PowerPC64 ELFv2 ABI 2/6: Remove function descriptors

This patch adds support for the ELFv2 ABI feature to remove function
descriptors.  See this GCC patch for in-depth discussion:
http://gcc.gnu.org/ml/gcc-patches/2013-11/msg01141.html

This mostly involves two types of changes: updating assembler source
files to the new logic, and updating the dynamic loader.

After the refactoring in the previous patch, most of the assembler source
changes can be handled simply by providing ELFv2 versions of the
macros in sysdep.h.   One somewhat non-obvious change is in __GI__setjmp:
this used to "fall through" to the immediately following __setjmp ENTRY
point.  This is no longer safe in the ELFv2 since ENTRY defines both
a global and a local entry point, and you cannot simply fall through
to a global entry point as it requires r12 to be set up.

Also, makecontext needs to be updated to set up registers according to
the new ABI for calling into the context's start routine.

The dynamic linker changes mostly consist of removing special code
to handle function descriptors.  We also need to support the new PLT
and glink format used by the the ELFv2 linker, see:
https://sourceware.org/ml/binutils/2013-10/msg00376.html

In addition, the dynamic linker now verifies that the dynamic libraries
it loads match its own ABI.

The hack in VDSO_IFUNC_RET to "synthesize" a function descriptor
for vDSO routines is also no longer necessary for ELFv2.

1 files changed, 6 insertions, 0 deletions

diff --git a/elf/elf.h b/elf/elf.h
index 6e2552e35d..7a9855c850 100644
--- a/elf/elf.h
+++ b/elf/elf.h
@@ -2272,6 +2272,12 @@ typedef Elf32_Addr Elf32_Conflict;
 #define R_PPC64_REL16_HI	251	/* half16   (sym+add-.)@h */
 #define R_PPC64_REL16_HA	252	/* half16   (sym+add-.)@ha */
 
+/* e_flags bits specifying ABI.
+   1 for original function descriptor using ABI,
+   2 for revised ABI without function descriptors,
+   0 for unspecified or not using any features affected by the differences.  */
+#define EF_PPC64_ABI	3
+
 /* PowerPC64 specific values for the Dyn d_tag field.  */
 #define DT_PPC64_GLINK  (DT_LOPROC + 0)
 #define DT_PPC64_OPD	(DT_LOPROC + 1)