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/* Definitions for thread-local data handling. Hurd/x86_64 version.
Copyright (C) 2003-2025 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 _X86_64_TLS_H
#define _X86_64_TLS_H
/* Some things really need not be machine-dependent. */
#include <sysdeps/mach/hurd/tls.h>
#ifndef __ASSEMBLER__
# include <dl-dtv.h>
# include <mach/machine/thread_status.h>
# include <errno.h>
# include <assert.h>
/* Type of the TCB. */
typedef struct
{
void *tcb; /* Points to this structure. */
dtv_t *dtv; /* Vector of pointers to TLS data. */
thread_t self_do_no_use; /* This thread's control port. */
int __glibc_padding1;
int multiple_threads;
int gscope_flag;
uintptr_t sysinfo;
uintptr_t stack_guard;
uintptr_t pointer_guard;
long __glibc_padding2[2];
int private_futex;
int __glibc_padding3;
/* Reservation of some values for the TM ABI. */
void *__private_tm[4];
/* GCC split stack support. */
void *__private_ss;
/* The lowest address of shadow stack. */
unsigned long long int ssp_base;
/* Keep these fields last, so offsets of fields above can continue being
compatible with the x86_64 NPTL version. */
mach_port_t reply_port; /* This thread's reply port. */
struct hurd_sigstate *_hurd_sigstate;
/* Used by the exception handling implementation in the dynamic loader. */
struct rtld_catch *rtld_catch;
} tcbhead_t;
/* GCC generates %fs:0x28 to access the stack guard. */
_Static_assert (offsetof (tcbhead_t, stack_guard) == 0x28,
"stack guard offset");
/* libgcc uses %fs:0x70 to access the split stack pointer. */
_Static_assert (offsetof (tcbhead_t, __private_ss) == 0x70,
"split stack pointer offset");
/* 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
/* Alignment requirement for TCB.
Some processors such as Intel Atom pay a big penalty on every
access using a segment override if that segment's base is not
aligned to the size of a cache line. (See Intel 64 and IA-32
Architectures Optimization Reference Manual, section 13.3.3.3,
"Segment Base".) On such machines, a cache line is 64 bytes. */
# define TCB_ALIGNMENT 64
# define THREAD_SELF \
(*(tcbhead_t * __seg_fs *) offsetof (tcbhead_t, tcb))
/* Read member of the thread descriptor directly. */
# define THREAD_GETMEM(descr, member) \
(*(__typeof (descr->member) __seg_fs *) offsetof (tcbhead_t, member))
/* Write member of the thread descriptor directly. */
# define THREAD_SETMEM(descr, member, value) \
(*(__typeof (descr->member) __seg_fs *) offsetof (tcbhead_t, member) = value)
/* Return the TCB address of a thread given its state.
Note: this is expensive. */
static inline tcbhead_t * __attribute__ ((unused))
THREAD_TCB (thread_t thread,
const void *all_state __attribute__ ((unused)))
{
error_t err;
/* Fetch the target thread's state. */
struct i386_fsgs_base_state state;
mach_msg_type_number_t state_count = i386_FSGS_BASE_STATE_COUNT;
err = __thread_get_state (thread, i386_FSGS_BASE_STATE,
(thread_state_t) &state,
&state_count);
assert_perror (err);
assert (state_count == i386_FSGS_BASE_STATE_COUNT);
return (tcbhead_t *) state.fs_base;
}
/* Install new dtv for current thread. */
# define INSTALL_NEW_DTV(dtvp) THREAD_SETMEM (THREAD_SELF, dtv, dtvp)
/* Return the address of the dtv for the current thread. */
# define THREAD_DTV() THREAD_GETMEM (THREAD_SELF, dtv)
/* Set the stack guard field in TCB head. */
# define THREAD_SET_STACK_GUARD(value) \
THREAD_SETMEM (THREAD_SELF, stack_guard, value)
# define THREAD_COPY_STACK_GUARD(descr) \
((descr)->stack_guard \
= THREAD_GETMEM (THREAD_SELF, stack_guard))
/* Set the pointer guard field in the TCB head. */
# define THREAD_SET_POINTER_GUARD(value) \
THREAD_SETMEM (THREAD_SELF, pointer_guard, value)
# define THREAD_COPY_POINTER_GUARD(descr) \
((descr)->pointer_guard \
= THREAD_GETMEM (THREAD_SELF, pointer_guard))
/* From hurd.h, reproduced here to avoid a circular include. */
extern thread_t __hurd_thread_self (void);
libc_hidden_proto (__hurd_thread_self)
/* Set up TLS in the new thread of a fork child, copying from the original. */
static inline kern_return_t __attribute__ ((unused))
_hurd_tls_fork (thread_t child, thread_t orig,
void *machine_state __attribute__ ((unused)))
{
error_t err;
struct i386_fsgs_base_state state;
mach_msg_type_number_t state_count = i386_FSGS_BASE_STATE_COUNT;
if (orig != __hurd_thread_self ())
{
err = __thread_get_state (orig, i386_FSGS_BASE_STATE,
(thread_state_t) &state,
&state_count);
if (err)
return err;
assert (state_count == i386_FSGS_BASE_STATE_COUNT);
}
else
{
/* It is illegal to call thread_get_state () on mach_thread_self ().
