* [PATCH v2 1/2] elf: Unify symbol address run-time calculation [BZ #19818]
2018-02-20 18:40 [PATCH v2 0/2] Correct absolute (SHN_ABS) symbol run-time calculation [BZ #19818] Maciej W. Rozycki
@ 2018-02-20 18:52 ` Maciej W. Rozycki
2018-03-07 20:23 ` Adhemerval Zanella
2018-02-20 20:24 ` [PATCH v2 2/2] elf: Correct absolute (SHN_ABS) symbol " Maciej W. Rozycki
2018-03-01 15:15 ` [PING][PATCH v2 0/2] " Maciej W. Rozycki
2 siblings, 1 reply; 9+ messages in thread
From: Maciej W. Rozycki @ 2018-02-20 18:52 UTC (permalink / raw)
To: libc-alpha; +Cc: H.J. Lu, Alan Modra, Cary Coutant
Wrap symbol address run-time calculation into a macro and use it
throughout, replacing inline calculations.
There are a couple of variants, most of them different in a functionally
insignificant way. Most calculations are right following RESOLVE_MAP,
at which point either the map or the symbol returned can be checked for
validity as the macro sets either both or neither. In some places both
the symbol and the map has to be checked however.
My initial implementation therefore always checked both, however that
resulted in code larger by as much as 0.3%, as many places know from
elsewhere that no check is needed. I have decided the size growth was
unacceptable.
Having looked closer I realized that it's the map that is the culprit.
Therefore I have modified LOOKUP_VALUE_ADDRESS to accept an additional
boolean argument telling it to access the map without checking it for
validity. This in turn has brought quite nice results, with new code
actually being smaller for i686, and MIPS o32, n32 and little-endian n64
targets, unchanged in size for x86-64 and, unusually, marginally larger
for big-endian MIPS n64, as follows:
i686:
text data bss dec hex filename
152255 4052 192 156499 26353 ld-2.27.9000-base.so
152159 4052 192 156403 262f3 ld-2.27.9000-elf-symbol-value.so
MIPS/o32/el:
text data bss dec hex filename
142906 4396 260 147562 2406a ld-2.27.9000-base.so
142890 4396 260 147546 2405a ld-2.27.9000-elf-symbol-value.so
MIPS/n32/el:
text data bss dec hex filename
142267 4404 260 146931 23df3 ld-2.27.9000-base.so
142171 4404 260 146835 23d93 ld-2.27.9000-elf-symbol-value.so
MIPS/n64/el:
text data bss dec hex filename
149835 7376 408 157619 267b3 ld-2.27.9000-base.so
149787 7376 408 157571 26783 ld-2.27.9000-elf-symbol-value.so
MIPS/o32/eb:
text data bss dec hex filename
142870 4396 260 147526 24046 ld-2.27.9000-base.so
142854 4396 260 147510 24036 ld-2.27.9000-elf-symbol-value.so
MIPS/n32/eb:
text data bss dec hex filename
142019 4404 260 146683 23cfb ld-2.27.9000-base.so
141923 4404 260 146587 23c9b ld-2.27.9000-elf-symbol-value.so
MIPS/n64/eb:
text data bss dec hex filename
149763 7376 408 157547 2676b ld-2.27.9000-base.so
149779 7376 408 157563 2677b ld-2.27.9000-elf-symbol-value.so
x86-64:
text data bss dec hex filename
148462 6452 400 155314 25eb2 ld-2.27.9000-base.so
148462 6452 400 155314 25eb2 ld-2.27.9000-elf-symbol-value.so
[BZ #19818]
* sysdeps/generic/ldsodefs.h (LOOKUP_VALUE_ADDRESS): Add `set'
parameter.
(SYMBOL_ADDRESS): New macro.
[!ELF_FUNCTION_PTR_IS_SPECIAL] (DL_SYMBOL_ADDRESS): Use
SYMBOL_ADDRESS for symbol address calculation.
* elf/dl-runtime.c (_dl_fixup): Likewise.
(_dl_profile_fixup): Likewise.
* elf/dl-symaddr.c (_dl_symbol_address): Likewise.
* elf/rtld.c (dl_main): Likewise.
* sysdeps/aarch64/dl-machine.h (elf_machine_rela): Likewise.
* sysdeps/alpha/dl-machine.h (elf_machine_rela): Likewise.
* sysdeps/arm/dl-machine.h (elf_machine_rel): Likewise.
(elf_machine_rela): Likewise.
* sysdeps/hppa/dl-machine.h (elf_machine_rela): Likewise.
* sysdeps/hppa/dl-symaddr.c (_dl_symbol_address): Likewise.
* sysdeps/i386/dl-machine.h (elf_machine_rel): Likewise.
(elf_machine_rela): Likewise.
* sysdeps/ia64/dl-machine.h (elf_machine_rela): Likewise.
* sysdeps/m68k/dl-machine.h (elf_machine_rela): Likewise.
* sysdeps/microblaze/dl-machine.h (elf_machine_rela): Likewise.
* sysdeps/mips/dl-machine.h (ELF_MACHINE_BEFORE_RTLD_RELOC):
Likewise.
(elf_machine_reloc): Likewise.
(elf_machine_got_rel): Likewise.
* sysdeps/mips/dl-trampoline.c (__dl_runtime_resolve): Likewise.
* sysdeps/nios2/dl-machine.h (elf_machine_rela): Likewise.
* sysdeps/powerpc/powerpc32/dl-machine.h (elf_machine_rela):
Likewise.
* sysdeps/powerpc/powerpc64/dl-machine.h (elf_machine_rela):
Likewise.
* sysdeps/riscv/dl-machine.h (elf_machine_rela): Likewise.
* sysdeps/s390/s390-32/dl-machine.h (elf_machine_rela):
Likewise.
* sysdeps/s390/s390-64/dl-machine.h (elf_machine_rela):
Likewise.
