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/* Copyright 2013-2021 Free Software Foundation, Inc.
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 3 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
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <unistd.h>
#include <fcntl.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <assert.h>
#include "sym-file-loader.h"
#include <inttypes.h>
#include <ansidecl.h>
#include <elf/common.h>
#include <elf/external.h>
#ifdef TARGET_LP64
typedef Elf64_External_Phdr Elf_External_Phdr;
typedef Elf64_External_Ehdr Elf_External_Ehdr;
typedef Elf64_External_Shdr Elf_External_Shdr;
typedef Elf64_External_Sym Elf_External_Sym;
typedef uint64_t Elf_Addr;
#elif defined TARGET_ILP32
typedef Elf32_External_Phdr Elf_External_Phdr;
typedef Elf32_External_Ehdr Elf_External_Ehdr;
typedef Elf32_External_Shdr Elf_External_Shdr;
typedef Elf32_External_Sym Elf_External_Sym;
typedef uint32_t Elf_Addr;
#endif
#define GET(hdr, field) (\
sizeof ((hdr)->field) == 1 ? (uint64_t) (hdr)->field[0] : \
sizeof ((hdr)->field) == 2 ? (uint64_t) *(uint16_t *) (hdr)->field : \
sizeof ((hdr)->field) == 4 ? (uint64_t) *(uint32_t *) (hdr)->field : \
sizeof ((hdr)->field) == 8 ? *(uint64_t *) (hdr)->field : \
*(uint64_t *) NULL)
#define GETADDR(hdr, field) (\
sizeof ((hdr)->field) == sizeof (Elf_Addr) ? *(Elf_Addr *) (hdr)->field : \
*(Elf_Addr *) NULL)
struct segment
{
uint8_t *mapped_addr;
size_t mapped_size;
Elf_External_Phdr *phdr;
struct segment *next;
};
struct library
{
int fd;
Elf_External_Ehdr *ehdr;
struct segment *segments;
};
static Elf_External_Shdr *find_shdr (Elf_External_Ehdr *ehdr,
const char *section);
static int translate_offset (uint64_t file_offset, struct segment *seg,
void **addr);
#ifdef TARGET_LP64
uint8_t
elf_st_type (uint8_t st_info)
{
return ELF64_ST_TYPE (st_info);
}
#elif defined TARGET_ILP32
uint8_t
elf_st_type (uint8_t st_info)
{
return ELF32_ST_TYPE (st_info);
}
#endif
/* Load a program segment. */
static struct segment *
load (uint8_t *addr, Elf_External_Phdr *phdr, struct segment *tail_seg)
{
struct segment *seg = NULL;
uint8_t *mapped_addr = NULL;
size_t mapped_size = 0;
void *from = NULL;
void *to = NULL;
/* For the sake of simplicity all operations are permitted. */
unsigned perm = PROT_READ | PROT_WRITE | PROT_EXEC;
mapped_addr = (uint8_t *) mmap ((void *) GETADDR (phdr, p_vaddr),
GET (phdr, p_memsz), perm,
MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
assert (mapped_addr != MAP_FAILED);
mapped_size = GET (phdr, p_memsz);
from = (void *) (addr + GET (phdr, p_offset));
to = (void *) mapped_addr;
memcpy (to, from, GET (phdr, p_filesz));
seg = (struct segment *) malloc (sizeof (struct segment));
if (seg == 0)
return 0;
seg->mapped_addr = mapped_addr;
seg->mapped_size = mapped_size;
seg->phdr = phdr;
seg->next = 0;
if (tail_seg != 0)
tail_seg->next = seg;
return seg;
}
#ifdef __linux__
# define SELF_LINK "/proc/self/exe"
#elif defined NETBSD
# define SELF_LINK "/proc/curproc/exe"
#elif defined __OpenBSD__ || defined __FreeBSD__ || defined __DragonFly__
# define SELF_LINK "/proc/curproc/file"
#elif defined SunOS
# define SELF_LINK "/proc/self/path/a.out"
#endif
/* Like RPATH=$ORIGIN, return the dirname of the current
executable. */
static const char *
get_origin (void)
{
static char self_path[PATH_MAX];
static ssize_t self_path_len;
if (self_path_len == 0)
{
#ifdef SELF_LINK
self_path_len = readlink (SELF_LINK, self_path, PATH_MAX - 1);
if (self_path_len != -1)
{
char *dirsep;
self_path[self_path_len] = '\0';
dirsep = strrchr (self_path, '/');
*dirsep = '\0';
}
#else
self_path_len = -1;
#endif
}
if (self_path_len == -1)
return NULL;
else
return self_path;
}
/* Unload/unmap a segment. */
static void
unload (struct segment *seg)
{
munmap (seg->mapped_addr, seg->mapped_size);
free (seg);
}
void
unload_shlib (struct library *lib)
{
struct segment *seg, *next_seg;
for (seg = lib->segments; seg != NULL; seg = next_seg)
{
next_seg = seg->next;
unload (seg);
}
close (lib->fd);
free (lib);
}
/* Mini shared library loader. No reallocation
is performed for the sake of simplicity. */
struct library *
load_shlib (const char *file)
{
struct library *lib;
uint64_t i;
int fd = -1;
off_t fsize;
uint8_t *addr;
Elf_External_Ehdr *ehdr;
Elf_External_Phdr *phdr;
struct segment *head_seg = NULL;
struct segment *tail_seg = NULL;
const char *origin;
char *path;
/* Map the lib in memory for reading.
