/* Handle an undefined symbol. We really only support ET_REL for Linux
kernel modules, and offline archives. The behavior of the Linux module
loader is very simple and easy to mimic. It only matches magically
exported symbols, and we match any defined symbols. But we get the same
answer except when the module's symbols are undefined and would prevent
it from being loaded. */
static Dwfl_Error
resolve_symbol (Dwfl_Module *referer, struct reloc_symtab_cache *symtab,
GElf_Sym *sym, GElf_Word shndx)
{
/* First we need its name. */
if (sym->st_name != 0)
{
if (symtab->symstrdata == NULL)
{
/* Cache the strtab for this symtab. */
assert (referer->symfile == NULL
|| referer->symfile->elf != symtab->symelf);
symtab->symstrdata = elf_getdata (elf_getscn (symtab->symelf,
symtab->strtabndx),
NULL);
if (unlikely (symtab->symstrdata == NULL))
return DWFL_E_LIBELF;
}
if (unlikely (sym->st_name >= symtab->symstrdata->d_size))
return DWFL_E_BADSTROFF;
const char *name = symtab->symstrdata->d_buf;
name += sym->st_name;
for (Dwfl_Module *m = referer->dwfl->modulelist; m != NULL; m = m->next)
if (m != referer)
{
/* Get this module's symtab.
If we got a fresh error reading the table, report it.
If we just have no symbols in this module, no harm done. */
if (m->symdata == NULL
&& m->symerr == DWFL_E_NOERROR
&& INTUSE(dwfl_module_getsymtab) (m) < 0
&& m->symerr != DWFL_E_NO_SYMTAB)
return m->symerr;
for (size_t ndx = 1; ndx < m->syments; ++ndx)
{
sym = gelf_getsymshndx (m->symdata, m->symxndxdata,
ndx, sym, &shndx);
if (unlikely (sym == NULL))
return DWFL_E_LIBELF;
if (sym->st_shndx != SHN_XINDEX)
shndx = sym->st_shndx;
/* We are looking for a defined global symbol with a name. */
if (shndx == SHN_UNDEF || shndx == SHN_COMMON
|| GELF_ST_BIND (sym->st_info) == STB_LOCAL
|| sym->st_name == 0)
continue;
/* Get this candidate symbol's name. */
if (unlikely (sym->st_name >= m->symstrdata->d_size))
return DWFL_E_BADSTROFF;
const char *n = m->symstrdata->d_buf;
n += sym->st_name;
/* Does the name match? */
if (strcmp (name, n))
continue;
/* We found it! */
if (shndx == SHN_ABS) /* XXX maybe should apply bias? */
return DWFL_E_NOERROR;
if (m->e_type != ET_REL)
{
sym->st_value = dwfl_adjusted_st_value (m, sym->st_value);
return DWFL_E_NOERROR;
}
/* In an ET_REL file, the symbol table values are relative
to the section, not to the module's load base. */
size_t symshstrndx = SHN_UNDEF;
return __libdwfl_relocate_value (m, m->symfile->elf,
&symshstrndx,
shndx, &sym->st_value);
}
}
}
return DWFL_E_RELUNDEF;
}
internal_function
__libdwfl_getsym (Dwfl_Module *mod, int ndx, GElf_Sym *sym, GElf_Addr *addr,
GElf_Word *shndxp, Elf **elfp, Dwarf_Addr *biasp,
bool *resolved, bool adjust_st_value)
{
if (unlikely (mod == NULL))
return NULL;
if (unlikely (mod->symdata == NULL))
{
int result = INTUSE(dwfl_module_getsymtab) (mod);
if (result < 0)
return NULL;
}
/* All local symbols should come before all global symbols. If we
have an auxiliary table make sure all the main locals come first,
then all aux locals, then all main globals and finally all aux globals.
And skip the auxiliary table zero undefined entry. */
GElf_Word shndx;
int tndx = ndx;
int skip_aux_zero = (mod->syments > 0 && mod->aux_syments > 0) ? 1 : 0;
Elf *elf;
Elf_Data *symdata;
Elf_Data *symxndxdata;
Elf_Data *symstrdata;
if (mod->aux_symdata == NULL
|| ndx < mod->first_global)
{
/* main symbol table (locals). */
tndx = ndx;
elf = mod->symfile->elf;
symdata = mod->symdata;
symxndxdata = mod->symxndxdata;
symstrdata = mod->symstrdata;
}
else if (ndx < mod->first_global + mod->aux_first_global - skip_aux_zero)
{
/* aux symbol table (locals). */
tndx = ndx - mod->first_global + skip_aux_zero;
elf = mod->aux_sym.elf;
symdata = mod->aux_symdata;
symxndxdata = mod->aux_symxndxdata;
symstrdata = mod->aux_symstrdata;
}
else if ((size_t) ndx < mod->syments + mod->aux_first_global - skip_aux_zero)
{
/* main symbol table (globals). */
tndx = ndx - mod->aux_first_global + skip_aux_zero;
elf = mod->symfile->elf;
symdata = mod->symdata;
symxndxdata = mod->symxndxdata;
symstrdata = mod->symstrdata;
}
else
{
/* aux symbol table (globals). */
tndx = ndx - mod->syments + skip_aux_zero;
elf = mod->aux_sym.elf;
symdata = mod->aux_symdata;
symxndxdata = mod->aux_symxndxdata;
symstrdata = mod->aux_symstrdata;
