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glibc/sysdeps/s390/nptl/tls.h
Florian Weimer 627f5ede70 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 23c77f6018
("nptl: Increase default TCB alignment to 32").

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
2021-12-09 23:47:49 +01:00

177 lines
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/* Definition for thread-local data handling. NPTL/s390 version.
Copyright (C) 2003-2021 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/>. */
#ifndef _TLS_H
#define _TLS_H 1
#include <dl-sysdep.h>
#ifndef __ASSEMBLER__
# include <stdbool.h>
# include <stddef.h>
# include <stdint.h>
# include <stdlib.h>
# include <list.h>
# include <kernel-features.h>
# include <dl-dtv.h>
typedef struct
{
void *tcb; /* Pointer to the TCB. Not necessary the
thread descriptor used by libpthread. */
dtv_t *dtv;
void *self; /* Pointer to the thread descriptor. */
int multiple_threads;
uintptr_t sysinfo;
uintptr_t stack_guard;
int gscope_flag;
int __glibc_reserved1;
/* GCC split stack support. */
void *__private_ss;
} tcbhead_t;
# ifndef __s390x__
# define TLS_MULTIPLE_THREADS_IN_TCB 1
# endif
#else /* __ASSEMBLER__ */
# include <tcb-offsets.h>
#endif
/* Alignment requirement for the stack. For IA-32 this is governed by
the SSE memory functions. */
#define STACK_ALIGN 16
#ifndef __ASSEMBLER__
/* Get system call information. */
# include <sysdep.h>
/* This is the size of the initial TCB. Can't be just sizeof (tcbhead_t),
because NPTL getpid, __libc_alloca_cutoff etc. need (almost) the whole
struct pthread even when not linked with -lpthread. */
# define TLS_INIT_TCB_SIZE sizeof (struct pthread)
/* This is the size of the TCB. */
# define TLS_TCB_SIZE sizeof (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
# define TLS_DTV_AT_TP 0
/* Get the thread descriptor definition. */
# include <nptl/descr.h>
/* Install the dtv pointer. The pointer passed is to the element with
index -1 which contain the length. */
# define INSTALL_DTV(descr, dtvp) \
((tcbhead_t *) (descr))->dtv = (dtvp) + 1
/* Install new dtv for current thread. */
# define INSTALL_NEW_DTV(dtv) \
(((tcbhead_t *) __builtin_thread_pointer ())->dtv = (dtv))
/* Return dtv of given thread descriptor. */
# define GET_DTV(descr) \
(((tcbhead_t *) (descr))->dtv)
#if defined NEED_DL_SYSINFO && defined SHARED
# define INIT_SYSINFO \
_head->sysinfo = GLRO(dl_sysinfo)
#else
# define INIT_SYSINFO
#endif
/* Code to initially initialize the thread pointer. This might need
special attention since 'errno' is not yet available and if the
operation can cause a failure 'errno' must not be touched. */
# define TLS_INIT_TP(thrdescr) \
({ void *_thrdescr = (thrdescr); \
tcbhead_t *_head = _thrdescr; \
\
_head->tcb = _thrdescr; \
/* For now the thread descriptor is at the same address. */ \
_head->self = _thrdescr; \
/* New syscall handling support. */ \
INIT_SYSINFO; \
\
__builtin_set_thread_pointer (_thrdescr); \
NULL; \
})
/* Value passed to 'clone' for initialization of the thread register. */
# define TLS_DEFINE_INIT_TP(tp, pd) void *tp = (pd)
/* Return the address of the dtv for the current thread. */
# define THREAD_DTV() \
(((tcbhead_t *) __builtin_thread_pointer ())->dtv)
/* Return the thread descriptor for the current thread. */
# define THREAD_SELF ((struct pthread *) __builtin_thread_pointer ())
/* Magic for libthread_db to know how to do THREAD_SELF. */
# define DB_THREAD_SELF REGISTER (32, 32, 18 * 4, 0) \
REGISTER (64, __WORDSIZE, 18 * 8, 0)
# include <tcb-access.h>
/* Set the stack guard field in TCB head. */
#define THREAD_SET_STACK_GUARD(value) \
do \
{ \
__asm__ __volatile__ ("" : : : "a0", "a1"); \
THREAD_SETMEM (THREAD_SELF, header.stack_guard, value); \
} \
while (0)
#define THREAD_COPY_STACK_GUARD(descr) \
((descr)->header.stack_guard \
= THREAD_GETMEM (THREAD_SELF, header.stack_guard))
/* s390 doesn't have HP_TIMING_*, so for the time being
use stack_guard as pointer_guard. */
#define THREAD_GET_POINTER_GUARD() \
THREAD_GETMEM (THREAD_SELF, header.stack_guard)
#define THREAD_SET_POINTER_GUARD(value) ((void) (value))
#define THREAD_COPY_POINTER_GUARD(descr)
/* Get and set the global scope generation counter in struct pthread. */
#define THREAD_GSCOPE_FLAG_UNUSED 0
#define THREAD_GSCOPE_FLAG_USED 1
#define THREAD_GSCOPE_FLAG_WAIT 2
#define THREAD_GSCOPE_RESET_FLAG() \
do \
{ int __res \
= atomic_exchange_rel (&THREAD_SELF->header.gscope_flag, \
THREAD_GSCOPE_FLAG_UNUSED); \
if (__res == THREAD_GSCOPE_FLAG_WAIT) \
lll_futex_wake (&THREAD_SELF->header.gscope_flag, 1, LLL_PRIVATE); \
} \
while (0)
#define THREAD_GSCOPE_SET_FLAG() \
do \
{ \
THREAD_SELF->header.gscope_flag = THREAD_GSCOPE_FLAG_USED; \
atomic_write_barrier (); \
} \
while (0)
#endif /* __ASSEMBLER__ */
#endif /* tls.h */
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