plt.c revision e99af270a60891e68d465c4cd97dbe29cd1a05e4 
1/*
2 * This file is part of ltrace.
3 * Copyright (C) 2008,2009 Juan Cespedes
4 * Copyright (C) 2006 Ian Wienand
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License as
8 * published by the Free Software Foundation; either version 2 of the
9 * License, or (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful, but
12 * WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14 * General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
19 * 02110-1301 USA
20 */
21
22#include <gelf.h>
23
24#include "proc.h"
25#include "common.h"
26#include "library.h"
27
28/* A bundle is 128 bits */
29#define BUNDLE_SIZE 16
30
31/*
32
33  The PLT has
34
35  ] 3 bundles as a header
36
37  ] The special reserved entry
38
39  ] Following that, each PLT entry has it's initial code that the GOT entry
40    points to.  Each PLT entry has one bundle allocated.
41
42  ] Following that, each PLT entry has two bundles of actual PLT code,
43    i.e. load up the address from the GOT and jump to it.  This is the
44    point we want to insert the breakpoint, as this will be captured
45    every time we jump to the PLT entry in the code.
46
47*/
48
49GElf_Addr
50arch_plt_sym_val(struct ltelf *lte, size_t ndx, GElf_Rela * rela) {
51	/* Find number of entires by removing header and special
52	 * entry, dividing total size by three, since each PLT entry
53	 * will have 3 bundles (1 for inital entry and two for the PLT
54	 * code). */
55	int entries = (lte->plt_size - 4 * BUNDLE_SIZE) / (3 * BUNDLE_SIZE);
56
57	/* Now the point we want to break on is the PLT entry after
58	 * all the header stuff */
59	unsigned long addr =
60	    lte->plt_addr + (4 * BUNDLE_SIZE) + (BUNDLE_SIZE * entries) +
61	    (2 * ndx * BUNDLE_SIZE);
62	debug(3, "Found PLT %zd entry at %lx\n", ndx, addr);
63
64	return addr;
65}
66
67void *
68sym2addr(Process *proc, struct library_symbol *sym) {
69	return sym->enter_addr;
70}
71