[2.27 COMMITTED] x86: Make strncmp usable from rtld

[Florian Weimer]

Due to the way the conditions were written, the rtld build of strncmp
ended up with no definition of the strncmp symbol at all: The
implementations were renamed for use within an IFUNC resolver, but the
IFUNC resolver itself was missing (because rtld does not use IFUNCs).

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
(cherry picked from commit e826574c985a15a500262f2fbd21c7e9259d3d11)

2018-06-12  Florian Weimer  <fweimer@redhat.com>

	x86: Make strncmp usable from rtld.
	* sysdeps/i386/i686/multiarch/strncmp-c.c: Only rename strncmp to
	__strncmp_ia32 if in libc (and not in rtld).
	* sysdeps/x86_64/multiarch/strncmp-sse2.S: Rename strcmp to
	strncmp if not in libc (and not to __strncmp_sse2).

diff --git a/sysdeps/i386/i686/multiarch/strncmp-c.c b/sysdeps/i386/i686/multiarch/strncmp-c.c
index cc059da494..2e3eca9b2b 100644
--- a/sysdeps/i386/i686/multiarch/strncmp-c.c
+++ b/sysdeps/i386/i686/multiarch/strncmp-c.c
@@ -1,4 +1,4 @@
-#ifdef SHARED
+#if defined (SHARED) && IS_IN (libc)
 # define STRNCMP __strncmp_ia32
 # undef libc_hidden_builtin_def
 # define libc_hidden_builtin_def(name)  \
diff --git a/sysdeps/x86_64/multiarch/strncmp-sse2.S b/sysdeps/x86_64/multiarch/strncmp-sse2.S
index cc5252d826..a5ecb82b13 100644
--- a/sysdeps/x86_64/multiarch/strncmp-sse2.S
+++ b/sysdeps/x86_64/multiarch/strncmp-sse2.S
@@ -18,10 +18,13 @@
 
 #include <sysdep.h>
 
-#define STRCMP	__strncmp_sse2
-
-#undef libc_hidden_builtin_def
-#define libc_hidden_builtin_def(strcmp)
+#if IS_IN (libc)
+# define STRCMP __strncmp_sse2
+# undef libc_hidden_builtin_def
+# define libc_hidden_builtin_def(strcmp)
+#else
+# define STRCMP strncmp
+#endif
 
 #define USE_AS_STRNCMP
 #include <sysdeps/x86_64/strcmp.S>