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, 52 insertions, 2 deletions

diff --git a/sysdeps/powerpc/powerpc64/sysdep.h b/sysdeps/powerpc/powerpc64/sysdep.h
index cc89b3ce80..779fd90265 100644
--- a/sysdeps/powerpc/powerpc64/sysdep.h
+++ b/sysdeps/powerpc/powerpc64/sysdep.h
@@ -74,6 +74,8 @@
 #endif
 	.endm
 
+#if _CALL_ELF != 2
+
 /* Macro to prepare for calling via a function pointer.  */
 	.macro PPC64_LOAD_FUNCPTR PTR
 	ld      r12,0(\PTR)
@@ -115,13 +117,37 @@ name##: OPD_ENT (name);				\
 	.size name,.-BODY_LABEL(name);		\
 	.size BODY_LABEL(name),.-BODY_LABEL(name);
 #endif
+#define LOCALENTRY(name)
+
+#else /* _CALL_ELF */
+
+/* Macro to prepare for calling via a function pointer.  */
+	.macro PPC64_LOAD_FUNCPTR PTR
+	mr	r12,\PTR
+	mtctr   r12
+	.endm
+
+#define DOT_LABEL(X) X
+#define BODY_LABEL(X) X
+#define ENTRY_2(name)	\
+	.globl name;				\
+	.type name,@function;
+#define END_2(name)	\
+	.size name,.-name;
+#define LOCALENTRY(name)	\
+1:      addis	r2,r12,.TOC.-1b@ha; \
+        addi	r2,r2,.TOC.-1b@l; \
+	.localentry name,.-name;
+
+#endif /* _CALL_ELF */
 
 #define ENTRY(name)	\
 	.section	".text";		\
 	ENTRY_2(name)				\
 	.align ALIGNARG(2);			\
 BODY_LABEL(name):				\
-	cfi_startproc;
+	cfi_startproc;				\
+	LOCALENTRY(name)
 
 #define EALIGN_W_0  /* No words to insert.  */
 #define EALIGN_W_1  nop
@@ -140,7 +166,8 @@ BODY_LABEL(name):				\
 	.align ALIGNARG(alignt);		\
 	EALIGN_W_##words;			\
 BODY_LABEL(name):				\
-	cfi_startproc;
+	cfi_startproc;				\
+	LOCALENTRY(name)
 
 /* Local labels stripped out by the linker.  */
 #undef L
@@ -295,6 +322,8 @@ LT_LABELSUFFIX(name,_name_end): ; \
 
 #else /* !__ASSEMBLER__ */
 
+#if _CALL_ELF != 2
+
 #define PPC64_LOAD_FUNCPTR(ptr) \
 	"ld 	12,0(" #ptr ");\n"					\
 	"ld	2,8(" #ptr ");\n"					\
@@ -335,5 +364,26 @@ LT_LABELSUFFIX(name,_name_end): ; \
 	".size " #name ",.-" BODY_PREFIX #name ";\n"			\
 	".size " BODY_PREFIX #name ",.-" BODY_PREFIX #name ";"
 #endif
+#define LOCALENTRY(name)
+
+#else /* _CALL_ELF */
+
+#define PPC64_LOAD_FUNCPTR(ptr) \
+	"mr	12," #ptr ";\n"						\
+	"mtctr 	12;"
+
+#define DOT_PREFIX ""
+#define BODY_PREFIX ""
+#define ENTRY_2(name)	\
+	".type " #name ",@function;\n"					\
+	".globl " #name ";"
+#define END_2(name)	\
+	".size " #name ",.-" #name ";"
+#define LOCALENTRY(name)	\
+	"1: addis 2,12,.TOC.-1b@ha;\n"					\
+	"addi	2,2,.TOC.-1b@l;\n"					\
+	".localentry " #name ",.-" #name ";"
+
+#endif /* _CALL_ELF */
 
 #endif	/* __ASSEMBLER__ */