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Bug 20292 - Simplify and test _dl_addr_inside_object

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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.
This commit is contained in:
Carlos O'Donell
2016-09-29 21:54:31 -04:00
parent 29cb929332
commit d61ef7352b
6 changed files with 325 additions and 35 deletions
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75
elf/dl-addr-obj.c Normal file
View File

@ -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;
}