[11/23] elf: Move static TLS size and alignment into _rtld_global_ro

  This helps to clarify that the caching of these fields in libpthread
(in __static_tls_size, __static_tls_align_m1) is unnecessary.
---
 elf/dl-reloc.c             |  6 +++---
 elf/dl-tls.c               | 22 +++++++++++-----------
 elf/rtld_static_init.c     |  6 ++++++
 sysdeps/generic/ldsodefs.h | 10 ++++++----
 4 files changed, 26 insertions(+), 18 deletions(-)
  

On 12/05/2021 13:58, Florian Weimer via Libc-alpha wrote:
> This helps to clarify that the caching of these fields in libpthread
> (in __static_tls_size, __static_tls_align_m1) is unnecessary.

LGTM.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  elf/dl-reloc.c             |  6 +++---
>  elf/dl-tls.c               | 22 +++++++++++-----------
>  elf/rtld_static_init.c     |  6 ++++++
>  sysdeps/generic/ldsodefs.h | 10 ++++++----
>  4 files changed, 26 insertions(+), 18 deletions(-)
> 
> diff --git a/elf/dl-reloc.c b/elf/dl-reloc.c
> index bb9ca1a101..e13a672ade 100644
> --- a/elf/dl-reloc.c
> +++ b/elf/dl-reloc.c
> @@ -53,14 +53,14 @@ _dl_try_allocate_static_tls (struct link_map *map, bool optional)
>    /* If we've already used the variable with dynamic access, or if the
>       alignment requirements are too high, fail.  */
>    if (map->l_tls_offset == FORCED_DYNAMIC_TLS_OFFSET
> -      || map->l_tls_align > GL(dl_tls_static_align))
> +      || map->l_tls_align > GLRO (dl_tls_static_align))
>      {
>      fail:
>        return -1;
>      }
>  
>  #if TLS_TCB_AT_TP
> -  size_t freebytes = GL(dl_tls_static_size) - GL(dl_tls_static_used);
> +  size_t freebytes = GLRO (dl_tls_static_size) - GL(dl_tls_static_used);
>    if (freebytes < TLS_TCB_SIZE)
>      goto fail;
>    freebytes -= TLS_TCB_SIZE;
> @@ -89,7 +89,7 @@ _dl_try_allocate_static_tls (struct link_map *map, bool optional)
>  		   + map->l_tls_firstbyte_offset);
>    size_t used = offset + map->l_tls_blocksize;
>  
> -  if (used > GL(dl_tls_static_size))
> +  if (used > GLRO (dl_tls_static_size))
>      goto fail;
>  
>    /* Account optional static TLS surplus usage.  */

Ok.

> diff --git a/elf/dl-tls.c b/elf/dl-tls.c
> index 67781bc108..91031c2b72 100644
> --- a/elf/dl-tls.c
> +++ b/elf/dl-tls.c
> @@ -300,9 +300,9 @@ _dl_determine_tlsoffset (void)
>      }
>  
>    GL(dl_tls_static_used) = offset;
> -  GL(dl_tls_static_size) = (roundup (offset + GLRO(dl_tls_static_surplus),
> -				     max_align)
> -			    + TLS_TCB_SIZE);
> +  GLRO (dl_tls_static_size) = (roundup (offset + GLRO(dl_tls_static_surplus),
> +					max_align)
> +			       + TLS_TCB_SIZE);

Ok.

