Remove TLS_TCB_ALIGN and TLS_INIT_TCB_ALIGN

  TLS_INIT_TCB_ALIGN is not actually used.  TLS_TCB_ALIGN was likely
introduced to support a configuration where the thread pointer
has not the same alignment as THREAD_SELF.  Only ia64 seems to use
that, but for the stack/pointer guard, not for storing tcbhead_t.
Some ports use TLS_TCB_OFFSET and TLS_PRE_TCB_SIZE to shift
the thread pointer, potentially landing in a different residue class
modulo the alignment, but the changes should not impact that.

In general, given that TLS variables have their own alignment
requirements, having different alignment for the (unshifted) thread
pointer and struct pthread would potentially result in dynamic
offsets, leading to more complexity.

hppa had different values before: __alignof__ (tcbhead_t), which
seems to be 4, and __alignof__ (struct pthread), which was 8
(old default) and is now 32.  However, it defines THREAD_SELF as:

/* Return the thread descriptor for the current thread.  */
# define THREAD_SELF \
  ({ struct pthread *__self;			\
	__self = __get_cr27();			\
	__self - 1;				\
   })

So the thread pointer points after struct pthread (hence __self - 1),
and they have to have the same alignment on hppa as well.

Similarly, on ia64, the definitions were different.  We have:

# define TLS_PRE_TCB_SIZE \
  (sizeof (struct pthread)						\
   + (PTHREAD_STRUCT_END_PADDING < 2 * sizeof (uintptr_t)		\
      ? ((2 * sizeof (uintptr_t) + __alignof__ (struct pthread) - 1)	\
	 & ~(__alignof__ (struct pthread) - 1))				\
      : 0))
# define THREAD_SELF \
  ((struct pthread *) ((char *) __thread_self - TLS_PRE_TCB_SIZE))

And TLS_PRE_TCB_SIZE is a multiple of the struct pthread alignment
(confirmed by the new _Static_assert in sysdeps/ia64/libc-tls.c).

On m68k, we have a larger gap between tcbhead_t and struct pthread.
But as far as I can tell, the port is fine with that.  The definition
of TCB_OFFSET is sufficient to handle the shifted TCB scenario.

This fixes commit 23c77f60181eb549f11ec2f913b4270af29eee38
("nptl: Increase default TCB alignment to 32").

Testing:

I ran a build on armhfp with a glibc 2.34 backport to a tree that
exhibited the bug before the rseq changes.  Also tested on
i686-linux-gnu and x86_64-linux-gnu.

---
 csu/libc-tls.c                |  5 +++--
 elf/dl-tls.c                  |  4 ++--
 sysdeps/aarch64/nptl/tls.h    |  6 ------
 sysdeps/alpha/nptl/tls.h      |  6 ------
 sysdeps/arc/nptl/tls.h        |  6 ------
 sysdeps/arm/nptl/tls.h        |  6 ------
 sysdeps/csky/nptl/tls.h       |  6 ------
 sysdeps/generic/tls.h         | 14 +++++---------
 sysdeps/hppa/nptl/tls.h       |  6 ------
 sysdeps/i386/nptl/tls.h       |  6 ------
 sysdeps/ia64/libc-tls.c       |  3 +++
 sysdeps/ia64/nptl/tls.h       |  6 ------
 sysdeps/m68k/nptl/tls.h       |  9 ++-------
 sysdeps/mach/hurd/tls.h       |  8 --------
 sysdeps/microblaze/nptl/tls.h |  6 ------
 sysdeps/mips/nptl/tls.h       |  9 ++-------
 sysdeps/nios2/nptl/tls.h      |  9 ++-------
 sysdeps/powerpc/nptl/tls.h    |  9 ++-------
 sysdeps/riscv/nptl/tls.h      |  9 ++-------
 sysdeps/s390/nptl/tls.h       |  6 ------
 sysdeps/sh/nptl/tls.h         |  6 ------
 sysdeps/sparc/nptl/tls.h      |  6 ------
 sysdeps/x86_64/nptl/tls.h     |  6 ------
 23 files changed, 23 insertions(+), 134 deletions(-)
  

