From: Mark Wielaard <mark@klomp.org>
Date: Sat, 1 May 2021 16:00:49 +0000 (+0200)
Subject: libdw: Document and handle DW_FORM_indirect in __libdw_form_val_compute_len
X-Git-Tag: elfutils-0.184~1
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=09184fc04f3cd54600dee562ea48d281d2087e21;p=thirdparty%2Felfutils.git

libdw: Document and handle DW_FORM_indirect in __libdw_form_val_compute_len

Update the documentation in __libdw_form_val_compute_len for handling
DW_FORM_indirect and make sure the indirect form isn't DW_FORM_indirect
itself or DW_FORM_implicit_const.

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

diff --git a/libdw/ChangeLog b/libdw/ChangeLog
index e3e467eec..aa3e5ee29 100644
--- a/libdw/ChangeLog
+++ b/libdw/ChangeLog
@@ -1,3 +1,8 @@
+2021-05-01  Mark Wielaard  <mark@klomp.org>
+
+	* libdw_form.c (__libdw_form_val_compute_len): Check indirect
+	form is not DW_FORM_indirect or DW_FORM_implicit_const.
+
 2021-04-23  Omar Sandoval  <osandov@fb.com>
 
 	* dwarf_child.c (__libdw_find_attr): Handle DW_FORM_indirect.
diff --git a/libdw/libdw_form.c b/libdw/libdw_form.c
index 584c84671..c83dfb397 100644
--- a/libdw/libdw_form.c
+++ b/libdw/libdw_form.c
@@ -116,8 +116,12 @@ __libdw_form_val_compute_len (struct Dwarf_CU *cu, unsigned int form,
       break;
 
     case DW_FORM_indirect:
+      /* The amount of data to skip in the DIE is the size of the actual
+	 FORM data (which is __libdw_form_val_len) plus the size of the
+	 uleb128 encoding that FORM (which is valp - startp).  */
       get_uleb128 (u128, valp, endp);
-      // XXX Is this really correct?
+      if (*valp == DW_FORM_indirect || *valp == DW_FORM_implicit_const)
+	return (size_t) -1;
       result = __libdw_form_val_len (cu, u128, valp);
       if (result != (size_t) -1)
 	result += valp - startp;