/* Find the main ELF file for this module and open libelf on it.
When we return success, MOD->main.elf and MOD->main.bias are set up. */
void
internal_function
__libdwfl_getelf (Dwfl_Module *mod)
{
if (mod->main.elf != NULL /* Already done. */
|| mod->elferr != DWFL_E_NOERROR) /* Cached failure. */
return;
mod->main.fd = (*mod->dwfl->callbacks->find_elf) (MODCB_ARGS (mod),
&mod->main.name,
&mod->main.elf);
const bool fallback = mod->main.elf == NULL && mod->main.fd < 0;
mod->elferr = open_elf (mod, &mod->main);
if (mod->elferr != DWFL_E_NOERROR)
return;
if (!mod->main.valid)
{
/* Clear any explicitly reported build ID, just in case it was wrong.
We'll fetch it from the file when asked. */
free (mod->build_id_bits);
mod->build_id_bits = NULL;
mod->build_id_len = 0;
}
else if (fallback)
mod_verify_build_id (mod);
mod->main_bias = mod->e_type == ET_REL ? 0 : mod->low_addr - mod->main.vaddr;
}
void
ltrace_init(int argc, char **argv) {
struct opt_p_t *opt_p_tmp;
atexit(normal_exit);
signal(SIGINT, signal_exit); /* Detach processes when interrupted */
signal(SIGTERM, signal_exit); /* ... or killed */
argv = process_options(argc, argv);
init_global_config();
while (opt_F) {
/* If filename begins with ~, expand it to the user's home */
/* directory. This does not correctly handle ~yoda, but that */
/* isn't as bad as it seems because the shell will normally */
/* be doing the expansion for us; only the hardcoded */
/* ~/.ltrace.conf should ever use this code. */
if (opt_F->filename[0] == '~') {
char path[PATH_MAX];
char *home_dir = getenv("HOME");
if (home_dir) {
strncpy(path, home_dir, PATH_MAX - 1);
path[PATH_MAX - 1] = '\0';
strncat(path, opt_F->filename + 1,
PATH_MAX - strlen(path) - 1);
read_config_file(path);
}
} else {
read_config_file(opt_F->filename);
}
struct opt_F_t *next = opt_F->next;
if (opt_F->own_filename)
free(opt_F->filename);
free(opt_F);
opt_F = next;
}
if (command) {
/* Check that the binary ABI is supported before
* calling execute_program. */
struct ltelf lte = {};
open_elf(<e, command);
do_close_elf(<e);
pid_t pid = execute_program(command, argv);
struct Process *proc = open_program(command, pid);
if (proc == NULL) {
fprintf(stderr, "couldn't open program '%s': %s\n",
command, strerror(errno));
exit(EXIT_FAILURE);
}
trace_set_options(proc);
continue_process(pid);
}
opt_p_tmp = opt_p;
while (opt_p_tmp) {
open_pid(opt_p_tmp->pid);
opt_p_tmp = opt_p_tmp->next;
}
}
void
ltrace_init(int argc, char **argv) {
struct opt_p_t *opt_p_tmp;
#ifdef HAVE_PYTHON
Py_Initialize();
#endif
atexit(normal_exit);
signal(SIGINT, signal_exit); /* Detach processes when interrupted */
signal(SIGTERM, signal_exit); /* ... or killed */
argv = process_options(argc, argv);
while (opt_F) {
/* If filename begins with ~, expand it to the user's home */
/* directory. This does not correctly handle ~yoda, but that */
/* isn't as bad as it seems because the shell will normally */
/* be doing the expansion for us; only the hardcoded */
/* ~/.ltrace.conf should ever use this code. */
if (opt_F->filename[0] == '~') {
char path[PATH_MAX];
char *home_dir = getenv("HOME");
if (home_dir) {
strncpy(path, home_dir, PATH_MAX - 1);
path[PATH_MAX - 1] = '\0';
strncat(path, opt_F->filename + 1,
PATH_MAX - strlen(path) - 1);
read_config_file(path);
}
} else {
read_config_file(opt_F->filename);
}
opt_F = opt_F->next;
}
if (opt_e) {
struct opt_e_t *tmp = opt_e;
while (tmp) {
debug(1, "Option -e: %s\n", tmp->name);
tmp = tmp->next;
}
}
if (command) {
/* Check that the binary ABI is supported before
* calling execute_program. */
struct ltelf lte = {};
open_elf(<e, command);
open_program(command, execute_program(command, argv), 0);
}
opt_p_tmp = opt_p;
while (opt_p_tmp) {
open_pid(opt_p_tmp->pid);
opt_p_tmp = opt_p_tmp->next;
}
}
/* Find the main ELF file for this module and open libelf on it.
When we return success, MOD->main.elf and MOD->main.bias are set up. */
static void
find_file (Dwfl_Module *mod)
{
if (mod->main.elf != NULL /* Already done. */
|| mod->elferr != DWFL_E_NOERROR) /* Cached failure. */
return;
mod->main.fd = (*mod->dwfl->callbacks->find_elf) (MODCB_ARGS (mod),
&mod->main.name,
&mod->main.elf);
mod->elferr = open_elf (mod, &mod->main);
if (mod->elferr == DWFL_E_NOERROR && !mod->main.valid)
{
/* Clear any explicitly reported build ID, just in case it was wrong.
We'll fetch it from the file when asked. */
free (mod->build_id_bits);
mod->build_id_bits = NULL;
mod->build_id_len = 0;
}
}
/* Search an ELF file for a ".gnu_debuglink" section. */
static const char *
find_debuglink (Elf *elf, GElf_Word *crc)
{
size_t shstrndx;
if (elf_getshstrndx (elf, &shstrndx) < 0)
return NULL;
Elf_Scn *scn = NULL;
while ((scn = elf_nextscn (elf, scn)) != NULL)
{
GElf_Shdr shdr_mem;
GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
if (shdr == NULL)
return NULL;
const char *name = elf_strptr (elf, shstrndx, shdr->sh_name);
if (name == NULL)
return NULL;
if (!strcmp (name, ".gnu_debuglink"))
break;
}
if (scn == NULL)
return NULL;
/* Found the .gnu_debuglink section. Extract its contents. */
Elf_Data *rawdata = elf_rawdata (scn, NULL);
if (rawdata == NULL)
return NULL;
Elf_Data crcdata =
{
.d_type = ELF_T_WORD,
.d_buf = crc,
.d_size = sizeof *crc,
.d_version = EV_CURRENT,
};
Elf_Data conv =
{
.d_type = ELF_T_WORD,
.d_buf = rawdata->d_buf + rawdata->d_size - sizeof *crc,
.d_size = sizeof *crc,
.d_version = EV_CURRENT,
};
GElf_Ehdr ehdr_mem;
GElf_Ehdr *ehdr = gelf_getehdr (elf, &ehdr_mem);
if (ehdr == NULL)
return NULL;
Elf_Data *d = gelf_xlatetom (elf, &crcdata, &conv, ehdr->e_ident[EI_DATA]);
if (d == NULL)
return NULL;
assert (d == &crcdata);
return rawdata->d_buf;
}
/* Find the separate debuginfo file for this module and open libelf on it.
