libdw: Support DW_OP_addrx/constx and split DWARF addrx/constx support.

DW_OP_addrx/constx and GNU DebugFission DW_OP_GNU_addr/const_index take
as argument an index into the .debug_addr section for the associated CU.
This index gets resolved through dwarf_getlocation_attr. A new fake addr
CU is created per Dwarf for use with this new attribute. For split DWARF
files, the IDX_debug_addr gets replaced with the skeleton section and the
addr base is resolved immediately when constructing the split DWARF CU.
Move __libdw_cu_addr_base to libdwP.h to share with eu-readelf. Also
make it possible to resolve addrx[1234]/GNU_addr_index also as constant
indexes to (also) show when displaying these attributes in eu-readelf.

A new varlocs tests is added to test the resolving for both the DWARF4
and DWARF5 DW_OP variants. And now that addrx forms are resolved in
split DWARF files add the new DIEs with "single ranges" (those DIEs that
have a lowpc/highpc attribute pair) to run-all-dwarf-ranges.sh.

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

8 files changed, 158 insertions, 20 deletions

diff --git a/libdw/ChangeLog b/libdw/ChangeLog
index 08c8f7be..f5689632 100644
--- a/libdw/ChangeLog
+++ b/libdw/ChangeLog
@@ -1,3 +1,22 @@
+2018-05-21  Mark Wielaard  <mark@klomp.org>
+
+	* dwarf_begin_elf.c (valid_p): Add a fake_addr_cu to the result.
+	* dwarf_end.c (cu_free): Disconnect the fake_addr_cu from the split
+	dwarf if shared with skeleton.
+	(dwarf_end): release fake_addr_cu.
+	* dwarf_formaddr.c (__libdw_cu_addr_base): Move to...
+	* libdwP.h (__libdw_cu_addr_base): ... here.
+	(struct Dwarf): Add fake_addr_cu field.
+	* dwarf_formudata.c (dwarf_formudata): Handle
+	DW_FORM_GNU_addr_index and DW_FORM_addrx[1234].
+	* dwarf_getlocation_attr.c (addr_valp): New static function.
+	(dwarf_getlocation_attr): Create attribute for values of
+	DW_OP_GNU_const_index, DW_OP_constx and DW_OP_GNU_addr_index and
+	DW_OP_addrx.
+	* libdw_find_split_unit.c (__libdw_find_split_unit): Connect
+	IDX_debug_addr sectiondata and fake_addr_cu between split and
+	skeleton.
+
 2018-05-20  Mark Wielaard  <mark@klomp.org>
 
 	* dwarf_cu_info.c: New file.
diff --git a/libdw/dwarf_begin_elf.c b/libdw/dwarf_begin_elf.c
index 0e435c57..5d8e79e3 100644
--- a/libdw/dwarf_begin_elf.c
+++ b/libdw/dwarf_begin_elf.c
@@ -246,6 +246,33 @@ valid_p (Dwarf *result)
 	}
     }
 
+  /* For DW_OP_constx/GNU_const_index and DW_OP_addrx/GNU_addr_index
+     the dwarf_location_attr () will need a "fake" address CU to
+     indicate where the attribute data comes from.  This is a just
+     inside the .debug_addr section, if it exists.  */
+  if (result != NULL && result->sectiondata[IDX_debug_addr] != NULL)
+    {
+      result->fake_addr_cu = (Dwarf_CU *) calloc (1, sizeof (Dwarf_CU));
+      if (unlikely (result->fake_addr_cu == NULL))
+	{
+	  Dwarf_Sig8_Hash_free (&result->sig8_hash);
+	  __libdw_seterrno (DWARF_E_NOMEM);
+	  free (result->fake_loc_cu);
+	  free (result);
+	  result = NULL;
+	}
+      else
+	{
+	  result->fake_addr_cu->sec_idx = IDX_debug_addr;
+	  result->fake_addr_cu->dbg = result;
+	  result->fake_addr_cu->startp
+	    = result->sectiondata[IDX_debug_addr]->d_buf;
+	  result->fake_addr_cu->endp
+	    = (result->sectiondata[IDX_debug_addr]->d_buf
+	       + result->sectiondata[IDX_debug_addr]->d_size);
+	}
+    }
+
   if (result != NULL)
     result->debugdir = __libdw_debugdir (result->elf->fildes);
 
diff --git a/libdw/dwarf_end.c b/libdw/dwarf_end.c
index 4702f1b1..19546741 100644
--- a/libdw/dwarf_end.c
+++ b/libdw/dwarf_end.c
@@ -59,7 +59,12 @@ cu_free (void *arg)
   /* Free split dwarf one way (from skeleton to split).  */
   if (p->unit_type == DW_UT_skeleton
       && p->split != NULL && p->split != (void *)-1)
-    INTUSE(dwarf_end) (p->split->dbg);
+    {
+      /* The fake_addr_cu might be shared, only release one.  */
+      if (p->dbg->fake_addr_cu == p->split->dbg->fake_addr_cu)
+	p->split->dbg->fake_addr_cu = NULL;
+      INTUSE(dwarf_end) (p->split->dbg);
+    }
 }
 
