
            APPEND_ESC(1*BUF_LEN/10, buf_dirname);
            APPEND("</dir>");
         }
         APPEND(maybe_newline);
         APPEND("<file>");
         APPEND_ESC(1*BUF_LEN/10, buf_srcloc);
         APPEND("</file>");
         APPEND(maybe_newline);
         APPEND("<line>");
         VG_(sprintf)(ibuf,"%d",lineno);
         APPEND(ibuf);
         APPEND("</line>");
      }
      APPEND(maybe_newline2);
      APPEND("</frame>");

   } else {

      /* Print for humans to read */
      VG_(sprintf)(ibuf,"0x%llX: ", (ULong)eip);
      APPEND(ibuf);
      if (know_fnname) {
         APPEND(buf_fn);
         if (!know_srcloc && know_objname) {
            APPEND(" (in ");
            APPEND(buf_obj);
            APPEND(")");
         }
      } else if (know_objname && !know_srcloc) {
         APPEND("(within ");
         APPEND(buf_obj);
         APPEND(")");
      } else {
         APPEND("???");
      }
      if (know_srcloc) {
         APPEND(" (");
         APPEND(buf_srcloc);
         APPEND(":");
         VG_(sprintf)(ibuf,"%d",lineno);
         APPEND(ibuf);
         APPEND(")");
      }

   }
   return buf;

#  undef APPEND
#  undef APPEND_ESC
#  undef BUF_LEN
}


/*--------------------------------------------------------------*/
/*---                                                        ---*/
/*--- TOP LEVEL: FOR UNWINDING THE STACK USING               ---*/
/*---            DWARF3 .eh_frame INFO                       ---*/
/*---                                                        ---*/
/*--------------------------------------------------------------*/

/* Gather up all the constant pieces of info needed to evaluate
   a CfiExpr into one convenient struct. */
typedef
   struct {
      Addr ipHere;
      Addr spHere;
      Addr fpHere;
      Addr min_accessible;
      Addr max_accessible;
   }
   CfiExprEvalContext;

/* Evaluate the CfiExpr rooted at ix in exprs given the context eec.
   *ok is set to False on failure, but not to True on success.  The
   caller must set it to True before calling. */
static
UWord evalCfiExpr ( XArray* exprs, Int ix,
                    CfiExprEvalContext* eec, Bool* ok )
{
   UWord wL, wR;
   Addr  a;
   CfiExpr* e = VG_(indexXA)( exprs, ix );
   switch (e->tag) {
      case Cex_Binop:
         wL = evalCfiExpr( exprs, e->Cex.Binop.ixL, eec, ok );
         if (!(*ok)) return 0;
         wR = evalCfiExpr( exprs, e->Cex.Binop.ixR, eec, ok );
         if (!(*ok)) return 0;
         switch (e->Cex.Binop.op) {
            case Cop_Add: return wL + wR;
            case Cop_Sub: return wL - wR;
            case Cop_And: return wL & wR;
            case Cop_Mul: return wL * wR;
            default: goto unhandled;
         }
         /*NOTREACHED*/
      case Cex_CfiReg:
         switch (e->Cex.CfiReg.reg) {
            case Creg_IP: return (Addr)eec->ipHere;
            case Creg_SP: return (Addr)eec->spHere;
            case Creg_FP: return (Addr)eec->fpHere;
            default: goto unhandled;
         }
         /*NOTREACHED*/
      case Cex_Const:
         return e->Cex.Const.con;
      case Cex_Deref:
         a = evalCfiExpr( exprs, e->Cex.Deref.ixAddr, eec, ok );
         if (!(*ok)) return 0;
         if (a < eec->min_accessible
             || (a + sizeof(UWord) - 1) > eec->max_accessible) {
            *ok = False;
            return 0;
         }
         /* let's hope it doesn't trap! */
         return * ((UWord*)a);
      default:
         goto unhandled;
   }
   /*NOTREACHED*/
  unhandled:
   VG_(printf)("\n\nevalCfiExpr: unhandled\n");
   ML_(ppCfiExpr)( exprs, ix );
   VG_(printf)("\n");
   vg_assert(0);
   /*NOTREACHED*/
   return 0;
}