When we return success, MOD->debug is set up. */
static Dwfl_Error
find_debuginfo (Dwfl_Module *mod)
{
if (mod->debug.elf != NULL)
return DWFL_E_NOERROR;
GElf_Word debuglink_crc = 0;
const char *debuglink_file = find_debuglink (mod->main.elf, &debuglink_crc);
mod->debug.fd = (*mod->dwfl->callbacks->find_debuginfo) (MODCB_ARGS (mod),
mod->main.name,
debuglink_file,
debuglink_crc,
&mod->debug.name);
return open_elf (mod, &mod->debug);
}
/* Try to find a symbol table in FILE.
Returns DWFL_E_NOERROR if a proper one is found.
Returns DWFL_E_NO_SYMTAB if not, but still sets results for SHT_DYNSYM. */
static Dwfl_Error
load_symtab (struct dwfl_file *file, struct dwfl_file **symfile,
Elf_Scn **symscn, Elf_Scn **xndxscn,
size_t *syments, GElf_Word *strshndx)
{
bool symtab = false;
Elf_Scn *scn = NULL;
while ((scn = elf_nextscn (file->elf, scn)) != NULL)
{
GElf_Shdr shdr_mem, *shdr = gelf_getshdr (scn, &shdr_mem);
if (shdr != NULL)
switch (shdr->sh_type)
{
case SHT_SYMTAB:
symtab = true;
*symscn = scn;
*symfile = file;
*strshndx = shdr->sh_link;
*syments = shdr->sh_size / shdr->sh_entsize;
if (*xndxscn != NULL)
return DWFL_E_NOERROR;
break;
case SHT_DYNSYM:
if (symtab)
break;
/* Use this if need be, but keep looking for SHT_SYMTAB. */
*symscn = scn;
*symfile = file;
*strshndx = shdr->sh_link;
*syments = shdr->sh_size / shdr->sh_entsize;
break;
case SHT_SYMTAB_SHNDX:
*xndxscn = scn;
if (symtab)
return DWFL_E_NOERROR;
break;
default:
break;
}
}
if (symtab)
/* We found one, though no SHT_SYMTAB_SHNDX to go with it. */
return DWFL_E_NOERROR;
/* We found no SHT_SYMTAB, so any SHT_SYMTAB_SHNDX was bogus.
We might have found an SHT_DYNSYM and set *SYMSCN et al though. */
*xndxscn = NULL;
return DWFL_E_NO_SYMTAB;
}
/* Translate addresses into file offsets.
OFFS[*] start out zero and remain zero if unresolved. */
static void
find_offsets (Elf *elf, const GElf_Ehdr *ehdr, size_t n,
GElf_Addr addrs[n], GElf_Off offs[n])
{
size_t unsolved = n;
for (uint_fast16_t i = 0; i < ehdr->e_phnum; ++i)
{
GElf_Phdr phdr_mem;
GElf_Phdr *phdr = gelf_getphdr (elf, i, &phdr_mem);
if (phdr != NULL && phdr->p_type == PT_LOAD && phdr->p_memsz > 0)
for (size_t j = 0; j < n; ++j)
if (offs[j] == 0
&& addrs[j] >= phdr->p_vaddr
&& addrs[j] - phdr->p_vaddr < phdr->p_filesz)
{
offs[j] = addrs[j] - phdr->p_vaddr + phdr->p_offset;
if (--unsolved == 0)
break;
}
}
}
/* If the main file might have been prelinked, then we need to
discover the correct synchronization address between the main and
debug files. Because of prelink's section juggling, we cannot rely
on the address_sync computed from PT_LOAD segments (see open_elf).
We will attempt to discover a synchronization address based on the
section headers instead. But finding a section address that is
safe to use requires identifying which sections are SHT_PROGBITS.
We can do that in the main file, but in the debug file all the
allocated sections have been transformed into SHT_NOBITS so we have
lost the means to match them up correctly.
The only method left to us is to decode the .gnu.prelink_undo
section in the prelinked main file. This shows what the sections
looked like before prelink juggled them--when they still had a
direct correspondence to the debug file. */
static Dwfl_Error
find_prelink_address_sync (Dwfl_Module *mod, struct dwfl_file *file)
{
/* The magic section is only identified by name. */
size_t shstrndx;
if (elf_getshdrstrndx (mod->main.elf, &shstrndx) < 0)
return DWFL_E_LIBELF;
Elf_Scn *scn = NULL;
while ((scn = elf_nextscn (mod->main.elf, scn)) != NULL)
{
GElf_Shdr shdr_mem;
GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
if (unlikely (shdr == NULL))
return DWFL_E_LIBELF;
if (shdr->sh_type == SHT_PROGBITS
&& !(shdr->sh_flags & SHF_ALLOC)
&& shdr->sh_name != 0)
{
const char *secname = elf_strptr (mod->main.elf, shstrndx,
shdr->sh_name);
if (unlikely (secname == NULL))
return DWFL_E_LIBELF;
if (!strcmp (secname, ".gnu.prelink_undo"))
break;
}
}
if (scn == NULL)
/* There was no .gnu.prelink_undo section. */
return DWFL_E_NOERROR;
Elf_Data *undodata = elf_rawdata (scn, NULL);
if (unlikely (undodata == NULL))
return DWFL_E_LIBELF;
/* Decode the section. It consists of the original ehdr, phdrs,
and shdrs (but omits section 0). */
union
{
Elf32_Ehdr e32;
Elf64_Ehdr e64;
} ehdr;
Elf_Data dst =
{
.d_buf = &ehdr,
.d_size = sizeof ehdr,
.d_type = ELF_T_EHDR,
.d_version = EV_CURRENT
};
Elf_Data src = *undodata;
src.d_size = gelf_fsize (mod->main.elf, ELF_T_EHDR, 1, EV_CURRENT);
src.d_type = ELF_T_EHDR;
if (unlikely (gelf_xlatetom (mod->main.elf, &dst, &src,
elf_getident (mod->main.elf, NULL)[EI_DATA])
== NULL))
return DWFL_E_LIBELF;
size_t shentsize = gelf_fsize (mod->main.elf, ELF_T_SHDR, 1, EV_CURRENT);
size_t phentsize = gelf_fsize (mod->main.elf, ELF_T_PHDR, 1, EV_CURRENT);
uint_fast16_t phnum;
uint_fast16_t shnum;
if (ehdr.e32.e_ident[EI_CLASS] == ELFCLASS32)
{
if (ehdr.e32.e_shentsize != shentsize
|| ehdr.e32.e_phentsize != phentsize)
return DWFL_E_BAD_PRELINK;
phnum = ehdr.e32.e_phnum;
shnum = ehdr.e32.e_shnum;
}
else
{
if (ehdr.e64.e_shentsize != shentsize
|| ehdr.e64.e_phentsize != phentsize)
return DWFL_E_BAD_PRELINK;
phnum = ehdr.e64.e_phnum;
shnum = ehdr.e64.e_shnum;
}
/* Since prelink does not store the zeroth section header in the undo
section, it cannot support SHN_XINDEX encoding. */
if (unlikely (shnum >= SHN_LORESERVE)
|| unlikely (undodata->d_size != (src.d_size
+ phnum * phentsize
+ (shnum - 1) * shentsize)))
return DWFL_E_BAD_PRELINK;
/* We look at the allocated SHT_PROGBITS (or SHT_NOBITS) sections. (Most
every file will have some SHT_PROGBITS sections, but it's possible to
have one with nothing but .bss, i.e. SHT_NOBITS.) The special sections
that can be moved around have different sh_type values--except for
.interp, the section that became the PT_INTERP segment. So we exclude
the SHT_PROGBITS section whose address matches the PT_INTERP p_vaddr.
