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From: "jakub at redhat dot com" <sourceware-bugzilla@sourceware.org>
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Subject: [Bug dynamic-link/27004] ld.so is miscompiled by GCC 11
Date: Thu, 03 Dec 2020 11:24:03 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D27004

Jakub Jelinek <jakub at redhat dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at redhat dot com

--- Comment #2 from Jakub Jelinek <jakub at redhat dot com> ---
Only lightly tested fix, i?86 will need similar change (with __seg_gs):

diff --git a/sysdeps/x86_64/nptl/tls.h b/sysdeps/x86_64/nptl/tls.h
index a08bf972de..ccb5f24d92 100644
--- a/sysdeps/x86_64/nptl/tls.h
+++ b/sysdeps/x86_64/nptl/tls.h
@@ -180,11 +180,16 @@ _Static_assert (offsetof (tcbhead_t, __glibc_unused2)=
 =3D=3D
0x80,
    assignments like
        pthread_descr self =3D thread_self();
    do not get optimized away.  */
-# define THREAD_SELF \
+# if __GNUC_PREREQ (6, 0)
+#  define THREAD_SELF \
+  (*(struct pthread *__seg_fs *) offsetof (struct pthread, header.self))
+# else
+#  define THREAD_SELF \
   ({ struct pthread *__self;                                              =
   \
      asm ("mov %%fs:%c1,%0" : "=3Dr" (__self)                             =
     \
          : "i" (offsetof (struct pthread, header.self)));                 =
   \
      __self;})
+# endif

 /* Magic for libthread_db to know how to do THREAD_SELF.  */
 # define DB_THREAD_SELF_INCLUDE  <sys/reg.h> /* For the FS constant.  */

--=20
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