[07/13] elf: Introduce __tls_pre_init_tp

This is an early variant of __tls_init_tp, primarily for initializing
thread-related elements of _rtld_global/GL.

Some existing initialization code not needed for NPTL is moved into
the generic version of this function.
---
 csu/libc-tls.c                |  2 ++
 elf/dl-mutex.c                |  2 +-
 elf/dl-tls_init_tp.c          | 29 ++++++++++++++++++++++++++
 elf/rtld.c                    | 38 +----------------------------------
 sysdeps/generic/ldsodefs.h    |  4 ++++
 sysdeps/nptl/dl-tls_init_tp.c | 25 +++++++++++++++++++++--
 6 files changed, 60 insertions(+), 40 deletions(-)

On 5/6/21 2:10 PM, Florian Weimer via Libc-alpha wrote:
> This is an early variant of __tls_init_tp, primarily for initializing
> thread-related elements of _rtld_global/GL.
> 
> Some existing initialization code not needed for NPTL is moved into
> the generic version of this function.

LGTM.

Tested on x86_64 and i686 without regression.

Tested-by: Carlos O'Donell <carlos@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>

> ---
>  csu/libc-tls.c                |  2 ++
>  elf/dl-mutex.c                |  2 +-
>  elf/dl-tls_init_tp.c          | 29 ++++++++++++++++++++++++++
>  elf/rtld.c                    | 38 +----------------------------------
>  sysdeps/generic/ldsodefs.h    |  4 ++++
>  sysdeps/nptl/dl-tls_init_tp.c | 25 +++++++++++++++++++++--
>  6 files changed, 60 insertions(+), 40 deletions(-)
> 
> diff --git a/csu/libc-tls.c b/csu/libc-tls.c
> index 22f8e4838d..5515204863 100644
> --- a/csu/libc-tls.c
> +++ b/csu/libc-tls.c
> @@ -114,6 +114,8 @@ __libc_setup_tls (void)
>  
>    struct link_map *main_map = GL(dl_ns)[LM_ID_BASE]._ns_loaded;
>  
> +  __tls_pre_init_tp ();
> +
>    /* Look through the TLS segment if there is any.  */
>    if (_dl_phdr != NULL)
>      for (phdr = _dl_phdr; phdr < &_dl_phdr[_dl_phnum]; ++phdr)
> diff --git a/elf/dl-mutex.c b/elf/dl-mutex.c
> index 2cd9d49c2e..ae1d8a84f0 100644
> --- a/elf/dl-mutex.c
> +++ b/elf/dl-mutex.c
> @@ -16,4 +16,4 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>  
> -/* The generic version initialization happpens in dl_main.  */
> +/* Initialization happens in __tls_pre_init_tp in dl-tls_init_tp.c.  */
> diff --git a/elf/dl-tls_init_tp.c b/elf/dl-tls_init_tp.c
> index 728cd84c00..d84adc992c 100644
> --- a/elf/dl-tls_init_tp.c
> +++ b/elf/dl-tls_init_tp.c
> @@ -18,6 +18,35 @@
>  
>  #include <ldsodefs.h>
>  
> +#if defined SHARED && defined _LIBC_REENTRANT \
> +    && defined __rtld_lock_default_lock_recursive
> +static void
> +rtld_lock_default_lock_recursive (void *lock)
> +{
> +  __rtld_lock_default_lock_recursive (lock);
> +}
> +
> +static void
> +rtld_lock_default_unlock_recursive (void *lock)
> +{
> +  __rtld_lock_default_unlock_recursive (lock);
> +}
> +#endif
> +
> +void
> +__tls_pre_init_tp (void)
> +{
> +#if !THREAD_GSCOPE_IN_TCB
> +  GL(dl_init_static_tls) = &_dl_nothread_init_static_tls;

OK.