For this reason, we must examine the phdrs first to find PT_INTERP. */
GElf_Addr main_interp = 0;
{
size_t main_phnum;
if (unlikely (elf_getphdrnum (mod->main.elf, &main_phnum)))
return DWFL_E_LIBELF;
for (size_t i = 0; i < main_phnum; ++i)
{
GElf_Phdr phdr;
if (unlikely (gelf_getphdr (mod->main.elf, i, &phdr) == NULL))
return DWFL_E_LIBELF;
if (phdr.p_type == PT_INTERP)
{
main_interp = phdr.p_vaddr;
break;
}
}
}
src.d_buf += src.d_size;
src.d_type = ELF_T_PHDR;
src.d_size = phnum * phentsize;
GElf_Addr undo_interp = 0;
bool class32 = ehdr.e32.e_ident[EI_CLASS] == ELFCLASS32;
{
size_t phdr_size = class32 ? sizeof (Elf32_Phdr) : sizeof (Elf64_Phdr);
if (unlikely (phnum > SIZE_MAX / phdr_size))
return DWFL_E_NOMEM;
const size_t phdrs_bytes = phnum * phdr_size;
void *phdrs = malloc (phdrs_bytes);
if (unlikely (phdrs == NULL))
return DWFL_E_NOMEM;
dst.d_buf = phdrs;
dst.d_size = phdrs_bytes;
if (unlikely (gelf_xlatetom (mod->main.elf, &dst, &src,
ehdr.e32.e_ident[EI_DATA]) == NULL))
{
free (phdrs);
return DWFL_E_LIBELF;
}
if (class32)
{
Elf32_Phdr (*p32)[phnum] = phdrs;
for (uint_fast16_t i = 0; i < phnum; ++i)
if ((*p32)[i].p_type == PT_INTERP)
{
undo_interp = (*p32)[i].p_vaddr;
break;
}
}
else
{
Elf64_Phdr (*p64)[phnum] = phdrs;
for (uint_fast16_t i = 0; i < phnum; ++i)
if ((*p64)[i].p_type == PT_INTERP)
{
undo_interp = (*p64)[i].p_vaddr;
break;
}
}
free (phdrs);
}
if (unlikely ((main_interp == 0) != (undo_interp == 0)))
return DWFL_E_BAD_PRELINK;
src.d_buf += src.d_size;
src.d_type = ELF_T_SHDR;
src.d_size = gelf_fsize (mod->main.elf, ELF_T_SHDR, shnum - 1, EV_CURRENT);
size_t shdr_size = class32 ? sizeof (Elf32_Shdr) : sizeof (Elf64_Shdr);
if (unlikely (shnum - 1 > SIZE_MAX / shdr_size))
return DWFL_E_NOMEM;
const size_t shdrs_bytes = (shnum - 1) * shdr_size;
void *shdrs = malloc (shdrs_bytes);
if (unlikely (shdrs == NULL))
return DWFL_E_NOMEM;
dst.d_buf = shdrs;
dst.d_size = shdrs_bytes;
if (unlikely (gelf_xlatetom (mod->main.elf, &dst, &src,
ehdr.e32.e_ident[EI_DATA]) == NULL))
{
free (shdrs);
return DWFL_E_LIBELF;
}
/* Now we can look at the original section headers of the main file
before it was prelinked. First we'll apply our method to the main
file sections as they are after prelinking, to calculate the
synchronization address of the main file. Then we'll apply that
same method to the saved section headers, to calculate the matching
synchronization address of the debug file.
The method is to consider SHF_ALLOC sections that are either
SHT_PROGBITS or SHT_NOBITS, excluding the section whose sh_addr
matches the PT_INTERP p_vaddr. The special sections that can be
moved by prelink have other types, except for .interp (which
becomes PT_INTERP). The "real" sections cannot move as such, but
.bss can be split into .dynbss and .bss, with the total memory
image remaining the same but being spread across the two sections.
So we consider the highest section end, which still matches up. */
GElf_Addr highest;
inline void consider_shdr (GElf_Addr interp,
GElf_Word sh_type,
GElf_Xword sh_flags,
GElf_Addr sh_addr,
GElf_Xword sh_size)
{
if ((sh_flags & SHF_ALLOC)
&& ((sh_type == SHT_PROGBITS && sh_addr != interp)
|| sh_type == SHT_NOBITS))
{
const GElf_Addr sh_end = sh_addr + sh_size;
if (sh_end > highest)
highest = sh_end;
}
}
highest = 0;
scn = NULL;
while ((scn = elf_nextscn (mod->main.elf, scn)) != NULL)
{
GElf_Shdr sh_mem;
GElf_Shdr *sh = gelf_getshdr (scn, &sh_mem);
if (unlikely (sh == NULL))
{
free (shdrs);
return DWFL_E_LIBELF;
}
consider_shdr (main_interp, sh->sh_type, sh->sh_flags,
sh->sh_addr, sh->sh_size);
}
if (highest > mod->main.vaddr)
{
mod->main.address_sync = highest;
highest = 0;
if (class32)
{
Elf32_Shdr (*s32)[shnum - 1] = shdrs;
for (size_t i = 0; i < shnum - 1; ++i)
consider_shdr (undo_interp, (*s32)[i].sh_type,
(*s32)[i].sh_flags, (*s32)[i].sh_addr,
(*s32)[i].sh_size);
}
else
{
Elf64_Shdr (*s64)[shnum - 1] = shdrs;
for (size_t i = 0; i < shnum - 1; ++i)
consider_shdr (undo_interp, (*s64)[i].sh_type,
(*s64)[i].sh_flags, (*s64)[i].sh_addr,
(*s64)[i].sh_size);
}
if (highest > file->vaddr)
file->address_sync = highest;
else
{
free (shdrs);
return DWFL_E_BAD_PRELINK;
}
}
free (shdrs);
return DWFL_E_NOERROR;
}
/* Find the separate debuginfo file for this module and open libelf on it.
