Fix the problem that surfaced with the new binutils import on sparc64

(and that is for now being worked around by a binutils patch).

The rtld code tested &_DYNAMIC against 0 to see whether rtld itself
was built as PIC or not. While the sparc64 MD code did not rely
on the preset value of the GOT slot for _DYNAMIC any more due
to previous binutils changes, it still used to not be 0, so
that this check did work. The new binutils do however initialize
this slot with 0. As a consequence, rtld would not properly initialize
itself and crash.
Fix that by introducing a new macro, RTLD_IS_DYNAMIC, to take the role
of this test. For sparc64, it is implemented using the rtld_dynamic()
code that was already there. If an architecture does not provide its
own implementation, we default to the old check.

While being there, mark _DYNAMIC as a weak symbol in the sparc64
rtld_start.S. This is needed in the LDSCRIPT case, which is however
not currently supported for want of an actual ldscript.

Sanity checked with md5 on alpha, amd64, i386 and ia64.

3 files changed, 10 insertions, 4 deletions

diff --git a/libexec/rtld-elf/rtld.c b/libexec/rtld-elf/rtld.c
index cd8385d..62ca650 100644
--- a/libexec/rtld-elf/rtld.c
+++ b/libexec/rtld-elf/rtld.c
@@ -162,6 +162,9 @@ static Elf_Sym sym_zero;	/* For resolving undefined weak refs. */
 
 extern Elf_Dyn _DYNAMIC;
 #pragma weak _DYNAMIC
+#ifndef RTLD_IS_DYNAMIC
+#define	RTLD_IS_DYNAMIC()	(&_DYNAMIC != NULL)
+#endif
 
 /*
  * These are the functions the dynamic linker exports to application
@@ -1008,7 +1011,7 @@ init_rtld(caddr_t mapbase)
 #ifdef PIC
     objtmp.relocbase = mapbase;
 #endif
-    if (&_DYNAMIC != 0) {
+    if (RTLD_IS_DYNAMIC()) {
 	objtmp.dynamic = rtld_dynamic(&objtmp);
 	digest_dynamic(&objtmp, 1);
 	assert(objtmp.needed == NULL);
diff --git a/libexec/rtld-elf/sparc64/rtld_machdep.h b/libexec/rtld-elf/sparc64/rtld_machdep.h
index d92055c..27276ee 100644
--- a/libexec/rtld-elf/sparc64/rtld_machdep.h
+++ b/libexec/rtld-elf/sparc64/rtld_machdep.h
@@ -37,7 +37,9 @@
 struct Struct_Obj_Entry;
 
 /* Return the address of the .dynamic section in the dynamic linker. */
-Elf_Dyn *rtld_dynamic(const struct Struct_Obj_Entry *);
+Elf_Dyn *rtld_dynamic_addr();
+#define	rtld_dynamic(obj)	rtld_dynamic_addr()
+#define	RTLD_IS_DYNAMIC()	(rtld_dynamic_addr() != NULL)
 
 Elf_Addr reloc_jmpslot(Elf_Addr *, Elf_Addr,
 		       const struct Struct_Obj_Entry *,
diff --git a/libexec/rtld-elf/sparc64/rtld_start.S b/libexec/rtld-elf/sparc64/rtld_start.S
index 146c6314..58bdd1b 100644
--- a/libexec/rtld-elf/sparc64/rtld_start.S
+++ b/libexec/rtld-elf/sparc64/rtld_start.S
@@ -71,8 +71,9 @@ END(.rtld_start)
  * Find the address of _DYNAMIC by disassembling a call instruction to it.
  * Binutils may not fill in the GOT as expected on other architectures.
  */
+.weak	_DYNAMIC
 
-ENTRY(rtld_dynamic)
+ENTRY(rtld_dynamic_addr)
 	save	%sp, -CCFSZ, %sp
 	call	1f
 	 nop
@@ -82,7 +83,7 @@ ENTRY(rtld_dynamic)
 	sra	%o0, 0, %o0
 	ret
 	 restore %o0, %o7, %o0
-END(rtld_dynamic)
+END(rtld_dynamic_addr)
 
 	/*
 	 * We have two separate entry points to the runtime linker.