On Thu, Dec 9, 2021 at 12:29 PM Florian Weimer via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> TLS_INIT_TCB_ALIGN is not actually used.  TLS_TCB_ALIGN was likely
> introduced to support a configuration where the thread pointer
> has not the same alignment as THREAD_SELF.  Only ia64 seems to use
> that, but for the stack/pointer guard, not for storing tcbhead_t.
> Some ports use TLS_TCB_OFFSET and TLS_PRE_TCB_SIZE to shift
> the thread pointer, potentially landing in a different residue class
> modulo the alignment, but the changes should not impact that.
>
> In general, given that TLS variables have their own alignment
> requirements, having different alignment for the (unshifted) thread
> pointer and struct pthread would potentially result in dynamic
> offsets, leading to more complexity.
>
> hppa had different values before: __alignof__ (tcbhead_t), which
> seems to be 4, and __alignof__ (struct pthread), which was 8
> (old default) and is now 32.  However, it defines THREAD_SELF as:
>
> /* Return the thread descriptor for the current thread.  */
> # define THREAD_SELF \
>   ({ struct pthread *__self;                    \
>         __self = __get_cr27();                  \
>         __self - 1;                             \
>    })
>
> So the thread pointer points after struct pthread (hence __self - 1),
> and they have to have the same alignment on hppa as well.
>
> Similarly, on ia64, the definitions were different.  We have:
>
> # define TLS_PRE_TCB_SIZE \
>   (sizeof (struct pthread)                                              \
>    + (PTHREAD_STRUCT_END_PADDING < 2 * sizeof (uintptr_t)               \
>       ? ((2 * sizeof (uintptr_t) + __alignof__ (struct pthread) - 1)    \
>          & ~(__alignof__ (struct pthread) - 1))                         \
>       : 0))
> # define THREAD_SELF \
>   ((struct pthread *) ((char *) __thread_self - TLS_PRE_TCB_SIZE))
>
> And TLS_PRE_TCB_SIZE is a multiple of the struct pthread alignment
> (confirmed by the new _Static_assert in sysdeps/ia64/libc-tls.c).
>
> On m68k, we have a larger gap between tcbhead_t and struct pthread.
> But as far as I can tell, the port is fine with that.  The definition
> of TCB_OFFSET is sufficient to handle the shifted TCB scenario.
>
> This fixes commit 23c77f60181eb549f11ec2f913b4270af29eee38
> ("nptl: Increase default TCB alignment to 32").
>
> Testing:
>
> I ran a build on armhfp with a glibc 2.34 backport to a tree that
> exhibited the bug before the rseq changes.  Also tested on
> i686-linux-gnu and x86_64-linux-gnu.
>
> ---
>  csu/libc-tls.c                |  5 +++--
>  elf/dl-tls.c                  |  4 ++--
>  sysdeps/aarch64/nptl/tls.h    |  6 ------
>  sysdeps/alpha/nptl/tls.h      |  6 ------
>  sysdeps/arc/nptl/tls.h        |  6 ------
>  sysdeps/arm/nptl/tls.h        |  6 ------
>  sysdeps/csky/nptl/tls.h       |  6 ------
>  sysdeps/generic/tls.h         | 14 +++++---------
>  sysdeps/hppa/nptl/tls.h       |  6 ------
>  sysdeps/i386/nptl/tls.h       |  6 ------
>  sysdeps/ia64/libc-tls.c       |  3 +++
>  sysdeps/ia64/nptl/tls.h       |  6 ------
>  sysdeps/m68k/nptl/tls.h       |  9 ++-------
>  sysdeps/mach/hurd/tls.h       |  8 --------
>  sysdeps/microblaze/nptl/tls.h |  6 ------
>  sysdeps/mips/nptl/tls.h       |  9 ++-------
>  sysdeps/nios2/nptl/tls.h      |  9 ++-------
>  sysdeps/powerpc/nptl/tls.h    |  9 ++-------
>  sysdeps/riscv/nptl/tls.h      |  9 ++-------
>  sysdeps/s390/nptl/tls.h       |  6 ------