* sysdeps/sh/dl-machine.h (elf_machine_rela): Likewise.
* sysdeps/sparc/sparc32/dl-machine.h (elf_machine_rela):
Likewise.
* sysdeps/sparc/sparc64/dl-machine.h (elf_machine_rela):
Likewise.
* sysdeps/tile/dl-machine.h (elf_machine_rela): Likewise.
* sysdeps/x86_64/dl-machine.h (elf_machine_rela): Likewise.
---
Changes from v1:
- remove extraneous parentheses from the bodies of SYMBOL_ADDRESS and
DL_SYMBOL_ADDRESS.
OK to apply?
Maciej
---
elf/dl-runtime.c | 11 ++++-------
elf/dl-symaddr.c | 2 +-
elf/rtld.c | 2 +-
sysdeps/aarch64/dl-machine.h | 2 +-
sysdeps/alpha/dl-machine.h | 2 +-
sysdeps/arm/dl-machine.h | 6 +++---
sysdeps/generic/ldsodefs.h | 10 ++++++++--
sysdeps/hppa/dl-machine.h | 10 +++++-----
sysdeps/hppa/dl-symaddr.c | 2 +-
sysdeps/i386/dl-machine.h | 4 ++--
sysdeps/ia64/dl-machine.h | 2 +-
sysdeps/m68k/dl-machine.h | 2 +-
sysdeps/microblaze/dl-machine.h | 2 +-
sysdeps/mips/dl-machine.h | 14 +++++++-------
sysdeps/mips/dl-trampoline.c | 4 ++--
sysdeps/nios2/dl-machine.h | 2 +-
sysdeps/powerpc/powerpc32/dl-machine.h | 2 +-
sysdeps/powerpc/powerpc64/dl-machine.h | 3 +--
sysdeps/riscv/dl-machine.h | 2 +-
sysdeps/s390/s390-32/dl-machine.h | 2 +-
sysdeps/s390/s390-64/dl-machine.h | 2 +-
sysdeps/sh/dl-machine.h | 4 ++--
sysdeps/sparc/sparc32/dl-machine.h | 2 +-
sysdeps/sparc/sparc64/dl-machine.h | 2 +-
sysdeps/tile/dl-machine.h | 2 +-
sysdeps/x86_64/dl-machine.h | 3 +--
26 files changed, 51 insertions(+), 50 deletions(-)
glibc-elf-symbol-value.diff
Index: glibc/elf/dl-runtime.c
===================================================================
--- glibc.orig/elf/dl-runtime.c 2018-02-19 13:10:21.217296821 +0000
+++ glibc/elf/dl-runtime.c 2018-02-19 13:22:14.645504959 +0000
@@ -124,14 +124,13 @@ _dl_fixup (
of the object that defines sym. Now add in the symbol
offset. */
value = DL_FIXUP_MAKE_VALUE (result,
- sym ? (LOOKUP_VALUE_ADDRESS (result)
- + sym->st_value) : 0);
+ SYMBOL_ADDRESS (result, sym, false));
}
else
{
/* We already found the symbol. The module (and therefore its load
address) is also known. */
- value = DL_FIXUP_MAKE_VALUE (l, l->l_addr + sym->st_value);
+ value = DL_FIXUP_MAKE_VALUE (l, SYMBOL_ADDRESS (l, sym, true));
result = l;
}
@@ -241,9 +240,7 @@ _dl_profile_fixup (
of the object that defines sym. Now add in the symbol
offset. */
value = DL_FIXUP_MAKE_VALUE (result,
- defsym != NULL
- ? LOOKUP_VALUE_ADDRESS (result)
- + defsym->st_value : 0);
+ SYMBOL_ADDRESS (result, defsym, false));
if (defsym != NULL
&& __builtin_expect (ELFW(ST_TYPE) (defsym->st_info)
@@ -254,7 +251,7 @@ _dl_profile_fixup (
{
/* We already found the symbol. The module (and therefore its load
address) is also known. */
- value = DL_FIXUP_MAKE_VALUE (l, l->l_addr + refsym->st_value);
+ value = DL_FIXUP_MAKE_VALUE (l, SYMBOL_ADDRESS (l, refsym, true));
if (__builtin_expect (ELFW(ST_TYPE) (refsym->st_info)
== STT_GNU_IFUNC, 0))
Index: glibc/elf/dl-symaddr.c
===================================================================
--- glibc.orig/elf/dl-symaddr.c 2018-02-19 13:10:21.229481824 +0000
+++ glibc/elf/dl-symaddr.c 2018-02-19 13:22:14.668735741 +0000
@@ -22,7 +22,7 @@
void *
_dl_symbol_address (struct link_map *map, const ElfW(Sym) *ref)
{
- ElfW(Addr) value = (map ? map->l_addr : 0) + ref->st_value;
+ ElfW(Addr) value = SYMBOL_ADDRESS (map, ref, false);
/* Return the pointer to function descriptor. */
if (ELFW(ST_TYPE) (ref->st_info) == STT_FUNC)
Index: glibc/elf/rtld.c
===================================================================
--- glibc.orig/elf/rtld.c 2018-02-19 13:10:21.236569266 +0000
+++ glibc/elf/rtld.c 2018-02-19 13:22:14.682984971 +0000
@@ -1917,7 +1917,7 @@ ERROR: ld.so: object '%s' cannot be load
NULL, ELF_RTYPE_CLASS_PLT,
DL_LOOKUP_ADD_DEPENDENCY, NULL);
- loadbase = LOOKUP_VALUE_ADDRESS (result);
+ loadbase = LOOKUP_VALUE_ADDRESS (result, false);
_dl_printf ("%s found at 0x%0*Zd in object at 0x%0*Zd\n",
_dl_argv[i],
Index: glibc/sysdeps/aarch64/dl-machine.h
===================================================================
--- glibc.orig/sysdeps/aarch64/dl-machine.h 2018-02-19 13:10:21.281087487 +0000
+++ glibc/sysdeps/aarch64/dl-machine.h 2018-02-19 13:22:14.737587104 +0000
@@ -254,7 +254,7 @@ elf_machine_rela (struct link_map *map,
{
const ElfW(Sym) *const refsym = sym;
struct link_map *sym_map = RESOLVE_MAP (&sym, version, r_type);
