sysdeps/s390/dl-tls.h

   1 /* Thread-local storage handling in the ELF dynamic linker.  s390 version.
   2    Copyright (C) 2003-2014 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19
  20 /* Type used for the representation of TLS information in the GOT.  */
  21 typedef struct
  22 {
  23   unsigned long int ti_module;
  24   unsigned long int ti_offset;
  25 } tls_index;
  26
  27
  28 #ifdef SHARED
  29
  30 extern unsigned long __tls_get_offset (unsigned long got_offset);
  31
  32 # ifdef IS_IN_rtld
  33
  34 #  include <shlib-compat.h>
  35
  36 extern void *__tls_get_addr (tls_index *ti) attribute_hidden;
  37 /* Make a temporary alias of __tls_get_addr to remove the hidden
  38    attribute.  Then export __tls_get_addr as __tls_get_addr_internal
  39    for use from libc.  We do not want to export __tls_get_addr, but we
  40    do need to use it from libc when looking up the address of a TLS
  41    variable. We don't use __tls_get_offset because it requires r12 to
  42    be setup and that might not always be true. Either way it's more
  43    optimal to use __tls_get_addr directly (that's what
  44    __tls_get_offset does anyways).  */
  45 strong_alias (__tls_get_addr, __tls_get_addr_internal_tmp);
  46 versioned_symbol (ld, __tls_get_addr_internal_tmp,
  47                   __tls_get_addr_internal, GLIBC_PRIVATE);
  48
  49 /* The special thing about the s390 TLS ABI is that we do not have the
  50    standard __tls_get_addr function but the __tls_get_offset function
  51    which differs in two important aspects:
  52    1) __tls_get_offset gets a got offset instead of a pointer to the
  53       tls_index structure
  54    2) __tls_get_offset returns the offset of the requested variable to
  55       the thread descriptor instead of a pointer to the variable.
  56  */
  57 #  ifdef __s390x__
  58 asm("\n\
  59         .text\n\
  60         .globl __tls_get_offset\n\
  61         .type __tls_get_offset, @function\n\
  62         .align 4\n\
  63 __tls_get_offset:\n\
  64         la      %r2,0(%r2,%r12)\n\
  65         jg      __tls_get_addr\n\
  66 ");
  67 #  elif defined __s390__
  68 asm("\n\
  69         .text\n\
  70         .globl __tls_get_offset\n\
  71         .type __tls_get_offset, @function\n\
  72         .align 4\n\
  73 __tls_get_offset:\n\
  74         basr    %r3,0\n\
  75 0:      la      %r2,0(%r2,%r12)\n\
  76         l       %r4,1f-0b(%r3)\n\
  77         b       0(%r4,%r3)\n\
  78 1:      .long   __tls_get_addr - 0b\n\
  79 ");
  80 #  endif
  81 # else /* IS_IN_rtld */
  82 extern void *__tls_get_addr_internal (tls_index *ti);
  83 # endif /* !IS_IN_rtld */
  84
  85 # define GET_ADDR_OFFSET \
  86   (ti->ti_offset - (unsigned long) __builtin_thread_pointer ())
  87
  88 /* Use the privately exported __tls_get_addr_internal instead of
  89    __tls_get_offset in order to avoid the __tls_get_offset special
  90    linkage requiring the GOT pointer to be set up in r12.  The
  91    compiler will take care of setting up r12 only if itself issued the
  92    __tls_get_offset call.  */
  93 # define __TLS_GET_ADDR(__ti)                                   \
  94   ({ (void *) __tls_get_addr_internal ((char *) (__ti))         \
  95       + (unsigned long) __builtin_thread_pointer (); })
  96
  97 #endif
  98
  99 /* Value used for dtv entries for which the allocation is delayed.  */
 100 #define TLS_DTV_UNALLOCATED     ((void *) -1l)