elf: Do not run IFUNC resolvers for LD_DEBUG=unused [BZ #24214]

This commit adds missing skip_ifunc checks to aarch64, arm, i386,
sparc, and x86_64.  A new test case ensures that IRELATIVE IFUNC
resolvers do not run in various diagnostic modes of the dynamic
loader.

Reviewed-By: Szabolcs Nagy <szabolcs.nagy@arm.com>

elf/Makefile

@@ -348,6 +348,7 @@ tests-ifuncstatic := ifuncmain1static ifuncmain1picstatic \
 tests-static += $(tests-ifuncstatic)
 tests-internal += $(tests-ifuncstatic)
 ifeq (yes,$(build-shared))
+tests += tst-ifunc-fault-lazy tst-ifunc-fault-bindnow
 # Note: sysdeps/x86_64/ifuncmain8.c uses ifuncmain8.
 tests-internal += \
 	 ifuncmain1 ifuncmain1pic ifuncmain1vis ifuncmain1vispic \
@@ -1354,6 +1355,21 @@ $(objpfx)ifuncmain5static: $(addprefix $(objpfx),ifuncdep5.o)
 $(objpfx)ifuncmain5staticpic: $(addprefix $(objpfx),ifuncdep5pic.o)
 $(objpfx)ifuncmain5picstatic: $(addprefix $(objpfx),ifuncdep5pic.o)
 
+LDFLAGS-tst-ifunc-fault-lazy = -Wl,-z,lazy
+LDFLAGS-tst-ifunc-fault-bindnow = -Wl,-z,now
+define tst-ifunc-fault-script
+( $(objpfx)ld.so --verify --library-path  $(objpfx) $^ \
+  && LD_TRACE_LOADED_OBJECTS=1 $(objpfx)ld.so --library-path $(objpfx) $^ \
+  && LD_TRACE_LOADED_OBJECTS=1 LD_DEBUG=unused \
+    $(objpfx)ld.so --library-path  $(objpfx) $^ \
+) > $@; $(evaluate-test)
+endef
+$(objpfx)tst-ifunc-fault-lazy.out: $(objpfx)tst-ifunc-fault-lazy $(objpfx)ld.so
+	$(tst-ifunc-fault-script)
+$(objpfx)tst-ifunc-fault-bindnow.out: $(objpfx)tst-ifunc-fault-bindnow \
+   $(objpfx)ld.so
+	$(tst-ifunc-fault-script)
+
 $(objpfx)tst-unique1: $(libdl)
 $(objpfx)tst-unique1.out: $(objpfx)tst-unique1mod1.so \
 			  $(objpfx)tst-unique1mod2.so

elf/tst-ifunc-fault-bindnow.c

@@ -0,0 +1,21 @@
+/* Program with local IFUNC resolver which crashes.  BIND_NOW variant.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+/* The code is the same as the lazy variant.  It is just linked
+   differently.  */
+#include "tst-ifunc-fault-lazy.c"

elf/tst-ifunc-fault-lazy.c

@@ -0,0 +1,57 @@
+/* Program with local IFUNC resolver which crashes, for testing bug 24214.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+/* The construct below is expected to produce an IRELATIVE relocation
+   with an IFUNC resolver that crashes. ldd should not performs such
+   relocations.  */
+
+#include <config.h>
+
+#ifdef HAVE_GCC_IFUNC
+
+# include <stddef.h>
+
+static void
+implementation (void)
+{
+  /* Produce a crash, without depending on any relocations.  */
+  volatile char *volatile p = NULL;
+  *p = 0;
+}
+
+static __typeof__ (implementation) *
+resolver (void)
+{
+  /* Produce a crash, without depending on any relocations.  */
+  volatile char *volatile p = NULL;
+  *p = 0;
+  return implementation;
+}
+
+static void magic (void) __attribute__ ((ifunc ("resolver")));
+
+void (*magic_ptr) (void) = magic;
+
+#endif /* HAVE_GCC_IFUNC */
+
+/* The program is expected not to run.  */
+int
+main (void)
+{
+  return 1;
+}