/* The main function for DWARF2/3 CFI-based stack unwinding.
   Given an IP/SP/FP triple, produce the IP/SP/FP values for the
   previous frame, if possible. */
/* Returns True if OK.  If not OK, *{ip,sp,fp}P are not changed. */
/* NOTE: this function may rearrange the order of entries in the
   DebugInfo list. */
Bool VG_(use_CF_info) ( /*MOD*/Addr* ipP,
                        /*MOD*/Addr* spP,
                        /*MOD*/Addr* fpP,
                        Addr min_accessible,
                        Addr max_accessible )
{
   Bool     ok;
   Int      i;
   DebugInfo* si;
   DiCfSI*  cfsi = NULL;
   Addr     cfa, ipHere, spHere, fpHere, ipPrev, spPrev, fpPrev;

   CfiExprEvalContext eec;

   static UInt n_search = 0;
   static UInt n_steps = 0;
   n_search++;

   if (0) VG_(printf)("search for %p\n", *ipP);

   for (si = debugInfo_list; si != NULL; si = si->next) {
      n_steps++;

      /* Use the per-DebugInfo summary address ranges to skip
         inapplicable DebugInfos quickly. */
      if (si->cfsi_used == 0)
         continue;
      if (*ipP < si->cfsi_minavma || *ipP > si->cfsi_maxavma)
         continue;

      i = ML_(search_one_cfitab)( si, *ipP );
      if (i != -1) {
         vg_assert(i >= 0 && i < si->cfsi_used);
         cfsi = &si->cfsi[i];
         break;
      }
   }

   if (cfsi == NULL)
      return False;

   if (0 && ((n_search & 0x7FFFF) == 0))
      VG_(printf)("VG_(use_CF_info): %u searches, "
                  "%u DebugInfos looked at\n",
                  n_search, n_steps);

   /* Start of performance-enhancing hack: once every 64 (chosen
      hackily after profiling) successful searches, move the found
      DebugInfo one step closer to the start of the list.  This makes
      future searches cheaper.  For starting konqueror on amd64, this
      in fact reduces the total amount of searching done by the above
      find-the-right-DebugInfo loop by more than a factor of 20. */
   if ((n_search & 0x3F) == 0) {
      /* Move si one step closer to the start of the list. */
      move_DebugInfo_one_step_forward( si );
   }
   /* End of performance-enhancing hack. */

   if (0) {
      VG_(printf)("found cfisi: ");
      ML_(ppDiCfSI)(si->cfsi_exprs, cfsi);
   }

   ipPrev = spPrev = fpPrev = 0;

   ipHere = *ipP;
   spHere = *spP;
   fpHere = *fpP;

   /* First compute the CFA. */
   cfa = 0;
   switch (cfsi->cfa_how) {
      case CFIC_SPREL:
         cfa = cfsi->cfa_off + spHere;
         break;
      case CFIC_FPREL:
         cfa = cfsi->cfa_off + fpHere;
         break;
      case CFIC_EXPR:
         if (0) {
            VG_(printf)("CFIC_EXPR: ");
            ML_(ppCfiExpr)(si->cfsi_exprs, cfsi->cfa_off);
            VG_(printf)("\n");
         }
         eec.ipHere = ipHere;
         eec.spHere = spHere;
         eec.fpHere = fpHere;
         eec.min_accessible = min_accessible;
         eec.max_accessible = max_accessible;
         ok = True;
         cfa = evalCfiExpr(si->cfsi_exprs, cfsi->cfa_off, &eec, &ok );
         if (!ok) return False;
         break;
      default:
         vg_assert(0);
   }

   /* Now we know the CFA, use it to roll back the registers we're
      interested in. */

#  define COMPUTE(_prev, _here, _how, _off)             \
      do {                                              \
         switch (_how) {                                \
            case CFIR_UNKNOWN:                          \
               return False;                            \
            case CFIR_SAME:                             \
               _prev = _here; break;                    \
            case CFIR_MEMCFAREL: {                      \
               Addr a = cfa + (Word)_off;               \
               if (a < min_accessible                   \
                   || a+sizeof(Addr) > max_accessible)  \
                  return False;                         \
               _prev = *(Addr*)a;                       \
               break;                                   \
            }                                           \
            case CFIR_CFAREL:                           \
               _prev = cfa + (Word)_off;                \
               break;                                   \
            case CFIR_EXPR:                             \
               if (0)                                   \
                  ML_(ppCfiExpr)(si->cfsi_exprs,_off);  \
               eec.ipHere = ipHere;                     \
               eec.spHere = spHere;                     \
               eec.fpHere = fpHere;                     \
               eec.min_accessible = min_accessible;     \
               eec.max_accessible = max_accessible;     \
               ok = True;                               \
               _prev = evalCfiExpr(si->cfsi_exprs, _off, &eec, &ok ); \
               if (!ok) return False;                   \
               break;                                   \
            default:                                    \
               vg_assert(0);                            \
         }                                              \
      } while (0)

