x86: Check IFUNC definition in unrelocated executable [BZ #20019]

Calling an IFUNC function defined in unrelocated executable also leads to
segfault.  Issue a fatal error message when calling IFUNC function defined
in the unrelocated executable from a shared library.

On x86, ifuncmain6pie failed with:

[hjl@gnu-cfl-2 build-i686-linux]$ ./elf/ifuncmain6pie --direct
./elf/ifuncmain6pie: IFUNC symbol 'foo' referenced in '/export/build/gnu/tools-build/glibc-32bit/build-i686-linux/elf/ifuncmod6.so' is defined in the executable and creates an unsatisfiable circular dependency.
[hjl@gnu-cfl-2 build-i686-linux]$ readelf -rW elf/ifuncmod6.so | grep foo
00003ff4  00000706 R_386_GLOB_DAT         0000400c   foo_ptr
00003ff8  00000406 R_386_GLOB_DAT         00000000   foo
0000400c  00000401 R_386_32               00000000   foo
[hjl@gnu-cfl-2 build-i686-linux]$

Remove non-JUMP_SLOT relocations against foo in ifuncmod6.so, which
trigger the circular IFUNC dependency, and build ifuncmain6pie with
-Wl,-z,lazy.

(cherry picked from commits 6ea5b57afa5cdc9ce367d2b69a2cebfb273e4617
 and 7137d682ebfcb6db5dfc5f39724718699922f06c)

3 files changed, 9 insertions, 15 deletions

diff --git a/elf/Makefile b/elf/Makefile
index 0b78721848..355e70037b 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -1381,6 +1381,8 @@ CFLAGS-ifuncmain7pie.c += $(pie-ccflag)
 CFLAGS-ifuncmain9pie.c += $(pie-ccflag)
 CFLAGS-tst-ifunc-textrel.c += $(pic-ccflag)
 
+LDFLAGS-ifuncmain6pie = -Wl,-z,lazy
+
 $(objpfx)ifuncmain1pie: $(objpfx)ifuncmod1.so
 $(objpfx)ifuncmain1staticpie: $(objpfx)ifuncdep1pic.o
 $(objpfx)ifuncmain1vispie: $(objpfx)ifuncmod1.so
diff --git a/elf/ifuncmain6pie.c b/elf/ifuncmain6pie.c
index 04faeb86ef..4a01906836 100644
--- a/elf/ifuncmain6pie.c
+++ b/elf/ifuncmain6pie.c
@@ -9,7 +9,6 @@
 #include "ifunc-sel.h"
 
 typedef int (*foo_p) (void);
-extern foo_p foo_ptr;
 
 static int
 one (void)
@@ -28,20 +27,17 @@ foo_ifunc (void)
 }
 
 extern int foo (void);
-extern foo_p get_foo (void);
+extern int call_foo (void);
 extern foo_p get_foo_p (void);
 
-foo_p my_foo_ptr = foo;
+foo_p foo_ptr = foo;
 
 int
 main (void)
 {
   foo_p p;
 
-  p = get_foo ();
-  if (p != foo)
-    abort ();
-  if ((*p) () != -30)
+  if (call_foo () != -30)
     abort ();
 
   p = get_foo_p ();
@@ -52,12 +48,8 @@ main (void)
 
   if (foo_ptr != foo)
     abort ();
-  if (my_foo_ptr != foo)
-    abort ();
   if ((*foo_ptr) () != -30)
     abort ();
-  if ((*my_foo_ptr) () != -30)
-    abort ();
   if (foo () != -30)
     abort ();
 
diff --git a/elf/ifuncmod6.c b/elf/ifuncmod6.c
index 2e16c1d06d..2f6d0715e6 100644
--- a/elf/ifuncmod6.c
+++ b/elf/ifuncmod6.c
@@ -4,7 +4,7 @@ extern int foo (void);
 
 typedef int (*foo_p) (void);
 
-foo_p foo_ptr = foo;
+extern foo_p foo_ptr;
 
 foo_p
 get_foo_p (void)
@@ -12,8 +12,8 @@ get_foo_p (void)
   return foo_ptr;
 }
 
-foo_p
-get_foo (void)
+int
+call_foo (void)
 {
-  return foo;
+  return foo ();
 }