Dwfl_Error
internal_function
__libdwfl_relocate (Dwfl_Module *mod, Elf *debugfile, bool debug)
{
assert (mod->e_type == ET_REL);
GElf_Ehdr ehdr_mem;
const GElf_Ehdr *ehdr = gelf_getehdr (debugfile, &ehdr_mem);
if (ehdr == NULL)
return DWFL_E_LIBELF;
size_t d_shstrndx;
if (elf_getshdrstrndx (debugfile, &d_shstrndx) < 0)
return DWFL_E_LIBELF;
RELOC_SYMTAB_CACHE (reloc_symtab);
/* Look at each section in the debuginfo file, and process the
relocation sections for debugging sections. */
Dwfl_Error result = DWFL_E_NOERROR;
Elf_Scn *scn = NULL;
while (result == DWFL_E_NOERROR
&& (scn = elf_nextscn (debugfile, scn)) != NULL)
{
GElf_Shdr shdr_mem;
GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
if ((shdr->sh_type == SHT_REL || shdr->sh_type == SHT_RELA)
&& shdr->sh_size != 0)
{
/* It's a relocation section. */
Elf_Scn *tscn = elf_getscn (debugfile, shdr->sh_info);
if (unlikely (tscn == NULL))
result = DWFL_E_LIBELF;
else
result = relocate_section (mod, debugfile, ehdr, d_shstrndx,
&reloc_symtab, scn, shdr, tscn,
debug, !debug);
}
}
return result;
}
Dwfl_Error
internal_function
__libdwfl_relocate_section (Dwfl_Module *mod, Elf *relocated,
Elf_Scn *relocscn, Elf_Scn *tscn, bool partial)
{
GElf_Ehdr ehdr_mem;
GElf_Shdr shdr_mem;
RELOC_SYMTAB_CACHE (reloc_symtab);
size_t shstrndx;
if (elf_getshdrstrndx (relocated, &shstrndx) < 0)
return DWFL_E_LIBELF;
return (__libdwfl_module_getebl (mod)
?: relocate_section (mod, relocated,
gelf_getehdr (relocated, &ehdr_mem), shstrndx,
&reloc_symtab,
relocscn, gelf_getshdr (relocscn, &shdr_mem),
tscn, false, partial));
}
static Dwfl_Error
relocate_section (Dwfl_Module *mod, Elf *relocated, const GElf_Ehdr *ehdr,
size_t shstrndx, struct reloc_symtab_cache *reloc_symtab,
Elf_Scn *scn, GElf_Shdr *shdr,
Elf_Scn *tscn, bool debugscn, bool partial)
{
/* First, fetch the name of the section these relocations apply to. */
GElf_Shdr tshdr_mem;
GElf_Shdr *tshdr = gelf_getshdr (tscn, &tshdr_mem);
const char *tname = elf_strptr (relocated, shstrndx, tshdr->sh_name);
if (tname == NULL)
return DWFL_E_LIBELF;
if (unlikely (tshdr->sh_type == SHT_NOBITS) || unlikely (tshdr->sh_size == 0))
/* No contents to relocate. */
return DWFL_E_NOERROR;
if (debugscn && ! ebl_debugscn_p (mod->ebl, tname))
/* This relocation section is not for a debugging section.
Nothing to do here. */
return DWFL_E_NOERROR;
/* Fetch the section data that needs the relocations applied. */
Elf_Data *tdata = elf_rawdata (tscn, NULL);
if (tdata == NULL)
return DWFL_E_LIBELF;
/* Apply one relocation. Returns true for any invalid data. */
Dwfl_Error relocate (GElf_Addr offset, const GElf_Sxword *addend,
int rtype, int symndx)
{
/* First see if this is a reloc we can handle.
If we are skipping it, don't bother resolving the symbol. */
if (unlikely (rtype == 0))
/* In some odd situations, the linker can leave R_*_NONE relocs
behind. This is probably bogus ld -r behavior, but the only
cases it's known to appear in are harmless: DWARF data
referring to addresses in a section that has been discarded.
