Re: [PATCH v2 3/4] hurd: Implement TLS for x86_64

[Samuel Thibault]

Applied, thanks!

Sergey Bugaev via Libc-alpha, le mer. 22 févr. 2023 00:19:31 +0300, a ecrit:
> Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
> ---
>  sysdeps/mach/hurd/x86/init-first.c |  14 +-
>  sysdeps/mach/hurd/x86_64/tls.h     | 215 +++++++++++++++++++++++++++++
>  2 files changed, 228 insertions(+), 1 deletion(-)
>  create mode 100644 sysdeps/mach/hurd/x86_64/tls.h
> 
> diff --git a/sysdeps/mach/hurd/x86/init-first.c 
> b/sysdeps/mach/hurd/x86/init-first.c
> index a187af82..04480ed3 100644
> --- a/sysdeps/mach/hurd/x86/init-first.c
> +++ b/sysdeps/mach/hurd/x86/init-first.c
> @@ -41,8 +41,14 @@ extern char **__libc_argv attribute_hidden;
>  extern char **_dl_argv;
>  
>  #ifndef SHARED
> -unsigned short __init1_desc;
>  static tcbhead_t __init1_tcbhead;
> +# ifndef __x86_64__
> +unsigned short __init1_desc;
> +# endif
> +#endif
> +
> +#ifdef __x86_64__
> +unsigned char __libc_tls_initialized;
>  #endif
>  
>  /* Things that want to be run before _hurd_init or much anything else.
> @@ -174,7 +180,13 @@ first_init (void)
>    /* In the static case, we need to set up TLS early so that the stack
>       protection guard can be read at gs:0x14 by the gcc-generated snippets.  
> */
>    _hurd_tls_init (&__init1_tcbhead);
> +
> +  /* Make sure __LIBC_NO_TLS () keeps evaluating to 1.  */
> +# ifdef __x86_64__
> +  __libc_tls_initialized = 0;
> +# else
>    asm ("movw %%gs,%w0" : "=m" (__init1_desc));
> +# endif
>  #endif
>  
>    RUN_RELHOOK (_hurd_preinit_hook, ());
> diff --git a/sysdeps/mach/hurd/x86_64/tls.h b/sysdeps/mach/hurd/x86_64/tls.h
> new file mode 100644
> index 00000000..cf74e1f4
> --- /dev/null
> +++ b/sysdeps/mach/hurd/x86_64/tls.h
> @@ -0,0 +1,215 @@
> +/* Definitions for thread-local data handling.  Hurd/x86_64 version.
> +   Copyright (C) 2003-2023 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;             /* 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");
> +
> +extern unsigned char __libc_tls_initialized;
> +
> +# define __LIBC_NO_TLS() __builtin_expect (!__libc_tls_initialized, 0)
> +
> +/* 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 TLS_INIT_TP(descr) _hurd_tls_init ((tcbhead_t *) (descr))
> +
> +# 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))
> +
> +/* 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;
> +  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);
> +
> +  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;
> +  tcb->self = child;
> +
> +  /* 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);
> +}
> +
> +static inline bool __attribute__ ((unused))
> +_hurd_tls_init (tcbhead_t *tcb)
> +{
> +  error_t err;
> +  thread_t self = __mach_thread_self ();
> +
> +  /* We always at least start the sigthread anyway.  */
> +  tcb->multiple_threads = 1;
> +
> +  err = _hurd_tls_new (self, tcb);
> +  __mach_port_deallocate (__mach_task_self (), self);
> +  __libc_tls_initialized = 1;
> +  return err == 0;
> +}
> +
> +
> +/* 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 */
> -- 
> 2.39.2
> 

-- 
Samuel
---
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