- ElfW(Addr) value = sym_map == NULL ? 0 : sym_map->l_addr + sym->st_value;
+ ElfW(Addr) value = SYMBOL_ADDRESS (sym_map, sym, true);
if (sym != NULL
&& __glibc_unlikely (ELFW(ST_TYPE) (sym->st_info) == STT_GNU_IFUNC)
Index: glibc/sysdeps/alpha/dl-machine.h
===================================================================
--- glibc.orig/sysdeps/alpha/dl-machine.h 2018-02-19 13:10:21.303514845 +0000
+++ glibc/sysdeps/alpha/dl-machine.h 2018-02-19 13:22:14.768016799 +0000
@@ -419,7 +419,7 @@ elf_machine_rela (struct link_map *map,
if (sym_map)
{
sym_raw_value += sym->st_value;
- sym_value = sym_raw_value + sym_map->l_addr;
+ sym_value += SYMBOL_ADDRESS (sym_map, sym, true);
}
if (r_type == R_ALPHA_GLOB_DAT)
Index: glibc/sysdeps/arm/dl-machine.h
===================================================================
--- glibc.orig/sysdeps/arm/dl-machine.h 2018-02-19 13:10:21.321668903 +0000
+++ glibc/sysdeps/arm/dl-machine.h 2018-02-19 13:22:14.779148198 +0000
@@ -392,7 +392,7 @@ elf_machine_rel (struct link_map *map, c
{
const Elf32_Sym *const refsym = sym;
struct link_map *sym_map = RESOLVE_MAP (&sym, version, r_type);
- Elf32_Addr value = sym_map == NULL ? 0 : sym_map->l_addr + sym->st_value;
+ Elf32_Addr value = SYMBOL_ADDRESS (sym_map, sym, true);
if (sym != NULL
&& __builtin_expect (ELFW(ST_TYPE) (sym->st_info) == STT_GNU_IFUNC, 0)
@@ -452,7 +452,7 @@ elf_machine_rel (struct link_map *map, c
binding found in the user program or a loaded library
rather than the dynamic linker's built-in definitions
used while loading those libraries. */
- value -= map->l_addr + refsym->st_value;
+ value -= SYMBOL_ADDRESS (map, refsym, true);
# endif
/* Support relocations on mis-aligned offsets. */
((struct unaligned *) reloc_addr)->x += value;
@@ -553,7 +553,7 @@ elf_machine_rela (struct link_map *map,
const Elf32_Sym *const refsym = sym;
# endif
struct link_map *sym_map = RESOLVE_MAP (&sym, version, r_type);
- Elf32_Addr value = sym_map == NULL ? 0 : sym_map->l_addr + sym->st_value;
+ Elf32_Addr value = SYMBOL_ADDRESS (sym_map, sym, true);
if (sym != NULL
&& __builtin_expect (ELFW(ST_TYPE) (sym->st_info) == STT_GNU_IFUNC, 0)
Index: glibc/sysdeps/generic/ldsodefs.h
===================================================================
--- glibc.orig/sysdeps/generic/ldsodefs.h 2018-02-19 13:10:21.336828083 +0000
+++ glibc/sysdeps/generic/ldsodefs.h 2018-02-20 16:32:02.743558607 +0000
@@ -66,14 +66,20 @@ __BEGIN_DECLS
/* Result of the lookup functions and how to retrieve the base address. */
typedef struct link_map *lookup_t;
#define LOOKUP_VALUE(map) map
-#define LOOKUP_VALUE_ADDRESS(map) ((map) ? (map)->l_addr : 0)
+#define LOOKUP_VALUE_ADDRESS(map, set) ((set) || (map) ? (map)->l_addr : 0)
+
+/* Calculate the address of symbol REF using the base address from map MAP,
+ if non-NULL. Don't check for NULL map if MAP_SET is TRUE. */
+#define SYMBOL_ADDRESS(map, ref, map_set) \
+ ((ref) == NULL ? 0 \
+ : LOOKUP_VALUE_ADDRESS (map, map_set) + (ref)->st_value)
/* On some architectures a pointer to a function is not just a pointer
to the actual code of the function but rather an architecture
specific descriptor. */
#ifndef ELF_FUNCTION_PTR_IS_SPECIAL
# define DL_SYMBOL_ADDRESS(map, ref) \
- (void *) (LOOKUP_VALUE_ADDRESS (map) + ref->st_value)
+ (void *) SYMBOL_ADDRESS (map, ref, false)
# define DL_LOOKUP_ADDRESS(addr) ((ElfW(Addr)) (addr))
# define DL_CALL_DT_INIT(map, start, argc, argv, env) \
((init_t) (start)) (argc, argv, env)
Index: glibc/sysdeps/hppa/dl-machine.h
===================================================================
--- glibc.orig/sysdeps/hppa/dl-machine.h 2018-02-19 13:10:21.357039796 +0000
+++ glibc/sysdeps/hppa/dl-machine.h 2018-02-19 13:22:14.828577350 +0000
@@ -562,7 +562,7 @@ elf_machine_rela (struct link_map *map,
if (sym_map)
{
- value = sym ? sym_map->l_addr + sym->st_value : 0;
+ value = SYMBOL_ADDRESS (sym_map, sym, true);
value += reloc->r_addend;
}
else
@@ -586,8 +586,8 @@ elf_machine_rela (struct link_map *map,
case R_PARISC_DIR21L:
{
unsigned int insn = *(unsigned int *)reloc_addr;
- value = sym_map->l_addr + sym->st_value
- + ((reloc->r_addend + 0x1000) & -0x2000);
+ value = (SYMBOL_ADDRESS (sym_map, sym, true)
+ + ((reloc->r_addend + 0x1000) & -0x2000));
value = value >> 11;
insn = (insn &~ 0x1fffff) | reassemble_21 (value);
