Bug 20292 - Simplify and test _dl_addr_inside_object

The function _dl_addr_inside_object is simplified by removing
the conditional 'reladdr - l->l_phdr[n].p_vaddr >= 0' which is
always true. The function is refactored into it's own object file
and a unit test added to verify the correct behaviour of the
function.

1 files changed, 75 insertions, 0 deletions

diff --git a/elf/dl-addr-obj.c b/elf/dl-addr-obj.c
new file mode 100644
index 0000000..f640761
--- /dev/null
+++ b/elf/dl-addr-obj.c
@@ -0,0 +1,75 @@
+/* Determine if address is inside object load segments.
+   Copyright (C) 1996-2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <link.h>
+#include <elf.h>
+
+/* Return non-zero if ADDR lies within one of L's loadable segments.
+   We have three cases we care about.
+
+   Case 1: addr is above a segment.
+   +==================+<- l_map_end
+   |                  |<- addr
+   |------------------|<- l_addr + p_vaddr + p_memsz
+   |                  |
+   |                  |
+   |------------------|<- l_addr + p_vaddr
+   |------------------|<- l_addr
+   |                  |
+   +==================+<- l_map_start
+
+   Case 2: addr is within a segments.
+   +==================+<- l_map_end
+   |                  |
+   |------------------|<- l_addr + p_vaddr + p_memsz
+   |                  |<- addr
+   |                  |
+   |------------------|<- l_addr + p_vaddr
+   |------------------|<- l_addr
+   |                  |
+   +==================+<- l_map_start
+
+   Case 3: addr is below a segments.
+   +==================+<- l_map_end
+   |                  |
+   |------------------|<- l_addr + p_vaddr + p_memsz
+   |                  |
+   |                  |
+   |------------------|<- l_addr + p_vaddr
+   |------------------|<- l_addr
+   |                  |<- addr
+   +==================+<- l_map_start
+
+   All the arithmetic is unsigned and we shift all the values down by
+   l_addr + p_vaddr and then compare the normalized addr to the range
+   of interest i.e. 0 <= addr < p_memsz.
+
+*/
+int
+internal_function
+_dl_addr_inside_object (struct link_map *l, const ElfW(Addr) addr)
+{
+  int n = l->l_phnum;
+  const ElfW(Addr) reladdr = addr - l->l_addr;
+
+  while (--n >= 0)
+    if (l->l_phdr[n].p_type == PT_LOAD
+	&& reladdr - l->l_phdr[n].p_vaddr < l->l_phdr[n].p_memsz)
+      return 1;
+  return 0;
+}