Fix signal trampolines.

* LP32 should use sa_restorer too. gdb expects this, and future (>= 3.15) x86
  kernels will apparently stop supporting the case where SA_RESTORER isn't
  set.

* gdb and libunwind care about the exact instruction sequences, so we need to
  modify the code slightly in a few cases to match what they're looking for.

* gdb also cares about the exact function names (for some architectures),
  so we need to use __restore and __restore_rt rather than __sigreturn and
  __rt_sigreturn.

* It's possible that we don't have a VDSO; dl_iterate_phdr shouldn't assume
  that getauxval(AT_SYSINFO_EHDR) will return a non-null pointer.

This fixes unwinding through a signal handler in gdb for all architectures.
It doesn't fix libunwind for arm and arm64. I'll keep investigating that...

Bug: 17436734
Change-Id: Ic1ea1184db6655c5d96180dc07bcc09628e647cb
Merge "Fix signal trampolines."
Add benchmarks for pthread_rw_locks

Benchmarks for the following sequences:
1) pthread_rwlock_rdlock -> pthread_rwlock_unlock
2) pthread_rwlock_wrlock -> pthread_rwlock_unlock

Change-Id: I8d87d4d8afab8637ea7ff5d23a0b3a81d6d40835
Merge "Add benchmarks for pthread_rw_locks"
Fix 32-bit arm unwinding through signal frames.

gdb was already okay; libgcc and libunwind need a little extra help.

Bug: 17436734
Change-Id: I1f5108f9877373be078554a1ea4938aa4436204e
Merge "Fix 32-bit arm unwinding through signal frames."
Remove has_DT_SYMBOLIC flag

  From the elf-spec: "Symbolically bound shared objects are
  identified by the .dynamic entry DT_SYMBOLIC. This tag is
  informational only; the runtime linker processes symbol
  lookups from these objects in the same manner as any
  other object."

Change-Id: I4aae0e502ed9fac096fbf076f4d6b2e055d784f6
Merge "Remove has_DT_SYMBOLIC flag"
No arm source refers to SOFTFLOAT.

So why bother #defining it?

Change-Id: I539e91916cee082cacac594ddf628419b737fa9d
Merge "No arm source refers to SOFTFLOAT."
Fix some unused DT_ warnings

 * DT_PLTGOT - ignored for non-mips
 * DT_RELCOUNT/RELACOUNT - ignored
 * DT_RELENT/RELAENT - sanity checks
 * DT_SYMENT - sanity check
 * DT_SONAME - ignore for now.

Change-Id: Ied90748d12f733a84f6c38a1250567a2f77608b7
Merge "Fix some unused DT_ warnings"
Fix 64bit build

Change-Id: I6ef55b5951270c46ee5e9a11385bd09e33a9f969
Merge "Fix 64bit build"