*(unsigned int *)reloc_addr = insn;
@@ -597,8 +597,8 @@ elf_machine_rela (struct link_map *map,
case R_PARISC_DIR14R:
{
unsigned int insn = *(unsigned int *)reloc_addr;
- value = ((sym_map->l_addr + sym->st_value) & 0x7ff)
- + (((reloc->r_addend & 0x1fff) ^ 0x1000) - 0x1000);
+ value = ((SYMBOL_ADDRESS (sym_map, sym, true) & 0x7ff)
+ + (((reloc->r_addend & 0x1fff) ^ 0x1000) - 0x1000));
insn = (insn &~ 0x3fff) | reassemble_14 (value);
*(unsigned int *)reloc_addr = insn;
}
Index: glibc/sysdeps/hppa/dl-symaddr.c
===================================================================
--- glibc.orig/sysdeps/hppa/dl-symaddr.c 2018-02-19 13:10:21.371154652 +0000
+++ glibc/sysdeps/hppa/dl-symaddr.c 2018-02-19 13:22:14.846783200 +0000
@@ -23,7 +23,7 @@ void *
_dl_symbol_address (struct link_map *map, const ElfW(Sym) *ref)
{
/* Find the "ip" from the "map" and symbol "ref" */
- Elf32_Addr value = (map ? map->l_addr : 0) + ref->st_value;
+ Elf32_Addr value = SYMBOL_ADDRESS (map, ref, false);
/* On hppa, we have to return the pointer to function descriptor.
This involves an "| 2" to inform $$dyncall that this is a plabel32 */
Index: glibc/sysdeps/i386/dl-machine.h
===================================================================
--- glibc.orig/sysdeps/i386/dl-machine.h 2018-02-19 13:10:21.385393392 +0000
+++ glibc/sysdeps/i386/dl-machine.h 2018-02-19 13:22:14.857907255 +0000
@@ -320,7 +320,7 @@ elf_machine_rel (struct link_map *map, c
const Elf32_Sym *const refsym = sym;
# endif
struct link_map *sym_map = RESOLVE_MAP (&sym, version, r_type);
- Elf32_Addr value = sym_map == NULL ? 0 : sym_map->l_addr + sym->st_value;
+ Elf32_Addr value = SYMBOL_ADDRESS (sym_map, sym, true);
if (sym != NULL
&& __glibc_unlikely (ELFW(ST_TYPE) (sym->st_info) == STT_GNU_IFUNC)
@@ -500,7 +500,7 @@ elf_machine_rela (struct link_map *map,
const Elf32_Sym *const refsym = sym;
# endif
struct link_map *sym_map = RESOLVE_MAP (&sym, version, r_type);
- Elf32_Addr value = sym == NULL ? 0 : sym_map->l_addr + sym->st_value;
+ Elf32_Addr value = SYMBOL_ADDRESS (sym_map, sym, true);
if (sym != NULL
&& __glibc_likely (sym->st_shndx != SHN_UNDEF)
Index: glibc/sysdeps/ia64/dl-machine.h
===================================================================
--- glibc.orig/sysdeps/ia64/dl-machine.h 2018-02-19 13:10:21.406734115 +0000
+++ glibc/sysdeps/ia64/dl-machine.h 2018-02-19 13:22:14.890118190 +0000
@@ -419,7 +419,7 @@ elf_machine_rela (struct link_map *map,
/* RESOLVE_MAP() will return NULL if it fail to locate the symbol. */
if ((sym_map = RESOLVE_MAP (&sym, version, r_type)))
{
- value = sym_map->l_addr + sym->st_value + reloc->r_addend;
+ value = SYMBOL_ADDRESS (sym_map, sym, true) + reloc->r_addend;
if (R_IA64_TYPE (r_type) == R_IA64_TYPE (R_IA64_DIR64LSB))
;/* No adjustment. */
Index: glibc/sysdeps/m68k/dl-machine.h
===================================================================
--- glibc.orig/sysdeps/m68k/dl-machine.h 2018-02-19 13:10:21.419970047 +0000
+++ glibc/sysdeps/m68k/dl-machine.h 2018-02-19 13:22:14.913295094 +0000
@@ -229,7 +229,7 @@ elf_machine_rela (struct link_map *map,
{
const Elf32_Sym *const refsym = sym;
struct link_map *sym_map = RESOLVE_MAP (&sym, version, r_type);
- Elf32_Addr value = sym == NULL ? 0 : sym_map->l_addr + sym->st_value;
+ Elf32_Addr value = SYMBOL_ADDRESS (sym_map, sym, true);
switch (r_type)
{
Index: glibc/sysdeps/microblaze/dl-machine.h
===================================================================
--- glibc.orig/sysdeps/microblaze/dl-machine.h 2018-02-19 13:10:21.439274732 +0000
+++ glibc/sysdeps/microblaze/dl-machine.h 2018-02-19 13:22:14.939542016 +0000
@@ -223,7 +223,7 @@ elf_machine_rela (struct link_map *map,
{
const Elf32_Sym *const refsym = sym;
struct link_map *sym_map = RESOLVE_MAP (&sym, version, r_type);
- Elf32_Addr value = sym == NULL ? 0 : sym_map->l_addr + sym->st_value;
+ Elf32_Addr value = SYMBOL_ADDRESS (sym_map, sym, true);
value += reloc->r_addend;
if (r_type == R_MICROBLAZE_GLOB_DAT ||
Index: glibc/sysdeps/mips/dl-machine.h
===================================================================
--- glibc.orig/sysdeps/mips/dl-machine.h 2018-02-19 13:10:21.449367276 +0000
+++ glibc/sysdeps/mips/dl-machine.h 2018-02-19 13:22:14.967751342 +0000
@@ -220,7 +220,7 @@ do { \
while (i--) \
{ \