When we return success, MOD->debug is set up. */
static Dwfl_Error
find_debuginfo (Dwfl_Module *mod)
{
if (mod->debug.elf != NULL)
return DWFL_E_NOERROR;
GElf_Word debuglink_crc = 0;
const char *debuglink_file;
debuglink_file = INTUSE(dwelf_elf_gnu_debuglink) (mod->main.elf,
&debuglink_crc);
mod->debug.fd = (*mod->dwfl->callbacks->find_debuginfo) (MODCB_ARGS (mod),
mod->main.name,
debuglink_file,
debuglink_crc,
&mod->debug.name);
Dwfl_Error result = open_elf (mod, &mod->debug);
if (result == DWFL_E_NOERROR && mod->debug.address_sync != 0)
result = find_prelink_address_sync (mod, &mod->debug);
return result;
}
/* Try to find the alternative debug link for the given DWARF and set
it if found. Only called when mod->dw is already setup but still
might need an alternative (dwz multi) debug file. filename is either
the main or debug name from which the Dwarf was created. */
static void
find_debug_altlink (Dwfl_Module *mod, const char *filename)
{
assert (mod->dw != NULL);
const char *altname;
const void *build_id;
ssize_t build_id_len = INTUSE(dwelf_dwarf_gnu_debugaltlink) (mod->dw,
&altname,
&build_id);
if (build_id_len > 0)
{
/* We could store altfile in the module, but don't really need it. */
char *altfile = NULL;
mod->alt_fd = (*mod->dwfl->callbacks->find_debuginfo) (MODCB_ARGS (mod),
filename,
altname,
0,
&altfile);
/* The (internal) callbacks might just set mod->alt_elf directly
because they open the Elf anyway for sanity checking.
Otherwise open either the given file name or use the fd
returned. */
Dwfl_Error error = open_elf_file (&mod->alt_elf, &mod->alt_fd,
&altfile);
if (error == DWFL_E_NOERROR)
{
mod->alt = INTUSE(dwarf_begin_elf) (mod->alt_elf,
DWARF_C_READ, NULL);
if (mod->alt == NULL)
{
elf_end (mod->alt_elf);
mod->alt_elf = NULL;
close (mod->alt_fd);
mod->alt_fd = -1;
}
else
dwarf_setalt (mod->dw, mod->alt);
}
free (altfile); /* See above, we don't really need it. */
}
}
static int try_load_elf(elf_prog_t *prog, long bailout)
{
int err, has_interp;
char i_filename[PATH_MAX]; /* so much easier */
elf_bin_t *bin=&prog->bin, *interp=&prog->interp;
if ( (err = open_elf(prog->filename, bin)) < 0 )
return err;
Elf32_Phdr phdr_bin_tmp[bin->hdr.e_phnum];
bin->phdr = phdr_bin_tmp; /* point to mmapped region later if any */
if (read_at(bin->fd, bin->hdr.e_phoff, bin->phdr,
sizeof(*bin->phdr)*bin->hdr.e_phnum) !=
(long)sizeof(*bin->phdr)*bin->hdr.e_phnum)
return -EIO;
if ( (err = find_interp_name(bin, i_filename, PATH_MAX)) < 0 )
return err;
has_interp = err;
interp->phdr = NULL;
interp->hdr.e_phnum = 0;
if ( has_interp && (err = open_elf(i_filename, interp)) < 0)
return err;
Elf32_Phdr phdr_interp_tmp[interp->hdr.e_phnum];
if ( has_interp )
{
interp->phdr = phdr_interp_tmp; /* point to mmapped region later */
if (read_at(interp->fd, interp->hdr.e_phoff, interp->phdr,
sizeof(*interp->phdr)*interp->hdr.e_phnum) !=
(long)sizeof(*interp->phdr)*interp->hdr.e_phnum)
return -EIO;
}
/* point of no return */
if (bailout)
return 0;
int stack_prot = get_stack_prot(bin);
err = alloc_user_stack(prog, stack_prot);
if ( mmap_binary(bin, 0) & PG_MASK )
raise(SIGKILL);
if ( has_interp && (mmap_binary(interp, 1) & PG_MASK) )
raise(SIGKILL);
/* set up stack */
bin->phdr = mapped_phdr(bin);
if ( has_interp )
interp->phdr = mapped_phdr(interp);
init_user_stack(prog, stack_prot);
if (err & PG_MASK)
raise(SIGKILL);
if (has_interp)
prog->entry = (void *)(interp->base + interp->hdr.e_entry);
else
prog->entry = (void *)(bin->base + bin->hdr.e_entry);
return 0;
}
/**
* Extract the ELF interpreter of @path in @u_interp. This function
* returns -errno if an error occured, 1 if a ELF interpreter was
* found and extracted, otherwise 0.
*/
int extract_elf_interp(struct tracee_info *tracee,
const char *t_path,
char u_interp[PATH_MAX],
char argument[ARG_MAX])
{
union elf_header elf_header;
union program_header program_header;
size_t extra_size;
int status;
int fd;
uint64_t segment_offset;
uint64_t segment_size;
u_interp[0] = '\0';
argument[0] = '\0';
fd = open_elf(t_path, &elf_header);
if (fd < 0)
return fd;
status = find_program_header(fd, &elf_header, &program_header,
PT_INTERP, (uint64_t) -1);
if (status < 0) {
status = -EACCES;
goto end;
}
if (status == 0)
goto end;
segment_offset = PROGRAM_FIELD(elf_header, program_header, offset);
segment_size = PROGRAM_FIELD(elf_header, program_header, filesz);
status = (int) lseek(fd, segment_offset, SEEK_SET);
if (status < 0) {
status = -EACCES;
goto end;
}
/* If we are executing a host binary under a QEMUlated
* environment, we have to access its ELF interpreter through
* the "host-rootfs" binding. Technically it means the host
* ELF interpreter "/lib/ld-linux.so.2" is accessed as
* "${host_rootfs}/lib/ld-linux.so.2" to avoid conflict with
* the guest "/lib/ld-linux.so.2". */
if (config.qemu) {
strcpy(u_interp, config.host_rootfs);
extra_size = strlen(config.host_rootfs);
}
else
extra_size = 0;
if (segment_size + extra_size >= PATH_MAX) {
status = -EACCES;
goto end;
}
status = read(fd, u_interp + extra_size, segment_size);
if (status < 0) {
status = -EACCES;
goto end;
}
u_interp[segment_size + extra_size] = '\0';
end:
close(fd);
/* Delayed error handling */
if (status < 0)
return status;
/* Is there an INTERP entry? */
if (u_interp[0] == '\0')
return 0;
else
return 1;
}
int
do_init_elf(struct ltelf *lte, const char *filename) {
int i;
GElf_Addr relplt_addr = 0;
size_t relplt_size = 0;
debug(DEBUG_FUNCTION, "do_init_elf(filename=%s)", filename);
debug(1, "Reading ELF from %s...", filename);
if (open_elf(lte, filename) < 0)
return -1;
Elf_Data *plt_data = NULL;
GElf_Addr ppcgot = 0;
for (i = 1; i < lte->ehdr.e_shnum; ++i) {
Elf_Scn *scn;
GElf_Shdr shdr;
const char *name;