   COMPUTE(ipPrev, ipHere, cfsi->ra_how, cfsi->ra_off);
   COMPUTE(spPrev, spHere, cfsi->sp_how, cfsi->sp_off);
   COMPUTE(fpPrev, fpHere, cfsi->fp_how, cfsi->fp_off);

#  undef COMPUTE

   *ipP = ipPrev;
   *spP = spPrev;
   *fpP = fpPrev;
   return True;
}


/*--------------------------------------------------------------*/
/*---                                                        ---*/
/*--- TOP LEVEL: GENERATE DESCRIPTION OF DATA ADDRESSES      ---*/
/*---            FROM DWARF3 DEBUG INFO                      ---*/
/*---                                                        ---*/
/*--------------------------------------------------------------*/

/* Evaluate the location expression/list for var, to see whether or
   not data_addr falls within the variable.  If so also return the
   offset of data_addr from the start of the variable.  Note that
   regs, which supplies ip,sp,fp values, will be NULL for global
   variables, and non-NULL for local variables. */
static Bool data_address_is_in_var ( /*OUT*/UWord* offset,
                                     DiVariable*   var,
                                     RegSummary*   regs,
                                     Addr          data_addr,
                                     Addr          data_bias )
{
   MaybeUWord muw;
   SizeT      var_szB;
   GXResult   res;
   Bool       show = False;
   vg_assert(var->name);
   vg_assert(var->type);
   vg_assert(var->gexpr);

   /* Figure out how big the variable is. */
   muw = ML_(sizeOfType)(var->type);
   /* if this var has a type whose size is unknown, it should never
      have been added.  ML_(addVar) should have rejected it. */
   vg_assert(muw.b == True);

   var_szB = muw.w;

   if (show) {
      VG_(printf)("VVVV: data_address_%p_is_in_var: %s :: ",
                  data_addr, var->name );
      ML_(pp_Type_C_ishly)( var->type );
      VG_(printf)("\n");
   }

   /* ignore zero-sized vars; they can never match anything. */
   if (var_szB == 0) {
      if (show)
         VG_(printf)("VVVV: -> Fail (variable is zero sized)\n");
      return False;
   }

   res = ML_(evaluate_GX)( var->gexpr, var->fbGX, regs, data_bias );

   if (show) {
      VG_(printf)("VVVV: -> ");
      ML_(pp_GXResult)( res );
      VG_(printf)("\n");
   }

   if (res.kind == GXR_Value
       && res.word <= data_addr
       && data_addr < res.word + var_szB) {
      *offset = data_addr - res.word;
      return True;
   } else {
      return False;
   }
}


/* Format the acquired information into dname1[0 .. n_dname-1] and
   dname2[0 .. n_dname-1] in an understandable way.  Not so easy.
   If frameNo is -1, this is assumed to be a global variable; else
   a local variable. */
static void format_message ( /*OUT*/Char* dname1,
                             /*OUT*/Char* dname2,
                             Int      n_dname,
                             Addr     data_addr,
                             DiVariable* var,
                             OffT     var_offset,
                             OffT     residual_offset,
                             XArray* /*UChar*/ described,
                             Int      frameNo,
                             ThreadId tid )
{
   Bool have_descr, have_srcloc;
   UChar* vo_plural = var_offset == 1 ? "" : "s";
   UChar* ro_plural = residual_offset == 1 ? "" : "s";

   vg_assert(frameNo >= -1);
   vg_assert(dname1 && dname2 && n_dname > 1);
   vg_assert(described);
   vg_assert(var && var->name);
   have_descr = VG_(sizeXA)(described) > 0
                && *(UChar*)VG_(indexXA)(described,0) != '\0';
   have_srcloc = var->fileName && var->lineNo > 0;

   dname1[0] = dname2[0] = '\0';