If the file name is relative, try looking it up relative to the
main executable's path. I.e., emulate RPATH=$ORIGIN. */
if (file[0] != '/')
{
origin = get_origin ();
if (origin == NULL)
{
fprintf (stderr, "get_origin not implemented.");
return NULL;
}
path = alloca (strlen (origin) + 1 + strlen (file) + 1);
sprintf (path, "%s/%s", origin, file);
fd = open (path, O_RDONLY);
}
if (fd < 0)
fd = open (file, O_RDONLY);
if (fd < 0)
{
perror ("fopen failed.");
return NULL;
}
fsize = lseek (fd, 0, SEEK_END);
if (fsize < 0)
{
perror ("lseek failed.");
return NULL;
}
addr = (uint8_t *) mmap (NULL, fsize, PROT_READ, MAP_PRIVATE, fd, 0);
if (addr == MAP_FAILED)
{
perror ("mmap failed.");
return NULL;
}
/* Check if the lib is an ELF file. */
ehdr = (Elf_External_Ehdr *) addr;
if (ehdr->e_ident[EI_MAG0] != ELFMAG0
|| ehdr->e_ident[EI_MAG1] != ELFMAG1
|| ehdr->e_ident[EI_MAG2] != ELFMAG2
|| ehdr->e_ident[EI_MAG3] != ELFMAG3)
{
printf ("Not an ELF file: %x\n", ehdr->e_ident[EI_MAG0]);
return NULL;
}
if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
{
if (sizeof (void *) != 4)
{
printf ("Architecture mismatch.");
return NULL;
}
}
else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
{
if (sizeof (void *) != 8)
{
printf ("Architecture mismatch.");
return NULL;
}
}
lib = malloc (sizeof (struct library));
if (lib == NULL)
{
printf ("malloc failed.");
return NULL;
}
lib->fd = fd;
/* Load the program segments. For the sake of simplicity
assume that no reallocation is needed. */
phdr = (Elf_External_Phdr *) (addr + GET (ehdr, e_phoff));
for (i = 0; i < GET (ehdr, e_phnum); i++, phdr++)
{
if (GET (phdr, p_type) == PT_LOAD)
{
struct segment *next_seg = load (addr, phdr, tail_seg);
if (next_seg == 0)
continue;
tail_seg = next_seg;
if (head_seg == 0)
head_seg = next_seg;
}
}
lib->ehdr = ehdr;
lib->segments = head_seg;
return lib;
}
int
get_text_addr (struct library *lib, void **text_addr)
{
Elf_External_Shdr *text;
/* Get the text section. */
text = find_shdr (lib->ehdr, ".text");
if (text == NULL)
return -1;
if (translate_offset (GET (text, sh_offset), lib->segments, text_addr)
!= 0)
return -1;
return 0;
}
/* Return the section-header table. */
Elf_External_Shdr *
find_shdrtab (Elf_External_Ehdr *ehdr)
{
return (Elf_External_Shdr *) (((uint8_t *) ehdr) + GET (ehdr, e_shoff));
}
/* Return the string table of the section headers. */
const char *
find_shstrtab (Elf_External_Ehdr *ehdr, uint64_t *size)
{
const Elf_External_Shdr *shdr;
const Elf_External_Shdr *shstr;
if (GET (ehdr, e_shnum) <= GET (ehdr, e_shstrndx))
{
printf ("The index of the string table is corrupt.");
return NULL;
}
shdr = find_shdrtab (ehdr);
shstr = &shdr[GET (ehdr, e_shstrndx)];
*size = GET (shstr, sh_size);
return ((const char *) ehdr) + GET (shstr, sh_offset);
}
/* Return the string table named SECTION. */
const char *
find_strtab (Elf_External_Ehdr *ehdr,
const char *section, uint64_t *strtab_size)
{
uint64_t shstrtab_size = 0;
const char *shstrtab;
uint64_t i;
