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glibc  2.9
Functions | Variables
libc-tls.c File Reference
#include <errno.h>
#include <ldsodefs.h>
#include <tls.h>
#include <unistd.h>
#include <stdio.h>
#include <sys/param.h>
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Functions

 ElfW (Phdr)
static void init_slotinfo (void)
static void init_static_tls (size_t memsz, size_t align)
void __libc_setup_tls (size_t tcbsize, size_t tcbalign)
int internal_function _dl_tls_setup (void)
void __attribute__ ((weak))

Variables

 static_slotinfo
static struct link_map
size_t _dl_tls_max_dtv_idx
bool _dl_tls_dtv_gaps
struct dtv_slotinfo_list_dl_tls_dtv_slotinfo_list
size_t _dl_tls_static_nelem
size_t _dl_tls_static_size = 2048
size_t _dl_tls_static_used
size_t _dl_tls_static_align
size_t _dl_tls_generation

Function Documentation

void __attribute__ ( (weak )

Definition at line 245 of file libc-tls.c.

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void __libc_setup_tls ( size_t  tcbsize,
size_t  tcbalign 
)

Definition at line 110 of file libc-tls.c.

{
  void *tlsblock;
  size_t memsz = 0;
  size_t filesz = 0;
  void *initimage = NULL;
  size_t align = 0;
  size_t max_align = tcbalign;
  size_t tcb_offset;
  ElfW(Phdr) *phdr;

  /* Look through the TLS segment if there is any.  */
  if (_dl_phdr != NULL)
    for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr)
      if (phdr->p_type == PT_TLS)
       {
         /* Remember the values we need.  */
         memsz = phdr->p_memsz;
         filesz = phdr->p_filesz;
         initimage = (void *) phdr->p_vaddr;
         align = phdr->p_align;
         if (phdr->p_align > max_align)
           max_align = phdr->p_align;
         break;
       }

  /* We have to set up the TCB block which also (possibly) contains
     'errno'.  Therefore we avoid 'malloc' which might touch 'errno'.
     Instead we use 'sbrk' which would only uses 'errno' if it fails.
     In this case we are right away out of memory and the user gets
     what she/he deserves.

     The initialized value of _dl_tls_static_size is provided by dl-open.c
     to request some surplus that permits dynamic loading of modules with
     IE-model TLS.  */
#if TLS_TCB_AT_TP
  tcb_offset = roundup (memsz + GL(dl_tls_static_size), tcbalign);
  tlsblock = __sbrk (tcb_offset + tcbsize + max_align);
#elif TLS_DTV_AT_TP
  tcb_offset = roundup (tcbsize, align ?: 1);
  tlsblock = __sbrk (tcb_offset + memsz + max_align
                   + TLS_PRE_TCB_SIZE + GL(dl_tls_static_size));
  tlsblock += TLS_PRE_TCB_SIZE;
#else
  /* In case a model with a different layout for the TCB and DTV
     is defined add another #elif here and in the following #ifs.  */
# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
#endif

  /* Align the TLS block.  */
  tlsblock = (void *) (((uintptr_t) tlsblock + max_align - 1)
                     & ~(max_align - 1));

  /* Initialize the dtv.  [0] is the length, [1] the generation counter.  */
  static_dtv[0].counter = (sizeof (static_dtv) / sizeof (static_dtv[0])) - 2;
  // static_dtv[1].counter = 0;           would be needed if not already done

  /* Initialize the TLS block.  */
#if TLS_TCB_AT_TP
  static_dtv[2].pointer.val = ((char *) tlsblock + tcb_offset
                            - roundup (memsz, align ?: 1));
  static_map.l_tls_offset = roundup (memsz, align ?: 1);
#elif TLS_DTV_AT_TP
  static_dtv[2].pointer.val = (char *) tlsblock + tcb_offset;
  static_map.l_tls_offset = tcb_offset;
#else
# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
#endif
  static_dtv[2].pointer.is_static = true;
  /* sbrk gives us zero'd memory, so we don't need to clear the remainder.  */
  memcpy (static_dtv[2].pointer.val, initimage, filesz);