>  sysdeps/sh/nptl/tls.h         |  6 ------
>  sysdeps/sparc/nptl/tls.h      |  6 ------
>  sysdeps/x86_64/nptl/tls.h     |  6 ------
>  23 files changed, 23 insertions(+), 134 deletions(-)
>
> diff --git a/csu/libc-tls.c b/csu/libc-tls.c
> index 5515204863..d83e69f625 100644
> --- a/csu/libc-tls.c
> +++ b/csu/libc-tls.c
> @@ -24,6 +24,7 @@
>  #include <stdio.h>
>  #include <sys/param.h>
>  #include <array_length.h>
> +#include <pthreadP.h>
>
>  #ifdef SHARED
>   #error makefile bug, this file is for static only
> @@ -89,7 +90,7 @@ init_static_tls (size_t memsz, size_t align)
>  {
>    /* That is the size of the TLS memory for this object.  */
>    GL(dl_tls_static_size) = roundup (memsz + GLRO(dl_tls_static_surplus),
> -                                   TLS_TCB_ALIGN);
> +                                   TCB_ALIGNMENT);
>  #if TLS_TCB_AT_TP
>    GL(dl_tls_static_size) += TLS_TCB_SIZE;
>  #endif
> @@ -214,5 +215,5 @@ __libc_setup_tls (void)
>    memsz += tcb_offset;
>  #endif
>
> -  init_static_tls (memsz, MAX (TLS_TCB_ALIGN, max_align));
> +  init_static_tls (memsz, MAX (TCB_ALIGNMENT, max_align));
>  }
> diff --git a/elf/dl-tls.c b/elf/dl-tls.c
> index 9260d2d696..273f60f233 100644
> --- a/elf/dl-tls.c
> +++ b/elf/dl-tls.c
> @@ -219,7 +219,7 @@ _dl_count_modids (void)
>  void
>  _dl_determine_tlsoffset (void)
>  {
> -  size_t max_align = TLS_TCB_ALIGN;
> +  size_t max_align = TCB_ALIGNMENT;
>    size_t freetop = 0;
>    size_t freebottom = 0;
>
> @@ -350,7 +350,7 @@ _dl_determine_tlsoffset (void)
>
>    GL(dl_tls_static_used) = offset;
>    GLRO (dl_tls_static_size) = roundup (offset + GLRO(dl_tls_static_surplus),
> -                                      TLS_TCB_ALIGN);
> +                                      TCB_ALIGNMENT);
>  #else
>  # error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
>  #endif
> diff --git a/sysdeps/aarch64/nptl/tls.h b/sysdeps/aarch64/nptl/tls.h
> index c9ae564bf2..860776bb4b 100644
> --- a/sysdeps/aarch64/nptl/tls.h
> +++ b/sysdeps/aarch64/nptl/tls.h
> @@ -52,18 +52,12 @@ typedef struct
>  /* This is the size of the initial TCB.  */
>  # define TLS_INIT_TCB_SIZE     sizeof (tcbhead_t)
>
> -/* Alignment requirements for the initial TCB.  */
> -# define TLS_INIT_TCB_ALIGN    __alignof__ (struct pthread)
> -
>  /* This is the size of the TCB.  */
>  # define TLS_TCB_SIZE          sizeof (tcbhead_t)
>
>  /* This is the size we need before TCB.  */
>  # define TLS_PRE_TCB_SIZE      sizeof (struct pthread)
>
> -/* Alignment requirements for the TCB.  */
> -# define TLS_TCB_ALIGN         __alignof__ (struct pthread)
> -
>  /* Install the dtv pointer.  The pointer passed is to the element with
>     index -1 which contain the length.  */
>  # define INSTALL_DTV(tcbp, dtvp) \
> diff --git a/sysdeps/alpha/nptl/tls.h b/sysdeps/alpha/nptl/tls.h
> index eef922f268..860cc46d88 100644
> --- a/sysdeps/alpha/nptl/tls.h
> +++ b/sysdeps/alpha/nptl/tls.h
> @@ -46,18 +46,12 @@ typedef struct
>  /* This is the size of the initial TCB.  */
>  # define TLS_INIT_TCB_SIZE     sizeof (tcbhead_t)
>
> -/* Alignment requirements for the initial TCB.  */
> -# define TLS_INIT_TCB_ALIGN    16
> -
>  /* This is the size of the TCB.  */
>  # define TLS_TCB_SIZE          sizeof (tcbhead_t)
>
>  /* This is the size we need before TCB.  */
>  # define TLS_PRE_TCB_SIZE      sizeof (struct pthread)
>
> -/* Alignment requirements for the TCB.  */
> -# define TLS_TCB_ALIGN         16
> -
>  /* Install the dtv pointer.  The pointer passed is to the element with