if (sym->st_shndx == SHN_UNDEF || sym->st_shndx == SHN_COMMON) \
- *got = map->l_addr + sym->st_value; \
+ *got = SYMBOL_ADDRESS (map, sym, true); \
else if (ELFW(ST_TYPE) (sym->st_info) == STT_FUNC \
&& *got != sym->st_value) \
*got += map->l_addr; \
@@ -230,7 +230,7 @@ do { \
*got += map->l_addr; \
} \
else \
- *got = map->l_addr + sym->st_value; \
+ *got = SYMBOL_ADDRESS (map, sym, true); \
\
got++; \
sym++; \
@@ -598,7 +598,7 @@ elf_machine_reloc (struct link_map *map,
#ifndef RTLD_BOOTSTRAP
if (map != &GL(dl_rtld_map))
#endif
- reloc_value += sym->st_value + map->l_addr;
+ reloc_value += SYMBOL_ADDRESS (map, sym, true);
}
else
{
@@ -663,7 +663,7 @@ elf_machine_reloc (struct link_map *map,
"found jump slot relocation with non-zero addend");
sym_map = RESOLVE_MAP (&sym, version, r_type);
- value = sym_map == NULL ? 0 : sym_map->l_addr + sym->st_value;
+ value = SYMBOL_ADDRESS (sym_map, sym, true);
*addr_field = value;
break;
@@ -677,7 +677,7 @@ elf_machine_reloc (struct link_map *map,
/* Calculate the address of the symbol. */
sym_map = RESOLVE_MAP (&sym, version, r_type);
- value = sym_map == NULL ? 0 : sym_map->l_addr + sym->st_value;
+ value = SYMBOL_ADDRESS (sym_map, sym, true);
if (__builtin_expect (sym == NULL, 0))
/* This can happen in trace mode if an object could not be
@@ -798,7 +798,7 @@ elf_machine_got_rel (struct link_map *ma
= vernum ? &map->l_versions[vernum[sym_index] & 0x7fff] : NULL; \
struct link_map *sym_map; \
sym_map = RESOLVE_MAP (&ref, version, reloc); \
- ref ? sym_map->l_addr + ref->st_value : 0; \
+ SYMBOL_ADDRESS (sym_map, ref, true); \
})
if (map->l_info[VERSYMIDX (DT_VERSYM)] != NULL)
@@ -842,7 +842,7 @@ elf_machine_got_rel (struct link_map *ma
&& !(sym->st_other & STO_MIPS_PLT))
{
if (lazy)
- *got = sym->st_value + map->l_addr;
+ *got = SYMBOL_ADDRESS (map, sym, true);
else
/* This is a lazy-binding stub, so we don't need the
canonical address. */
Index: glibc/sysdeps/mips/dl-trampoline.c
===================================================================
--- glibc.orig/sysdeps/mips/dl-trampoline.c 2018-02-19 13:10:21.460633510 +0000
+++ glibc/sysdeps/mips/dl-trampoline.c 2018-02-19 13:22:14.977836168 +0000
@@ -192,12 +192,12 @@ __dl_runtime_resolve (ElfW(Word) sym_ind
/* Currently value contains the base load address of the object
that defines sym. Now add in the symbol offset. */
- value = (sym ? sym_map->l_addr + sym->st_value : 0);
+ value = SYMBOL_ADDRESS (sym_map, sym, true);
}
else
/* We already found the symbol. The module (and therefore its load
address) is also known. */
- value = l->l_addr + sym->st_value;
+ value = SYMBOL_ADDRESS (l, sym, true);
/* Apply the relocation with that value. */
*(got + local_gotno + sym_index - gotsym) = value;
Index: glibc/sysdeps/nios2/dl-machine.h
===================================================================
--- glibc.orig/sysdeps/nios2/dl-machine.h 2018-02-19 13:10:21.493021733 +0000
+++ glibc/sysdeps/nios2/dl-machine.h 2018-02-19 13:22:15.012164183 +0000
@@ -250,7 +250,7 @@ elf_machine_rela (struct link_map *map,
{
const Elf32_Sym *const refsym = sym;
struct link_map *sym_map = RESOLVE_MAP (&sym, version, r_type);
- Elf32_Addr value = sym == NULL ? 0 : sym_map->l_addr + sym->st_value;
+ Elf32_Addr value = SYMBOL_ADDRESS (sym_map, sym, true);
switch (r_type)
{
Index: glibc/sysdeps/powerpc/powerpc32/dl-machine.h
===================================================================
--- glibc.orig/sysdeps/powerpc/powerpc32/dl-machine.h 2018-02-19 13:10:21.522544522 +0000
+++ glibc/sysdeps/powerpc/powerpc32/dl-machine.h 2018-02-19 13:22:15.038500645 +0000
@@ -317,7 +317,7 @@ elf_machine_rela (struct link_map *map,
else
{
sym_map = RESOLVE_MAP (&sym, version, r_type);
- value = sym_map == NULL ? 0 : sym_map->l_addr + sym->st_value;
+ value = SYMBOL_ADDRESS (sym_map, sym, true);
}
value += reloc->r_addend;
#else
Index: glibc/sysdeps/powerpc/powerpc64/dl-machine.h
===================================================================
--- glibc.orig/sysdeps/powerpc/powerpc64/dl-machine.h 2018-02-19 13:10:21.561010840 +0000
+++ glibc/sysdeps/powerpc/powerpc64/dl-machine.h 2018-02-19 13:22:15.057749426 +0000
@@ -708,8 +708,7 @@ elf_machine_rela (struct link_map *map,
/* We need SYM_MAP even in the absence of TLS, for elf_machine_fixup_plt
and STT_GNU_IFUNC. */
struct link_map *sym_map = RESOLVE_MAP (&sym, version, r_type);
