[PATCH v3 23/37] nptl: Move part of TCB initialization from libpthread to __tls_init_tp
Adhemerval Zanella
adhemerval.zanella@linaro.org
Wed Mar 24 13:56:39 GMT 2021
On 16/03/2021 14:30, Florian Weimer via Libc-alpha wrote:
> This initalization should only happen once for the main thread's TCB.
> At present, auditors can achieve this by not linking against
> libpthread. If libpthread becomes part of libc, doing this
> initialization in libc would happen for every audit namespace,
> or too late (if it happens from the main libc only). That's why
> moving this code into ld.so seems the right thing to do, right after
> the TCB initialization.
Make sense.
>
> For !__ASSUME_SET_ROBUST_LIST ports, this also moves the symbol
> __set_robust_list_avail into ld.so, as __nptl_set_robust_list_avail.
> It also turned into a proper boolean flag.
>
> Inline the __pthread_initialize_pids function because it seems no
> longer useful as a separate function.
LGTM, with just a suggestion below.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
> ---
> nptl/Versions | 6 +++++
> nptl/nptl-init.c | 36 ++-----------------------
> nptl/pthread-pids.h | 29 --------------------
> nptl/pthreadP.h | 6 +++--
> nptl/pthread_create.c | 4 +--
> nptl/pthread_mutex_init.c | 2 +-
> sysdeps/nptl/dl-tls_init_tp.c | 37 ++++++++++++++++++++++++++
> sysdeps/unix/sysv/linux/pthread-pids.h | 29 --------------------
> 8 files changed, 52 insertions(+), 97 deletions(-)
> delete mode 100644 nptl/pthread-pids.h
> delete mode 100644 sysdeps/unix/sysv/linux/pthread-pids.h
>
> diff --git a/nptl/Versions b/nptl/Versions
> index b619df41fb..c50a5442af 100644
> --- a/nptl/Versions
> +++ b/nptl/Versions
> @@ -417,3 +417,9 @@ libpthread {
> __pthread_initialize_minimal;
> }
> }
> +
> +ld {
> + GLIBC_PRIVATE {
> + __nptl_set_robust_list_avail;
> + }
> +}
> \ No newline at end of file
Ok.
> diff --git a/nptl/nptl-init.c b/nptl/nptl-init.c
> index de64e34783..5913bf7272 100644
> --- a/nptl/nptl-init.c
> +++ b/nptl/nptl-init.c
> @@ -36,7 +36,6 @@
> #include <futex-internal.h>
> #include <kernel-features.h>
> #include <libc-pointer-arith.h>
> -#include <pthread-pids.h>
> #include <pthread_mutex_conf.h>
>
> #ifndef TLS_MULTIPLE_THREADS_IN_TCB
> @@ -48,15 +47,6 @@ int *__libc_multiple_threads_ptr attribute_hidden;
> size_t __static_tls_size;
> size_t __static_tls_align_m1;
>
> -#ifndef __ASSUME_SET_ROBUST_LIST
> -/* Negative if we do not have the system call and we can use it. */
> -int __set_robust_list_avail;
> -# define set_robust_list_not_avail() \
> - __set_robust_list_avail = -1
> -#else
> -# define set_robust_list_not_avail() do { } while (0)
> -#endif
> -
> /* Version of the library, used in libthread_db to detect mismatches. */
> static const char nptl_version[] __attribute_used__ = VERSION;
>
> @@ -194,31 +184,9 @@ static bool __nptl_initial_report_events __attribute_used__;
> void
> __pthread_initialize_minimal_internal (void)
> {
> - /* Minimal initialization of the thread descriptor. */
> + /* Partial initialization of the TCB already happened in TLS_INIT_TP
> + and __tls_init_tp. */
> struct pthread *pd = THREAD_SELF;
> - __pthread_initialize_pids (pd);
> - THREAD_SETMEM (pd, specific[0], &pd->specific_1stblock[0]);
> - THREAD_SETMEM (pd, user_stack, true);
> -
> - /* Initialize the robust mutex data. */
> - {
> -#if __PTHREAD_MUTEX_HAVE_PREV
> - pd->robust_prev = &pd->robust_head;
> -#endif
> - pd->robust_head.list = &pd->robust_head;
> - pd->robust_head.futex_offset = (offsetof (pthread_mutex_t, __data.__lock)
> - - offsetof (pthread_mutex_t,
> - __data.__list.__next));
> - int res = INTERNAL_SYSCALL_CALL (set_robust_list, &pd->robust_head,
> - sizeof (struct robust_list_head));
> - if (INTERNAL_SYSCALL_ERROR_P (res))
> - set_robust_list_not_avail ();
> - }
> -
> - /* Set initial thread's stack block from 0 up to __libc_stack_end.
