plt.c revision 929bd57ca202fd2f2e8485ebf65d683e664f67b5 
1/*
2 * This file is part of ltrace.
3 * Copyright (C) 2012 Petr Machata, Red Hat Inc.
4 * Copyright (C) 2008,2009 Juan Cespedes
5 * Copyright (C) 2006 Ian Wienand
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License as
9 * published by the Free Software Foundation; either version 2 of the
10 * License, or (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful, but
13 * WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15 * General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
20 * 02110-1301 USA
21 */
22
23#include <errno.h>
24#include <gelf.h>
25#include <stdio.h>
26#include <string.h>
27#include <sys/ptrace.h>
28
29#include "proc.h"
30#include "common.h"
31#include "library.h"
32
33/* A bundle is 128 bits.  */
34#define BUNDLE_SIZE 16
35
36/* The PLT has
37 *
38 * - 3 bundles as a header
39 *
40 * - The special reserved entry
41 *
42 * - Following that, each PLT entry has it's initial code that the GOT
43 *   entry points to.  Each PLT entry has one bundle allocated.
44 *
45 * - Following that, each PLT entry has two bundles of actual PLT
46 *   code, i.e. load up the address from the GOT and jump to it.  This
47 *   is the point we want to insert the breakpoint, as this will be
48 *   captured every time we jump to the PLT entry in the code.
49 */
50
51GElf_Addr
52arch_plt_sym_val(struct ltelf *lte, size_t ndx, GElf_Rela * rela)
53{
54	/* Find number of entires by removing header and special
55	 * entry, dividing total size by three, since each PLT entry
56	 * will have 3 bundles (1 for inital entry and two for the PLT
57	 * code). */
58	int entries = (lte->plt_size - 4 * BUNDLE_SIZE) / (3 * BUNDLE_SIZE);
59
60	/* Now the point we want to break on is the PLT entry after
61	 * all the header stuff */
62	unsigned long addr =
63	    lte->plt_addr + (4 * BUNDLE_SIZE) + (BUNDLE_SIZE * entries) +
64	    (2 * ndx * BUNDLE_SIZE);
65	debug(3, "Found PLT %zd entry at %lx", ndx, addr);
66
67	return addr;
68}
69
70void *
71sym2addr(struct process *proc, struct library_symbol *sym)
72{
73	return sym->enter_addr;
74}
75
76int
77arch_translate_address_dyn(struct process *proc,
78			   arch_addr_t addr, arch_addr_t *ret)
79{
80	errno = 0;
81	unsigned long l = ptrace(PTRACE_PEEKTEXT, proc->pid, addr, 0);
82	if (l == -1UL && errno) {
83		fprintf(stderr,	"dynamic .opd translation of %p: %s\n",
84			addr, strerror(errno));
85		return -1;
86	}
87
88	/* XXX The double cast should be removed when
89	 * arch_addr_t becomes integral type.  */
90	*ret = (arch_addr_t)(uintptr_t)l;
91	return 0;
92}
93
94int
95arch_translate_address(struct ltelf *lte,
96		       arch_addr_t addr, arch_addr_t *ret)
97{
98	*ret = addr;
99	return 0;
100}
101