sysdeps/i386/nptl/tls.h

   1 /* Definition for thread-local data handling.  nptl/i386 version.
   2    Copyright (C) 2002-2021 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _TLS_H
  20 #define _TLS_H  1
  21
  22 #include <dl-sysdep.h>
  23 #ifndef __ASSEMBLER__
  24 # include <stdbool.h>
  25 # include <stddef.h>
  26 # include <stdint.h>
  27 # include <stdlib.h>
  28 # include <sysdep.h>
  29 # include <libc-pointer-arith.h> /* For cast_to_integer. */
  30 # include <kernel-features.h>
  31 # include <dl-dtv.h>
  32
  33 typedef struct
  34 {
  35   void *tcb;            /* Pointer to the TCB.  Not necessarily the
  36                            thread descriptor used by libpthread.  */
  37   dtv_t *dtv;
  38   void *self;           /* Pointer to the thread descriptor.  */
  39   int multiple_threads;
  40   uintptr_t sysinfo;
  41   uintptr_t stack_guard;
  42   uintptr_t pointer_guard;
  43   int gscope_flag;
  44   /* Bit 0: X86_FEATURE_1_IBT.
  45      Bit 1: X86_FEATURE_1_SHSTK.
  46    */
  47   unsigned int feature_1;
  48   /* Reservation of some values for the TM ABI.  */
  49   void *__private_tm[3];
  50   /* GCC split stack support.  */
  51   void *__private_ss;
  52   /* The lowest address of shadow stack,  */
  53   unsigned long ssp_base;
  54 } tcbhead_t;
  55
  56 /* morestack.S in libgcc uses offset 0x30 to access __private_ss,   */
  57 _Static_assert (offsetof (tcbhead_t, __private_ss) == 0x30,
  58                 "offset of __private_ss != 0x30");
  59
  60 # define TLS_MULTIPLE_THREADS_IN_TCB 1
  61
  62 #else /* __ASSEMBLER__ */
  63 # include <tcb-offsets.h>
  64 #endif
  65
  66
  67 /* Alignment requirement for the stack.  For IA-32 this is governed by
  68    the SSE memory functions.  */
  69 #define STACK_ALIGN     16
  70
  71 #ifndef __ASSEMBLER__
  72 /* Get system call information.  */
  73 # include <sysdep.h>
  74
  75 /* The old way: using LDT.  */
  76
  77 /* Structure passed to `modify_ldt', 'set_thread_area', and 'clone' calls.  */
  78 struct user_desc
  79 {
  80   unsigned int entry_number;
  81   unsigned long int base_addr;
  82   unsigned int limit;
  83   unsigned int seg_32bit:1;
  84   unsigned int contents:2;
  85   unsigned int read_exec_only:1;
  86   unsigned int limit_in_pages:1;
  87   unsigned int seg_not_present:1;
  88   unsigned int useable:1;
  89   unsigned int empty:25;
  90 };
  91
  92 /* Initializing bit fields is slow.  We speed it up by using a union.  */
  93 union user_desc_init
  94 {
  95   struct user_desc desc;
  96   unsigned int vals[4];
  97 };
  98
  99
 100 /* This is the size of the initial TCB.  Can't be just sizeof (tcbhead_t),
 101    because NPTL getpid, __libc_alloca_cutoff etc. need (almost) the whole
 102    struct pthread even when not linked with -lpthread.  */
 103 # define TLS_INIT_TCB_SIZE sizeof (struct pthread)
 104
 105 /* Alignment requirements for the initial TCB.  */
 106 # define TLS_INIT_TCB_ALIGN __alignof__ (struct pthread)
 107
 108 /* This is the size of the TCB.  */
 109 # define TLS_TCB_SIZE sizeof (struct pthread)
 110
 111 /* Alignment requirements for the TCB.  */
 112 # define TLS_TCB_ALIGN __alignof__ (struct pthread)
 113
 114 /* The TCB can have any size and the memory following the address the
 115    thread pointer points to is unspecified.  Allocate the TCB there.  */
 116 # define TLS_TCB_AT_TP  1
 117 # define TLS_DTV_AT_TP  0
 118
 119 /* Get the thread descriptor definition.  */
 120 # include <nptl/descr.h>
 121
 122
 123 /* Install the dtv pointer.  The pointer passed is to the element with
 124    index -1 which contain the length.  */
 125 # define INSTALL_DTV(descr, dtvp) \
 126   ((tcbhead_t *) (descr))->dtv = (dtvp) + 1
 127
 128 /* Install new dtv for current thread.  */
 129 # define INSTALL_NEW_DTV(dtvp) \
 130   ({ struct pthread *__pd;                                                    \
 131      THREAD_SETMEM (__pd, header.dtv, (dtvp)); })
 132
 133 /* Return dtv of given thread descriptor.  */
 134 # define GET_DTV(descr) \
 135   (((tcbhead_t *) (descr))->dtv)
 136
 137 /* Macros to load from and store into segment registers.  */
 138 # ifndef TLS_GET_GS
 139 #  define TLS_GET_GS() \
 140   ({ int __seg; __asm ("movw %%gs, %w0" : "=q" (__seg)); __seg & 0xffff; })
 141 # endif
 142 # ifndef TLS_SET_GS
 143 #  define TLS_SET_GS(val) \
 144   __asm ("movw %w0, %%gs" :: "q" (val))
 145 # endif
 146
 147 #ifdef NEED_DL_SYSINFO
 148 # define INIT_SYSINFO \
 149   _head->sysinfo = GLRO(dl_sysinfo)
 150 # define SETUP_THREAD_SYSINFO(pd) \
 151   ((pd)->header.sysinfo = THREAD_GETMEM (THREAD_SELF, header.sysinfo))
 152 # define CHECK_THREAD_SYSINFO(pd) \