scn = elf_getscn(lte->elf, i);
if (scn == NULL || gelf_getshdr(scn, &shdr) == NULL)
error(EXIT_FAILURE, 0,
"Couldn't get section header from \"%s\"",
filename);
name = elf_strptr(lte->elf, lte->ehdr.e_shstrndx, shdr.sh_name);
if (name == NULL)
error(EXIT_FAILURE, 0,
"Couldn't get section header from \"%s\"",
filename);
if (shdr.sh_type == SHT_SYMTAB) {
Elf_Data *data;
lte->symtab = elf_getdata(scn, NULL);
lte->symtab_count = shdr.sh_size / shdr.sh_entsize;
if ((lte->symtab == NULL
|| elf_getdata(scn, lte->symtab) != NULL)
&& opt_x != NULL)
error(EXIT_FAILURE, 0,
"Couldn't get .symtab data from \"%s\"",
filename);
scn = elf_getscn(lte->elf, shdr.sh_link);
if (scn == NULL || gelf_getshdr(scn, &shdr) == NULL)
error(EXIT_FAILURE, 0,
"Couldn't get section header from \"%s\"",
filename);
data = elf_getdata(scn, NULL);
if (data == NULL || elf_getdata(scn, data) != NULL
|| shdr.sh_size != data->d_size || data->d_off)
error(EXIT_FAILURE, 0,
"Couldn't get .strtab data from \"%s\"",
filename);
lte->strtab = data->d_buf;
} else if (shdr.sh_type == SHT_DYNSYM) {
Elf_Data *data;
lte->dynsym = elf_getdata(scn, NULL);
lte->dynsym_count = shdr.sh_size / shdr.sh_entsize;
if (lte->dynsym == NULL
|| elf_getdata(scn, lte->dynsym) != NULL)
error(EXIT_FAILURE, 0,
"Couldn't get .dynsym data from \"%s\"",
filename);
scn = elf_getscn(lte->elf, shdr.sh_link);
if (scn == NULL || gelf_getshdr(scn, &shdr) == NULL)
error(EXIT_FAILURE, 0,
"Couldn't get section header from \"%s\"",
filename);
data = elf_getdata(scn, NULL);
if (data == NULL || elf_getdata(scn, data) != NULL
|| shdr.sh_size != data->d_size || data->d_off)
error(EXIT_FAILURE, 0,
"Couldn't get .dynstr data from \"%s\"",
filename);
lte->dynstr = data->d_buf;
} else if (shdr.sh_type == SHT_DYNAMIC) {
Elf_Data *data;
size_t j;
lte->dyn_addr = shdr.sh_addr;
lte->dyn_sz = shdr.sh_size;
data = elf_getdata(scn, NULL);
if (data == NULL || elf_getdata(scn, data) != NULL)
error(EXIT_FAILURE, 0,
"Couldn't get .dynamic data from \"%s\"",
filename);
for (j = 0; j < shdr.sh_size / shdr.sh_entsize; ++j) {
GElf_Dyn dyn;
if (gelf_getdyn(data, j, &dyn) == NULL)
error(EXIT_FAILURE, 0,
"Couldn't get .dynamic data from \"%s\"",
filename);
#ifdef __mips__
/**
MIPS ABI Supplement:
DT_PLTGOT This member holds the address of the .got section.
DT_MIPS_SYMTABNO This member holds the number of entries in the
.dynsym section.
DT_MIPS_LOCAL_GOTNO This member holds the number of local global
offset table entries.
DT_MIPS_GOTSYM This member holds the index of the first dyamic
symbol table entry that corresponds to an entry in the gobal offset
table.
*/
if(dyn.d_tag==DT_PLTGOT){
lte->pltgot_addr=dyn.d_un.d_ptr;
}
if(dyn.d_tag==DT_MIPS_LOCAL_GOTNO){
lte->mips_local_gotno=dyn.d_un.d_val;
}
if(dyn.d_tag==DT_MIPS_GOTSYM){
lte->mips_gotsym=dyn.d_un.d_val;
}
#endif // __mips__
if (dyn.d_tag == DT_JMPREL)
relplt_addr = dyn.d_un.d_ptr;
else if (dyn.d_tag == DT_PLTRELSZ)
relplt_size = dyn.d_un.d_val;
else if (dyn.d_tag == DT_PPC_GOT) {
ppcgot = dyn.d_un.d_val;
debug(1, "ppcgot %#" PRIx64, ppcgot);
}
}
} else if (shdr.sh_type == SHT_HASH) {
Elf_Data *data;
size_t j;
lte->hash_type = SHT_HASH;
data = elf_getdata(scn, NULL);
if (data == NULL || elf_getdata(scn, data) != NULL
|| data->d_off || data->d_size != shdr.sh_size)
error(EXIT_FAILURE, 0,
"Couldn't get .hash data from \"%s\"",
filename);
if (shdr.sh_entsize == 4) {
/* Standard conforming ELF. */
if (data->d_type != ELF_T_WORD)
error(EXIT_FAILURE, 0,
"Couldn't get .hash data from \"%s\"",
filename);
lte->hash = (Elf32_Word *) data->d_buf;
} else if (shdr.sh_entsize == 8) {
/* Alpha or s390x. */
Elf32_Word *dst, *src;
size_t hash_count = data->d_size / 8;
lte->hash = (Elf32_Word *)
malloc(hash_count * sizeof(Elf32_Word));
if (lte->hash == NULL)
error(EXIT_FAILURE, 0,
"Couldn't convert .hash section from \"%s\"",
filename);
lte->lte_flags |= LTE_HASH_MALLOCED;
dst = lte->hash;
src = (Elf32_Word *) data->d_buf;
if ((data->d_type == ELF_T_WORD
&& __BYTE_ORDER == __BIG_ENDIAN)
|| (data->d_type == ELF_T_XWORD
&& lte->ehdr.e_ident[EI_DATA] ==
ELFDATA2MSB))
++src;
for (j = 0; j < hash_count; ++j, src += 2)
*dst++ = *src;
} else
error(EXIT_FAILURE, 0,
"Unknown .hash sh_entsize in \"%s\"",
filename);
} else if (shdr.sh_type == SHT_GNU_HASH
&& lte->hash == NULL) {
Elf_Data *data;
lte->hash_type = SHT_GNU_HASH;
if (shdr.sh_entsize != 0
&& shdr.sh_entsize != 4) {
error(EXIT_FAILURE, 0,
".gnu.hash sh_entsize in \"%s\" "
"should be 4, but is %#" PRIx64,
filename, shdr.sh_entsize);
}
data = loaddata(scn, &shdr);
if (data == NULL)
error(EXIT_FAILURE, 0,
"Couldn't get .gnu.hash data from \"%s\"",
filename);
lte->hash = (Elf32_Word *) data->d_buf;
} else if (shdr.sh_type == SHT_PROGBITS
|| shdr.sh_type == SHT_NOBITS) {
if (strcmp(name, ".plt") == 0) {
lte->plt_addr = shdr.sh_addr;
lte->plt_size = shdr.sh_size;
if (shdr.sh_flags & SHF_EXECINSTR) {
lte->lte_flags |= LTE_PLT_EXECUTABLE;
}
if (lte->ehdr.e_machine == EM_PPC) {
plt_data = loaddata(scn, &shdr);
if (plt_data == NULL)
fprintf(stderr,
"Can't load .plt data\n");
}
}
#ifdef ARCH_SUPPORTS_OPD
else if (strcmp(name, ".opd") == 0) {
lte->opd_addr = (GElf_Addr *) (long) shdr.sh_addr;
lte->opd_size = shdr.sh_size;
lte->opd = elf_rawdata(scn, NULL);
}
#endif
}
}
if (lte->dynsym == NULL || lte->dynstr == NULL)
error(EXIT_FAILURE, 0,
"Couldn't find .dynsym or .dynstr in \"%s\"", filename);
if (!relplt_addr || !lte->plt_addr) {
debug(1, "%s has no PLT relocations", filename);
lte->relplt = NULL;
lte->relplt_count = 0;
} else if (relplt_size == 0) {
debug(1, "%s has unknown PLT size", filename);
lte->relplt = NULL;
lte->relplt_count = 0;
} else {
if (lte->ehdr.e_machine == EM_PPC) {
GElf_Addr glink_vma