   /* ------ local cases ------ */

   if ( frameNo >= 0 && (!have_srcloc) && (!have_descr) ) {
      /* no srcloc, no description:
         Location 0x7fefff6cf is 543 bytes inside local var "a",
         in frame #1 of thread 1
      */
      VG_(snprintf)(
         dname1, n_dname,
         "Location 0x%lx is %lu byte%s inside local var \"%s\",",
         data_addr, var_offset, vo_plural, var->name );
      VG_(snprintf)(
         dname2, n_dname,
         "in frame #%d of thread %d", frameNo, (Int)tid);
   }
   else
   if ( frameNo >= 0 && have_srcloc && (!have_descr) ) {
      /* no description:
         Location 0x7fefff6cf is 543 bytes inside local var "a"
         declared at dsyms7.c:17, in frame #1 of thread 1
      */
      VG_(snprintf)(
         dname1, n_dname,
         "Location 0x%lx is %lu byte%s inside local var \"%s\"",
         data_addr, var_offset, vo_plural, var->name );
      VG_(snprintf)(
         dname2, n_dname,
         "declared at %s:%d, in frame #%d of thread %d",
         var->fileName, var->lineNo, frameNo, (Int)tid);
   }
   else
   if ( frameNo >= 0 && (!have_srcloc) && have_descr ) {
      /* no srcloc:
         Location 0x7fefff6cf is 2 bytes inside a[3].xyzzy[21].c2
         in frame #1 of thread 1
      */
      VG_(snprintf)(
         dname1, n_dname,
         "Location 0x%lx is %lu byte%s inside %s%s",
         data_addr, residual_offset, ro_plural, var->name,
         VG_(indexXA)(described,0) );
      VG_(snprintf)(
         dname2, n_dname,
         "in frame #%d of thread %d", frameNo, (Int)tid);
   }
   else
   if ( frameNo >= 0 && have_srcloc && have_descr ) {
     /* Location 0x7fefff6cf is 2 bytes inside a[3].xyzzy[21].c2,
        declared at dsyms7.c:17, in frame #1 of thread 1 */
      VG_(snprintf)(
         dname1, n_dname,
         "Location 0x%lx is %lu byte%s inside %s%s,",
         data_addr, residual_offset, ro_plural, var->name,
         VG_(indexXA)(described,0) );
      VG_(snprintf)(
         dname2, n_dname,
         "declared at %s:%d, in frame #%d of thread %d",
         var->fileName, var->lineNo, frameNo, (Int)tid);
   }
   else
   /* ------ global cases ------ */
   if ( frameNo >= -1 && (!have_srcloc) && (!have_descr) ) {
      /* no srcloc, no description:
         Location 0x7fefff6cf is 543 bytes inside global var "a"
      */
      VG_(snprintf)(
         dname1, n_dname,
         "Location 0x%lx is %lu byte%s inside global var \"%s\"",
         data_addr, var_offset, vo_plural, var->name );
   }
   else
   if ( frameNo >= -1 && have_srcloc && (!have_descr) ) {
      /* no description:
         Location 0x7fefff6cf is 543 bytes inside global var "a"
         declared at dsyms7.c:17
      */
      VG_(snprintf)(
         dname1, n_dname,
         "Location 0x%lx is %lu byte%s inside global var \"%s\"",
         data_addr, var_offset, vo_plural, var->name );
      VG_(snprintf)(
         dname2, n_dname,
         "declared at %s:%d",
         var->fileName, var->lineNo);
   }
   else
   if ( frameNo >= -1 && (!have_srcloc) && have_descr ) {
      /* no srcloc:
         Location 0x7fefff6cf is 2 bytes inside a[3].xyzzy[21].c2,
         a global variable
      */
      VG_(snprintf)(
         dname1, n_dname,
         "Location 0x%lx is %lu byte%s inside %s%s,",
         data_addr, residual_offset, ro_plural, var->name,
         VG_(indexXA)(described,0) );
      VG_(snprintf)(
         dname2, n_dname,
         "a global variable");
   }
   else
   if ( frameNo >= -1 && have_srcloc && have_descr ) {
     /* Location 0x7fefff6cf is 2 bytes inside a[3].xyzzy[21].c2,
        a global variable declared at dsyms7.c:17 */
      VG_(snprintf)(
         dname1, n_dname,
         "Location 0x%lx is %lu byte%s inside %s%s,",
         data_addr, residual_offset, ro_plural, var->name,
         VG_(indexXA)(described,0) );
      VG_(snprintf)(
         dname2, n_dname,
         "a global variable declared at %s:%d",
         var->fileName, var->lineNo);
   }
   else
      vg_assert(0);

   dname1[n_dname-1] = dname2[n_dname-1] = 0;
}


/* Determine if data_addr is a local variable in the frame
   characterised by (ip,sp,fp), and if so write its description into
   dname{1,2}[0..n_dname-1], and return True.  If not, return
   False. */
static
Bool consider_vars_in_frame ( /*OUT*/Char* dname1,
                              /*OUT*/Char* dname2,
                              Int n_dname,
                              Addr data_addr,
                              Addr ip, Addr sp, Addr fp,
                              /* shown to user: */
                              ThreadId tid, Int frameNo )
{
   Word       i;
   DebugInfo* di;
   RegSummary regs;
   Bool debug = False;

   static UInt n_search = 0;
   static UInt n_steps = 0;
   n_search++;
   if (debug)
      VG_(printf)("QQQQ: cvif: ip,sp,fp %p,%p,%p\n", ip,sp,fp);
   /* first, find the DebugInfo that pertains to 'ip'. */
   for (di = debugInfo_list; di; di = di->next) {
      n_steps++;
      /* text segment missing? unlikely, but handle it .. */
      if (!di->text_present || di->text_size == 0)
         continue;
      /* Ok.  So does this text mapping bracket the ip? */
      if (di->text_avma <= ip && ip < di->text_avma + di->text_size)
         break;
   }