sysdeps/aarch64/dl-machine.h

@@ -358,6 +358,7 @@ elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
 
 	case AARCH64_R(IRELATIVE):
 	  value = map->l_addr + reloc->r_addend;
+	  if (__glibc_likely (!skip_ifunc))
 	    value = elf_ifunc_invoke (value);
 	  *reloc_addr = value;
 	  break;

sysdeps/arm/dl-machine.h

@@ -522,6 +522,7 @@ elf_machine_rel (struct link_map *map, const Elf32_Rel *reloc,
 	  break;
 	case R_ARM_IRELATIVE:
 	  value = map->l_addr + *reloc_addr;
+	  if (__glibc_likely (!skip_ifunc))
 	    value = ((Elf32_Addr (*) (int)) value) (GLRO(dl_hwcap));
 	  *reloc_addr = value;
 	  break;
@@ -614,6 +615,7 @@ elf_machine_rela (struct link_map *map, const Elf32_Rela *reloc,
 	  break;
 	case R_ARM_IRELATIVE:
 	  value = map->l_addr + reloc->r_addend;
+	  if (__glibc_likely (!skip_ifunc))
 	    value = ((Elf32_Addr (*) (int)) value) (GLRO(dl_hwcap));
 	  *reloc_addr = value;
 	  break;

sysdeps/i386/dl-machine.h

@@ -480,6 +480,7 @@ elf_machine_rel (struct link_map *map, const Elf32_Rel *reloc,
 	  break;
 	case R_386_IRELATIVE:
 	  value = map->l_addr + *reloc_addr;
+	  if (__glibc_likely (!skip_ifunc))
 	    value = ((Elf32_Addr (*) (void)) value) ();
 	  *reloc_addr = value;
 	  break;
@@ -627,6 +628,7 @@ elf_machine_rela (struct link_map *map, const Elf32_Rela *reloc,
 #  endif /* !RESOLVE_CONFLICT_FIND_MAP */
 	case R_386_IRELATIVE:
 	  value = map->l_addr + reloc->r_addend;
+	  if (__glibc_likely (!skip_ifunc))
 	    value = ((Elf32_Addr (*) (void)) value) ();
 	  *reloc_addr = value;
 	  break;

sysdeps/sparc/sparc32/dl-machine.h

@@ -425,10 +425,12 @@ elf_machine_rela (struct link_map *map, const Elf32_Rela *reloc,
       *reloc_addr = value;
       break;
     case R_SPARC_IRELATIVE:
+      if (__glibc_likely (!skip_ifunc))
 	value = ((Elf32_Addr (*) (int)) value) (GLRO(dl_hwcap));
       *reloc_addr = value;
       break;
     case R_SPARC_JMP_IREL:
+      if (__glibc_likely (!skip_ifunc))
 	value = ((Elf32_Addr (*) (int)) value) (GLRO(dl_hwcap));
       /* Fall thru */
     case R_SPARC_JMP_SLOT:

sysdeps/sparc/sparc64/dl-machine.h

@@ -450,10 +450,12 @@ elf_machine_rela (struct link_map *map, const Elf64_Rela *reloc,
       *reloc_addr = value;
       break;
     case R_SPARC_IRELATIVE:
+      if (__glibc_likely (!skip_ifunc))
 	value = ((Elf64_Addr (*) (int)) value) (GLRO(dl_hwcap));
       *reloc_addr = value;
       break;
     case R_SPARC_JMP_IREL:
+      if (__glibc_likely (!skip_ifunc))
 	value = ((Elf64_Addr (*) (int)) value) (GLRO(dl_hwcap));
       /* 'high' is always zero, for large PLT entries the linker
 	 emits an R_SPARC_IRELATIVE.  */

sysdeps/x86_64/dl-machine.h

@@ -512,6 +512,7 @@ elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc,
 #  endif
 	case R_X86_64_IRELATIVE:
 	  value = map->l_addr + reloc->r_addend;
+	  if (__glibc_likely (!skip_ifunc))
 	    value = ((ElfW(Addr) (*) (void)) value) ();
 	  *reloc_addr = value;
 	  break;