= get_glink_vma(lte, ppcgot, plt_data);
assert (relplt_size % 12 == 0);
size_t count = relplt_size / 12; // size of RELA entry
lte->plt_stub_vma = glink_vma
- (GElf_Addr)count * PPC_PLT_STUB_SIZE;
debug(1, "stub_vma is %#" PRIx64, lte->plt_stub_vma);
}
for (i = 1; i < lte->ehdr.e_shnum; ++i) {
Elf_Scn *scn;
GElf_Shdr shdr;
scn = elf_getscn(lte->elf, i);
if (scn == NULL || gelf_getshdr(scn, &shdr) == NULL)
error(EXIT_FAILURE, 0,
"Couldn't get section header from \"%s\"",
filename);
if (shdr.sh_addr == relplt_addr
&& shdr.sh_size == relplt_size) {
lte->relplt = elf_getdata(scn, NULL);
lte->relplt_count =
shdr.sh_size / shdr.sh_entsize;
if (lte->relplt == NULL
|| elf_getdata(scn, lte->relplt) != NULL)
error(EXIT_FAILURE, 0,
"Couldn't get .rel*.plt data from \"%s\"",
filename);
break;
}
}
if (i == lte->ehdr.e_shnum)
error(EXIT_FAILURE, 0,
"Couldn't find .rel*.plt section in \"%s\"",
filename);
debug(1, "%s %zd PLT relocations", filename, lte->relplt_count);
}
return 0;
}
/* Search an ELF file for a ".gnu_debuglink" section. */
static const char *
find_debuglink (Elf *elf, GElf_Word *crc)
{
size_t shstrndx;
if (elf_getshdrstrndx (elf, &shstrndx) < 0)
return NULL;
Elf_Scn *scn = NULL;
while ((scn = elf_nextscn (elf, scn)) != NULL)
{
GElf_Shdr shdr_mem;
GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
if (shdr == NULL)
return NULL;
const char *name = elf_strptr (elf, shstrndx, shdr->sh_name);
if (name == NULL)
return NULL;
if (!strcmp (name, ".gnu_debuglink"))
break;
}
if (scn == NULL)
return NULL;
/* Found the .gnu_debuglink section. Extract its contents. */
Elf_Data *rawdata = elf_rawdata (scn, NULL);
if (rawdata == NULL)
return NULL;
Elf_Data crcdata =
{
.d_type = ELF_T_WORD,
.d_buf = crc,
.d_size = sizeof *crc,
.d_version = EV_CURRENT,
};
Elf_Data conv =
{
.d_type = ELF_T_WORD,
.d_buf = rawdata->d_buf + rawdata->d_size - sizeof *crc,
.d_size = sizeof *crc,
.d_version = EV_CURRENT,
};
GElf_Ehdr ehdr_mem;
GElf_Ehdr *ehdr = gelf_getehdr (elf, &ehdr_mem);
if (ehdr == NULL)
return NULL;
Elf_Data *d = gelf_xlatetom (elf, &crcdata, &conv, ehdr->e_ident[EI_DATA]);
if (d == NULL)
return NULL;
assert (d == &crcdata);
return rawdata->d_buf;
}
/* If the main file might have been prelinked, then we need to
discover the correct synchronization address between the main and
debug files. Because of prelink's section juggling, we cannot rely
on the address_sync computed from PT_LOAD segments (see open_elf).
We will attempt to discover a synchronization address based on the
section headers instead. But finding a section address that is
safe to use requires identifying which sections are SHT_PROGBITS.
We can do that in the main file, but in the debug file all the
allocated sections have been transformed into SHT_NOBITS so we have
lost the means to match them up correctly.
The only method left to us is to decode the .gnu.prelink_undo
section in the prelinked main file. This shows what the sections
looked like before prelink juggled them--when they still had a
direct correspondence to the debug file. */
static Dwfl_Error
find_prelink_address_sync (Dwfl_Module *mod, struct dwfl_file *file)
{
/* The magic section is only identified by name. */
size_t shstrndx;
if (elf_getshdrstrndx (mod->main.elf, &shstrndx) < 0)
return DWFL_E_LIBELF;
Elf_Scn *scn = NULL;
while ((scn = elf_nextscn (mod->main.elf, scn)) != NULL)
{
GElf_Shdr shdr_mem;
GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
if (unlikely (shdr == NULL))
return DWFL_E_LIBELF;
if (shdr->sh_type == SHT_PROGBITS
&& !(shdr->sh_flags & SHF_ALLOC)
&& shdr->sh_name != 0)
{
const char *secname = elf_strptr (mod->main.elf, shstrndx,
shdr->sh_name);
if (unlikely (secname == NULL))
return DWFL_E_LIBELF;
if (!strcmp (secname, ".gnu.prelink_undo"))
break;
}
}
if (scn == NULL)
/* There was no .gnu.prelink_undo section. */
return DWFL_E_NOERROR;
Elf_Data *undodata = elf_rawdata (scn, NULL);
if (unlikely (undodata == NULL))
return DWFL_E_LIBELF;
/* Decode the section. It consists of the original ehdr, phdrs,
and shdrs (but omits section 0). */
union
{
Elf32_Ehdr e32;
Elf64_Ehdr e64;
} ehdr;
Elf_Data dst =
{
.d_buf = &ehdr,
.d_size = sizeof ehdr,
.d_type = ELF_T_EHDR,
.d_version = EV_CURRENT
};
Elf_Data src = *undodata;
src.d_size = gelf_fsize (mod->main.elf, ELF_T_EHDR, 1, EV_CURRENT);
src.d_type = ELF_T_EHDR;
if (unlikely (gelf_xlatetom (mod->main.elf, &dst, &src,
elf_getident (mod->main.elf, NULL)[EI_DATA])
== NULL))
return DWFL_E_LIBELF;
size_t shentsize = gelf_fsize (mod->main.elf, ELF_T_SHDR, 1, EV_CURRENT);
size_t phentsize = gelf_fsize (mod->main.elf, ELF_T_PHDR, 1, EV_CURRENT);
uint_fast16_t phnum;
uint_fast16_t shnum;
if (ehdr.e32.e_ident[EI_CLASS] == ELFCLASS32)
{
if (ehdr.e32.e_shentsize != shentsize
|| ehdr.e32.e_phentsize != phentsize)
return DWFL_E_BAD_PRELINK;
phnum = ehdr.e32.e_phnum;
shnum = ehdr.e32.e_shnum;
}
else
{
if (ehdr.e64.e_shentsize != shentsize
|| ehdr.e64.e_phentsize != phentsize)
return DWFL_E_BAD_PRELINK;
phnum = ehdr.e64.e_phnum;
shnum = ehdr.e64.e_shnum;
}
/* Since prelink does not store the zeroth section header in the undo
section, it cannot support SHN_XINDEX encoding. */
if (unlikely (shnum >= SHN_LORESERVE)
|| unlikely (undodata->d_size != (src.d_size
+ phnum * phentsize
+ (shnum - 1) * shentsize)))
return DWFL_E_BAD_PRELINK;
/* We look at the allocated SHT_PROGBITS (or SHT_NOBITS) sections. (Most
every file will have some SHT_PROGBITS sections, but it's possible to
have one with nothing but .bss, i.e. SHT_NOBITS.) The special sections
that can be moved around have different sh_type values--except for
.interp, the section that became the PT_INTERP segment. So we exclude
the SHT_PROGBITS section whose address matches the PT_INTERP p_vaddr.
