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.

2 files changed, 11 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/ldsodefs.h b/sysdeps/unix/sysv/linux/powerpc/powerpc64/ldsodefs.h
index 4263b1a..d043968 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/ldsodefs.h
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/ldsodefs.h
@@ -23,6 +23,8 @@
 
 /* Now define our stuff.  */
 
+#if _CALL_ELF != 2
+
 static __always_inline bool
 _dl_ppc64_is_opd_sym (const struct link_map *l, const ElfW(Sym) *sym)
 {
@@ -73,4 +75,6 @@ _dl_ppc64_addr_sym_match (const struct link_map *l, const ElfW(Sym) *sym,
 #define DL_ADDR_SYM_MATCH(L, SYM, MATCHSYM, ADDR) \
   _dl_ppc64_addr_sym_match (L, SYM, MATCHSYM, ADDR)
 
+#endif
+
 #endif /* ldsodefs.h */
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S b/sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S
index a7b0a18..b6d82bd 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/makecontext.S
@@ -111,6 +111,7 @@ L(parmloop):
 
 L(noparms):
 
+#if _CALL_ELF != 2
   /* Load the function address and TOC from the function descriptor
      and store them in the ucontext as NIP and r2.  Store the 3rd
      field of the function descriptor into the ucontext as r11 in case
@@ -121,6 +122,12 @@ L(noparms):
   std   r0,(SIGCONTEXT_GP_REGS+(PT_NIP*8))(r3)
   std   r10,(SIGCONTEXT_GP_REGS+(PT_R2*8))(r3)
   std   r9,(SIGCONTEXT_GP_REGS+(PT_R11*8))(r3)
+#else
+  /* In the ELFv2 ABI, the function pointer is already the address.
+     Store it as NIP and r12 as required by the ABI.  */
+  std   r4,(SIGCONTEXT_GP_REGS+(PT_NIP*8))(r3)
+  std   r4,(SIGCONTEXT_GP_REGS+(PT_R12*8))(r3)
+#endif
 
   /* If the target function returns we need to do some cleanup.  We use a
      code trick to get the address of our cleanup function into the link