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authorCarlos O'Donell <carlos@redhat.com>2016-09-29 21:54:31 -0400
committerCarlos O'Donell <carlos@redhat.com>2016-09-30 01:36:56 -0400
commitd61ef7352b0026d9eeaf457dbfbb2e3fd8401e92 (patch)
tree798532132a35db0935de8cff3f10e8642e3457bb /elf/dl-addr-obj.c
parent29cb9293326a27576965a40d50a898ee660dff81 (diff)
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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.
Diffstat (limited to 'elf/dl-addr-obj.c')
-rw-r--r--elf/dl-addr-obj.c75
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;
+}