>     index -1 which contain the length.  */
>  # define INSTALL_DTV(tcbp, dtvp) \
> diff --git a/sysdeps/arc/nptl/tls.h b/sysdeps/arc/nptl/tls.h
> index f6853867b2..06d8a48fea 100644
> --- a/sysdeps/arc/nptl/tls.h
> +++ b/sysdeps/arc/nptl/tls.h
> @@ -48,17 +48,11 @@ typedef struct
>  /* This is the size of the initial TCB.  */
>  # define TLS_INIT_TCB_SIZE     sizeof (tcbhead_t)
>
> -/* Alignment requirements for the initial TCB.  */
> -# define TLS_INIT_TCB_ALIGN    __alignof__ (struct pthread)
> -
>  /* This is the size of the TCB.  */
>  #ifndef TLS_TCB_SIZE
>  # define TLS_TCB_SIZE          sizeof (tcbhead_t)
>  #endif
>
> -/* Alignment requirements for the TCB.  */
> -# define TLS_TCB_ALIGN         __alignof__ (struct pthread)
> -
>  /* This is the size we need before TCB.  */
>  # define TLS_PRE_TCB_SIZE      sizeof (struct pthread)
>
> diff --git a/sysdeps/arm/nptl/tls.h b/sysdeps/arm/nptl/tls.h
> index 06612b5449..57e039fc0f 100644
> --- a/sysdeps/arm/nptl/tls.h
> +++ b/sysdeps/arm/nptl/tls.h
> @@ -50,18 +50,12 @@ typedef struct
>  /* This is the size of the initial TCB.  */
>  # define TLS_INIT_TCB_SIZE     sizeof (tcbhead_t)
>
> -/* Alignment requirements for the initial TCB.  */
> -# define TLS_INIT_TCB_ALIGN    16
> -
>  /* This is the size of the TCB.  */
>  # define TLS_TCB_SIZE          sizeof (tcbhead_t)
>
>  /* This is the size we need before TCB.  */
>  # define TLS_PRE_TCB_SIZE      sizeof (struct pthread)
>
> -/* Alignment requirements for the TCB.  */
> -# define TLS_TCB_ALIGN         16
> -
>  /* Install the dtv pointer.  The pointer passed is to the element with
>     index -1 which contain the length.  */
>  # define INSTALL_DTV(tcbp, dtvp) \
> diff --git a/sysdeps/csky/nptl/tls.h b/sysdeps/csky/nptl/tls.h
> index 39fd640459..64dcaec279 100644
> --- a/sysdeps/csky/nptl/tls.h
> +++ b/sysdeps/csky/nptl/tls.h
> @@ -61,15 +61,9 @@ typedef struct
>  /* This is the size of the initial TCB.  */
>  # define TLS_INIT_TCB_SIZE     sizeof (tcbhead_t)
>
> -/* Alignment requirements for the initial TCB.  */
> -# define TLS_INIT_TCB_ALIGN    8
> -
>  /* This is the size of the TCB.  */
>  # define TLS_TCB_SIZE          sizeof (tcbhead_t)
>
> -/* Alignment requirements for the TCB.  */
> -# define TLS_TCB_ALIGN         8
> -
>  /* This is the size we need before TCB.  */
>  # define TLS_PRE_TCB_SIZE      sizeof (struct pthread)
>
> diff --git a/sysdeps/generic/tls.h b/sysdeps/generic/tls.h
> index f581c9a992..b7aafce251 100644
> --- a/sysdeps/generic/tls.h
> +++ b/sysdeps/generic/tls.h
> @@ -19,6 +19,11 @@
>  /* An architecture-specific version of this file has to defined a
>     number of symbols:
>
> +     TCB_ALIGNMENT
> +
> +     Alignment of THREAD_SELF (struct pthread *) and the thread
> +     pointer.
> +
>       TLS_TCB_AT_TP  or  TLS_DTV_AT_TP
>
>       The presence of one of these symbols signals which variant of
> @@ -43,15 +48,6 @@
>       dynamic linker itself.  There are no threads in use at that time.
>
>
> -     TLS_TCB_ALIGN
> -
> -     Alignment requirements for the TCB structure.
> -
> -     TLS_INIT_TCB_ALIGN
> -
> -     Similarly, but for the structure used at startup time.
> -
> -
>       INSTALL_DTV(tcb, init_dtv)
>
>       This macro must install the given initial DTV into the thread control
> diff --git a/sysdeps/hppa/nptl/tls.h b/sysdeps/hppa/nptl/tls.h
> index 5f550227f2..62bfb96548 100644
> --- a/sysdeps/hppa/nptl/tls.h
> +++ b/sysdeps/hppa/nptl/tls.h
> @@ -52,15 +52,9 @@ typedef struct