   /* Didn't find it.  Strange -- means ip is a code address outside
      of any mapped text segment.  Unlikely but not impossible -- app
      could be generating code to run. */
   if (!di)
      return False;

   if (0 && ((n_search & 0x1) == 0))
      VG_(printf)("consider_vars_in_frame: %u searches, "
                  "%u DebugInfos looked at\n",
                  n_search, n_steps);
   /* Start of performance-enhancing hack: once every ??? (chosen
      hackily after profiling) successful searches, move the found
      DebugInfo one step closer to the start of the list.  This makes
      future searches cheaper. */
   if ((n_search & 0xFFFF) == 0) {
      /* Move si one step closer to the start of the list. */
      move_DebugInfo_one_step_forward( di );
   }
   /* End of performance-enhancing hack. */

   /* any var info at all? */
   if (!di->varinfo)
      return False;

   /* Work through the scopes from most deeply nested outwards,
      looking for code address ranges that bracket 'ip'.  The
      variables on each such address range found are in scope right
      now.  Don't descend to level zero as that is the global
      scope. */
   regs.ip = ip;
   regs.sp = sp;
   regs.fp = fp;

   /* "for each scope, working outwards ..." */
   for (i = VG_(sizeXA)(di->varinfo) - 1; i >= 1; i--) {
      XArray*      vars;
      Word         j;
      DiAddrRange* arange;
      OSet*        this_scope
         = *(OSet**)VG_(indexXA)( di->varinfo, i );
      if (debug)
         VG_(printf)("QQQQ:   considering scope %ld\n", (Word)i);
      if (!this_scope)
         continue;
      /* Find the set of variables in this scope that
         bracket the program counter. */
      arange = VG_(OSetGen_LookupWithCmp)(
                  this_scope, &ip,
                  ML_(cmp_for_DiAddrRange_range)
               );
      if (!arange)
         continue;
      /* stay sane */
      vg_assert(arange->aMin <= arange->aMax);
      /* It must bracket the ip we asked for, else
         ML_(cmp_for_DiAddrRange_range) is somehow broken. */
      vg_assert(arange->aMin <= ip && ip <= arange->aMax);
      /* It must have an attached XArray of DiVariables. */
      vars = arange->vars;
      vg_assert(vars);
      /* But it mustn't cover the entire address range.  We only
         expect that to happen for the global scope (level 0), which
         we're not looking at here.  Except, it may cover the entire
         address range, but in that case the vars array must be
         empty. */
      vg_assert(! (arange->aMin == (Addr)0
                   && arange->aMax == ~(Addr)0
                   && VG_(sizeXA)(vars) > 0) );
      for (j = 0; j < VG_(sizeXA)( vars ); j++) {
         DiVariable* var = (DiVariable*)VG_(indexXA)( vars, j );
         SizeT       offset;
         if (debug)
            VG_(printf)("QQQQ:    var:name=%s %p-%p %p\n",
                        var->name,arange->aMin,arange->aMax,ip);
         if (data_address_is_in_var( &offset, var, &regs, data_addr,
                                     di->data_bias )) {
            OffT residual_offset = 0;
            XArray* described = ML_(describe_type)( &residual_offset,
                                                    var->type, offset );
            format_message( dname1, dname2, n_dname,
                            data_addr, var, offset, residual_offset,
                            described, frameNo, tid );
            VG_(deleteXA)( described );
            return True;
         }
      }
   }

   return False;
}

/* Try to form some description of data_addr by looking at the DWARF3
   debug info we have.  This considers all global variables, and all
   frames in the stacks of all threads.  Result (or as much as will
   fit) is put into into dname{1,2}[0 .. n_dname-1] and is guaranteed
   to be zero terminated. */
Bool VG_(get_data_description)( /*OUT*/Char* dname1,
                                /*OUT*/Char* dname2,
                                Int  n_dname,
                                Addr data_addr )
{
#  define N_FRAMES 8
   Addr ips[N_FRAMES], sps[N_FRAMES], fps[N_FRAMES];
   UInt n_frames;