For this reason, we must examine the phdrs first to find PT_INTERP. */
GElf_Addr main_interp = 0;
{
size_t main_phnum;
if (unlikely (elf_getphdrnum (mod->main.elf, &main_phnum)))
return DWFL_E_LIBELF;
for (size_t i = 0; i < main_phnum; ++i)
{
GElf_Phdr phdr;
if (unlikely (gelf_getphdr (mod->main.elf, i, &phdr) == NULL))
return DWFL_E_LIBELF;
if (phdr.p_type == PT_INTERP)
{
main_interp = phdr.p_vaddr;
break;
}
}
}
src.d_buf += src.d_size;
src.d_type = ELF_T_PHDR;
src.d_size = phnum * phentsize;
GElf_Addr undo_interp = 0;
{
union
{
Elf32_Phdr p32[phnum];
Elf64_Phdr p64[phnum];
} phdr;
dst.d_buf = &phdr;
dst.d_size = sizeof phdr;
if (unlikely (gelf_xlatetom (mod->main.elf, &dst, &src,
ehdr.e32.e_ident[EI_DATA]) == NULL))
return DWFL_E_LIBELF;
if (ehdr.e32.e_ident[EI_CLASS] == ELFCLASS32)
{
for (uint_fast16_t i = 0; i < phnum; ++i)
if (phdr.p32[i].p_type == PT_INTERP)
{
undo_interp = phdr.p32[i].p_vaddr;
break;
}
}
else
{
for (uint_fast16_t i = 0; i < phnum; ++i)
if (phdr.p64[i].p_type == PT_INTERP)
{
undo_interp = phdr.p64[i].p_vaddr;
break;
}
}
}
if (unlikely ((main_interp == 0) != (undo_interp == 0)))
return DWFL_E_BAD_PRELINK;
src.d_buf += src.d_size;
src.d_type = ELF_T_SHDR;
src.d_size = gelf_fsize (mod->main.elf, ELF_T_SHDR, shnum - 1, EV_CURRENT);
union
{
Elf32_Shdr s32[shnum - 1];
Elf64_Shdr s64[shnum - 1];
} shdr;
dst.d_buf = &shdr;
dst.d_size = sizeof shdr;
if (unlikely (gelf_xlatetom (mod->main.elf, &dst, &src,
ehdr.e32.e_ident[EI_DATA]) == NULL))
return DWFL_E_LIBELF;
/* Now we can look at the original section headers of the main file
before it was prelinked. First we'll apply our method to the main
file sections as they are after prelinking, to calculate the
synchronization address of the main file. Then we'll apply that
same method to the saved section headers, to calculate the matching
synchronization address of the debug file.
The method is to consider SHF_ALLOC sections that are either
SHT_PROGBITS or SHT_NOBITS, excluding the section whose sh_addr
matches the PT_INTERP p_vaddr. The special sections that can be
moved by prelink have other types, except for .interp (which
becomes PT_INTERP). The "real" sections cannot move as such, but
.bss can be split into .dynbss and .bss, with the total memory
image remaining the same but being spread across the two sections.
So we consider the highest section end, which still matches up. */
GElf_Addr highest;
inline void consider_shdr (GElf_Addr interp,
GElf_Word sh_type,
GElf_Xword sh_flags,
GElf_Addr sh_addr,
GElf_Xword sh_size)
{
if ((sh_flags & SHF_ALLOC)
&& ((sh_type == SHT_PROGBITS && sh_addr != interp)
|| sh_type == SHT_NOBITS))
{
const GElf_Addr sh_end = sh_addr + sh_size;
if (sh_end > highest)
highest = sh_end;
}
}
highest = 0;
scn = NULL;
while ((scn = elf_nextscn (mod->main.elf, scn)) != NULL)
{
GElf_Shdr sh_mem;
GElf_Shdr *sh = gelf_getshdr (scn, &sh_mem);
if (unlikely (sh == NULL))
return DWFL_E_LIBELF;
consider_shdr (main_interp, sh->sh_type, sh->sh_flags,
sh->sh_addr, sh->sh_size);
}
if (highest > mod->main.vaddr)
{
mod->main.address_sync = highest;
highest = 0;
if (ehdr.e32.e_ident[EI_CLASS] == ELFCLASS32)
for (size_t i = 0; i < shnum - 1; ++i)
consider_shdr (undo_interp, shdr.s32[i].sh_type, shdr.s32[i].sh_flags,
shdr.s32[i].sh_addr, shdr.s32[i].sh_size);
else
for (size_t i = 0; i < shnum - 1; ++i)
consider_shdr (undo_interp, shdr.s64[i].sh_type, shdr.s64[i].sh_flags,
shdr.s64[i].sh_addr, shdr.s64[i].sh_size);
if (highest > file->vaddr)
file->address_sync = highest;
else
return DWFL_E_BAD_PRELINK;
}
return DWFL_E_NOERROR;
}
/* Find the separate debuginfo file for this module and open libelf on it.
When we return success, MOD->debug is set up. */
static Dwfl_Error
find_debuginfo (Dwfl_Module *mod)
{
if (mod->debug.elf != NULL)
return DWFL_E_NOERROR;
GElf_Word debuglink_crc = 0;
const char *debuglink_file = find_debuglink (mod->main.elf, &debuglink_crc);
mod->debug.fd = (*mod->dwfl->callbacks->find_debuginfo) (MODCB_ARGS (mod),
mod->main.name,
debuglink_file,
debuglink_crc,
&mod->debug.name);
Dwfl_Error result = open_elf (mod, &mod->debug);
if (result == DWFL_E_NOERROR && mod->debug.address_sync != 0)
result = find_prelink_address_sync (mod, &mod->debug);
return result;
}
/* Try to find a symbol table in FILE.
