Use the first element of GOT for ld.so addresses

	[BZ #14538]
	* sysdeps/x86_64/dl-machine.h (elf_machine_dynamic): Use the
	first element of the GOT.
	(elf_machine_load_address): Return the difference between
	the runtime address of _DYNAMIC and elf_machine_dynamic ().

diff --git a/ChangeLog b/ChangeLog
index ad8f23e37f0b217e1a7a548b4773dc560862a300..c130d9de87077bccaf7042d6177976b798afb56c 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,8 +1,16 @@
+2012-09-02  H.J. Lu  <hongjiu.lu@intel.com>
+
+       [BZ #14538]
+       * sysdeps/x86_64/dl-machine.h (elf_machine_dynamic): Use the
+       first element of the GOT.
+       (elf_machine_load_address): Return the difference between
+       the runtime address of _DYNAMIC and elf_machine_dynamic ().
+
 2012-09-01  Allan McRae  <allan@archlinux.org>
 
-        [BZ #13412]
-        * configure.in (AWK): Require gawk version 3.0 or later.
-        * configure: Regenerated.
+       [BZ #13412]
+       * configure.in (AWK): Require gawk version 3.0 or later.
+       * configure: Regenerated.
 
 2012-09-01  Joseph Myers  <joseph@codesourcery.com>
 

diff --git a/NEWS b/NEWS
index c10e993a99ffecb65f0084351fcc9ffb86439ebf..e0dcdf4696fb5fc51cc909d13b3e8fab12cd16ed 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -12,7 +12,7 @@ Version 2.17
   3479, 5400, 6778, 6808, 9685, 11607, 13412, 13717, 13696, 13939, 14042,
   14090, 14166, 14150, 14151, 14154, 14157, 14166, 14173, 14195, 14252,
   14283, 14298, 14303, 14307, 14328, 14331, 14336, 14337, 14347, 14349,
-  14459, 14476, 14505, 14516, 14519, 14532
+  14459, 14476, 14505, 14516, 14519, 14532, 14538
 
 * Support for STT_GNU_IFUNC symbols added for s390 and s390x.
   Optimized versions of memcpy, memset, and memcmp added for System z10 and

diff --git a/sysdeps/x86_64/dl-machine.h b/sysdeps/x86_64/dl-machine.h
index 9c27ecffd86f9c240f034be1a7825e8cb4f4f795..d2654aa04b522e23e568071ede3a9c6e9db97e67 100644 (file)
--- a/sysdeps/x86_64/dl-machine.h
+++ b/sysdeps/x86_64/dl-machine.h
@@ -41,13 +41,9 @@ elf_machine_matches_host (const ElfW(Ehdr) *ehdr)
 static inline ElfW(Addr) __attribute__ ((unused))
 elf_machine_dynamic (void)
 {
-  ElfW(Addr) addr;
-
-  /* This works because we have our GOT address available in the small PIC
-     model.  */
-  addr = (ElfW(Addr)) &_DYNAMIC;
-
-  return addr;
+  /* This produces an IP-relative reloc which is resolved at link time. */
+  extern const ElfW(Addr) _GLOBAL_OFFSET_TABLE_[] attribute_hidden;
+  return _GLOBAL_OFFSET_TABLE_[0];
 }
 
 
@@ -55,31 +51,11 @@ elf_machine_dynamic (void)
 static inline ElfW(Addr) __attribute__ ((unused))
 elf_machine_load_address (void)
 {
-  ElfW(Addr) addr;
-
-  /* The easy way is just the same as on x86:
-       leaq _dl_start, %0
-       leaq _dl_start(%%rip), %1
-       subq %0, %1
-     but this does not work with binutils since we then have
-     a R_X86_64_32S relocation in a shared lib.
-
-     Instead we store the address of _dl_start in the data section
-     and compare it with the current value that we can get via
-     an RIP relative addressing mode.  Note that this is the address
-     of _dl_start before any relocation performed at runtime.  In case
-     the binary is prelinked the resulting "address" is actually a
-     load offset which is zero if the binary was loaded at the address
-     it is prelinked for.  */
-
-  asm ("lea _dl_start(%%rip), %0\n\t"
-       "sub 1f(%%rip), %0\n\t"
-       ".section\t.data.rel.ro\n"
-       "1:\t" ASM_ADDR " _dl_start\n\t"
-       ".previous\n\t"
-       : "=r" (addr) : : "cc");
-
-  return addr;
+  /* Compute the difference between the runtime address of _DYNAMIC as seen
+     by an IP-relative reference, and the link-time address found in the
+     special unrelocated first GOT entry.  */
+  extern ElfW(Dyn) _DYNAMIC[] attribute_hidden;
+  return (ElfW(Addr)) &_DYNAMIC - elf_machine_dynamic ();
 }
 
 /* Set up the loaded object described by L so its unrelocated PLT