 153   assert ((pd)->header.sysinfo == THREAD_GETMEM (THREAD_SELF, header.sysinfo))
 154 #else
 155 # define INIT_SYSINFO
 156 #endif
 157
 158 #define LOCK_PREFIX "lock;"
 159
 160 static inline void __attribute__ ((unused, always_inline))
 161 tls_fill_user_desc (union user_desc_init *desc,
 162                     unsigned int entry_number,
 163                     void *pd)
 164 {
 165   desc->vals[0] = entry_number;
 166   /* The 'base_addr' field.  Pointer to the TCB.  */
 167   desc->vals[1] = (unsigned long int) pd;
 168   /* The 'limit' field.  We use 4GB which is 0xfffff pages.  */
 169   desc->vals[2] = 0xfffff;
 170   /* Collapsed value of the bitfield:
 171      .seg_32bit = 1
 172      .contents = 0
 173      .read_exec_only = 0
 174      .limit_in_pages = 1
 175      .seg_not_present = 0
 176      .useable = 1 */
 177   desc->vals[3] = 0x51;
 178 }
 179
 180 /* Code to initially initialize the thread pointer.  This might need
 181    special attention since 'errno' is not yet available and if the
 182    operation can cause a failure 'errno' must not be touched.  */
 183 # define TLS_INIT_TP(thrdescr) \
 184   ({ void *_thrdescr = (thrdescr);                                            \
 185      tcbhead_t *_head = _thrdescr;                                            \
 186      union user_desc_init _segdescr;                                          \
 187      int _result;                                                             \
 188                                                                               \
 189      _head->tcb = _thrdescr;                                                  \
 190      /* For now the thread descriptor is at the same address.  */             \
 191      _head->self = _thrdescr;                                                 \
 192      /* New syscall handling support.  */                                     \
 193      INIT_SYSINFO;                                                            \
 194                                                                               \
 195      /* Let the kernel pick a value for the 'entry_number' field.  */         \
 196      tls_fill_user_desc (&_segdescr, -1, _thrdescr);                          \
 197                                                                               \
 198      /* Install the TLS.  */                                                  \
 199      _result = INTERNAL_SYSCALL_CALL (set_thread_area, &_segdescr.desc);      \
 200                                                                               \
 201      if (_result == 0)                                                        \
 202        /* We know the index in the GDT, now load the segment register.        \
 203           The use of the GDT is described by the value 3 in the lower         \
 204           three bits of the segment descriptor value.                         \
 205                                                                               \
 206           Note that we have to do this even if the numeric value of           \
 207           the descriptor does not change.  Loading the segment register       \
 208           causes the segment information from the GDT to be loaded            \
 209           which is necessary since we have changed it.   */                   \
 210        TLS_SET_GS (_segdescr.desc.entry_number * 8 + 3);                      \
 211                                                                               \
 212      _result == 0 ? NULL                                                      \
 213      : "set_thread_area failed when setting up thread-local storage\n"; })
 214
 215 # define TLS_DEFINE_INIT_TP(tp, pd)                                           \
 216   union user_desc_init _segdescr;                                             \
 217   /* Find the 'entry_number' field that the kernel selected in TLS_INIT_TP.   \
 218      The first three bits of the segment register value select the GDT,       \
 219      ignore them.  We get the index from the value of the %gs register in     \
 220      the current thread.  */                                                  \
 221   tls_fill_user_desc (&_segdescr, TLS_GET_GS () >> 3, pd);                    \
 222   const struct user_desc *tp = &_segdescr.desc
 223
 224
 225 /* Return the address of the dtv for the current thread.  */
 226 # define THREAD_DTV() \
 227   ({ struct pthread *__pd;                                                    \
 228      THREAD_GETMEM (__pd, header.dtv); })
 229
 230
 231 /* Return the thread descriptor for the current thread.