   Addr       stack_min, stack_max;
   ThreadId   tid;
   Bool       found;
   DebugInfo* di;
   Word       j;

   vg_assert(n_dname > 1);
   dname1[n_dname-1] = dname2[n_dname-1] = 0;

   if (0) VG_(printf)("get_data_description: dataaddr %p\n", data_addr);
   /* First, see if data_addr is (or is part of) a global variable.
      Loop over the DebugInfos we have.  Check data_addr against the
      outermost scope of all of them, as that should be a global
      scope. */
   for (di = debugInfo_list; di != NULL; di = di->next) {
      OSet*        global_scope;
      Int          gs_size;
      Addr         zero;
      DiAddrRange* global_arange;
      Word         i;
      XArray*      vars;

      /* text segment missing? unlikely, but handle it .. */
      if (!di->text_present || di->text_size == 0)
         continue;
      /* any var info at all? */
      if (!di->varinfo)
         continue;
      /* perhaps this object didn't contribute any vars at all? */
      if (VG_(sizeXA)( di->varinfo ) == 0)
         continue;
      global_scope = *(OSet**)VG_(indexXA)( di->varinfo, 0 );
      vg_assert(global_scope);
      gs_size = VG_(OSetGen_Size)( global_scope );
      /* The global scope might be completely empty if this
         compilation unit declared locals but nothing global. */
      if (gs_size == 0)
          continue;
      /* But if it isn't empty, then it must contain exactly one
         element, which covers the entire address range. */
      vg_assert(gs_size == 1);
      /* Fish out the global scope and check it is as expected. */
      zero = 0;
      global_arange
         = VG_(OSetGen_Lookup)( global_scope, &zero );
      /* The global range from (Addr)0 to ~(Addr)0 must exist */
      vg_assert(global_arange);
      vg_assert(global_arange->aMin == (Addr)0
                && global_arange->aMax == ~(Addr)0);
      /* Any vars in this range? */
      if (!global_arange->vars)
         continue;
      /* Ok, there are some vars in the global scope of this
         DebugInfo.  Wade through them and see if the data addresses
         of any of them bracket data_addr. */
      vars = global_arange->vars;
      for (i = 0; i < VG_(sizeXA)( vars ); i++) {
         SizeT offset;
         DiVariable* var = (DiVariable*)VG_(indexXA)( vars, i );
         vg_assert(var->name);
         /* Note we use a NULL RegSummary* here.  It can't make any
            sense for a global variable to have a location expression
            which depends on a SP/FP/IP value.  So don't supply any.
            This means, if the evaluation of the location
            expression/list requires a register, we have to let it
            fail. */
         if (data_address_is_in_var( &offset, var,
                                     NULL/* RegSummary* */,
                                     data_addr, di->data_bias )) {
            OffT residual_offset = 0;
            XArray* described = ML_(describe_type)( &residual_offset,
                                                    var->type, offset );
            format_message( dname1, dname2, n_dname,
                            data_addr, var, offset, residual_offset,
                            described, -1/*frameNo*/, tid );
            VG_(deleteXA)( described );
            dname1[n_dname-1] = dname2[n_dname-1] = 0;
            return True;
         }
      }
   }

   /* Ok, well it's not a global variable.  So now let's snoop around
      in the stacks of all the threads.  First try to figure out which
      thread's stack data_addr is in. */

   /* --- KLUDGE --- Try examining the top frame of all thread stacks.
      This finds variables which are not stack allocated but are not
      globally visible either; specifically it appears to pick up
      variables which are visible only within a compilation unit.
      These will have the address range of the compilation unit and
      tend to live at Scope level 1. */
   VG_(thread_stack_reset_iter)(&tid);
   while ( VG_(thread_stack_next)(&tid, &stack_min, &stack_max) ) {
      if (stack_min >= stack_max)
         continue; /* ignore obviously stupid cases */
      if (consider_vars_in_frame( dname1, dname2, n_dname,
                                  data_addr,
                                  VG_(get_IP)(tid),
                                  VG_(get_SP)(tid),
                                  VG_(get_FP)(tid), tid, 0 )) {
         dname1[n_dname-1] = dname2[n_dname-1] = 0;
         return True;
      }
   }
   /* --- end KLUDGE --- */

