1/*
2 * This file is part of ltrace.
3 * Copyright (C) 2006,2010,2012,2013 Petr Machata, Red Hat Inc.
4 * Copyright (C) 2010 Zachary T Welch
5 * Copyright (C) 2001,2004,2007,2009 Juan Cespedes
6 * Copyright (C) 2006 Ian Wienand
7 *
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License as
10 * published by the Free Software Foundation; either version 2 of the
11 * License, or (at your option) any later version.
12 *
13 * This program is distributed in the hope that it will be useful, but
14 * WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
16 * General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License
19 * along with this program; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
21 * 02110-1301 USA
22 */
23
24#ifndef LTRACE_ELF_H
25#define LTRACE_ELF_H
26
27#include <gelf.h>
28#include <stdlib.h>
29#include <callback.h>
30
31#include "forward.h"
32#include "sysdep.h"
33#include "vect.h"
34
35/* XXX Ok, the original idea was to separate the low-level ELF data
36 * from the abstract "struct library" object, but we use some of the
37 * following extensively in the back end.  Not all though.  So what we
38 * use should be move to struct library, and the rest of this
39 * structure maybe could be safely hidden in .c.  How to integrate the
40 * arch-specific bits into struct library is unclear as of now.  */
41struct ltelf {
42	int fd;
43	Elf *elf;
44	GElf_Ehdr ehdr;
45	Elf_Data *dynsym;
46	size_t dynsym_count;
47	const char *dynstr;
48	GElf_Addr plt_addr;
49	GElf_Word plt_flags;
50	size_t plt_size;
51	Elf_Data *plt_data;
52
53	/* Vector of GElf_Rela with PLT relocations.  */
54	struct vect plt_relocs;
55
56	Elf_Data *symtab;
57	const char *strtab;
58	const char *soname;
59	size_t symtab_count;
60	Elf_Data *opd;
61	GElf_Addr *opd_addr;
62	size_t opd_size;
63	GElf_Addr dyn_addr;
64	size_t dyn_sz;
65	GElf_Addr bias;
66	GElf_Addr entry_addr;
67	GElf_Addr base_addr;
68	struct arch_ltelf_data arch;
69};
70
71int ltelf_init(struct ltelf *lte, const char *filename);
72void ltelf_destroy(struct ltelf *lte);
73
74/* XXX is it possible to put breakpoints in VDSO and VSYSCALL
75 * pseudo-libraries?  For now we assume that all libraries can be
76 * opened via a filesystem.  BASE is ignored for ET_EXEC files.  */
77int ltelf_read_library(struct library *lib, struct process *proc,
78		       const char *filename, GElf_Addr bias);
79
80/* Create a library object representing the main binary.  The entry
81 * point address is stored to *ENTRYP.  */
82struct library *ltelf_read_main_binary(struct process *proc, const char *path);
83
84/* This is called for every PLT relocation R in ELF file LTE, that
85 * ltrace is about to add to a library constructed in process PROC.
86 * The corresponding PLT entry is for symbol called NAME, and it's
87 * I-th relocation in the file.  *RET shall be initialized and
88 * symbol(s) corresponding to the given PLT entry will be added to the
89 * front.  Returns 0 for success, or a negative value for failures.
90 *
91 * This calls os_elf_add_plt_entry and arch_elf_add_plt_entry in the
92 * background (see backend.h for documentation).  The arch callback is
93 * called first.  If it returns PLT_DEFAULT, the os callback is called
94 * next.  If that returns PLT_DEFAULT, default_elf_add_plt_entry is
95 * called.  */
96int elf_add_plt_entry(struct process *proc, struct ltelf *lte,
97		      const char *name, GElf_Rela *rela, size_t idx,
98		      struct library_symbol **ret);
99
100/* Create a default PLT entry.  This can be used instead (or in
101 * addition to) returning PLT_DEFAULT from arch_elf_add_plt_entry.