>  #elif TLS_DTV_AT_TP
>    /* The TLS blocks start right after the TCB.  */
>    size_t offset = TLS_TCB_SIZE;
> @@ -345,14 +345,14 @@ _dl_determine_tlsoffset (void)
>      }
>  
>    GL(dl_tls_static_used) = offset;
> -  GL(dl_tls_static_size) = roundup (offset + GLRO(dl_tls_static_surplus),
> -				    TLS_TCB_ALIGN);
> +  GLRO (dl_tls_static_size) = roundup (offset + GLRO(dl_tls_static_surplus),
> +				       TLS_TCB_ALIGN);
>  #else
>  # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
>  #endif
>  
>    /* The alignment requirement for the static TLS block.  */
> -  GL(dl_tls_static_align) = max_align;
> +  GLRO (dl_tls_static_align) = max_align;
>  }
>  #endif /* SHARED */
>  
> @@ -391,8 +391,8 @@ allocate_dtv (void *result)
>  void
>  _dl_get_tls_static_info (size_t *sizep, size_t *alignp)
>  {
> -  *sizep = GL(dl_tls_static_size);
> -  *alignp = GL(dl_tls_static_align);
> +  *sizep = GLRO (dl_tls_static_size);
> +  *alignp = GLRO (dl_tls_static_align);
>  }
>  
>  /* Derive the location of the pointer to the start of the original
> @@ -416,7 +416,7 @@ void *
>  _dl_allocate_tls_storage (void)
>  {
>    void *result;
> -  size_t size = GL(dl_tls_static_size);
> +  size_t size = GLRO (dl_tls_static_size);
>  
>  #if TLS_DTV_AT_TP
>    /* Memory layout is:
> @@ -427,7 +427,7 @@ _dl_allocate_tls_storage (void)
>  
>    /* Perform the allocation.  Reserve space for the required alignment
>       and the pointer to the original allocation.  */
> -  size_t alignment = GL(dl_tls_static_align);
> +  size_t alignment = GLRO (dl_tls_static_align);
>    void *allocated = malloc (size + alignment + sizeof (void *));
>    if (__glibc_unlikely (allocated == NULL))
>      return NULL;
> @@ -436,7 +436,7 @@ _dl_allocate_tls_storage (void)
>  #if TLS_TCB_AT_TP
>    /* The TCB follows the TLS blocks, which determine the alignment.
>       (TCB alignment requirements have been taken into account when
> -     calculating GL(dl_tls_static_align).)  */
> +     calculating GLRO (dl_tls_static_align).)  */
>    void *aligned = (void *) roundup ((uintptr_t) allocated, alignment);
>    result = aligned + size - TLS_TCB_SIZE;
>  

Ok.

> diff --git a/elf/rtld_static_init.c b/elf/rtld_static_init.c
> index cd823096d6..bded6bd2d4 100644
> --- a/elf/rtld_static_init.c
> +++ b/elf/rtld_static_init.c
> @@ -51,6 +51,12 @@ __rtld_static_init (struct link_map *map)
>    dl->_dl_hwcap2 = _dl_hwcap2;
>    extern __typeof (dl->_dl_pagesize) _dl_pagesize attribute_hidden;
>    dl->_dl_pagesize = _dl_pagesize;
> +  extern __typeof (dl->_dl_tls_static_align) _dl_tls_static_align
> +    attribute_hidden;
> +  dl->_dl_tls_static_align = _dl_tls_static_align;
> +  extern __typeof (dl->_dl_tls_static_size) _dl_tls_static_size
> +    attribute_hidden;
> +  dl->_dl_tls_static_size = _dl_tls_static_size;
>  
>    __rtld_static_init_arch (map, dl);
>  }

Ok.

> diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
> index c288f3a2a1..e383aa1dc3 100644
> --- a/sysdeps/generic/ldsodefs.h
> +++ b/sysdeps/generic/ldsodefs.h
> @@ -437,12 +437,8 @@ struct rtld_global
>    } *_dl_tls_dtv_slotinfo_list;
>    /* Number of modules in the static TLS block.  */
>    EXTERN size_t _dl_tls_static_nelem;
> -  /* Size of the static TLS block.  */
> -  EXTERN size_t _dl_tls_static_size;
>    /* Size actually allocated in the static TLS block.  */
>    EXTERN size_t _dl_tls_static_used;
> -  /* Alignment requirement of the static TLS block.  */
> -  EXTERN size_t _dl_tls_static_align;
>    /* Remaining amount of static TLS that may be used for optimizing
>       dynamic TLS access (e.g. with TLSDESC).  */
>    EXTERN size_t _dl_tls_static_optional;
> @@ -610,6 +606,12 @@ struct rtld_global_ro
>       binaries, don't honor for PIEs).  */
>    EXTERN ElfW(Addr) _dl_use_load_bias;
>  
> +  /* Size of the static TLS block.  */
> +  EXTERN size_t _dl_tls_static_size;
> +
> +  /* Alignment requirement of the static TLS block.  */
> +  EXTERN size_t _dl_tls_static_align;
> +
>    /* Size of surplus space in the static TLS area for dynamically
>       loaded modules with IE-model TLS or for TLSDESC optimization.
>       See comments in elf/dl-tls.c where it is initialized.  */
> 

Ok.