>  /* This is the size of the initial TCB.  */
>  # define TLS_INIT_TCB_SIZE     sizeof (tcbhead_t)
>
> -/* Alignment requirements for the initial TCB.  */
> -# define TLS_INIT_TCB_ALIGN    __alignof__ (tcbhead_t)
> -
>  /* This is the size of the TCB.  */
>  # define TLS_TCB_SIZE          sizeof (tcbhead_t)
>
> -/* Alignment requirements for the TCB.  */
> -# define TLS_TCB_ALIGN         __alignof__ (struct pthread)
> -
>  /* This is the size we need before TCB */
>  # define TLS_PRE_TCB_SIZE      sizeof (struct pthread)
>
> diff --git a/sysdeps/i386/nptl/tls.h b/sysdeps/i386/nptl/tls.h
> index d010e14920..e5f4e83eb4 100644
> --- a/sysdeps/i386/nptl/tls.h
> +++ b/sysdeps/i386/nptl/tls.h
> @@ -102,15 +102,9 @@ union user_desc_init
>     struct pthread even when not linked with -lpthread.  */
>  # define TLS_INIT_TCB_SIZE sizeof (struct pthread)
>
> -/* Alignment requirements for the initial TCB.  */
> -# define TLS_INIT_TCB_ALIGN __alignof__ (struct pthread)
> -
>  /* This is the size of the TCB.  */
>  # define TLS_TCB_SIZE sizeof (struct pthread)
>
> -/* Alignment requirements for the TCB.  */
> -# define TLS_TCB_ALIGN __alignof__ (struct pthread)
> -
>  /* The TCB can have any size and the memory following the address the
>     thread pointer points to is unspecified.  Allocate the TCB there.  */
>  # define TLS_TCB_AT_TP 1
> diff --git a/sysdeps/ia64/libc-tls.c b/sysdeps/ia64/libc-tls.c
> index a01edceab3..ede1e8f463 100644
> --- a/sysdeps/ia64/libc-tls.c
> +++ b/sysdeps/ia64/libc-tls.c
> @@ -18,6 +18,9 @@
>
>  #include <csu/libc-tls.c>
>
> +_Static_assert (TLS_PRE_TCB_SIZE % __alignof (struct pthread) == 0,
> +               "__thread_self and THREAD_SELF have same alignment");
> +
>  /* On IA-64, as it lacks linker optimizations, __tls_get_addr can be
>     called even in statically linked binaries.
>     In this case module must be always 1 and PT_TLS segment
> diff --git a/sysdeps/ia64/nptl/tls.h b/sysdeps/ia64/nptl/tls.h
> index 44951da24b..3c23a2e042 100644
> --- a/sysdeps/ia64/nptl/tls.h
> +++ b/sysdeps/ia64/nptl/tls.h
> @@ -53,9 +53,6 @@ register struct pthread *__thread_self __asm__("r13");
>  /* This is the size of the initial TCB.  */
>  # define TLS_INIT_TCB_SIZE sizeof (tcbhead_t)
>
> -/* Alignment requirements for the initial TCB.  */
> -# define TLS_INIT_TCB_ALIGN __alignof__ (tcbhead_t)
> -
>  /* This is the size of the TCB.  */
>  # define TLS_TCB_SIZE sizeof (tcbhead_t)
>
> @@ -70,9 +67,6 @@ register struct pthread *__thread_self __asm__("r13");
>          & ~(__alignof__ (struct pthread) - 1))                         \
>        : 0))
>
> -/* Alignment requirements for the TCB.  */
> -# define TLS_TCB_ALIGN __alignof__ (struct pthread)
> -
>  /* The DTV is allocated at the TP; the TCB is placed elsewhere.  */
>  # define TLS_DTV_AT_TP 1
>  # define TLS_TCB_AT_TP 0
> diff --git a/sysdeps/m68k/nptl/tls.h b/sysdeps/m68k/nptl/tls.h
> index 257af6bddc..3acedc8465 100644
> --- a/sysdeps/m68k/nptl/tls.h
> +++ b/sysdeps/m68k/nptl/tls.h
> @@ -53,20 +53,15 @@ typedef struct
>     pointer, we don't need this.  */
>  # define TLS_INIT_TCB_SIZE     0
>
> -/* Alignment requirements for the initial TCB.  */
> -# define TLS_INIT_TCB_ALIGN    __alignof__ (struct pthread)
> -
>  /* This is the size of the TCB.  Because our TCB is before the thread
>     pointer, we don't need this.  */
>  # define TLS_TCB_SIZE          0
>
> -/* Alignment requirements for the TCB.  */
> -# define TLS_TCB_ALIGN         __alignof__ (struct pthread)