> - It will be bigger than it actually is, but for unwind.c/pt-longjmp.c
> - purposes this is good enough. */
> - THREAD_SETMEM (pd, stackblock_size, (size_t) __libc_stack_end);
>
> /* Before initializing GL (dl_stack_user), the debugger could not
> find us and had to set __nptl_initial_report_events. Propagate
Ok.
> diff --git a/nptl/pthread-pids.h b/nptl/pthread-pids.h
> deleted file mode 100644
> index 1a0e9ade41..0000000000
> --- a/nptl/pthread-pids.h
> +++ /dev/null
> @@ -1,29 +0,0 @@
> -/* Initialize pid and tid fields of struct pthread. Stub version.
> - Copyright (C) 2015-2021 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/>. */
> -
> -#include <pthreadP.h>
> -
> -/* Initialize PD->pid and PD->tid for the initial thread. If there is
> - setup required to arrange that __exit_thread causes PD->tid to be
> - cleared and futex-woken, then this function should do that as well. */
> -static inline void
> -__pthread_initialize_pids (struct pthread *pd)
> -{
> -#error "sysdeps pthread-pids.h file required"
> - pd->pid = pd->tid = -1;
> -}
Ok.
> diff --git a/nptl/pthreadP.h b/nptl/pthreadP.h
> index 4b486b3577..68f8ef5aa1 100644
> --- a/nptl/pthreadP.h
> +++ b/nptl/pthreadP.h
> @@ -224,8 +224,10 @@ extern unsigned int __nptl_nthreads;
> libc_hidden_proto (__nptl_nthreads)
>
> #ifndef __ASSUME_SET_ROBUST_LIST
> -/* Negative if we do not have the system call and we can use it. */
> -extern int __set_robust_list_avail attribute_hidden;
> +/* True if the set_robust_list system call works. Initialized in
> + __tls_init_tp. */
> +extern bool __nptl_set_robust_list_avail;
> +rtld_hidden_proto (__nptl_set_robust_list_avail)
> #endif
>
> /* Thread Priority Protection. */
Now that you are touching it, maybe it would be better to move the
__ASSUME_SET_ROBUST_LIST handling only to the dl-tls_init_tp.c and
always define __nptl_set_robust_list_avail (at least one initialization
case)?
> diff --git a/nptl/pthread_create.c b/nptl/pthread_create.c
> index 58e10e7741..51340acc4d 100644
> --- a/nptl/pthread_create.c
> +++ b/nptl/pthread_create.c
> @@ -289,7 +289,7 @@ START_THREAD_DEFN
> __ctype_init ();
>
> #ifndef __ASSUME_SET_ROBUST_LIST
> - if (__set_robust_list_avail >= 0)
> + if (__nptl_set_robust_list_avail)
> #endif
> {
> /* This call should never fail because the initial call in init.c
> @@ -439,7 +439,7 @@ START_THREAD_DEFN
> /* We let the kernel do the notification if it is able to do so.
> If we have to do it here there for sure are no PI mutexes involved
> since the kernel support for them is even more recent. */
> - if (__set_robust_list_avail < 0
> + if (!__nptl_set_robust_list_avail
> && __builtin_expect (robust != (void *) &pd->robust_head, 0))
> {
> do
Ok.
