src/patches/glibc/glibc-rh905941.patch

   1 diff -pruN a/nptl/sysdeps/pthread/unwind-forcedunwind.c b/nptl/sysdeps/pthread/unwind-forcedunwind.c
   2 --- a/nptl/sysdeps/pthread/unwind-forcedunwind.c        2010-05-04 16:57:23.000000000 +0530
   3 +++ b/nptl/sysdeps/pthread/unwind-forcedunwind.c        2014-06-02 23:00:02.901013275 +0530
   4 @@ -45,8 +45,10 @@ pthread_cancel_init (void)
   5
   6    if (__builtin_expect (libgcc_s_handle != NULL, 1))
   7      {
   8 -      /* Force gcc to reload all values.  */
   9 -      asm volatile ("" ::: "memory");
  10 +      /* Order reads so as to prevent speculation of loads
  11 +        of libgcc_s_{resume,personality,forcedunwind,getcfa}
  12 +        to points prior to the write barrier.  */
  13 +      atomic_read_barrier ();
  14        return;
  15      }
  16
  17 @@ -72,9 +74,14 @@ pthread_cancel_init (void)
  18    libgcc_s_forcedunwind = forcedunwind;
  19    PTR_MANGLE (getcfa);
  20    libgcc_s_getcfa = getcfa;
  21 -  /* Make sure libgcc_s_handle is written last.  Otherwise,
  22 -     pthread_cancel_init might return early even when the pointer the
  23 -     caller is interested in is not initialized yet.  */
  24 +  /* At the point at which any thread writes the handle
  25 +     to libgcc_s_handle, the initialization is complete.
  26 +     The writing of libgcc_s_handle is atomic. All other
  27 +     threads reading libgcc_s_handle do so atomically. Any
  28 +     thread that does not execute this function must issue
  29 +     a read barrier to ensure that all of the above has
  30 +     actually completed and that the values of the
  31 +     function pointers are correct.   */
  32    atomic_write_barrier ();
  33    libgcc_s_handle = handle;
  34  }
  35 @@ -91,11 +98,19 @@ __unwind_freeres (void)
  36      }
  37  }
  38
  39 -void
  40 -_Unwind_Resume (struct _Unwind_Exception *exc)
  41 +static __always_inline void
  42 +_maybe_pthread_cancel_init (void)
  43  {
  44    if (__builtin_expect (libgcc_s_handle == NULL, 0))
  45      pthread_cancel_init ();
  46 +  else
  47 +    atomic_read_barrier ();
  48 +}
  49 +
  50 +void
  51 +_Unwind_Resume (struct _Unwind_Exception *exc)
  52 +{
  53 +  _maybe_pthread_cancel_init ();
  54
  55    void (*resume) (struct _Unwind_Exception *exc) = libgcc_s_resume;
  56    PTR_DEMANGLE (resume);
  57 @@ -108,8 +123,7 @@ __gcc_personality_v0 (int version, _Unwi
  58                        struct _Unwind_Exception *ue_header,
  59                        struct _Unwind_Context *context)
  60  {
  61 -  if (__builtin_expect (libgcc_s_handle == NULL, 0))
  62 -    pthread_cancel_init ();
  63 +  _maybe_pthread_cancel_init ();
  64
  65    _Unwind_Reason_Code (*personality)
  66      (int, _Unwind_Action, _Unwind_Exception_Class, struct _Unwind_Exception *,
  67 @@ -122,8 +136,7 @@ _Unwind_Reason_Code
  68  _Unwind_ForcedUnwind (struct _Unwind_Exception *exc, _Unwind_Stop_Fn stop,
  69                       void *stop_argument)
  70  {
  71 -  if (__builtin_expect (libgcc_s_handle == NULL, 0))
  72 -    pthread_cancel_init ();
  73 +  _maybe_pthread_cancel_init ();
  74
  75    _Unwind_Reason_Code (*forcedunwind)
  76      (struct _Unwind_Exception *, _Unwind_Stop_Fn, void *)
  77 @@ -135,8 +148,7 @@ _Unwind_ForcedUnwind (struct _Unwind_Exc
  78  _Unwind_Word
  79  _Unwind_GetCFA (struct _Unwind_Context *context)
  80  {
  81 -  if (__builtin_expect (libgcc_s_handle == NULL, 0))
  82 -    pthread_cancel_init ();
  83 +  _maybe_pthread_cancel_init ();
  84
  85    _Unwind_Word (*getcfa) (struct _Unwind_Context *) = libgcc_s_getcfa;
  86    PTR_DEMANGLE (getcfa);
  87 diff -pruN a/sysdeps/gnu/unwind-resume.c b/sysdeps/gnu/unwind-resume.c
  88 --- a/sysdeps/gnu/unwind-resume.c       2010-05-04 16:57:23.000000000 +0530
  89 +++ b/sysdeps/gnu/unwind-resume.c       2014-06-02 23:02:26.812007078 +0530
  90 @@ -20,8 +20,11 @@
  91  #include <dlfcn.h>
  92  #include <stdio.h>
  93  #include <unwind.h>
  94 +#include <pthreadP.h>
  95 +#include <sysdep.h>
  96  #include <libgcc_s.h>
  97
  98 +static void *libgcc_s_handle;
  99  static void (*libgcc_s_resume) (struct _Unwind_Exception *exc);
 100  static _Unwind_Reason_Code (*libgcc_s_personality)
 101    (int, _Unwind_Action, _Unwind_Exception_Class, struct _Unwind_Exception *,
 102 @@ -42,13 +45,32 @@ init (void)
 103
 104    libgcc_s_resume = resume;
 105    libgcc_s_personality = personality;
 106 +  atomic_write_barrier ();
 107 +  /* At the point at which any thread writes the handle
 108 +     to libgcc_s_handle, the initialization is complete.
 109 +     The writing of libgcc_s_handle is atomic. All other
 110 +     threads reading libgcc_s_handle do so atomically. Any
 111 +     thread that does not execute this function must issue
 112 +     a read barrier to ensure that all of the above has
 113 +     actually completed and that the values of the
 114 +     function pointers are correct.   */
 115 +  libgcc_s_handle = handle;
 116  }
 117
 118 +static __always_inline void
 119 +_maybe_init (void)
 120 +{
 121 +  if (__builtin_expect (libgcc_s_handle == NULL, 0))
 122 +    init ();
 123 +  else
 124 +    atomic_read_barrier ();
 125 +}
 126 +
 127 +
 128  void
 129  _Unwind_Resume (struct _Unwind_Exception *exc)
 130  {
 131 -  if (__builtin_expect (libgcc_s_resume == NULL, 0))
 132 -    init ();
 133 +  _maybe_init ();
 134    libgcc_s_resume (exc);
 135  }
 136
 137 @@ -58,8 +80,7 @@ __gcc_personality_v0 (int version, _Unwi
 138                        struct _Unwind_Exception *ue_header,
 139                        struct _Unwind_Context *context)
 140  {
 141 -  if (__builtin_expect (libgcc_s_personality == NULL, 0))
 142 -    init ();
 143 +  _maybe_init ();
 144    return libgcc_s_personality (version, actions, exception_class,
 145                                ue_header, context);
 146  }