> +#endif
> +
> +#if defined SHARED && defined _LIBC_REENTRANT \
> +    && defined __rtld_lock_default_lock_recursive
> +  GL(dl_rtld_lock_recursive) = rtld_lock_default_lock_recursive;
> +  GL(dl_rtld_unlock_recursive) = rtld_lock_default_unlock_recursive;
> +#endif
> +}
> +
>  void
>  __tls_init_tp (void)
>  {
> diff --git a/elf/rtld.c b/elf/rtld.c
> index a359167f8a..1255d5cc7d 100644
> --- a/elf/rtld.c
> +++ b/elf/rtld.c
> @@ -843,30 +843,6 @@ ERROR: ld.so: object '%s' from %s cannot be preloaded (%s): ignored.\n",
>    return 0;
>  }
>  
> -#if defined SHARED && defined _LIBC_REENTRANT \
> -    && defined __rtld_lock_default_lock_recursive
> -static void
> -rtld_lock_default_lock_recursive (void *lock)
> -{
> -  __rtld_lock_default_lock_recursive (lock);
> -}
> -
> -static void
> -rtld_lock_default_unlock_recursive (void *lock)
> -{
> -  __rtld_lock_default_unlock_recursive (lock);
> -}
> -#endif
> -#if PTHREAD_IN_LIBC
> -/* Dummy implementation.  See __rtld_mutex_init.  */
> -static int
> -rtld_mutex_dummy (pthread_mutex_t *lock)
> -{
> -  return 0;
> -}
> -#endif
> -
> -
>  static void
>  security_init (void)
>  {
> @@ -1147,19 +1123,7 @@ dl_main (const ElfW(Phdr) *phdr,
>    struct dl_main_state state;
>    dl_main_state_init (&state);
>  
> -#if !THREAD_GSCOPE_IN_TCB
> -  GL(dl_init_static_tls) = &_dl_nothread_init_static_tls;
> -#endif
> -
> -#if defined SHARED && defined _LIBC_REENTRANT \
> -    && defined __rtld_lock_default_lock_recursive
> -  GL(dl_rtld_lock_recursive) = rtld_lock_default_lock_recursive;
> -  GL(dl_rtld_unlock_recursive) = rtld_lock_default_unlock_recursive;
> -#endif
> -#if PTHREAD_IN_LIBC
> -  ___rtld_mutex_lock = rtld_mutex_dummy;
> -  ___rtld_mutex_unlock = rtld_mutex_dummy;
> -#endif
> +  __tls_pre_init_tp ();
>  
>    /* The explicit initialization here is cheaper than processing the reloc
>       in the _rtld_local definition's initializer.  */
> diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
> index 6d590d1335..ee851ac789 100644
> --- a/sysdeps/generic/ldsodefs.h
> +++ b/sysdeps/generic/ldsodefs.h
> @@ -1165,6 +1165,10 @@ extern void _dl_determine_tlsoffset (void) attribute_hidden;
>     number of audit modules are loaded.  */
>  void _dl_tls_static_surplus_init (size_t naudit) attribute_hidden;
>  
> +/* This function is called very early from dl_main to set up TLS and
> +   other thread-related data structures.  */
> +void __tls_pre_init_tp (void) attribute_hidden;
> +
>  /* This function is called after processor-specific initialization of
>     the TCB and thread pointer via TLS_INIT_TP, to complete very early
>     initialization of the thread library.  */
> diff --git a/sysdeps/nptl/dl-tls_init_tp.c b/sysdeps/nptl/dl-tls_init_tp.c
> index 05d2b6cfcc..cb29222727 100644
> --- a/sysdeps/nptl/dl-tls_init_tp.c
> +++ b/sysdeps/nptl/dl-tls_init_tp.c
> @@ -27,12 +27,33 @@ bool __nptl_set_robust_list_avail __attribute__ ((nocommon));
>  rtld_hidden_data_def (__nptl_set_robust_list_avail)
>  #endif
>  
> +#ifdef SHARED
> +/* Dummy implementation.  See __rtld_mutex_init.  */
> +static int
> +rtld_mutex_dummy (pthread_mutex_t *lock)
> +{
> +  return 0;
> +}
> +#endif
> +
>  void
> -__tls_init_tp (void)
> +__tls_pre_init_tp (void)
>  {
> -  /* Set up thread stack list management.  */
> +  /* The list data structures are not consistent until
> +     initialized.  */
>    INIT_LIST_HEAD (&GL (dl_stack_used));
>    INIT_LIST_HEAD (&GL (dl_stack_user));
> +
> +#ifdef SHARED
> +  ___rtld_mutex_lock = rtld_mutex_dummy;
> +  ___rtld_mutex_unlock = rtld_mutex_dummy;
> +#endif
> +}
> +
> +void
> +__tls_init_tp (void)
> +{
> +  /* Set up thread stack list management.  */
>    list_add (&THREAD_SELF->list, &GL (dl_stack_user));
>  
>     /* Early initialization of the TCB.   */
>