Make sure that calloc is called at least once

PLT relocations aren't required when -z now used.  Linker on master with:

commit 25070364b0ce33eed46aa5d78ebebbec6accec7e
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Sat May 16 07:00:21 2015 -0700

    Don't generate PLT relocations for now binding

    There is no need for PLT relocations with -z now. We can use GOT
    relocations, which take less space, instead and replace 16-byte .plt
    entres with 8-byte .plt.got entries.

    bfd/

      * elf32-i386.c (elf_i386_check_relocs): Create .plt.got section
      for now binding.
      (elf_i386_allocate_dynrelocs): Use .plt.got section for now
      binding.
      * elf64-x86-64.c (elf_x86_64_check_relocs): Create .plt.got
      section for now binding.
      (elf_x86_64_allocate_dynrelocs): Use .plt.got section for now
      binding.

won't generate PLT relocations with -z now.  elf/tst-audit2.c expect
certain order of execution in ld.so.  With PLT relocations, the GOTPLT
entry of calloc is update to calloc defined in tst-audit2:

(gdb) bt
    skip_ifunc=<optimized out>, reloc_addr_arg=<optimized out>,
    version=<optimized out>, sym=<optimized out>, map=<optimized out>)
    at ../sysdeps/i386/dl-machine.h:329
out>,
    nrelative=<optimized out>, relsize=<optimized out>,
    reladdr=<optimized out>, map=<optimized out>) at do-rel.h:137
reloc_mode=reloc_mode@entry=0,
    consider_profiling=1, consider_profiling@entry=0) at dl-reloc.c:258
    user_entry=0xffffcf1c, auxv=0xffffd0a8) at rtld.c:2133
    start_argptr=start_argptr@entry=0xffffcfb0,
    dl_main=dl_main@entry=0xf7fda6f0 <dl_main>) at
../elf/dl-sysdep.c:249
   from /export/build/gnu/glibc-32bit/build-i686-linux/elf/ld.so
(gdb)

and then calloc is called:

(gdb) c
Continuing.

Breakpoint 4, calloc (n=n@entry=20, m=4) at tst-audit2.c:18
18 {
(gdb) bt
    reloc_mode=reloc_mode@entry=0, consider_profiling=1,
    consider_profiling@entry=0) at dl-reloc.c:272
    user_entry=0xffffcf1c, auxv=0xffffd0a8) at rtld.c:2133
    start_argptr=start_argptr@entry=0xffffcfb0,
    dl_main=dl_main@entry=0xf7fda6f0 <dl_main>) at
../elf/dl-sysdep.c:249
   from /export/build/gnu/glibc-32bit/build-i686-linux/elf/ld.so
(gdb)

With GOT relocation, calloc in ld.so is called first:

(gdb) bt
    consider_profiling=1) at dl-reloc.c:272
    user_entry=0xffffcf0c, auxv=0xffffd098) at rtld.c:2074
    start_argptr=start_argptr@entry=0xffffcfa0,
    dl_main=dl_main@entry=0xf7fda6c0 <dl_main>) at
../elf/dl-sysdep.c:249
   from /export/build/gnu/glibc-32bit-test/build-i686-linux/elf/ld.so
(gdb)

and then the GOT entry of calloc is updated:

(gdb) bt
    skip_ifunc=<optimized out>, reloc_addr_arg=<optimized out>,
    version=<optimized out>, sym=<optimized out>, map=<optimized out>)
    at ../sysdeps/i386/dl-machine.h:329
out>,
    nrelative=<optimized out>, relsize=<optimized out>,
    reladdr=<optimized out>, map=<optimized out>) at do-rel.h:137
reloc_mode=reloc_mode@entry=0,
    consider_profiling=1, consider_profiling@entry=0) at dl-reloc.c:258
    user_entry=0xffffcf0c, auxv=0xffffd098) at rtld.c:2133
    start_argptr=start_argptr@entry=0xffffcfa0,
    dl_main=dl_main@entry=0xf7fda6c0 <dl_main>) at
../elf/dl-sysdep.c:249
   from /export/build/gnu/glibc-32bit-test/build-i686-linux/elf/ld.so
(gdb)

After that, since calloc isn't called from ld.so nor any other modules,
magic in tst-audit2 isn't updated.  Both orders are correct.  This patch
makes sure that calloc in tst-audit2.c is called at least once from ld.so.

	[BZ #18422]
	* Makefile ($(objpfx)tst-audit2): Depend on $(libdl).
	($(objpfx)tst-audit2.out): Also depend on
	$(objpfx)tst-auditmod9b.so.
	* elf/tst-audit2.c: Include <dlfcn.h>.
	(calloc_called): New.
	(calloc): Allow to be called more than once.
	(do_test): dllopen/dlclose $ORIGIN/tst-auditmod9b.so.

1 files changed, 20 insertions, 6 deletions

diff --git a/elf/tst-audit2.c b/elf/tst-audit2.c
index acad1b0..1d69cd6 100644
--- a/elf/tst-audit2.c
+++ b/elf/tst-audit2.c
@@ -3,26 +3,35 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <dlfcn.h>
 
 #define MAGIC1 0xabcdef72
 #define MAGIC2 0xd8675309
 static __thread unsigned int magic[] = { MAGIC1, MAGIC2 };
+static __thread int calloc_called;
 
 #undef calloc
 
 /* This calloc definition will be called by the dynamic linker itself.
-   We test that it has initialized our TLS block by the time it does so.  */
+   We test that interposed calloc is called by the dynamic loader, and
+   that TLS is fully initialized by then.  */
 
 void *
 calloc (size_t n, size_t m)
 {
-  if (magic[0] != MAGIC1 || magic[1] != MAGIC2)
+  if (!calloc_called)
     {
-      printf ("{%x, %x} != {%x, %x}\n", magic[0], magic[1], MAGIC1, MAGIC2);
-      abort ();
+      /* Allow our calloc to be called more than once.  */
+      calloc_called = 1;
+      if (magic[0] != MAGIC1 || magic[1] != MAGIC2)
+	{
+	  printf ("{%x, %x} != {%x, %x}\n",
+		  magic[0], magic[1], MAGIC1, MAGIC2);
+	  abort ();
+	}
+      magic[0] = MAGIC2;
+      magic[1] = MAGIC1;
     }
-  magic[0] = MAGIC2;
-  magic[1] = MAGIC1;
 
   n *= m;
   void *ptr = malloc (n);
@@ -34,6 +43,11 @@ calloc (size_t n, size_t m)
 static int
 do_test (void)
 {
+  /* Make sure that our calloc is called from the dynamic linker at least
+     once.  */
+  void *h = dlopen("$ORIGIN/tst-auditmod9b.so", RTLD_LAZY);
+  if (h != NULL)
+    dlclose (h);
   if (magic[1] != MAGIC1 || magic[0] != MAGIC2)
     {
       printf ("{%x, %x} != {%x, %x}\n", magic[0], magic[1], MAGIC2, MAGIC1);