Returns DWFL_E_NOERROR if a proper one is found.
Returns DWFL_E_NO_SYMTAB if not, but still sets results for SHT_DYNSYM. */
static Dwfl_Error
load_symtab (struct dwfl_file *file, struct dwfl_file **symfile,
Elf_Scn **symscn, Elf_Scn **xndxscn,
size_t *syments, int *first_global, GElf_Word *strshndx)
{
bool symtab = false;
Elf_Scn *scn = NULL;
while ((scn = elf_nextscn (file->elf, scn)) != NULL)
{
GElf_Shdr shdr_mem, *shdr = gelf_getshdr (scn, &shdr_mem);
if (shdr != NULL)
switch (shdr->sh_type)
{
case SHT_SYMTAB:
symtab = true;
*symscn = scn;
*symfile = file;
*strshndx = shdr->sh_link;
*syments = shdr->sh_size / shdr->sh_entsize;
*first_global = shdr->sh_info;
if (*xndxscn != NULL)
return DWFL_E_NOERROR;
break;
case SHT_DYNSYM:
if (symtab)
break;
/* Use this if need be, but keep looking for SHT_SYMTAB. */
*symscn = scn;
*symfile = file;
*strshndx = shdr->sh_link;
*syments = shdr->sh_size / shdr->sh_entsize;
*first_global = shdr->sh_info;
break;
case SHT_SYMTAB_SHNDX:
*xndxscn = scn;
if (symtab)
return DWFL_E_NOERROR;
break;
default:
break;
}
}
if (symtab)
/* We found one, though no SHT_SYMTAB_SHNDX to go with it. */
return DWFL_E_NOERROR;
/* We found no SHT_SYMTAB, so any SHT_SYMTAB_SHNDX was bogus.
We might have found an SHT_DYNSYM and set *SYMSCN et al though. */
*xndxscn = NULL;
return DWFL_E_NO_SYMTAB;
}
/* Translate addresses into file offsets.
OFFS[*] start out zero and remain zero if unresolved. */
static void
find_offsets (Elf *elf, size_t phnum, size_t n,
GElf_Addr addrs[n], GElf_Off offs[n])
{
size_t unsolved = n;
for (size_t i = 0; i < phnum; ++i)
{
GElf_Phdr phdr_mem;
GElf_Phdr *phdr = gelf_getphdr (elf, i, &phdr_mem);
if (phdr != NULL && phdr->p_type == PT_LOAD && phdr->p_memsz > 0)
for (size_t j = 0; j < n; ++j)
if (offs[j] == 0
&& addrs[j] >= phdr->p_vaddr
&& addrs[j] - phdr->p_vaddr < phdr->p_filesz)
{
offs[j] = addrs[j] - phdr->p_vaddr + phdr->p_offset;
if (--unsolved == 0)
break;
}
}
}
static int elf_read(struct mt_elf *mte, struct task *task, const char *filename)
{
unsigned long loadsize = 0;
unsigned long loadbase = ~0;
unsigned long align;
unsigned long vstart;
unsigned int loadsegs = 0;
debug(DEBUG_FUNCTION, "filename=%s", filename);
if (open_elf(mte, task, filename) < 0)
return -1;
GElf_Phdr phdr;
int i;
memset(&mte->txt_hdr, 0, sizeof(mte->txt_hdr));
memset(&mte->eh_hdr, 0, sizeof(mte->eh_hdr));
memset(&mte->exidx_hdr, 0, sizeof(mte->exidx_hdr));
for (i = 0; gelf_getphdr(mte->elf, i, &phdr) != NULL; ++i) {
switch (phdr.p_type) {
case PT_LOAD:
loadsegs++;
align = phdr.p_align;
if (align)
align -= 1;
vstart = phdr.p_vaddr & ~align;
if (mte->vstart > vstart)
mte->vstart = vstart;
if (loadbase > phdr.p_offset)
loadbase = phdr.p_offset;
if (loadsize < phdr.p_offset + phdr.p_filesz)
loadsize = phdr.p_offset + phdr.p_filesz;
if ((phdr.p_flags & (PF_X | PF_W)) == PF_X)
mte->txt_hdr = phdr;
break;
case PT_GNU_EH_FRAME:
mte->eh_hdr = phdr;
break;
#ifdef __arm__
case PT_ARM_EXIDX:
mte->exidx_hdr = phdr;
break;
#endif
case PT_INTERP:
mte->interp = phdr.p_vaddr;
break;
case PT_DYNAMIC:
mte->dyn = phdr.p_vaddr;
break;
default:
break;
}
}
if (!loadsegs) {
fprintf(stderr, "No loadable segemnts in %s\n", filename);
return -1;
}
mte->loadbase = loadbase & ~PAGEALIGN;
mte->loadsize = (loadsize + (loadbase - mte->loadbase) + PAGEALIGN) & ~PAGEALIGN;
debug(DEBUG_FUNCTION, "filename=`%s' text offset=%#llx addr=%#llx size=%#llx",
filename,
(unsigned long long)mte->txt_hdr.p_offset,
(unsigned long long)mte->txt_hdr.p_vaddr,
(unsigned long long)mte->txt_hdr.p_filesz);
for (i = 1; i < mte->ehdr.e_shnum; ++i) {
Elf_Scn *scn;
GElf_Shdr shdr;
const char *name;
scn = elf_getscn(mte->elf, i);
if (scn == NULL || gelf_getshdr(scn, &shdr) == NULL) {
fprintf(stderr, "Couldn't get section #%d from" " \"%s\": %s\n", i, filename, elf_errmsg(-1));
return -1;
}
name = elf_strptr(mte->elf, mte->ehdr.e_shstrndx, shdr.sh_name);
if (name == NULL) {
fprintf(stderr, "Couldn't get name of section #%d from \"%s\": %s\n", i, filename, elf_errmsg(-1));
return -1;
}
if (shdr.sh_type == SHT_SYMTAB) {
read_symbol_table(mte, filename, scn, &shdr, name, &mte->symtab, &mte->symtab_count, &mte->strtab);
} else if (shdr.sh_type == SHT_DYNSYM) {
read_symbol_table(mte, filename, scn, &shdr, name, &mte->dynsym, &mte->dynsym_count, &mte->dynstr);
} else if (shdr.sh_type == SHT_DYNAMIC) {
Elf_Data *data;
GElf_Dyn dyn;
int idx;
data = elf_getdata(scn, NULL);
if (data == NULL) {
fprintf(stderr, "Couldn't get .dynamic data from \"%s\": %s\n", filename, strerror(errno));
return -1;
}
for(idx = 0; gelf_getdyn(data, idx, &dyn); ++idx) {
if (dyn.d_tag == DT_PLTGOT) {
mte->pltgot = dyn.d_un.d_ptr;
break;
}
}
}
}
if (!mte->dynsym || !mte->dynstr) {
fprintf(stderr, "Couldn't find .dynsym or .dynstr in \"%s\"\n", filename);
return -1;
}
return 0;
}