- Elf64_Addr value = ((sym_map == NULL ? 0 : sym_map->l_addr + sym->st_value)
- + reloc->r_addend);
+ Elf64_Addr value = SYMBOL_ADDRESS (sym_map, sym, true) + reloc->r_addend;
if (sym != NULL
&& __builtin_expect (ELFW(ST_TYPE) (sym->st_info) == STT_GNU_IFUNC, 0)
Index: glibc/sysdeps/riscv/dl-machine.h
===================================================================
--- glibc.orig/sysdeps/riscv/dl-machine.h 2018-02-19 13:10:21.593351190 +0000
+++ glibc/sysdeps/riscv/dl-machine.h 2018-02-19 13:22:15.082971467 +0000
@@ -172,7 +172,7 @@ elf_machine_rela (struct link_map *map,
struct link_map *sym_map = RESOLVE_MAP (&sym, version, r_type);
ElfW(Addr) value = 0;
if (sym_map != NULL)
- value = sym_map->l_addr + sym->st_value + reloc->r_addend;
+ value = SYMBOL_ADDRESS (sym_map, sym, true) + reloc->r_addend;
switch (r_type)
{
Index: glibc/sysdeps/s390/s390-32/dl-machine.h
===================================================================
--- glibc.orig/sysdeps/s390/s390-32/dl-machine.h 2018-02-19 13:10:21.617644761 +0000
+++ glibc/sysdeps/s390/s390-32/dl-machine.h 2018-02-19 13:22:15.115293869 +0000
@@ -358,7 +358,7 @@ elf_machine_rela (struct link_map *map,
const Elf32_Sym *const refsym = sym;
#endif
struct link_map *sym_map = RESOLVE_MAP (&sym, version, r_type);
- Elf32_Addr value = sym == NULL ? 0 : sym_map->l_addr + sym->st_value;
+ Elf32_Addr value = SYMBOL_ADDRESS (sym_map, sym, true);
if (sym != NULL
&& __builtin_expect (ELFW(ST_TYPE) (sym->st_info) == STT_GNU_IFUNC, 0)
Index: glibc/sysdeps/s390/s390-64/dl-machine.h
===================================================================
--- glibc.orig/sysdeps/s390/s390-64/dl-machine.h 2018-02-19 13:10:21.652047072 +0000
+++ glibc/sysdeps/s390/s390-64/dl-machine.h 2018-02-19 13:22:15.137529070 +0000
@@ -305,7 +305,7 @@ elf_machine_rela (struct link_map *map,
const Elf64_Sym *const refsym = sym;
#endif
struct link_map *sym_map = RESOLVE_MAP (&sym, version, r_type);
- Elf64_Addr value = sym == NULL ? 0 : sym_map->l_addr + sym->st_value;
+ Elf64_Addr value = SYMBOL_ADDRESS (sym_map, sym, true);
if (sym != NULL
&& __builtin_expect (ELFW(ST_TYPE) (sym->st_info) == STT_GNU_IFUNC,
Index: glibc/sysdeps/sh/dl-machine.h
===================================================================
--- glibc.orig/sysdeps/sh/dl-machine.h 2018-02-19 13:10:21.690433963 +0000
+++ glibc/sysdeps/sh/dl-machine.h 2018-02-19 13:22:15.154759248 +0000
@@ -320,7 +320,7 @@ elf_machine_rela (struct link_map *map,
const Elf32_Sym *const refsym = sym;
struct link_map *sym_map = RESOLVE_MAP (&sym, version, r_type);
- value = sym_map == NULL ? 0 : sym_map->l_addr + sym->st_value;
+ value = SYMBOL_ADDRESS (sym_map, sym, true);
value += reloc->r_addend;
switch (r_type)
@@ -406,7 +406,7 @@ elf_machine_rela (struct link_map *map,
binding found in the user program or a loaded library
rather than the dynamic linker's built-in definitions
used while loading those libraries. */
- value -= map->l_addr + refsym->st_value + reloc->r_addend;
+ value -= SYMBOL_ADDRESS (map, refsym, true) + reloc->r_addend;
#endif
COPY_UNALIGNED_WORD (&value, reloc_addr_arg,
(int) reloc_addr_arg & 3);
Index: glibc/sysdeps/sparc/sparc32/dl-machine.h
===================================================================
--- glibc.orig/sysdeps/sparc/sparc32/dl-machine.h 2018-02-19 13:10:21.706556824 +0000
+++ glibc/sysdeps/sparc/sparc32/dl-machine.h 2018-02-19 13:22:15.183043504 +0000
@@ -382,7 +382,7 @@ elf_machine_rela (struct link_map *map,
else
{
sym_map = RESOLVE_MAP (&sym, version, r_type);
- value = sym_map == NULL ? 0 : sym_map->l_addr + sym->st_value;
+ value = SYMBOL_ADDRESS (sym_map, sym, true);
}
#else
value = 0;
Index: glibc/sysdeps/sparc/sparc64/dl-machine.h
===================================================================
--- glibc.orig/sysdeps/sparc/sparc64/dl-machine.h 2018-02-19 13:10:21.732877229 +0000
+++ glibc/sysdeps/sparc/sparc64/dl-machine.h 2018-02-19 13:22:15.199215250 +0000
@@ -409,7 +409,7 @@ elf_machine_rela (struct link_map *map,
else
{
sym_map = RESOLVE_MAP (&sym, version, r_type);
- value = sym_map == NULL ? 0 : sym_map->l_addr + sym->st_value;
+ value = SYMBOL_ADDRESS (sym_map, sym, true);
}
#else
value = 0;
Index: glibc/sysdeps/tile/dl-machine.h
===================================================================