   /* Perhaps it's on a thread's stack? */
   found = False;
   VG_(thread_stack_reset_iter)(&tid);
   while ( VG_(thread_stack_next)(&tid, &stack_min, &stack_max) ) {
      if (stack_min >= stack_max)
         continue; /* ignore obviously stupid cases */
      if (stack_min - VG_STACK_REDZONE_SZB <= data_addr
          && data_addr <= stack_max) {
         found = True;
         break;
      }
   }
   if (!found) {
      dname1[n_dname-1] = dname2[n_dname-1] = 0;
      return False;
   }

   /* We conclude data_addr is in thread tid's stack.  Unwind the
      stack to get a bunch of (ip,sp,fp) triples describing the
      frames, and for each frame, consider the local variables. */
   n_frames = VG_(get_StackTrace)( tid, ips, N_FRAMES,
                                   sps, fps, 0/*first_ip_delta*/ );
   /* Re ip_delta in the next loop: There's a subtlety in the meaning
      of the IP values in a stack obtained from VG_(get_StackTrace).
      The innermost value really is simply the thread's program
      counter at the time the snapshot was taken.  However, all the
      other values are actually return addresses, and so point just
      after the call instructions.  Hence they notionally reflect not
      what the program counters were at the time those calls were
      made, but what they will be when those calls return.  This can
      be of significance should an address range happen to end at the
      end of a call instruction -- we may ignore the range when in
      fact it should be considered.  Hence, back up the IPs by 1 for
      all non-innermost IPs.  Note that VG_(get_StackTrace_wrk) itself
      has to use the same trick in order to use CFI data to unwind the
      stack (as documented therein in comments). */
   /* As a result of KLUDGE above, starting the loop at j = 0
      duplicates examination of the top frame and so isn't necessary.
      Oh well. */
   vg_assert(n_frames >= 0 && n_frames <= N_FRAMES);
   for (j = 0; j < n_frames; j++) {
      Word ip_delta = j == 0 ? 0 : 1;
      if (consider_vars_in_frame( dname1, dname2, n_dname,
                                  data_addr,
                                  ips[j] - ip_delta,
                                  sps[j], fps[j], tid, j )) {
         dname1[n_dname-1] = dname2[n_dname-1] = 0;
         return True;
      }
      /* Now, it appears that gcc sometimes appears to produce
         location lists whose ranges don't actually cover the call
         instruction, even though the address of the variable in
         question is passed as a parameter in the call.  AFAICS this
         is simply a bug in gcc - how can the variable be claimed not
         exist in memory (on the stack) for the duration of a call in
         which its address is passed?  But anyway, in the particular
         case I investigated (memcheck/tests/varinfo6.c, call to croak
         on line 2999, local var budget declared at line 3115
         appearing not to exist across the call to mainSort on line
         3143, "gcc.orig (GCC) 3.4.4 20050721 (Red Hat 3.4.4-2)" on
         amd64), the variable's location list does claim it exists
         starting at the first byte of the first instruction after the
         call instruction.  So, call consider_vars_in_frame a second
         time, but this time don't subtract 1 from the IP.  GDB
         handles this example with no difficulty, which leads me to
         believe that either (1) I misunderstood something, or (2) GDB
         has an equivalent kludge. */
      if (consider_vars_in_frame( dname1, dname2, n_dname,
                                  data_addr,
                                  ips[j],
                                  sps[j], fps[j], tid, j )) {
         dname1[n_dname-1] = dname2[n_dname-1] = 0;
         return True;
      }
   }

   /* We didn't find anything useful. */
   dname1[n_dname-1] = dname2[n_dname-1] = 0;
   return False;
#  undef N_FRAMES
}


/*------------------------------------------------------------*/
/*--- DebugInfo accessor functions                         ---*/
/*------------------------------------------------------------*/

const DebugInfo* VG_(next_seginfo)(const DebugInfo* di)
{
   if (di == NULL)
      return debugInfo_list;
   return di->next;
}

Addr VG_(seginfo_get_text_avma)(const DebugInfo* di)
{
   return di->text_present ? di->text_avma : 0;
}

SizeT VG_(seginfo_get_text_size)(const DebugInfo* di)
{
   return di->text_present ? di->text_size : 0;
}

const UChar* VG_(seginfo_soname)(const DebugInfo* di)
{
   return di->soname;
}

const UChar* VG_(seginfo_filename)(const DebugInfo* di)
{
   return di->filename;
}

ULong VG_(seginfo_get_text_bias)(const DebugInfo* di)
{
   return di->text_present ? di->text_bias : 0;
}