const Elf_External_Shdr *shdr = find_shdrtab (ehdr);
/* Get the string table of the section headers. */
shstrtab = find_shstrtab (ehdr, &shstrtab_size);
if (shstrtab == NULL)
return NULL;
for (i = 0; i < GET (ehdr, e_shnum); i++)
{
uint64_t name = GET (shdr + i, sh_name);
if (GET (shdr + i, sh_type) == SHT_STRTAB && name <= shstrtab_size
&& strcmp ((const char *) &shstrtab[name], section) == 0)
{
*strtab_size = GET (shdr + i, sh_size);
return ((const char *) ehdr) + GET (shdr + i, sh_offset);
}
}
return NULL;
}
/* Return the section header named SECTION. */
static Elf_External_Shdr *
find_shdr (Elf_External_Ehdr *ehdr, const char *section)
{
uint64_t shstrtab_size = 0;
const char *shstrtab;
uint64_t i;
/* Get the string table of the section headers. */
shstrtab = find_shstrtab (ehdr, &shstrtab_size);
if (shstrtab == NULL)
return NULL;
Elf_External_Shdr *shdr = find_shdrtab (ehdr);
for (i = 0; i < GET (ehdr, e_shnum); i++)
{
uint64_t name = GET (shdr + i, sh_name);
if (name <= shstrtab_size)
{
if (strcmp ((const char *) &shstrtab[name], section) == 0)
return &shdr[i];
}
}
return NULL;
}
/* Return the symbol table. */
static Elf_External_Sym *
find_symtab (Elf_External_Ehdr *ehdr, uint64_t *symtab_size)
{
uint64_t i;
const Elf_External_Shdr *shdr = find_shdrtab (ehdr);
for (i = 0; i < GET (ehdr, e_shnum); i++)
{
if (GET (shdr + i, sh_type) == SHT_SYMTAB)
{
*symtab_size = GET (shdr + i, sh_size) / sizeof (Elf_External_Sym);
return (Elf_External_Sym *) (((const char *) ehdr) +
GET (shdr + i, sh_offset));
}
}
return NULL;
}
/* Translate a file offset to an address in a loaded segment. */
static int
translate_offset (uint64_t file_offset, struct segment *seg, void **addr)
{
while (seg)
{
uint64_t p_from, p_to;
Elf_External_Phdr *phdr = seg->phdr;
if (phdr == NULL)
{
seg = seg->next;
continue;
}
p_from = GET (phdr, p_offset);
p_to = p_from + GET (phdr, p_filesz);
if (p_from <= file_offset && file_offset < p_to)
{
*addr = (void *) (seg->mapped_addr + (file_offset - p_from));
return 0;
}
seg = seg->next;
}
return -1;
}
/* Lookup the address of FUNC. */
int
lookup_function (struct library *lib, const char *func, void **addr)
{
const char *strtab;
uint64_t strtab_size = 0;
Elf_External_Sym *symtab;
uint64_t symtab_size = 0;
uint64_t i;
Elf_External_Ehdr *ehdr = lib->ehdr;
struct segment *seg = lib->segments;
/* Get the string table for the symbols. */
strtab = find_strtab (ehdr, ".strtab", &strtab_size);
if (strtab == NULL)
{
printf (".strtab not found.");
return -1;
}
/* Get the symbol table. */
symtab = find_symtab (ehdr, &symtab_size);
if (symtab == NULL)
{
printf ("symbol table not found.");
return -1;
}
for (i = 0; i < symtab_size; i++)
{
Elf_External_Sym *sym = &symtab[i];
if (elf_st_type (GET (sym, st_info)) != STT_FUNC)
continue;
if (GET (sym, st_name) < strtab_size)
{
const char *name = &strtab[GET (sym, st_name)];
if (strcmp (name, func) == 0)
{
uint64_t offset = GET (sym, st_value);
return translate_offset (offset, seg, addr);
}
}
}
return -1;
}