--- glibc.orig/sysdeps/tile/dl-machine.h 2018-02-19 13:10:21.756279043 +0000
+++ glibc/sysdeps/tile/dl-machine.h 2018-02-19 13:22:15.212498221 +0000
@@ -430,7 +430,7 @@ elf_machine_rela (struct link_map *map,
else if (ELFW_ST_TYPE (sym->st_info) == STT_SECTION)
value = map->l_addr; /* like a RELATIVE reloc */
else
- value = sym_map->l_addr + sym->st_value;
+ value = SYMBOL_ADDRESS (sym_map, sym, true);
if (sym != NULL
&& __builtin_expect (ELFW(ST_TYPE) (sym->st_info) == STT_GNU_IFUNC, 0)
Index: glibc/sysdeps/x86_64/dl-machine.h
===================================================================
--- glibc.orig/sysdeps/x86_64/dl-machine.h 2018-02-19 13:10:21.776588898 +0000
+++ glibc/sysdeps/x86_64/dl-machine.h 2018-02-19 13:22:15.235786558 +0000
@@ -306,8 +306,7 @@ elf_machine_rela (struct link_map *map,
const ElfW(Sym) *const refsym = sym;
# endif
struct link_map *sym_map = RESOLVE_MAP (&sym, version, r_type);
- ElfW(Addr) value = (sym == NULL ? 0
- : (ElfW(Addr)) sym_map->l_addr + sym->st_value);
+ ElfW(Addr) value = SYMBOL_ADDRESS (sym_map, sym, true);
if (sym != NULL
&& __glibc_unlikely (ELFW(ST_TYPE) (sym->st_info) == STT_GNU_IFUNC)
^ permalink raw reply [flat|nested] 9+ messages in thread* [PATCH v2 2/2] elf: Correct absolute (SHN_ABS) symbol run-time calculation [BZ #19818]
2018-02-20 18:40 [PATCH v2 0/2] Correct absolute (SHN_ABS) symbol run-time calculation [BZ #19818] Maciej W. Rozycki
2018-02-20 18:52 ` [PATCH v2 1/2] elf: Unify symbol address " Maciej W. Rozycki
@ 2018-02-20 20:24 ` Maciej W. Rozycki
2018-03-07 20:25 ` Adhemerval Zanella
2018-03-01 15:15 ` [PING][PATCH v2 0/2] " Maciej W. Rozycki
2 siblings, 1 reply; 9+ messages in thread
From: Maciej W. Rozycki @ 2018-02-20 20:24 UTC (permalink / raw)
To: libc-alpha; +Cc: H.J. Lu, Alan Modra, Cary Coutant
Do not relocate absolute symbols by the base address. Such symbols have
SHN_ABS as the section index and their value is not supposed to be
affected by relocation as per the ELF gABI[1]:
"SHN_ABS
The symbol has an absolute value that will not change because of
relocation."
The reason for our non-conformance here seems to be an old SysV linker
bug causing symbols like _DYNAMIC to be incorrectly emitted as absolute
symbols[2]. However in a previous discussion it was pointed that this
is seriously flawed by preventing the lone purpose of the existence of
absolute symbols from being used[3]:
"On the contrary, the only interpretation that makes sense to me is that
it will not change because of relocation at link time or at load time.
Absolute symbols, from the days of the earliest linking loaders, have
been used to represent addresses that are outside the address space of
the module (e.g., memory-mapped addresses or kernel gateway pages).
They've even been used to represent true symbolic constants (e.g.,
system entry point numbers, sizes, version numbers). There's no other
way to represent a true absolute symbol, while the meaning you seek is
easily represented by giving the symbol a non-negative st_shndx value."
and we ought to stop supporting our current broken interpretation.
Update processing for dladdr(3) and dladdr1(3) so that SHN_ABS symbols
are ignored, because under the corrected interpretation they do not
represent addresses within a mapped file and therefore are not supposed
to be considered.
References:
[1] "System V Application Binary Interface - DRAFT - 19 October 2010",
The SCO Group, Section "Symbol Table",
<http://www.sco.com/developers/gabi/2012-12-31/ch4.symtab.html>
[2] Alan Modra, "Absolute symbols"
<https://sourceware.org/ml/binutils/2012-05/msg00019.html>
[3] Cary Coutant, "Re: Absolute symbols"
<https://sourceware.org/ml/binutils/2012-05/msg00020.html>
[BZ #19818]
* sysdeps/generic/ldsodefs.h (SYMBOL_ADDRESS): Handle SHN_ABS
symbols.
* elf/dl-addr.c (determine_info): Ignore SHN_ABS symbols.
* elf/tst-absolute-sym.c: New file.
* elf/tst-absolute-sym-lib.c: New file.
* elf/tst-absolute-sym-lib.lds: New file.
* elf/Makefile (tests): Add `tst-absolute-sym'.
(modules-names): Add `tst-absolute-sym-lib'.
(LDLIBS-tst-absolute-sym-lib.so): New variable.
($(objpfx)tst-absolute-sym-lib.so): New dependency.
($(objpfx)tst-absolute-sym): New dependency.
---
Changes from v1:
- Ignore SHN_ABS symbols in `determine_info',
- Regenerate for the 1/2 update.
OK to apply?