But we're only interested in the value of fs_base, and since we're
this thread, we know it points to our TCB. */
state.fs_base = (unsigned long) THREAD_SELF;
state.gs_base = 0;
}
return __thread_set_state (child, i386_FSGS_BASE_STATE,
(thread_state_t) &state,
state_count);
}
static inline kern_return_t __attribute__ ((unused))
_hurd_tls_new (thread_t child, tcbhead_t *tcb)
{
struct i386_fsgs_base_state state;
tcb->tcb = tcb;
/* Install the TCB address into FS base. */
state.fs_base = (uintptr_t) tcb;
state.gs_base = 0;
return __thread_set_state (child, i386_FSGS_BASE_STATE,
(thread_state_t) &state,
i386_FSGS_BASE_STATE_COUNT);
}
# if !defined (SHARED) || IS_IN (rtld)
extern unsigned char __libc_tls_initialized;
# define __LIBC_NO_TLS() __builtin_expect (!__libc_tls_initialized, 0)
static inline bool __attribute__ ((unused))
_hurd_tls_init (tcbhead_t *tcb, bool full)
{
error_t err;
thread_t self = __mach_thread_self ();
extern mach_port_t __hurd_reply_port0;
/* We always at least start the sigthread anyway. */
tcb->multiple_threads = 1;
if (full)
/* Take over the reply port we've been using. */
tcb->reply_port = __hurd_reply_port0;
err = _hurd_tls_new (self, tcb);
if (err == 0 && full)
{
__libc_tls_initialized = 1;
/* This port is now owned by the TCB. */
__hurd_reply_port0 = MACH_PORT_NULL;
}
__mach_port_deallocate (__mach_task_self (), self);
return err == 0;
}
# define TLS_INIT_TP(descr) _hurd_tls_init ((tcbhead_t *) (descr), 1)
# else /* defined (SHARED) && !IS_IN (rtld) */
# define __LIBC_NO_TLS() 0
# endif
/* Global scope switch support. */
# define THREAD_GSCOPE_FLAG_UNUSED 0
# define THREAD_GSCOPE_FLAG_USED 1
# define THREAD_GSCOPE_FLAG_WAIT 2
# define THREAD_GSCOPE_SET_FLAG() \
THREAD_SETMEM (THREAD_SELF, gscope_flag, THREAD_GSCOPE_FLAG_USED)
# define THREAD_GSCOPE_RESET_FLAG() \
({ \
int __flag; \
asm volatile ("xchgl %0, %%fs:%P1" \
: "=r" (__flag) \
: "i" (offsetof (tcbhead_t, gscope_flag)), \
"0" (THREAD_GSCOPE_FLAG_UNUSED)); \
if (__flag == THREAD_GSCOPE_FLAG_WAIT) \
lll_wake (THREAD_SELF->gscope_flag, LLL_PRIVATE); \
})
#endif /* __ASSEMBLER__ */
#endif /* x86_64/tls.h */
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