Int VG_(seginfo_syms_howmany) ( const DebugInfo *si )
{
   return si->symtab_used;
}

void VG_(seginfo_syms_getidx) ( const DebugInfo *si,
                                      Int idx,
                               /*OUT*/Addr*   avma,
                               /*OUT*/Addr*   tocptr,
                               /*OUT*/UInt*   size,
                               /*OUT*/HChar** name,
                               /*OUT*/Bool*   isText )
{
   vg_assert(idx >= 0 && idx < si->symtab_used);
   if (avma)   *avma   = si->symtab[idx].addr;
   if (tocptr) *tocptr = si->symtab[idx].tocptr;
   if (size)   *size   = si->symtab[idx].size;
   if (name)   *name   = (HChar*)si->symtab[idx].name;
   if (isText) *isText = si->symtab[idx].isText;
}


/*------------------------------------------------------------*/
/*--- SectKind query functions                             ---*/
/*------------------------------------------------------------*/

/* Convert a VgSectKind to a string, which must be copied if you want
   to change it. */
const HChar* VG_(pp_SectKind)( VgSectKind kind )
{
   switch (kind) {
      case Vg_SectUnknown: return "Unknown";
      case Vg_SectText:    return "Text";
      case Vg_SectData:    return "Data";
      case Vg_SectBSS:     return "BSS";
      case Vg_SectGOT:     return "GOT";
      case Vg_SectPLT:     return "PLT";
      case Vg_SectOPD:     return "OPD";
      default:             vg_assert(0);
   }
}

/* Given an address 'a', make a guess of which section of which object
   it comes from.  If name is non-NULL, then the last n_name-1
   characters of the object's name is put in name[0 .. n_name-2], and
   name[n_name-1] is set to zero (guaranteed zero terminated). */

VgSectKind VG_(seginfo_sect_kind)( /*OUT*/UChar* name, SizeT n_name,
                                   Addr a)
{
   DebugInfo* di;
   VgSectKind res = Vg_SectUnknown;

   for (di = debugInfo_list; di != NULL; di = di->next) {

      if (0)
         VG_(printf)(
            "addr=%p di=%p %s got=%p,%ld plt=%p,%ld data=%p,%ld bss=%p,%ld\n",
            a, di, di->filename,
            di->got_avma,  di->got_size,
            di->plt_avma,  di->plt_size,
            di->data_avma, di->data_size,
            di->bss_avma,  di->bss_size);

      if (di->text_present
          && di->text_size > 0
          && a >= di->text_avma && a < di->text_avma + di->text_size) {
         res = Vg_SectText;
         break;
      }
      if (di->data_present
          && di->data_size > 0
          && a >= di->data_avma && a < di->data_avma + di->data_size) {
         res = Vg_SectData;
         break;
      }
      if (di->sdata_present
          && di->sdata_size > 0
          && a >= di->sdata_avma && a < di->sdata_avma + di->sdata_size) {
         res = Vg_SectData;
         break;
      }
      if (di->bss_present
          && di->bss_size > 0
          && a >= di->bss_avma && a < di->bss_avma + di->bss_size) {
         res = Vg_SectBSS;
         break;
      }
      if (di->plt_present
          && di->plt_size > 0
          && a >= di->plt_avma && a < di->plt_avma + di->plt_size) {
         res = Vg_SectPLT;
         break;
      }
      if (di->got_present
          && di->got_size > 0
          && a >= di->got_avma && a < di->got_avma + di->got_size) {
         res = Vg_SectGOT;
         break;
      }
      if (di->opd_present
          && di->opd_size > 0
          && a >= di->opd_avma && a < di->opd_avma + di->opd_size) {
         res = Vg_SectOPD;
         break;
      }
      /* we could also check for .eh_frame, if anyone really cares */
   }

   vg_assert( (di == NULL && res == Vg_SectUnknown)
              || (di != NULL && res != Vg_SectUnknown) );

   if (name) {

      vg_assert(n_name >= 8);

      if (di && di->filename) {
         Int i, j;
         Int fnlen = VG_(strlen)(di->filename);
         Int start_at = 1 + fnlen - n_name;
         if (start_at < 0) start_at = 0;
         vg_assert(start_at < fnlen);
         i = start_at; j = 0;
         while (True) {
            vg_assert(j >= 0 && j+1 < n_name);
            vg_assert(i >= 0 && i <= fnlen);
            name[j] = di->filename[i];
            name[j+1] = 0;
            if (di->filename[i] == 0) break;
            i++; j++;
         }
      } else {
         VG_(snprintf)(name, n_name, "%s", "???");
      }

      name[n_name-1] = 0;
   }

   return res;

}


/*--------------------------------------------------------------------*/
/*--- end                                                          ---*/
/*--------------------------------------------------------------------*/