> diff --git a/nptl/pthread_mutex_init.c b/nptl/pthread_mutex_init.c
> index 233cebc504..f5c3a4b464 100644
> --- a/nptl/pthread_mutex_init.c
> +++ b/nptl/pthread_mutex_init.c
> @@ -95,7 +95,7 @@ __pthread_mutex_init (pthread_mutex_t *mutex,
> {
> #ifndef __ASSUME_SET_ROBUST_LIST
> if ((imutexattr->mutexkind & PTHREAD_MUTEXATTR_FLAG_PSHARED) != 0
> - && __set_robust_list_avail < 0)
> + && !__nptl_set_robust_list_avail)
> return ENOTSUP;
> #endif
>
Ok.
> diff --git a/sysdeps/nptl/dl-tls_init_tp.c b/sysdeps/nptl/dl-tls_init_tp.c
> index 8983808233..c5172b7613 100644
> --- a/sysdeps/nptl/dl-tls_init_tp.c
> +++ b/sysdeps/nptl/dl-tls_init_tp.c
> @@ -16,10 +16,17 @@
> License along with the GNU C Library; if not, see
> <https://www.gnu.org/licenses/>. */
>
> +#include <kernel-features.h>
> #include <ldsodefs.h>
> #include <list.h>
> +#include <nptl/pthreadP.h>
> #include <tls.h>
>
> +#ifndef __ASSUME_SET_ROBUST_LIST
> +bool __nptl_set_robust_list_avail;
> +rtld_hidden_data_def (__nptl_set_robust_list_avail)
> +#endif
> +
> void
> __tls_init_tp (void)
> {
> @@ -27,4 +34,34 @@ __tls_init_tp (void)
> INIT_LIST_HEAD (&GL (dl_stack_used));
> INIT_LIST_HEAD (&GL (dl_stack_user));
> list_add (&THREAD_SELF->list, &GL (dl_stack_user));
> +
> + /* Early initialization of the TCB. */
> + struct pthread *pd = THREAD_SELF;
> + pd->tid = INTERNAL_SYSCALL_CALL (set_tid_address, &pd->tid);
> + THREAD_SETMEM (pd, specific[0], &pd->specific_1stblock[0]);
> + THREAD_SETMEM (pd, user_stack, true);
> +
> + /* Initialize the robust mutex data. */
> + {
> +#if __PTHREAD_MUTEX_HAVE_PREV
> + pd->robust_prev = &pd->robust_head;
> +#endif
> + pd->robust_head.list = &pd->robust_head;
> + pd->robust_head.futex_offset = (offsetof (pthread_mutex_t, __data.__lock)
> + - offsetof (pthread_mutex_t,
> + __data.__list.__next));
> + int res = INTERNAL_SYSCALL_CALL (set_robust_list, &pd->robust_head,
> + sizeof (struct robust_list_head));
> + if (!INTERNAL_SYSCALL_ERROR_P (res))
> + {
> +#ifndef __ASSUME_SET_ROBUST_LIST
> + __nptl_set_robust_list_avail = true;
> +#endif
> + }
> + }
> +
> + /* Set initial thread's stack block from 0 up to __libc_stack_end.
> + It will be bigger than it actually is, but for unwind.c/pt-longjmp.c
> + purposes this is good enough. */
> + THREAD_SETMEM (pd, stackblock_size, (size_t) __libc_stack_end);
> }
Ok.
> diff --git a/sysdeps/unix/sysv/linux/pthread-pids.h b/sysdeps/unix/sysv/linux/pthread-pids.h
> deleted file mode 100644
> index 10b58899f5..0000000000
> --- a/sysdeps/unix/sysv/linux/pthread-pids.h
> +++ /dev/null
> @@ -1,29 +0,0 @@
> -/* Initialize pid and tid fields of struct pthread. Linux version.
> - Copyright (C) 2015-2021 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/>. */
> -
> -#include <pthreadP.h>
> -#include <sysdep.h>
> -
> -/* Initialize PD->pid and PD->tid for the initial thread. If there is
> - setup required to arrange that __exit_thread causes PD->tid to be
> - cleared and futex-woken, then this function should do that as well. */
> -static inline void
> -__pthread_initialize_pids (struct pthread *pd)
> -{
> - pd->tid = INTERNAL_SYSCALL_CALL (set_tid_address, &pd->tid);
> -}
>
Ok.
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