libdw: Handle split dwarf debuglines.

Split DWARF .dwo files do contain a .debug_line section, but only with
the file table, there is no actual line program. Also split DWARF CU DIEs
don't have a DW_AT_stmt_list attribute. To get at the file (and dir) table
for a split unit DIE take just the files from the .debug_line section
(at offset zero). To get the full line table use the skeleton DIE (which
does have a DW_AT_stmt_list).

Signed-off-by: Mark Wielaard <mark@klomp.org>

4 files changed, 76 insertions, 9 deletions

diff --git a/libdw/ChangeLog b/libdw/ChangeLog
index 72ff8a73..ab9675e4 100644
--- a/libdw/ChangeLog
+++ b/libdw/ChangeLog
@@ -1,3 +1,12 @@
+2018-05-18  Mark Wielaard  <mark@klomp.org>
+
+	* libdw_findcu.c (__libdw_intern_next_unit): Init files to NULL.
+	* dwarf_getsrclines.c (dwarf_getsrclines): Handle split units by
+	taking the line table from the skeleton.
+	* dwarf_getsrcfiles.c (dwarf_getsrcfiles): Handle split units by
+	only taking the files from .debug_line offset zero (if it exists),
+	otherwise fall back to the skeleton.
+
 2018-05-17  Mark Wielaard  <mark@klomp.org>
 
 	* dwarf_begin_elf.c (__libdw_debugdir): New function.
diff --git a/libdw/dwarf_getsrcfiles.c b/libdw/dwarf_getsrcfiles.c
index 5af6f68b..12fdabf2 100644
--- a/libdw/dwarf_getsrcfiles.c
+++ b/libdw/dwarf_getsrcfiles.c
@@ -1,7 +1,6 @@
 /* Return source file information of CU.
-   Copyright (C) 2004, 2005, 2013, 2015 Red Hat, Inc.
+   Copyright (C) 2004, 2005, 2013, 2015, 2018 Red Hat, Inc.
    This file is part of elfutils.
-   Written by Ulrich Drepper <drepper@redhat.com>, 2004.
 
    This file is free software; you can redistribute it and/or modify
    it under the terms of either
@@ -51,14 +50,47 @@ dwarf_getsrcfiles (Dwarf_Die *cudie, Dwarf_Files **files, size_t *nfiles)
 
   /* Get the information if it is not already known.  */
   struct Dwarf_CU *const cu = cudie->cu;
-  if (cu->lines == NULL)
+  if (cu->files == NULL)
     {
-      Dwarf_Lines *lines;
-      size_t nlines;
-
-      /* Let the more generic function do the work.  It'll create more
-	 data but that will be needed in an real program anyway.  */
-      res = INTUSE(dwarf_getsrclines) (cudie, &lines, &nlines);
+      /* For split units there might be a simple file table (without lines).
+	 If not, use the one from the skeleton.  */
+      if (cu->unit_type == DW_UT_split_compile
+	  || cu->unit_type == DW_UT_split_type)
+	{
+	  /* We tried, assume we fail...  */
+	  cu->files = (void *) -1;
+
+	  /* See if there is a .debug_line section, for split CUs
+	     the table is at offset zero.  */
+	  if (cu->dbg->sectiondata[IDX_debug_line] != NULL)
+	    {
+	      /* We are only interested in the files, the lines will
+		 always come from the skeleton.  */
+	      res = __libdw_getsrclines (cu->dbg, 0,
+					 __libdw_getcompdir (cudie),
+					 cu->address_size, NULL,
+					 &cu->files);
+	    }
+	  else
+	    {
+	      Dwarf_CU *skel = __libdw_find_split_unit (cu);
+	      if (skel != NULL)
+		{
+		  Dwarf_Die skeldie = CUDIE (skel);
+		  res = INTUSE(dwarf_getsrcfiles) (&skeldie, files, nfiles);
+		  cu->files = skel->files;
+		}
+	    }
+	}
+      else
+	{
+	  Dwarf_Lines *lines;
+	  size_t nlines;
+
+	  /* Let the more generic function do the work.  It'll create more
+	     data but that will be needed in an real program anyway.  */
+	  res = INTUSE(dwarf_getsrclines) (cudie, &lines, &nlines);
+	}
     }
   else if (cu->files != (void *) -1l)
     /* We already have the information.  */
diff --git a/libdw/dwarf_getsrclines.c b/libdw/dwarf_getsrclines.c
index 2f966ab7..2bf30984 100644
--- a/libdw/dwarf_getsrclines.c
+++ b/libdw/dwarf_getsrclines.c
@@ -1147,6 +1147,31 @@ dwarf_getsrclines (Dwarf_Die *cudie, Dwarf_Lines **lines, size_t *nlines)
   struct Dwarf_CU *const cu = cudie->cu;
   if (cu->lines == NULL)
     {
+      /* For split units always pick the lines from the skeleton.  */
+      if (cu->unit_type == DW_UT_split_compile
+	  || cu->unit_type == DW_UT_split_type)
+	{
+	  /* We tries, assume we fail...  */
+	  cu->lines = (void *) -1l;
+
+	  Dwarf_CU *skel = __libdw_find_split_unit (cu);
+	  if (skel != NULL)
+	    {
+	      Dwarf_Die skeldie = CUDIE (skel);
+	      int res = INTUSE(dwarf_getsrclines) (&skeldie, lines, nlines);
+	      if (res == 0)
+		{
+		  cu->lines = skel->lines;
+		  *lines = cu->lines;
+		  *nlines = cu->lines->nlines;
+		}
+	      return res;
+	    }
+
+	  __libdw_seterrno (DWARF_E_NO_DEBUG_LINE);
+	  return -1;
+	}
+
       /* Failsafe mode: no data found.  */
       cu->lines = (void *) -1l;
       cu->files = (void *) -1l;
diff --git a/libdw/libdw_findcu.c b/libdw/libdw_findcu.c
index d6975f34..d22ddae7 100644
--- a/libdw/libdw_findcu.c
+++ b/libdw/libdw_findcu.c
@@ -114,6 +114,7 @@ __libdw_intern_next_unit (Dwarf *dbg, bool debug_types)
   newp->subdie_offset = subdie_offset;
   Dwarf_Abbrev_Hash_init (&newp->abbrev_hash, 41);
   newp->orig_abbrev_offset = newp->last_abbrev_offset = abbrev_offset;
+  newp->files = NULL;
   newp->lines = NULL;
   newp->locs = NULL;
   newp->split = (Dwarf_CU *) -1;