Maciej
---
elf/Makefile | 8 ++++++--
elf/dl-addr.c | 2 ++
elf/tst-absolute-sym-lib.c | 25 +++++++++++++++++++++++++
elf/tst-absolute-sym-lib.lds | 19 +++++++++++++++++++
elf/tst-absolute-sym.c | 38 ++++++++++++++++++++++++++++++++++++++
sysdeps/generic/ldsodefs.h | 3 ++-
6 files changed, 92 insertions(+), 3 deletions(-)
glibc-elf-shn-abs.diff
Index: glibc/elf/Makefile
===================================================================
--- glibc.orig/elf/Makefile 2018-02-20 11:35:52.000000000 +0000
+++ glibc/elf/Makefile 2018-02-20 16:34:25.160539142 +0000
@@ -187,7 +187,7 @@ tests += restest1 preloadtest loadfail m
tst-tlsalign tst-tlsalign-extern tst-nodelete-opened \
tst-nodelete2 tst-audit11 tst-audit12 tst-dlsym-error tst-noload \
tst-latepthread tst-tls-manydynamic tst-nodelete-dlclose \
- tst-debug1 tst-main1
+ tst-debug1 tst-main1 tst-absolute-sym
# reldep9
tests-internal += loadtest unload unload2 circleload1 \
neededtest neededtest2 neededtest3 neededtest4 \
@@ -272,7 +272,7 @@ modules-names = testobj1 testobj2 testob
tst-audit12mod1 tst-audit12mod2 tst-audit12mod3 tst-auditmod12 \
tst-latepthreadmod $(tst-tls-many-dynamic-modules) \
tst-nodelete-dlclose-dso tst-nodelete-dlclose-plugin \
- tst-main1mod tst-libc_dlvsym-dso
+ tst-main1mod tst-libc_dlvsym-dso tst-absolute-sym-lib
ifeq (yes,$(have-mtls-dialect-gnu2))
tests += tst-gnu2-tls1
modules-names += tst-gnu2-tls1mod
@@ -1437,6 +1437,10 @@ tst-main1-no-pie = yes
LDLIBS-tst-main1 = $(libsupport)
tst-main1mod.so-no-z-defs = yes
+LDLIBS-tst-absolute-sym-lib.so = tst-absolute-sym-lib.lds
+$(objpfx)tst-absolute-sym-lib.so: $(LDLIBS-tst-absolute-sym-lib.so)
+$(objpfx)tst-absolute-sym: $(objpfx)tst-absolute-sym-lib.so
+
# Both the main program and the DSO for tst-libc_dlvsym need to link
# against libdl.
$(objpfx)tst-libc_dlvsym: $(libdl)
Index: glibc/elf/dl-addr.c
===================================================================
--- glibc.orig/elf/dl-addr.c 2018-02-20 11:35:52.000000000 +0000
+++ glibc/elf/dl-addr.c 2018-02-20 16:34:25.163584547 +0000
@@ -59,6 +59,7 @@ determine_info (const ElfW(Addr) addr, s
we can omit that test here. */
if ((symtab[symndx].st_shndx != SHN_UNDEF
|| symtab[symndx].st_value != 0)
+ && symtab[symndx].st_shndx != SHN_ABS
&& ELFW(ST_TYPE) (symtab[symndx].st_info) != STT_TLS
&& DL_ADDR_SYM_MATCH (match, &symtab[symndx],
matchsym, addr)
@@ -91,6 +92,7 @@ determine_info (const ElfW(Addr) addr, s
&& ELFW(ST_TYPE) (symtab->st_info) != STT_TLS
&& (symtab->st_shndx != SHN_UNDEF
|| symtab->st_value != 0)
+ && symtab->st_shndx != SHN_ABS
&& DL_ADDR_SYM_MATCH (match, symtab, matchsym, addr)
&& symtab->st_name < strtabsize)
matchsym = (ElfW(Sym) *) symtab;
Index: glibc/elf/tst-absolute-sym-lib.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ glibc/elf/tst-absolute-sym-lib.c 2018-02-20 16:34:25.185804348 +0000
@@ -0,0 +1,25 @@
+/* BZ #19818 absolute symbol calculation shared module.
+ Copyright (C) 2018 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+extern char absolute;
+
+void *
+get_absolute (void)
+{
+ return &absolute;
+}
Index: glibc/elf/tst-absolute-sym-lib.lds
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ glibc/elf/tst-absolute-sym-lib.lds 2018-02-20 16:34:25.204877904 +0000
@@ -0,0 +1,19 @@
+/* BZ #19818 absolute symbol calculation linker script.
+ Copyright (C) 2018 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+"absolute" = 0x55aa;
Index: glibc/elf/tst-absolute-sym.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ glibc/elf/tst-absolute-sym.c 2018-02-20 16:34:25.232178264 +0000
@@ -0,0 +1,38 @@
+/* BZ #19818 absolute symbol calculation main executable.
+ Copyright (C) 2018 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library 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
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#include <support/check.h>
+#include <support/support.h>
+#include <support/test-driver.h>
+
+void *get_absolute (void);
+
+static int
+do_test (void)
+{
+ void *ref = (void *) 0x55aa;
+ void *ptr;
+
+ ptr = get_absolute ();
+ if (ptr != ref)
+ FAIL_EXIT1 ("Got %p, expected %p\n", ptr, ref);
+
+ return 0;
+}
+
+#include <support/test-driver.c>
Index: glibc/sysdeps/generic/ldsodefs.h
===================================================================
--- glibc.orig/sysdeps/generic/ldsodefs.h 2018-02-20 16:32:02.000000000 +0000
+++ glibc/sysdeps/generic/ldsodefs.h 2018-02-20 16:34:25.271185000 +0000
@@ -72,7 +72,8 @@ typedef struct link_map *lookup_t;
if non-NULL. Don't check for NULL map if MAP_SET is TRUE. */
#define SYMBOL_ADDRESS(map, ref, map_set) \
((ref) == NULL ? 0 \
- : LOOKUP_VALUE_ADDRESS (map, map_set) + (ref)->st_value)
+ : (__glibc_unlikely ((ref)->st_shndx == SHN_ABS) ? 0 \
+ : LOOKUP_VALUE_ADDRESS (map, map_set)) + (ref)->st_value)
/* On some architectures a pointer to a function is not just a pointer
to the actual code of the function but rather an architecture
^ permalink raw reply [flat|nested] 9+ messages in thread