So we just pretend it's OK without further relocation. */
return DWFL_E_NOERROR;
Elf_Type type = ebl_reloc_simple_type (mod->ebl, rtype);
if (unlikely (type == ELF_T_NUM))
return DWFL_E_BADRELTYPE;
/* First, resolve the symbol to an absolute value. */
GElf_Addr value;
if (symndx == STN_UNDEF)
/* When strip removes a section symbol referring to a
section moved into the debuginfo file, it replaces
that symbol index in relocs with STN_UNDEF. We
don't actually need the symbol, because those relocs
are always references relative to the nonallocated
debugging sections, which start at zero. */
value = 0;
else
{
GElf_Sym sym;
GElf_Word shndx;
Dwfl_Error error = relocate_getsym (mod, relocated, reloc_symtab,
symndx, &sym, &shndx);
if (unlikely (error != DWFL_E_NOERROR))
return error;
if (shndx == SHN_UNDEF || shndx == SHN_COMMON)
{
/* Maybe we can figure it out anyway. */
error = resolve_symbol (mod, reloc_symtab, &sym, shndx);
if (error != DWFL_E_NOERROR
&& !(error == DWFL_E_RELUNDEF && shndx == SHN_COMMON))
return error;
}
value = sym.st_value;
}
/* These are the types we can relocate. */
#define TYPES DO_TYPE (BYTE, Byte); DO_TYPE (HALF, Half); \
DO_TYPE (WORD, Word); DO_TYPE (SWORD, Sword); \
DO_TYPE (XWORD, Xword); DO_TYPE (SXWORD, Sxword)
size_t size;
switch (type)
{
#define DO_TYPE(NAME, Name) \
case ELF_T_##NAME: \
size = sizeof (GElf_##Name); \
break
TYPES;
#undef DO_TYPE
default:
return DWFL_E_BADRELTYPE;
}
if (offset + size > tdata->d_size)
return DWFL_E_BADRELOFF;
#define DO_TYPE(NAME, Name) GElf_##Name Name;
union { TYPES; } tmpbuf;
#undef DO_TYPE
Elf_Data tmpdata =
{
.d_type = type,
.d_buf = &tmpbuf,
.d_size = size,
.d_version = EV_CURRENT,
};
Elf_Data rdata =
{
.d_type = type,
.d_buf = tdata->d_buf + offset,
.d_size = size,
.d_version = EV_CURRENT,
};
/* XXX check for overflow? */
if (addend)
{
/* For the addend form, we have the value already. */
value += *addend;
switch (type)
{
#define DO_TYPE(NAME, Name) \
case ELF_T_##NAME: \
tmpbuf.Name = value; \
break
TYPES;
#undef DO_TYPE
default:
abort ();
}
}
else
{
/* Extract the original value and apply the reloc. */
Elf_Data *d = gelf_xlatetom (relocated, &tmpdata, &rdata,
ehdr->e_ident[EI_DATA]);
if (d == NULL)
return DWFL_E_LIBELF;
assert (d == &tmpdata);
switch (type)
{
#define DO_TYPE(NAME, Name) \
case ELF_T_##NAME: \
tmpbuf.Name += (GElf_##Name) value; \
break
TYPES;
#undef DO_TYPE
default:
abort ();
}
}
/* Now convert the relocated datum back to the target
format. This will write into rdata.d_buf, which
points into the raw section data being relocated. */
Elf_Data *s = gelf_xlatetof (relocated, &rdata, &tmpdata,
ehdr->e_ident[EI_DATA]);
if (s == NULL)
return DWFL_E_LIBELF;
assert (s == &rdata);
/* We have applied this relocation! */
return DWFL_E_NOERROR;
}
/* Fetch the relocation section and apply each reloc in it. */
Elf_Data *reldata = elf_getdata (scn, NULL);
if (reldata == NULL)
return DWFL_E_LIBELF;
Dwfl_Error result = DWFL_E_NOERROR;
bool first_badreltype = true;
inline void check_badreltype (void)
{
if (first_badreltype)
{
first_badreltype = false;
if (ebl_get_elfmachine (mod->ebl) == EM_NONE)
/* This might be because ebl_openbackend failed to find
any libebl_CPU.so library. Diagnose that clearly. */
result = DWFL_E_UNKNOWN_MACHINE;
}
}
size_t nrels = shdr->sh_size / shdr->sh_entsize;
size_t complete = 0;
if (shdr->sh_type == SHT_REL)
for (size_t relidx = 0; !result && relidx < nrels; ++relidx)
