AuroraMiddleware/glibc
1
0
Fork 0
mirror of https://sourceware.org/git/glibc.git synced 2024-11-25 06:20:06 +00:00
Code Issues Packages Projects Releases Wiki Activity
a75b1e35c5
glibc/sysdeps/i386/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

286 lines
9.5 KiB
C
Raw Blame History

/* Definition for thread-local data handling. nptl/i386 version.
Copyright (C) 2002-2021 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 <sysdep.h>
# include <libc-pointer-arith.h> /* For cast_to_integer. */
# include <kernel-features.h>
# include <dl-dtv.h>
typedef struct
{
void *tcb; /* Pointer to the TCB. Not necessarily 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;
uintptr_t pointer_guard;
int gscope_flag;
/* Bit 0: X86_FEATURE_1_IBT.
Bit 1: X86_FEATURE_1_SHSTK.
*/
unsigned int feature_1;
/* Reservation of some values for the TM ABI. */
void *__private_tm[3];
/* GCC split stack support. */
void *__private_ss;
/* The lowest address of shadow stack, */
unsigned long ssp_base;
} tcbhead_t;
/* morestack.S in libgcc uses offset 0x30 to access __private_ss, */
_Static_assert (offsetof (tcbhead_t, __private_ss) == 0x30,
"offset of __private_ss != 0x30");
# define TLS_MULTIPLE_THREADS_IN_TCB 1
#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>
/* The old way: using LDT. */
/* Structure passed to `modify_ldt', 'set_thread_area', and 'clone' calls. */
struct user_desc
{
unsigned int entry_number;
unsigned long int base_addr;
unsigned int limit;
unsigned int seg_32bit:1;
unsigned int contents:2;
unsigned int read_exec_only:1;
unsigned int limit_in_pages:1;
unsigned int seg_not_present:1;
unsigned int useable:1;
unsigned int empty:25;
};
/* Initializing bit fields is slow. We speed it up by using a union. */
union user_desc_init
{
struct user_desc desc;
unsigned int vals[4];
};
/* 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(dtvp) \
({ struct pthread *__pd; \
THREAD_SETMEM (__pd, header.dtv, (dtvp)); })
/* Return dtv of given thread descriptor. */
# define GET_DTV(descr) \
(((tcbhead_t *) (descr))->dtv)
/* Macros to load from and store into segment registers. */
# ifndef TLS_GET_GS
# define TLS_GET_GS() \
({ int __seg; __asm ("movw %%gs, %w0" : "=q" (__seg)); __seg & 0xffff; })
# endif
# ifndef TLS_SET_GS
# define TLS_SET_GS(val) \
__asm ("movw %w0, %%gs" :: "q" (val))
# endif
#ifdef NEED_DL_SYSINFO
# define INIT_SYSINFO \
_head->sysinfo = GLRO(dl_sysinfo)
# define SETUP_THREAD_SYSINFO(pd) \
((pd)->header.sysinfo = THREAD_GETMEM (THREAD_SELF, header.sysinfo))
# define CHECK_THREAD_SYSINFO(pd) \
assert ((pd)->header.sysinfo == THREAD_GETMEM (THREAD_SELF, header.sysinfo))
#else
# define INIT_SYSINFO
#endif
#define LOCK_PREFIX "lock;"
static inline void __attribute__ ((unused, always_inline))
tls_fill_user_desc (union user_desc_init *desc,
unsigned int entry_number,
void *pd)
{
desc->vals[0] = entry_number;
/* The 'base_addr' field. Pointer to the TCB. */
desc->vals[1] = (unsigned long int) pd;
/* The 'limit' field. We use 4GB which is 0xfffff pages. */
desc->vals[2] = 0xfffff;
/* Collapsed value of the bitfield:
.seg_32bit = 1
.contents = 0
.read_exec_only = 0
.limit_in_pages = 1
.seg_not_present = 0
.useable = 1 */
desc->vals[3] = 0x51;
}
/* 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; \
union user_desc_init _segdescr; \