> -
>  /* This is the size we need before TCB - actually, it includes the TCB.  */
>  # define TLS_PRE_TCB_SIZE                                              \
>    (sizeof (struct pthread)                                             \
> -   + ((sizeof (tcbhead_t) + TLS_TCB_ALIGN - 1) & ~(TLS_TCB_ALIGN - 1)))
> +   + ((sizeof (tcbhead_t) + __alignof (struct pthread) - 1)            \
> +      & ~(__alignof (struct pthread) - 1)))
>
>  /* The thread pointer (TP) points to the end of the
>     TCB + 0x7000, as for PowerPC and MIPS.  This implies that TCB address is
> diff --git a/sysdeps/mach/hurd/tls.h b/sysdeps/mach/hurd/tls.h
> index 8e66d5ff53..e5f62dab78 100644
> --- a/sysdeps/mach/hurd/tls.h
> +++ b/sysdeps/mach/hurd/tls.h
> @@ -29,20 +29,12 @@
>  # include <mach.h>
>  # include <atomic.h>
>
> -
>  /* This is the size of the initial TCB.  */
>  # define TLS_INIT_TCB_SIZE sizeof (tcbhead_t)
>
> -/* Alignment requirements for the initial TCB.  */
> -# define TLS_INIT_TCB_ALIGN __alignof__ (tcbhead_t)
> -
>  /* This is the size of the TCB.  */
>  # define TLS_TCB_SIZE TLS_INIT_TCB_SIZE        /* XXX */
>
> -/* Alignment requirements for the TCB.  */
> -# define TLS_TCB_ALIGN TLS_INIT_TCB_ALIGN /* XXX */
> -
> -
>  /* Install the dtv pointer.  The pointer passed is to the element with
>     index -1 which contain the length.  */
>  # define INSTALL_DTV(descr, dtvp) \
> diff --git a/sysdeps/microblaze/nptl/tls.h b/sysdeps/microblaze/nptl/tls.h
> index a31703b247..de9d2b693b 100644
> --- a/sysdeps/microblaze/nptl/tls.h
> +++ b/sysdeps/microblaze/nptl/tls.h
> @@ -56,18 +56,12 @@ typedef struct
>  /* This is the size of the initial TCB.  */
>  # define TLS_INIT_TCB_SIZE  sizeof (tcbhead_t)
>
> -/* Alignment requirements for the initial TCB.  */
> -# define TLS_INIT_TCB_ALIGN __alignof__ (tcbhead_t)
> -
>  /* This is the size of the TCB.  */
>  # define TLS_TCB_SIZE       sizeof (tcbhead_t)
>
>  /* This is the size we need before TCB.  */
>  # define TLS_PRE_TCB_SIZE   sizeof (struct pthread)
>
> -/* Alignment requirements for the TCB.  */
> -# define TLS_TCB_ALIGN      __alignof__ (struct pthread)
> -
>  /* Install the dtv pointer.  The pointer passed is to the element with
>     index -1 which contain the length.  */
>  # define INSTALL_DTV(tcbp, dtvp) \
> diff --git a/sysdeps/mips/nptl/tls.h b/sysdeps/mips/nptl/tls.h
> index afb8308e1b..797e661dc1 100644
> --- a/sysdeps/mips/nptl/tls.h
> +++ b/sysdeps/mips/nptl/tls.h
> @@ -83,20 +83,15 @@ typedef struct
>     pointer, we don't need this.  */
>  # define TLS_INIT_TCB_SIZE     0
>
> -/* Alignment requirements for the initial TCB.  */
> -# define TLS_INIT_TCB_ALIGN    __alignof__ (struct pthread)
> -
>  /* This is the size of the TCB.  Because our TCB is before the thread
>     pointer, we don't need this.  */
>  # define TLS_TCB_SIZE          0
>
> -/* Alignment requirements for the TCB.  */
> -# define TLS_TCB_ALIGN         __alignof__ (struct pthread)
> -
>  /* This is the size we need before TCB - actually, it includes the TCB.  */
>  # define TLS_PRE_TCB_SIZE \
>    (sizeof (struct pthread)                                                   \
> -   + ((sizeof (tcbhead_t) + TLS_TCB_ALIGN - 1) & ~(TLS_TCB_ALIGN - 1)))
> +   + ((sizeof (tcbhead_t) + __alignof (struct pthread) - 1)                  \
> +      & ~(__alignof (struct pthread) - 1)))
>
>  /* The thread pointer (in hardware register $29) points to the end of
>     the TCB + 0x7000, as for PowerPC.  The pthread_descr structure is
