Re: [PATCH v3 22/37] elf: Introduce __tls_init_tp for second-phase TCB initialization

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 16/03/2021 14:30, Florian Weimer via Libc-alpha wrote:
> TLS_INIT_TP is processor-specific, so it is not a good place to
> put thread library initialization code (it would have to be repeated
> for all CPUs).  Introduce __tls_init_tp as a separate function,
> to be called immediately after TLS_INIT_TP.  Move the existing
> stack list setup code for NPTL to this function.

LGTM, thanks.

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

> ---
>   csu/libc-tls.c                |  8 +-------
>   elf/Makefile                  |  2 +-
>   elf/dl-tls_init_tp.c          | 24 ++++++++++++++++++++++++
>   elf/rtld.c                    | 14 ++------------
>   sysdeps/generic/ldsodefs.h    |  5 +++++
>   sysdeps/nptl/dl-tls_init_tp.c | 30 ++++++++++++++++++++++++++++++
>   6 files changed, 63 insertions(+), 20 deletions(-)
>   create mode 100644 elf/dl-tls_init_tp.c
>   create mode 100644 sysdeps/nptl/dl-tls_init_tp.c
> 
> diff --git a/csu/libc-tls.c b/csu/libc-tls.c
> index f3a6a6a075..22f8e4838d 100644
> --- a/csu/libc-tls.c
> +++ b/csu/libc-tls.c
> @@ -24,7 +24,6 @@
>   #include <stdio.h>
>   #include <sys/param.h>
>   #include <array_length.h>
> -#include <list.h>
>   
>   #ifdef SHARED
>    #error makefile bug, this file is for static only
> @@ -193,12 +192,7 @@ __libc_setup_tls (void)
>   #endif
>     if (__builtin_expect (lossage != NULL, 0))
>       _startup_fatal (lossage);
> -
> -#if THREAD_GSCOPE_IN_TCB
> -  INIT_LIST_HEAD (&_dl_stack_used);
> -  INIT_LIST_HEAD (&_dl_stack_user);
> -  list_add (&THREAD_SELF->list, &_dl_stack_user);
> -#endif
> +  __tls_init_tp ();
>   
>     /* Update the executable's link map with enough information to make
>        the TLS routines happy.  */

Ok.

> diff --git a/elf/Makefile b/elf/Makefile
> index deb76aed99..22b3a06cab 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -35,7 +35,7 @@ dl-routines	= $(addprefix dl-,load lookup object reloc deps \
>   				  execstack open close trampoline \
>   				  exception sort-maps lookup-direct \
>   				  call-libc-early-init write \
> -				  thread_gscope_wait)
> +				  thread_gscope_wait tls_init_tp)
>   ifeq (yes,$(use-ldconfig))
>   dl-routines += dl-cache
>   endif

Ok.

> diff --git a/elf/dl-tls_init_tp.c b/elf/dl-tls_init_tp.c
> new file mode 100644
> index 0000000000..728cd84c00
> --- /dev/null
> +++ b/elf/dl-tls_init_tp.c
> @@ -0,0 +1,24 @@
> +/* Completion of TCB initialization after TLS_INIT_TP.  Generic version.
> +   Copyright (C) 2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <ldsodefs.h>
> +
> +void
> +__tls_init_tp (void)
> +{
> +}

Ok.

> diff --git a/elf/rtld.c b/elf/rtld.c
> index c2ca4b7ce3..34879016ad 100644
> --- a/elf/rtld.c
> +++ b/elf/rtld.c
> @@ -48,7 +48,6 @@
>   #include <array_length.h>
>   #include <libc-early-init.h>
>   #include <dl-main.h>
> -#include <list.h>
>   #include <gnu/lib-names.h>
>   #include <dl-tunables.h>
>   
> @@ -807,9 +806,7 @@ cannot allocate TLS data structures for initial thread\n");
>     const char *lossage = TLS_INIT_TP (tcbp);
>     if (__glibc_unlikely (lossage != NULL))
>       _dl_fatal_printf ("cannot set up thread-local storage: %s\n", lossage);
> -#if THREAD_GSCOPE_IN_TCB
> -  list_add (&THREAD_SELF->list, &GL (dl_stack_user));
> -#endif
> +  __tls_init_tp ();
>     tls_init_tp_called = true;
>   
>     return tcbp;

Ok.

> @@ -1150,11 +1147,6 @@ dl_main (const ElfW(Phdr) *phdr,
>     GL(dl_rtld_unlock_recursive) = rtld_lock_default_unlock_recursive;
>   #endif
>   
> -#if THREAD_GSCOPE_IN_TCB
> -  INIT_LIST_HEAD (&GL (dl_stack_used));
> -  INIT_LIST_HEAD (&GL (dl_stack_user));
> -#endif
> -
>     /* The explicit initialization here is cheaper than processing the reloc
>        in the _rtld_local definition's initializer.  */

Ok.

>     GL(dl_make_stack_executable_hook) = &_dl_make_stack_executable;
> @@ -2454,9 +2446,7 @@ dl_main (const ElfW(Phdr) *phdr,
>         if (__glibc_unlikely (lossage != NULL))
>   	_dl_fatal_printf ("cannot set up thread-local storage: %s\n",
>   			  lossage);
> -#if THREAD_GSCOPE_IN_TCB
> -      list_add (&THREAD_SELF->list, &GL (dl_stack_user));
> -#endif
> +      __tls_init_tp ();
>       }
>   
>     /* Make sure no new search directories have been added.  */

Ok.

> diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
> index dfc117a445..67c6686015 100644
> --- a/sysdeps/generic/ldsodefs.h
> +++ b/sysdeps/generic/ldsodefs.h
> @@ -1163,6 +1163,11 @@ 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 after processor-specific initialization of
> +   the TCB and thread pointer via TLS_INIT_TP, to complete very early
> +   initialization of the thread library.  */
> +void __tls_init_tp (void) attribute_hidden;
> +
>   #ifndef SHARED
>   /* Set up the TCB for statically linked applications.  This is called
>      early during startup because we always use TLS (for errno and the

Ok.

> diff --git a/sysdeps/nptl/dl-tls_init_tp.c b/sysdeps/nptl/dl-tls_init_tp.c
> new file mode 100644
> index 0000000000..8983808233
> --- /dev/null
> +++ b/sysdeps/nptl/dl-tls_init_tp.c
> @@ -0,0 +1,30 @@
> +/* Completion of TCB initialization after TLS_INIT_TP.  NPTL version.
> +   Copyright (C) 2020-2021 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <ldsodefs.h>
> +#include <list.h>
> +#include <tls.h>
> +
> +void
> +__tls_init_tp (void)
> +{
> +  /* Set up thread stack list management.  */
> +  INIT_LIST_HEAD (&GL (dl_stack_used));
> +  INIT_LIST_HEAD (&GL (dl_stack_user));
> +  list_add (&THREAD_SELF->list, &GL (dl_stack_user));
> +}
> 

Ok.