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* This file is part of ltrace.
* Copyright (C) 2006,2010,2012,2013 Petr Machata, Red Hat Inc.
* Copyright (C) 2010 Zachary T Welch
* Copyright (C) 2001,2004,2007,2009 Juan Cespedes
* Copyright (C) 2006 Ian Wienand
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or (at your option) any later version.
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA
#ifndef LTRACE_ELF_H
#define LTRACE_ELF_H
#include <gelf.h>
#include <stdlib.h>
#include <callback.h>
#include "forward.h"
#include "sysdep.h"
#include "vect.h"
/* XXX Ok, the original idea was to separate the low-level ELF data
* from the abstract "struct library" object, but we use some of the
* following extensively in the back end. Not all though. So what we
* use should be move to struct library, and the rest of this
* structure maybe could be safely hidden in .c. How to integrate the
* arch-specific bits into struct library is unclear as of now. */
struct ltelf {
int fd;
Elf *elf;
GElf_Ehdr ehdr;
Elf_Data *dynsym;
size_t dynsym_count;
const char *dynstr;
GElf_Addr plt_addr;
GElf_Word plt_flags;
size_t plt_size;
Elf_Data *plt_data;
/* Vector of GElf_Rela with PLT relocations. */
struct vect plt_relocs;
Elf_Data *symtab;
const char *strtab;
const char *soname;
size_t symtab_count;
Elf_Data *opd;
GElf_Addr *opd_addr;
size_t opd_size;
GElf_Addr dyn_addr;
size_t dyn_sz;
GElf_Addr bias;
GElf_Addr entry_addr;
GElf_Addr base_addr;
struct arch_ltelf_data arch;
int ltelf_init(struct ltelf *lte, const char *filename);
void ltelf_destroy(struct ltelf *lte);
/* XXX is it possible to put breakpoints in VDSO and VSYSCALL
* pseudo-libraries? For now we assume that all libraries can be
* opened via a filesystem. BASE is ignored for ET_EXEC files. */
int ltelf_read_library(struct library *lib, struct process *proc,
const char *filename, GElf_Addr bias);
/* Create a library object representing the main binary. The entry
* point address is stored to *ENTRYP. */
struct library *ltelf_read_main_binary(struct process *proc, const char *path);
/* This is called for every PLT relocation R in ELF file LTE, that
* ltrace is about to add to a library constructed in process PROC.
* The corresponding PLT entry is for symbol called NAME, and it's
* I-th relocation in the file. *RET shall be initialized and
* symbol(s) corresponding to the given PLT entry will be added to the
* front. Returns 0 for success, or a negative value for failures.
* This calls os_elf_add_plt_entry and arch_elf_add_plt_entry in the
* background (see backend.h for documentation). The arch callback is
* called first. If it returns PLT_DEFAULT, the os callback is called
* next. If that returns PLT_DEFAULT, default_elf_add_plt_entry is
* called. */
int elf_add_plt_entry(struct process *proc, struct ltelf *lte,
const char *name, GElf_Rela *rela, size_t idx,
struct library_symbol **ret);
/* Create a default PLT entry. This can be used instead (or in
* addition to) returning PLT_DEFAULT from arch_elf_add_plt_entry.
* RET shall be initialized, the created symbol will be added to the
* beginning of the linked list at *RET. This function doesn't add
* the symbol to LTE. arch_elf_add_plt_entry has the chance to adjust
* symbol internals to its liking, and then return either PLT_DEFAULT
* or PLT_OK. */
int default_elf_add_plt_entry(struct process *proc, struct ltelf *lte,
const char *a_name, GElf_Rela *rela, size_t ndx,
struct library_symbol **ret);
Elf_Data *elf_loaddata(Elf_Scn *scn, GElf_Shdr *shdr);
/* The following three look for sections based on various criteria.
* They return 0 if there was no error, or a negative value if there
* was. If the section was found, it is returned in *TGT_SEC, and the
* header is stored to TGT_SHDR. If it wasn't found, *TGT_SEC is set
* to NULL. */
int elf_get_section_covering(struct ltelf *lte, GElf_Addr addr,
Elf_Scn **tgt_sec, GElf_Shdr *tgt_shdr);
int elf_get_section_type(struct ltelf *lte, GElf_Word type,
Elf_Scn **tgt_sec, GElf_Shdr *tgt_shdr);
int elf_get_section_named(struct ltelf *lte, const char *name,
Elf_Scn **tgt_sec, GElf_Shdr *tgt_shdr);
/* Iterate through all symbols in LTE. See callback.h for notes on
* iteration interfaces. START_AFTER is 0 in initial call. */
struct elf_each_symbol_t {
unsigned restart;
int status;
} elf_each_symbol(struct ltelf *lte, unsigned start_after,
enum callback_status (*cb)(GElf_Sym *symbol,
const char *name,
void *data),
void *data);
/* Read relocations from relocation section SCN with header SHDR and
* add them to RELA_VEC, which is a vector of GElf_Rela. Return 0 on
* success, or a negative value on failure. */
int elf_read_relocs(struct ltelf *lte, Elf_Scn *scn, GElf_Shdr *shdr,
struct vect *rela_vec);
/* Read a given DT_ TAG from LTE. Value is returned in *VALUEP.
* Returns 0 on success or a negative value on failure. */
int elf_load_dynamic_entry(struct ltelf *lte, int tag, GElf_Addr *valuep);
/* Read, respectively, 1, 2, 4, or 8 bytes from Elf data at given
* OFFSET, and store it in *RETP. Returns 0 on success or a negative
* value if there's not enough data. */
int elf_read_u8(Elf_Data *data, GElf_Xword offset, uint8_t *retp);
int elf_read_u16(Elf_Data *data, GElf_Xword offset, uint16_t *retp);
int elf_read_u32(Elf_Data *data, GElf_Xword offset, uint32_t *retp);
int elf_read_u64(Elf_Data *data, GElf_Xword offset, uint64_t *retp);
/* Read at most 64-bit quantity recorded in an ULEB128 variable-length
* encoding. */
int elf_read_uleb128(Elf_Data *data, GElf_Xword offset, uint64_t *retp);
/* These are same as above, but update *OFFSET with the width
* of read datum. */
int elf_read_next_u8(Elf_Data *data, GElf_Xword *offset, uint8_t *retp);
int elf_read_next_u16(Elf_Data *data, GElf_Xword *offset, uint16_t *retp);
int elf_read_next_u32(Elf_Data *data, GElf_Xword *offset, uint32_t *retp);
int elf_read_next_u64(Elf_Data *data, GElf_Xword *offset, uint64_t *retp);
int elf_read_next_uleb128(Elf_Data *data, GElf_Xword *offset, uint64_t *retp);
/* Return whether there's AMOUNT more bytes after OFFSET in DATA. */
int elf_can_read_next(Elf_Data *data, GElf_Xword offset, GElf_Xword amount);
#if __WORDSIZE == 32
#define PRI_ELF_ADDR PRIx32
#define GELF_ADDR_CAST(x) (void *)(uint32_t)(x)
#define PRI_ELF_ADDR PRIx64
#define GELF_ADDR_CAST(x) (void *)(x)