> diff --git a/sysdeps/nios2/nptl/tls.h b/sysdeps/nios2/nptl/tls.h
> index 173c395449..18daedd790 100644
> --- a/sysdeps/nios2/nptl/tls.h
> +++ b/sysdeps/nios2/nptl/tls.h
> @@ -59,20 +59,15 @@ register struct pthread *__thread_self __asm__("r23");
>     pointer, we don't need this.  */
>  # define TLS_INIT_TCB_SIZE     0
>
> -/* Alignment requirements for the initial TCB.  */
> -# define TLS_INIT_TCB_ALIGN    __alignof__ (struct pthread)
> -
>  /* This is the size of the TCB.  Because our TCB is before the thread
>     pointer, we don't need this.  */
>  # define TLS_TCB_SIZE          0
>
> -/* Alignment requirements for the TCB.  */
> -# define TLS_TCB_ALIGN         __alignof__ (struct pthread)
> -
>  /* This is the size we need before TCB - actually, it includes the TCB.  */
>  # define TLS_PRE_TCB_SIZE \
>    (sizeof (struct pthread)                                                   \
> -   + ((sizeof (tcbhead_t) + TLS_TCB_ALIGN - 1) & ~(TLS_TCB_ALIGN - 1)))
> +   + ((sizeof (tcbhead_t) + __alignof (struct pthread) - 1)                  \
> +      & ~(__alignof (struct pthread) - 1)))
>
>  /* The thread pointer (in hardware register r23) points to the end of
>     the TCB + 0x7000, as for PowerPC and MIPS.  */
> diff --git a/sysdeps/powerpc/nptl/tls.h b/sysdeps/powerpc/nptl/tls.h
> index 7d2f16dcf2..63098f4048 100644
> --- a/sysdeps/powerpc/nptl/tls.h
> +++ b/sysdeps/powerpc/nptl/tls.h
> @@ -108,19 +108,14 @@ typedef struct
>  /* This is the size of the initial TCB.  */
>  # define TLS_INIT_TCB_SIZE     0
>
> -/* Alignment requirements for the initial TCB.  */
> -# define TLS_INIT_TCB_ALIGN    __alignof__ (struct pthread)
> -
>  /* This is the size of the TCB.  */
>  # define TLS_TCB_SIZE          0
>
> -/* Alignment requirements for the TCB.  */
> -# define TLS_TCB_ALIGN         __alignof__ (struct pthread)
> -
>  /* This is the size we need before TCB.  */
>  # define TLS_PRE_TCB_SIZE \
>    (sizeof (struct pthread)                                                   \
> -   + ((sizeof (tcbhead_t) + TLS_TCB_ALIGN - 1) & ~(TLS_TCB_ALIGN - 1)))
> +   + ((sizeof (tcbhead_t) + __alignof (struct pthread) - 1)                  \
> +      & ~(__alignof (struct pthread) - 1)))
>
>  /* The following assumes that TP (R2 or R13) points to the end of the
>     TCB + 0x7000 (per the ABI).  This implies that TCB address is
> diff --git a/sysdeps/riscv/nptl/tls.h b/sysdeps/riscv/nptl/tls.h
> index a966d440c5..1f78cacdec 100644
> --- a/sysdeps/riscv/nptl/tls.h
> +++ b/sysdeps/riscv/nptl/tls.h
> @@ -50,20 +50,15 @@ typedef struct
>     pointer, we don't need this.  */
>  # define TLS_INIT_TCB_SIZE     0
>
> -/* Alignment requirements for the initial TCB.  */
> -# define TLS_INIT_TCB_ALIGN    __alignof__ (struct pthread)
> -
>  /* This is the size of the TCB.  Because our TCB is before the thread
>     pointer, we don't need this.  */
>  # define TLS_TCB_SIZE          0
>
> -/* Alignment requirements for the TCB.  */
> -# define TLS_TCB_ALIGN         __alignof__ (struct pthread)
> -
>  /* This is the size we need before TCB - actually, it includes the TCB.  */
>  # define TLS_PRE_TCB_SIZE \
>    (sizeof (struct pthread)                                                   \
> -   + ((sizeof (tcbhead_t) + TLS_TCB_ALIGN - 1) & ~(TLS_TCB_ALIGN - 1)))
> +   + ((sizeof (tcbhead_t) + __alignof (struct pthread) - 1)                  \
> +      & ~(__alignof (struct pthread) - 1)))
>
>  /* The thread pointer tp points to the end of the TCB.