 232
 233    The contained asm must *not* be marked volatile since otherwise
 234    assignments like
 235         pthread_descr self = thread_self();
 236    do not get optimized away.  */
 237 # if __GNUC_PREREQ (6, 0)
 238 #  define THREAD_SELF \
 239   (*(struct pthread *__seg_gs *) offsetof (struct pthread, header.self))
 240 # else
 241 #  define THREAD_SELF \
 242   ({ struct pthread *__self;                                                  \
 243      asm ("movl %%gs:%c1,%0" : "=r" (__self)                                  \
 244           : "i" (offsetof (struct pthread, header.self)));                    \
 245      __self;})
 246 # endif
 247
 248 /* Magic for libthread_db to know how to do THREAD_SELF.  */
 249 # define DB_THREAD_SELF \
 250   REGISTER_THREAD_AREA (32, offsetof (struct user_regs_struct, xgs), 3) \
 251   REGISTER_THREAD_AREA (64, 26 * 8, 3) /* x86-64's user_regs_struct->gs */
 252
 253 # include <tcb-access.h>
 254
 255 /* Set the stack guard field in TCB head.  */
 256 #define THREAD_SET_STACK_GUARD(value) \
 257   THREAD_SETMEM (THREAD_SELF, header.stack_guard, value)
 258 #define THREAD_COPY_STACK_GUARD(descr) \
 259   ((descr)->header.stack_guard                                                \
 260    = THREAD_GETMEM (THREAD_SELF, header.stack_guard))
 261
 262
 263 /* Set the pointer guard field in the TCB head.  */
 264 #define THREAD_SET_POINTER_GUARD(value) \
 265   THREAD_SETMEM (THREAD_SELF, header.pointer_guard, value)
 266 #define THREAD_COPY_POINTER_GUARD(descr) \
 267   ((descr)->header.pointer_guard                                              \
 268    = THREAD_GETMEM (THREAD_SELF, header.pointer_guard))
 269
 270
 271 /* Get and set the global scope generation counter in the TCB head.  */
 272 #define THREAD_GSCOPE_FLAG_UNUSED 0
 273 #define THREAD_GSCOPE_FLAG_USED   1
 274 #define THREAD_GSCOPE_FLAG_WAIT   2
 275 #define THREAD_GSCOPE_RESET_FLAG() \
 276   do                                                                          \
 277     { int __res;                                                              \
 278       asm volatile ("xchgl %0, %%gs:%P1"                                      \
 279                     : "=r" (__res)                                            \
 280                     : "i" (offsetof (struct pthread, header.gscope_flag)),    \
 281                       "0" (THREAD_GSCOPE_FLAG_UNUSED));                       \
 282       if (__res == THREAD_GSCOPE_FLAG_WAIT)                                   \
 283         lll_futex_wake (&THREAD_SELF->header.gscope_flag, 1, LLL_PRIVATE);    \
 284     }                                                                         \
 285   while (0)
 286 #define THREAD_GSCOPE_SET_FLAG() \
 287   THREAD_SETMEM (THREAD_SELF, header.gscope_flag, THREAD_GSCOPE_FLAG_USED)
 288
 289 #endif /* __ASSEMBLER__ */
 290
 291 #endif  /* tls.h */