 
@@ -108,6 +113,11 @@ dwarf_end (Dwarf *dwarf)
 	  cu_free (dwarf->fake_loc_cu);
 	  free (dwarf->fake_loc_cu);
 	}
+      if (dwarf->fake_addr_cu != NULL)
+	{
+	  cu_free (dwarf->fake_addr_cu);
+	  free (dwarf->fake_addr_cu);
+	}
 
       /* Did we find and allocate the alt Dwarf ourselves?  */
       if (dwarf->alt_fd != -1)
diff --git a/libdw/dwarf_formaddr.c b/libdw/dwarf_formaddr.c
index c917deac..3c89a5d2 100644
--- a/libdw/dwarf_formaddr.c
+++ b/libdw/dwarf_formaddr.c
@@ -136,21 +136,3 @@ dwarf_formaddr (Dwarf_Attribute *attr, Dwarf_Addr *return_addr)
   return 0;
 }
 INTDEF(dwarf_formaddr)
-
-Dwarf_Off __libdw_cu_addr_base (Dwarf_CU *cu)
-{
-  if (cu->addr_base == (Dwarf_Off) -1)
-    {
-      Dwarf_Die cu_die = CUDIE(cu);
-      Dwarf_Attribute attr;
-      if (dwarf_attr (&cu_die, DW_AT_GNU_addr_base, &attr) != NULL
-	  || dwarf_attr (&cu_die, DW_AT_addr_base, &attr) != NULL)
-	{
-	  Dwarf_Word off;
-	  if (dwarf_formudata (&attr, &off) == 0)
-	    cu->addr_base = off;
-	}
-    }
-
-  return cu->addr_base;
-}
diff --git a/libdw/dwarf_formudata.c b/libdw/dwarf_formudata.c
index 316ad865..d56e7dc1 100644
--- a/libdw/dwarf_formudata.c
+++ b/libdw/dwarf_formudata.c
@@ -288,6 +288,39 @@ dwarf_formudata (Dwarf_Attribute *attr, Dwarf_Word *return_uval)
       get_sleb128_unchecked (*return_uval, datap);
       break;
 
+    /* These are indexes into the .debug_addr section, normally resolved
+       with dwarf_formaddr.  Here treat as constants.  */
+    case DW_FORM_GNU_addr_index:
+    case DW_FORM_addrx:
+      if (datap >= endp)
+	goto invalid;
+      get_uleb128 (*return_uval, datap, endp);
+      break;
+
+    case DW_FORM_addrx1:
+      if (datap >= endp - 1)
+	goto invalid;
+      *return_uval = *datap;
+      break;
+
+    case DW_FORM_addrx2:
+      if (datap >= endp - 2)
+	goto invalid;
+      *return_uval = read_2ubyte_unaligned (attr->cu->dbg, datap);
+      break;
+
+    case DW_FORM_addrx3:
+      if (datap >= endp - 3)
+	goto invalid;
+      *return_uval = read_3ubyte_unaligned (attr->cu->dbg, datap);
+      break;
+
+    case DW_FORM_addrx4:
+      if (datap >= endp - 4)
+	goto invalid;
+      *return_uval = read_4ubyte_unaligned (attr->cu->dbg, datap);
+      break;
+
     default:
       __libdw_seterrno (DWARF_E_NO_CONSTANT);
       return -1;
diff --git a/libdw/dwarf_getlocation_attr.c b/libdw/dwarf_getlocation_attr.c
index 162330f6..62ef47ab 100644
--- a/libdw/dwarf_getlocation_attr.c
+++ b/libdw/dwarf_getlocation_attr.c
@@ -52,6 +52,18 @@ attr_form_cu (Dwarf_Attribute *attr)
     }
 }
 