  /* Install the pointer to the dtv.  */

  /* Initialize the thread pointer.  */
#if TLS_TCB_AT_TP
  INSTALL_DTV ((char *) tlsblock + tcb_offset, static_dtv);

  const char *lossage = TLS_INIT_TP ((char *) tlsblock + tcb_offset, 0);
#elif TLS_DTV_AT_TP
  INSTALL_DTV (tlsblock, static_dtv);
  const char *lossage = TLS_INIT_TP (tlsblock, 0);
#else
# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
#endif
  if (__builtin_expect (lossage != NULL, 0))
    __libc_fatal (lossage);

  /* We have to create a fake link map which normally would be created
     by the dynamic linker.  It just has to have enough information to
     make the TLS routines happy.  */
  static_map.l_tls_align = align;
  static_map.l_tls_blocksize = memsz;
  static_map.l_tls_initimage = initimage;
  static_map.l_tls_initimage_size = filesz;
  static_map.l_type = lt_executable;
  static_map.l_tls_modid = 1;

  init_slotinfo ();
  // static_slotinfo.si.slotinfo[1].gen = 0; already zero
  static_slotinfo.si.slotinfo[1].map = &static_map;

  memsz = roundup (memsz, align ?: 1);

#if TLS_TCB_AT_TP
  memsz += tcbsize;
#elif TLS_DTV_AT_TP
  memsz += tcb_offset;
#endif

  init_static_tls (memsz, MAX (TLS_TCB_ALIGN, max_align));
}

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Definition at line 228 of file libc-tls.c.

{
  init_slotinfo ();
  init_static_tls (
#if TLS_TCB_AT_TP
                 TLS_TCB_SIZE,
#else
                 0,
#endif
                 TLS_TCB_ALIGN);
  return 0;
}

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ElfW ( Phdr  )

Definition at line 32 of file libc-tls.c.

{
  struct dtv_slotinfo_list si;
  /* The dtv_slotinfo_list data structure does not include the actual
     information since it is defined as an array of size zero.  We define
     here the necessary entries.  Note that it is not important whether
     there is padding or not since we will always access the information
     through the 'si' element.  */
  struct dtv_slotinfo info[2 + TLS_SLOTINFO_SURPLUS];
} static_slotinfo;
static void init_slotinfo ( void  ) [inline, static]

Definition at line 80 of file libc-tls.c.

{
  /* Create the slotinfo list.  */
  static_slotinfo.si.len = (((char *) (&static_slotinfo + 1)
                          - (char *) &static_slotinfo.si.slotinfo[0])
                         / sizeof static_slotinfo.si.slotinfo[0]);
  // static_slotinfo.si.next = NULL;      already zero

  /* The slotinfo list.  Will be extended by the code doing dynamic
     linking.  */
  GL(dl_tls_max_dtv_idx) = 1;
  GL(dl_tls_dtv_slotinfo_list) = &static_slotinfo.si;
}

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static void init_static_tls ( size_t  memsz,
size_t  align 
) [inline, static]

Definition at line 95 of file libc-tls.c.

{
  /* That is the size of the TLS memory for this object.  The initialized
     value of _dl_tls_static_size is provided by dl-open.c to request some
     surplus that permits dynamic loading of modules with IE-model TLS.  */
  GL(dl_tls_static_size) = roundup (memsz + GL(dl_tls_static_size),
                                TLS_TCB_ALIGN);
  GL(dl_tls_static_used) = memsz;
  /* The alignment requirement for the static TLS block.  */
  GL(dl_tls_static_align) = align;
  /* Number of elements in the static TLS block.  */
  GL(dl_tls_static_nelem) = GL(dl_tls_max_dtv_idx);
}

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Variable Documentation

Definition at line 57 of file libc-tls.c.

Definition at line 59 of file libc-tls.c.

Definition at line 71 of file libc-tls.c.

Definition at line 55 of file libc-tls.c.

Definition at line 68 of file libc-tls.c.

Definition at line 61 of file libc-tls.c.

Definition at line 64 of file libc-tls.c.

Definition at line 66 of file libc-tls.c.

struct link_map [static]

Definition at line 51 of file libc-tls.c.

Definition at line 48 of file libc-tls.c.