int _result; \
\
_head->tcb = _thrdescr; \
/* For now the thread descriptor is at the same address. */ \
_head->self = _thrdescr; \
/* New syscall handling support. */ \
INIT_SYSINFO; \
\
/* Let the kernel pick a value for the 'entry_number' field. */ \
tls_fill_user_desc (&_segdescr, -1, _thrdescr); \
\
/* Install the TLS. */ \
_result = INTERNAL_SYSCALL_CALL (set_thread_area, &_segdescr.desc); \
\
if (_result == 0) \
/* We know the index in the GDT, now load the segment register. \
The use of the GDT is described by the value 3 in the lower \
three bits of the segment descriptor value. \
\
Note that we have to do this even if the numeric value of \
the descriptor does not change. Loading the segment register \
causes the segment information from the GDT to be loaded \
which is necessary since we have changed it. */ \
TLS_SET_GS (_segdescr.desc.entry_number * 8 + 3); \
\
_result == 0 ? NULL \
: "set_thread_area failed when setting up thread-local storage\n"; })
# define TLS_DEFINE_INIT_TP(tp, pd) \
union user_desc_init _segdescr; \
/* Find the 'entry_number' field that the kernel selected in TLS_INIT_TP. \
The first three bits of the segment register value select the GDT, \
ignore them. We get the index from the value of the %gs register in \
the current thread. */ \
tls_fill_user_desc (&_segdescr, TLS_GET_GS () >> 3, pd); \
const struct user_desc *tp = &_segdescr.desc
/* Return the address of the dtv for the current thread. */
# define THREAD_DTV() \
({ struct pthread *__pd; \
THREAD_GETMEM (__pd, header.dtv); })
/* Return the thread descriptor for the current thread.
The contained asm must *not* be marked volatile since otherwise
assignments like
pthread_descr self = thread_self();
do not get optimized away. */
# if __GNUC_PREREQ (6, 0)
# define THREAD_SELF \
(*(struct pthread *__seg_gs *) offsetof (struct pthread, header.self))
# else
# define THREAD_SELF \
({ struct pthread *__self; \
asm ("movl %%gs:%c1,%0" : "=r" (__self) \
: "i" (offsetof (struct pthread, header.self))); \
__self;})
# endif
/* Magic for libthread_db to know how to do THREAD_SELF. */
# define DB_THREAD_SELF \
REGISTER_THREAD_AREA (32, offsetof (struct user_regs_struct, xgs), 3) \
REGISTER_THREAD_AREA (64, 26 * 8, 3) /* x86-64's user_regs_struct->gs */
# include <tcb-access.h>
/* Set the stack guard field in TCB head. */
#define THREAD_SET_STACK_GUARD(value) \
THREAD_SETMEM (THREAD_SELF, header.stack_guard, value)
#define THREAD_COPY_STACK_GUARD(descr) \
((descr)->header.stack_guard \
= THREAD_GETMEM (THREAD_SELF, header.stack_guard))
/* Set the pointer guard field in the TCB head. */
#define THREAD_SET_POINTER_GUARD(value) \
THREAD_SETMEM (THREAD_SELF, header.pointer_guard, value)
#define THREAD_COPY_POINTER_GUARD(descr) \
((descr)->header.pointer_guard \
= THREAD_GETMEM (THREAD_SELF, header.pointer_guard))
/* Get and set the global scope generation counter in the TCB head. */
#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; \
asm volatile ("xchgl %0, %%gs:%P1" \
: "=r" (__res) \
: "i" (offsetof (struct pthread, header.gscope_flag)), \
"0" (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() \
THREAD_SETMEM (THREAD_SELF, header.gscope_flag, THREAD_GSCOPE_FLAG_USED)
#endif /* __ASSEMBLER__ */
#endif /* tls.h */
Reference in New Issue View Git Blame Copy Permalink