102 * RET shall be initialized, the created symbol will be added to the
103 * beginning of the linked list at *RET.  This function doesn't add
104 * the symbol to LTE.  arch_elf_add_plt_entry has the chance to adjust
105 * symbol internals to its liking, and then return either PLT_DEFAULT
106 * or PLT_OK.  */
107int default_elf_add_plt_entry(struct process *proc, struct ltelf *lte,
108			      const char *a_name, GElf_Rela *rela, size_t ndx,
109			      struct library_symbol **ret);
110
111Elf_Data *elf_loaddata(Elf_Scn *scn, GElf_Shdr *shdr);
112
113/* The following three look for sections based on various criteria.
114 * They return 0 if there was no error, or a negative value if there
115 * was.  If the section was found, it is returned in *TGT_SEC, and the
116 * header is stored to TGT_SHDR.  If it wasn't found, *TGT_SEC is set
117 * to NULL.  */
118int elf_get_section_covering(struct ltelf *lte, GElf_Addr addr,
119			     Elf_Scn **tgt_sec, GElf_Shdr *tgt_shdr);
120int elf_get_section_type(struct ltelf *lte, GElf_Word type,
121			 Elf_Scn **tgt_sec, GElf_Shdr *tgt_shdr);
122int elf_get_section_named(struct ltelf *lte, const char *name,
123			  Elf_Scn **tgt_sec, GElf_Shdr *tgt_shdr);
124
125/* Iterate through all symbols in LTE.  See callback.h for notes on
126 * iteration interfaces.  START_AFTER is 0 in initial call.  */
127struct elf_each_symbol_t {
128	unsigned restart;
129	int status;
130} elf_each_symbol(struct ltelf *lte, unsigned start_after,
131		  enum callback_status (*cb)(GElf_Sym *symbol,
132					     const char *name,
133					     void *data),
134		  void *data);
135
136/* Read relocations from relocation section SCN with header SHDR and
137 * add them to RELA_VEC, which is a vector of GElf_Rela.  Return 0 on
138 * success, or a negative value on failure.  */
139int elf_read_relocs(struct ltelf *lte, Elf_Scn *scn, GElf_Shdr *shdr,
140		    struct vect *rela_vec);
141
142/* Read a given DT_ TAG from LTE.  Value is returned in *VALUEP.
143 * Returns 0 on success or a negative value on failure.  */
144int elf_load_dynamic_entry(struct ltelf *lte, int tag, GElf_Addr *valuep);
145
146/* Read, respectively, 1, 2, 4, or 8 bytes from Elf data at given
147 * OFFSET, and store it in *RETP.  Returns 0 on success or a negative
148 * value if there's not enough data.  */
149int elf_read_u8(Elf_Data *data, GElf_Xword offset, uint8_t *retp);
150int elf_read_u16(Elf_Data *data, GElf_Xword offset, uint16_t *retp);
151int elf_read_u32(Elf_Data *data, GElf_Xword offset, uint32_t *retp);
152int elf_read_u64(Elf_Data *data, GElf_Xword offset, uint64_t *retp);
153
154/* Read at most 64-bit quantity recorded in an ULEB128 variable-length
155 * encoding.  */
156int elf_read_uleb128(Elf_Data *data, GElf_Xword offset, uint64_t *retp);
157
158/* These are same as above, but update *OFFSET with the width
159 * of read datum.  */
160int elf_read_next_u8(Elf_Data *data, GElf_Xword *offset, uint8_t *retp);
161int elf_read_next_u16(Elf_Data *data, GElf_Xword *offset, uint16_t *retp);
162int elf_read_next_u32(Elf_Data *data, GElf_Xword *offset, uint32_t *retp);
163int elf_read_next_u64(Elf_Data *data, GElf_Xword *offset, uint64_t *retp);
164int elf_read_next_uleb128(Elf_Data *data, GElf_Xword *offset, uint64_t *retp);
165
166/* Return whether there's AMOUNT more bytes after OFFSET in DATA.  */
167int elf_can_read_next(Elf_Data *data, GElf_Xword offset, GElf_Xword amount);
168
169#if __WORDSIZE == 32
170#define PRI_ELF_ADDR		PRIx32
171#define GELF_ADDR_CAST(x)	(void *)(uint32_t)(x)
172#else
173#define PRI_ELF_ADDR		PRIx64
174#define GELF_ADDR_CAST(x)	(void *)(x)
175#endif
176
177#endif
178