+static unsigned char *
+addr_valp (Dwarf_CU *cu, Dwarf_Word index)
+{
+  Elf_Data *debug_addr = cu->dbg->sectiondata[IDX_debug_addr];
+  Dwarf_Word offset = __libdw_cu_addr_base (cu) + (index * cu->address_size);
+  if (debug_addr == NULL)
+    /* This is really an error, will trigger with dwarf_formaddr.  */
+    return (unsigned char *) offset;
+
+  return (unsigned char *) debug_addr->d_buf + offset;
+}
+
 int
 dwarf_getlocation_attr (Dwarf_Attribute *attr, const Dwarf_Op *op, Dwarf_Attribute *result)
 {
@@ -83,6 +95,25 @@ dwarf_getlocation_attr (Dwarf_Attribute *attr, const Dwarf_Op *op, Dwarf_Attribu
 	result->cu = attr_form_cu (attr);
 	break;
 
+      case DW_OP_GNU_const_index:
+      case DW_OP_constx:
+	result->code = DW_AT_const_value;
+	if (attr->cu->address_size == 4)
+	  result->form = DW_FORM_data4;
+	else
+	  result->form = DW_FORM_data8;
+	result->valp = addr_valp (attr->cu, op->number);
+	result->cu = attr->cu->dbg->fake_addr_cu;
+	break;
+
+      case DW_OP_GNU_addr_index:
+      case DW_OP_addrx:
+	result->code = DW_AT_low_pc;
+	result->form = DW_FORM_addr;
+	result->valp = addr_valp (attr->cu, op->number);
+	result->cu = attr->cu->dbg->fake_addr_cu;
+	break;
+
       case DW_OP_call2:
       case DW_OP_call4:
       case DW_OP_call_ref:
diff --git a/libdw/libdwP.h b/libdw/libdwP.h
index 2b5b5ead..82ee5d03 100644
--- a/libdw/libdwP.h
+++ b/libdw/libdwP.h
@@ -204,6 +204,9 @@ struct Dwarf
      came from a location list entry in dwarf_getlocation_attr.  */
   struct Dwarf_CU *fake_loc_cu;
 
+  /* Similar for addrx/constx, which will come from .debug_addr section.  */
+  struct Dwarf_CU *fake_addr_cu;
+
   /* Internal memory handling.  This is basically a simplified
      reimplementation of obstacks.  Unfortunately the standard obstack
      implementation is not usable in libraries.  */
@@ -947,7 +950,26 @@ const char *__libdw_getcompdir (Dwarf_Die *cudie);
 Dwarf_Addr __libdw_cu_base_address (Dwarf_CU *cu);
 
 /* Get the address base for the CU, fetches it when not yet set.  */
-Dwarf_Off __libdw_cu_addr_base (Dwarf_CU *cu);
+static inline Dwarf_Off
+__libdw_cu_addr_base (Dwarf_CU *cu)
+{
+  if (cu->addr_base == (Dwarf_Off) -1)
+    {
+      Dwarf_Die cu_die = CUDIE(cu);
+      Dwarf_Attribute attr;
+      Dwarf_Off offset = 0;
+      if (dwarf_attr (&cu_die, DW_AT_GNU_addr_base, &attr) != NULL
+	  || dwarf_attr (&cu_die, DW_AT_addr_base, &attr) != NULL)
+	{
+	  Dwarf_Word off;
+	  if (dwarf_formudata (&attr, &off) == 0)
+	    offset = off;
+	}
+      cu->addr_base = offset;
+    }
+
+  return cu->addr_base;
+}
 
 /* Gets the .debug_str_offsets base offset to use.  static inline to
    be shared between libdw and eu-readelf.  */
diff --git a/libdw/libdw_find_split_unit.c b/libdw/libdw_find_split_unit.c
index bd48b9e5..78c9a2a5 100644
--- a/libdw/libdw_find_split_unit.c
+++ b/libdw/libdw_find_split_unit.c
@@ -88,6 +88,20 @@ __libdw_find_split_unit (Dwarf_CU *cu)
 			      cu->split = split;
 			      split->split = cu;
 
+			      /* Get .debug_addr and addr_base greedy.
+			         We also need it for the fake addr cu.
+				 There is only one per split debug.  */
+			      Dwarf *dbg = cu->dbg;
+			      Dwarf *sdbg = split->dbg;
+			      if (sdbg->sectiondata[IDX_debug_addr] == NULL
+				  && dbg->sectiondata[IDX_debug_addr] != NULL)
+				{
+				  sdbg->sectiondata[IDX_debug_addr]
+				    = dbg->sectiondata[IDX_debug_addr];
+				  split->addr_base = __libdw_cu_addr_base (cu);
+				  sdbg->fake_addr_cu = dbg->fake_addr_cu;
+			        }
+
 			      /* We have everything we need from this
 				 ELF file.  And we are going to close
 				 the fd to not run out of file