>     The pthread_descr structure is immediately in front of the TCB.  */
> diff --git a/sysdeps/s390/nptl/tls.h b/sysdeps/s390/nptl/tls.h
> index 16c5811e06..1655101b30 100644
> --- a/sysdeps/s390/nptl/tls.h
> +++ b/sysdeps/s390/nptl/tls.h
> @@ -66,15 +66,9 @@ typedef struct
>     struct pthread even when not linked with -lpthread.  */
>  # define TLS_INIT_TCB_SIZE sizeof (struct pthread)
>
> -/* Alignment requirements for the initial TCB.  */
> -# define TLS_INIT_TCB_ALIGN __alignof__ (struct pthread)
> -
>  /* This is the size of the TCB.  */
>  # define TLS_TCB_SIZE sizeof (struct pthread)
>
> -/* Alignment requirements for the TCB.  */
> -# define TLS_TCB_ALIGN __alignof__ (struct pthread)
> -
>  /* The TCB can have any size and the memory following the address the
>     thread pointer points to is unspecified.  Allocate the TCB there.  */
>  # define TLS_TCB_AT_TP 1
> diff --git a/sysdeps/sh/nptl/tls.h b/sysdeps/sh/nptl/tls.h
> index aadd5be022..cfbfe44523 100644
> --- a/sysdeps/sh/nptl/tls.h
> +++ b/sysdeps/sh/nptl/tls.h
> @@ -51,18 +51,12 @@ typedef struct
>  /* This is the size of the initial TCB.  */
>  # define TLS_INIT_TCB_SIZE sizeof (tcbhead_t)
>
> -/* Alignment requirements for the initial TCB.  */
> -# define TLS_INIT_TCB_ALIGN __alignof__ (tcbhead_t)
> -
>  /* This is the size of the TCB.  */
>  # define TLS_TCB_SIZE sizeof (tcbhead_t)
>
>  /* This is the size we need before TCB.  */
>  # define TLS_PRE_TCB_SIZE sizeof (struct pthread)
>
> -/* Alignment requirements for the TCB.  */
> -# define TLS_TCB_ALIGN __alignof__ (struct pthread)
> -
>  /* The TLS blocks start right after the TCB.  */
>  # define TLS_DTV_AT_TP 1
>  # define TLS_TCB_AT_TP 0
> diff --git a/sysdeps/sparc/nptl/tls.h b/sysdeps/sparc/nptl/tls.h
> index d4e6e525d9..4f823cd020 100644
> --- a/sysdeps/sparc/nptl/tls.h
> +++ b/sysdeps/sparc/nptl/tls.h
> @@ -63,15 +63,9 @@ register struct pthread *__thread_self __asm__("%g7");
>     struct pthread even when not linked with -lpthread.  */
>  # define TLS_INIT_TCB_SIZE sizeof (struct pthread)
>
> -/* Alignment requirements for the initial TCB.  */
> -# define TLS_INIT_TCB_ALIGN __alignof__ (struct pthread)
> -
>  /* This is the size of the TCB.  */
>  # define TLS_TCB_SIZE sizeof (struct pthread)
>
> -/* Alignment requirements for the TCB.  */
> -# define TLS_TCB_ALIGN __alignof__ (struct pthread)
> -
>  /* The TCB can have any size and the memory following the address the
>     thread pointer points to is unspecified.  Allocate the TCB there.  */
>  # define TLS_TCB_AT_TP 1
> diff --git a/sysdeps/x86_64/nptl/tls.h b/sysdeps/x86_64/nptl/tls.h
> index a39579897c..91ad21e478 100644
> --- a/sysdeps/x86_64/nptl/tls.h
> +++ b/sysdeps/x86_64/nptl/tls.h
> @@ -106,15 +106,9 @@ _Static_assert (offsetof (tcbhead_t, __glibc_unused2) == 0x80,
>     struct pthread even when not linked with -lpthread.  */
>  # define TLS_INIT_TCB_SIZE sizeof (struct pthread)
>
> -/* Alignment requirements for the initial TCB.  */
> -# define TLS_INIT_TCB_ALIGN __alignof__ (struct pthread)
> -
>  /* This is the size of the TCB.  */
>  # define TLS_TCB_SIZE sizeof (struct pthread)
>
> -/* Alignment requirements for the TCB.  */
> -# define TLS_TCB_ALIGN __alignof__ (struct pthread)
> -
>  /* The TCB can have any size and the memory following the address the
>     thread pointer points to is unspecified.  Allocate the TCB there.  */
>  # define TLS_TCB_AT_TP 1
>

LGTM.

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

Thanks.