{
GElf_Rel rel_mem, *r = gelf_getrel (reldata, relidx, &rel_mem);
if (r == NULL)
return DWFL_E_LIBELF;
result = relocate (r->r_offset, NULL,
GELF_R_TYPE (r->r_info),
GELF_R_SYM (r->r_info));
check_badreltype ();
if (partial)
switch (result)
{
case DWFL_E_NOERROR:
/* We applied the relocation. Elide it. */
memset (&rel_mem, 0, sizeof rel_mem);
gelf_update_rel (reldata, relidx, &rel_mem);
++complete;
break;
case DWFL_E_BADRELTYPE:
case DWFL_E_RELUNDEF:
/* We couldn't handle this relocation. Skip it. */
result = DWFL_E_NOERROR;
break;
default:
break;
}
}
else
for (size_t relidx = 0; !result && relidx < nrels; ++relidx)
{
GElf_Rela rela_mem, *r = gelf_getrela (reldata, relidx,
&rela_mem);
if (r == NULL)
return DWFL_E_LIBELF;
result = relocate (r->r_offset, &r->r_addend,
GELF_R_TYPE (r->r_info),
GELF_R_SYM (r->r_info));
check_badreltype ();
if (partial)
switch (result)
{
case DWFL_E_NOERROR:
/* We applied the relocation. Elide it. */
memset (&rela_mem, 0, sizeof rela_mem);
gelf_update_rela (reldata, relidx, &rela_mem);
++complete;
break;
case DWFL_E_BADRELTYPE:
case DWFL_E_RELUNDEF:
/* We couldn't handle this relocation. Skip it. */
result = DWFL_E_NOERROR;
break;
default:
break;
}
}
if (likely (result == DWFL_E_NOERROR))
{
if (!partial || complete == nrels)
/* Mark this relocation section as being empty now that we have
done its work. This affects unstrip -R, so e.g. it emits an
empty .rela.debug_info along with a .debug_info that has
already been fully relocated. */
nrels = 0;
else if (complete != 0)
{
/* We handled some of the relocations but not all.
We've zeroed out the ones we processed.
Now remove them from the section. */
size_t next = 0;
if (shdr->sh_type == SHT_REL)
for (size_t relidx = 0; relidx < nrels; ++relidx)
{
GElf_Rel rel_mem;
GElf_Rel *r = gelf_getrel (reldata, relidx, &rel_mem);
if (r->r_info != 0 || r->r_offset != 0)
{
if (next != relidx)
gelf_update_rel (reldata, next, r);
++next;
}
}
else
for (size_t relidx = 0; relidx < nrels; ++relidx)
{
GElf_Rela rela_mem;
GElf_Rela *r = gelf_getrela (reldata, relidx, &rela_mem);
if (r->r_info != 0 || r->r_offset != 0 || r->r_addend != 0)
{
if (next != relidx)
gelf_update_rela (reldata, next, r);
++next;
}
}
nrels = next;
}
shdr->sh_size = reldata->d_size = nrels * shdr->sh_entsize;
gelf_update_shdr (scn, shdr);
}
return result;
}
Dwfl_Error
internal_function
__libdwfl_relocate (Dwfl_Module *mod, Elf *debugfile, bool debug)
{
assert (mod->e_type == ET_REL);
GElf_Ehdr ehdr_mem;
const GElf_Ehdr *ehdr = gelf_getehdr (debugfile, &ehdr_mem);
if (ehdr == NULL)
return DWFL_E_LIBELF;
size_t d_shstrndx;
if (elf_getshdrstrndx (debugfile, &d_shstrndx) < 0)
return DWFL_E_LIBELF;
RELOC_SYMTAB_CACHE (reloc_symtab);
/* Look at each section in the debuginfo file, and process the
relocation sections for debugging sections. */
Dwfl_Error result = DWFL_E_NOERROR;
Elf_Scn *scn = NULL;
while (result == DWFL_E_NOERROR
&& (scn = elf_nextscn (debugfile, scn)) != NULL)
{
GElf_Shdr shdr_mem;
GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
if ((shdr->sh_type == SHT_REL || shdr->sh_type == SHT_RELA)
&& shdr->sh_size != 0)
{
/* It's a relocation section. */
Elf_Scn *tscn = elf_getscn (debugfile, shdr->sh_info);
if (unlikely (tscn == NULL))
result = DWFL_E_LIBELF;
else
result = relocate_section (mod, debugfile, ehdr, d_shstrndx,
&reloc_symtab, scn, shdr, tscn,
debug, !debug);
}
}
return result;
}
