text: /* Definition for thread-local data handling.  nptl/i386 version.
     Copyright (C) 2002-2020 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)
  
  /* 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
  # 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
  
  #ifndef LOCK_PREFIX
  # ifdef UP
  #  define LOCK_PREFIX  /* nothing */
  # else
  #  define LOCK_PREFIX "lock;"
  # endif
  #endif
  
  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.  */						      \
       INTERNAL_SYSCALL_DECL (err);					      \
       _result = INTERNAL_SYSCALL (set_thread_area, err, 1, &_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.  */
  # define THREAD_SELF \
    ({ struct pthread *__self;						      \
       asm ("movl %%gs:%c1,%0" : "=r" (__self)				      \
  	  : "i" (offsetof (struct pthread, header.self)));		      \
       __self;})
  
  /* 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 */
  
  
  /* Read member of the thread descriptor directly.  */
  # define THREAD_GETMEM(descr, member) \
    ({ __typeof (descr->member) __value;					      \
       if (sizeof (__value) == 1)						      \
         asm volatile ("movb %%gs:%P2,%b0"				      \
  		     : "=q" (__value)					      \
  		     : "0" (0), "i" (offsetof (struct pthread, member)));     \
       else if (sizeof (__value) == 4)					      \
         asm volatile ("movl %%gs:%P1,%0"					      \
  		     : "=r" (__value)					      \
  		     : "i" (offsetof (struct pthread, member)));	      \
       else								      \
         {								      \
  	 if (sizeof (__value) != 8)					      \
  	   /* There should not be any value with a size other than 1,	      \
  	      4 or 8.  */						      \
  	   abort ();							      \
  									      \
  	 asm volatile ("movl %%gs:%P1,%%eax\n\t"			      \
  		       "movl %%gs:%P2,%%edx"				      \
  		       : "=A" (__value)					      \
  		       : "i" (offsetof (struct pthread, member)),	      \
  			 "i" (offsetof (struct pthread, member) + 4));	      \
         }								      \
       __value; })
  
  
  /* Same as THREAD_GETMEM, but the member offset can be non-constant.  */
  # define THREAD_GETMEM_NC(descr, member, idx) \
    ({ __typeof (descr->member[0]) __value;				      \
       if (sizeof (__value) == 1)						      \
         asm volatile ("movb %%gs:%P2(%3),%b0"				      \
  		     : "=q" (__value)					      \
  		     : "0" (0), "i" (offsetof (struct pthread, member[0])),   \
  		     "r" (idx));					      \
       else if (sizeof (__value) == 4)					      \
         asm volatile ("movl %%gs:%P1(,%2,4),%0"				      \
  		     : "=r" (__value)					      \
  		     : "i" (offsetof (struct pthread, member[0])),	      \
  		       "r" (idx));					      \
       else								      \
         {								      \
  	 if (sizeof (__value) != 8)					      \
  	   /* There should not be any value with a size other than 1,	      \
  	      4 or 8.  */						      \
  	   abort ();							      \
  									      \
  	 asm volatile  ("movl %%gs:%P1(,%2,8),%%eax\n\t"		      \
  			"movl %%gs:4+%P1(,%2,8),%%edx"			      \
  			: "=&A" (__value)				      \
  			: "i" (offsetof (struct pthread, member[0])),	      \
  			  "r" (idx));					      \
         }								      \
       __value; })
  
  
  
  /* Set member of the thread descriptor directly.  */
  # define THREAD_SETMEM(descr, member, value) \
    ({ if (sizeof (descr->member) == 1)					      \
         asm volatile ("movb %b0,%%gs:%P1" :				      \
  		     : "iq" (value),					      \
  		       "i" (offsetof (struct pthread, member)));	      \
       else if (sizeof (descr->member) == 4)				      \
         asm volatile ("movl %0,%%gs:%P1" :				      \
  		     : "ir" (value),					      \
  		       "i" (offsetof (struct pthread, member)));	      \
       else								      \
         {								      \
  	 if (sizeof (descr->member) != 8)				      \
  	   /* There should not be any value with a size other than 1,	      \
  	      4 or 8.  */						      \
  	   abort ();							      \
  									      \
  	 asm volatile ("movl %%eax,%%gs:%P1\n\t"			      \
  		       "movl %%edx,%%gs:%P2" :				      \
  		       : "A" ((uint64_t) cast_to_integer (value)),	      \
  			 "i" (offsetof (struct pthread, member)),	      \
  			 "i" (offsetof (struct pthread, member) + 4));	      \
         }})
  
  
  /* Same as THREAD_SETMEM, but the member offset can be non-constant.  */
  # define THREAD_SETMEM_NC(descr, member, idx, value) \
    ({ if (sizeof (descr->member[0]) == 1)				      \
         asm volatile ("movb %b0,%%gs:%P1(%2)" :				      \
  		     : "iq" (value),					      \
  		       "i" (offsetof (struct pthread, member)),		      \
  		       "r" (idx));					      \
       else if (sizeof (descr->member[0]) == 4)				      \
         asm volatile ("movl %0,%%gs:%P1(,%2,4)" :			      \
  		     : "ir" (value),					      \
  		       "i" (offsetof (struct pthread, member)),		      \
  		       "r" (idx));					      \
       else								      \
         {								      \
  	 if (sizeof (descr->member[0]) != 8)				      \
  	   /* There should not be any value with a size other than 1,	      \
  	      4 or 8.  */						      \
  	   abort ();							      \
  									      \
  	 asm volatile ("movl %%eax,%%gs:%P1(,%2,8)\n\t"			      \
  		       "movl %%edx,%%gs:4+%P1(,%2,8)" :			      \
  		       : "A" ((uint64_t) cast_to_integer (value)),	      \
  			 "i" (offsetof (struct pthread, member)),	      \
  			 "r" (idx));					      \
         }})
  
  
  /* 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_IN_TCB      1
  #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)
  #define THREAD_GSCOPE_WAIT() \
    GL(dl_wait_lookup_done) ()
  
  #endif /* __ASSEMBLER__ */
  
  #endif	/* tls.h */
  