}
sym = gelf_getsymshndx (symdata, symxndxdata, tndx, sym, &shndx);
if (unlikely (sym == NULL))
{
__libdwfl_seterrno (DWFL_E_LIBELF);
return NULL;
}
if (sym->st_shndx != SHN_XINDEX)
shndx = sym->st_shndx;
/* Figure out whether this symbol points into an SHF_ALLOC section. */
bool alloc = true;
if ((shndxp != NULL || mod->e_type != ET_REL)
&& (sym->st_shndx == SHN_XINDEX
|| (sym->st_shndx < SHN_LORESERVE && sym->st_shndx != SHN_UNDEF)))
{
GElf_Shdr shdr_mem;
GElf_Shdr *shdr = gelf_getshdr (elf_getscn (elf, shndx), &shdr_mem);
alloc = unlikely (shdr == NULL) || (shdr->sh_flags & SHF_ALLOC);
}
/* In case of an value in an allocated section the main Elf Ebl
might know where the real value is (e.g. for function
descriptors). */
char *ident;
GElf_Addr st_value = sym->st_value & ebl_func_addr_mask (mod->ebl);
*resolved = false;
if (! adjust_st_value && mod->e_type != ET_REL && alloc
&& (GELF_ST_TYPE (sym->st_info) == STT_FUNC
|| (GELF_ST_TYPE (sym->st_info) == STT_GNU_IFUNC
&& (ident = elf_getident (elf, NULL)) != NULL
&& ident[EI_OSABI] == ELFOSABI_LINUX)))
{
if (likely (__libdwfl_module_getebl (mod) == DWFL_E_NOERROR))
{
if (elf != mod->main.elf)
{
st_value = dwfl_adjusted_st_value (mod, elf, st_value);
st_value = dwfl_deadjust_st_value (mod, mod->main.elf, st_value);
}
*resolved = ebl_resolve_sym_value (mod->ebl, &st_value);
if (! *resolved)
st_value = sym->st_value;
}
}
if (shndxp != NULL)
/* Yield -1 in case of a non-SHF_ALLOC section. */
*shndxp = alloc ? shndx : (GElf_Word) -1;
switch (sym->st_shndx)
{
case SHN_ABS: /* XXX sometimes should use bias?? */
case SHN_UNDEF:
case SHN_COMMON:
break;
default:
if (mod->e_type == ET_REL)
{
/* In an ET_REL file, the symbol table values are relative
to the section, not to the module's load base. */
size_t symshstrndx = SHN_UNDEF;
Dwfl_Error result = __libdwfl_relocate_value (mod, elf,
&symshstrndx,
shndx, &st_value);
if (unlikely (result != DWFL_E_NOERROR))
{
__libdwfl_seterrno (result);
return NULL;
}
}
else if (alloc)
/* Apply the bias to the symbol value. */
st_value = dwfl_adjusted_st_value (mod,
*resolved ? mod->main.elf : elf,
st_value);
break;
}
if (adjust_st_value)
sym->st_value = st_value;
if (addr != NULL)
*addr = st_value;
if (unlikely (sym->st_name >= symstrdata->d_size))
{
__libdwfl_seterrno (DWFL_E_BADSTROFF);
return NULL;
}
if (elfp)
*elfp = elf;
if (biasp)
*biasp = dwfl_adjusted_st_value (mod, elf, 0);
return (const char *) symstrdata->d_buf + sym->st_name;
}
const char *
dwfl_module_getsym (Dwfl_Module *mod, int ndx,
GElf_Sym *sym, GElf_Word *shndxp)
{
if (unlikely (mod == NULL))
return NULL;
if (unlikely (mod->symdata == NULL))
{
int result = INTUSE(dwfl_module_getsymtab) (mod);
if (result < 0)
return NULL;
}
GElf_Word shndx;
sym = gelf_getsymshndx (mod->symdata, mod->symxndxdata, ndx, sym, &shndx);
if (unlikely (sym == NULL))
{
__libdwfl_seterrno (DWFL_E_LIBELF);
return NULL;
}
if (sym->st_shndx != SHN_XINDEX)
shndx = sym->st_shndx;
/* Figure out whether this symbol points into an SHF_ALLOC section. */
bool alloc = true;
if ((shndxp != NULL || mod->e_type != ET_REL)
&& (sym->st_shndx == SHN_XINDEX
|| (sym->st_shndx < SHN_LORESERVE && sym->st_shndx != SHN_UNDEF)))
{
GElf_Shdr shdr_mem;
GElf_Shdr *shdr = gelf_getshdr (elf_getscn (mod->symfile->elf, shndx),
&shdr_mem);
alloc = unlikely (shdr == NULL) || (shdr->sh_flags & SHF_ALLOC);
}
if (shndxp != NULL)
/* Yield -1 in case of a non-SHF_ALLOC section. */
*shndxp = alloc ? shndx : (GElf_Word) -1;
switch (sym->st_shndx)
{
case SHN_ABS: /* XXX sometimes should use bias?? */
case SHN_UNDEF:
case SHN_COMMON:
break;
default:
if (mod->e_type == ET_REL)
{
/* In an ET_REL file, the symbol table values are relative
to the section, not to the module's load base. */
size_t symshstrndx = SHN_UNDEF;
Dwfl_Error result = __libdwfl_relocate_value (mod, mod->symfile->elf,
&symshstrndx,
shndx, &sym->st_value);
if (unlikely (result != DWFL_E_NOERROR))
{
__libdwfl_seterrno (result);
return NULL;
}
}
else if (alloc)
/* Apply the bias to the symbol value. */
sym->st_value = dwfl_adjusted_st_value (mod, sym->st_value);
break;
}
if (unlikely (sym->st_name >= mod->symstrdata->d_size))
{
__libdwfl_seterrno (DWFL_E_BADSTROFF);
return NULL;
}
return (const char *) mod->symstrdata->d_buf + sym->st_name;
}
