sysdeps/s390/dl-tls.h

   1 /* Thread-local storage handling in the ELF dynamic linker.  s390 version.
   2    Copyright (C) 2003-2024 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    <https://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 # if IS_IN (rtld)
  33
  34 #  include <shlib-compat.h>
  35
  36 /* dl-tls.c declares __tls_get_addr as an exported symbol if it is not defined
  37    as a macro.  It seems suitable to do that in the generic code because all
  38    architectures other than s390 export __tls_get_addr.  The declaration causes
  39    problems in s390 though, so we define __tls_get_addr here to avoid declaring
  40    __tls_get_addr again.  */
  41 #  define __tls_get_addr __tls_get_addr
  42
  43 extern void *__tls_get_addr (tls_index *ti) attribute_hidden;
  44 /* Make a temporary alias of __tls_get_addr to remove the hidden
  45    attribute.  Then export __tls_get_addr as __tls_get_addr_internal
  46    for use from libc.  We do not want to export __tls_get_addr, but we
  47    do need to use it from libc when looking up the address of a TLS
  48    variable. We don't use __tls_get_offset because it requires r12 to
  49    be setup and that might not always be true. Either way it's more
  50    optimal to use __tls_get_addr directly (that's what
  51    __tls_get_offset does anyways).  */
  52 strong_alias (__tls_get_addr, __tls_get_addr_internal_tmp);
  53 versioned_symbol (ld, __tls_get_addr_internal_tmp,
  54                   __tls_get_addr_internal, GLIBC_PRIVATE);
  55
  56 /* The special thing about the s390 TLS ABI is that we do not have the
  57    standard __tls_get_addr function but the __tls_get_offset function
  58    which differs in two important aspects:
  59    1) __tls_get_offset gets a got offset instead of a pointer to the
  60       tls_index structure
  61    2) __tls_get_offset returns the offset of the requested variable to
  62       the thread descriptor instead of a pointer to the variable.
  63  */
  64 #  ifdef __s390x__
  65 __asm__("\n\
  66         .text\n\
  67         .globl __tls_get_offset\n\
  68         .type __tls_get_offset, @function\n\
  69         .align 4\n\
  70 __tls_get_offset:\n\
  71         la      %r2,0(%r2,%r12)\n\
  72         jg      __tls_get_addr\n\
  73 ");
  74 #  elif defined __s390__
  75 __asm__("\n\
  76         .text\n\
  77         .globl __tls_get_offset\n\
  78         .type __tls_get_offset, @function\n\
  79         .align 4\n\
  80 __tls_get_offset:\n\
  81         basr    %r3,0\n\
  82 0:      la      %r2,0(%r2,%r12)\n\
  83         l       %r4,1f-0b(%r3)\n\
  84         b       0(%r4,%r3)\n\
  85 1:      .long   __tls_get_addr - 0b\n\
  86 ");
  87 #  endif
  88 # else /* IS_IN (rtld) */
  89 extern void *__tls_get_addr_internal (tls_index *ti);
  90 # endif /* !IS_IN (rtld) */
  91
  92 # define GET_ADDR_OFFSET \
  93   (ti->ti_offset - (unsigned long) __builtin_thread_pointer ())
  94
  95 /* Use the privately exported __tls_get_addr_internal instead of
  96    __tls_get_offset in order to avoid the __tls_get_offset special
  97    linkage requiring the GOT pointer to be set up in r12.  The
  98    compiler will take care of setting up r12 only if itself issued the
  99    __tls_get_offset call.  */
 100 # define __TLS_GET_ADDR(__ti)                                   \
 101   ({ __tls_get_addr_internal (__ti)                             \
 102       + (unsigned long) __builtin_thread_pointer (); })
 103
 104 #endif