diff options
38 files changed, 237 insertions, 5 deletions
@@ -68,6 +68,17 @@ Major new features: to be used by compilers for optimizing usage of 'memcmp' when its return value is only used for its boolean status. +* Support for automatically registering threads with the Linux rseq + system call has been added. This system call is implemented starting + from Linux 4.18. The Restartable Sequences ABI accelerates user-space + operations on per-cpu data. It allows user-space to perform updates + on per-cpu data without requiring heavy-weight atomic operations. + Automatically registering threads allows all libraries, including + libc, to make immediate use of the rseq support by using the + documented ABI, via the __rseq_flags, __rseq_offset, and __rseq_size + variables. The GNU C Library manual has details on integration of + Restartable Sequences. + Deprecated and removed features, and other changes affecting compatibility: * The r_version update in the debugger interface makes the glibc binary diff --git a/manual/threads.texi b/manual/threads.texi index 06b6b277a1..ab44a92ca0 100644 --- a/manual/threads.texi +++ b/manual/threads.texi @@ -629,6 +629,8 @@ the standard. * Waiting with Explicit Clocks:: Functions for waiting with an explicit clock specification. * Single-Threaded:: Detecting single-threaded execution. +* Restartable Sequences:: Linux-specific restartable sequences + integration. @end menu @node Default Thread Attributes @@ -958,6 +960,85 @@ application-created thread because future versions of @theglibc{} may create background threads after the first thread has been created, and the application has no way of knowning that these threads are present. +@node Restartable Sequences +@subsubsection Restartable Sequences + +This section describes restartable sequences integration for +@theglibc{}. This functionality is only available on Linux. + +@deftp {Data Type} {struct rseq} +@standards{Linux, sys/rseq.h} +The type of the restartable sequences area. Future versions +of Linux may add additional fields to the end of this structure. + + +Users need to obtain the address of the restartable sequences area using +the thread pointer and the @code{__rseq_offset} variable, described +below. + +One use of the restartable sequences area is to read the current CPU +number from its @code{cpu_id} field, as an inline version of +@code{sched_getcpu}. @Theglibc{} sets the @code{cpu_id} field to +@code{RSEQ_CPU_ID_REGISTRATION_FAILED} if registration failed or was +explicitly disabled. + +Furthermore, users can store the address of a @code{struct rseq_cs} +object into the @code{rseq_cs} field of @code{struct rseq}, thus +informing the kernel that the thread enters a restartable sequence +critical section. This pointer and the code areas it itself points to +must not be left pointing to memory areas which are freed or re-used. +Several approaches can guarantee this. If the application or library +can guarantee that the memory used to hold the @code{struct rseq_cs} and +the code areas it refers to are never freed or re-used, no special +action must be taken. Else, before that memory is re-used of freed, the +application is responsible for setting the @code{rseq_cs} field to +@code{NULL} in each thread's restartable sequence area to guarantee that +it does not leak dangling references. Because the application does not +typically have knowledge of libraries' use of restartable sequences, it +is recommended that libraries using restartable sequences which may end +up freeing or re-using their memory set the @code{rseq_cs} field to +@code{NULL} before returning from library functions which use +restartable sequences. + +The manual for the @code{rseq} system call can be found +at @uref{https://git.kernel.org/pub/scm/libs/librseq/librseq.git/tree/doc/man/rseq.2}. +@end deftp + +@deftypevar {int} __rseq_offset +@standards{Linux, sys/rseq.h} +This variable contains the offset between the thread pointer (as defined +by @code{__builtin_thread_pointer} or the thread pointer register for +the architecture) and the restartable sequences area. This value is the +same for all threads in the process. If the restartable sequences area +is located at a lower address than the location to which the thread +pointer points, the value is negative. +@end deftypevar + +@deftypevar {unsigned int} __rseq_size +@standards{Linux, sys/rseq.h} +This variable is either zero (if restartable sequence registration +failed or has been disabled) or the size of the restartable sequence +registration. This can be different from the size of @code{struct rseq} +if the kernel has extended the size of the registration. If +registration is successful, @code{__rseq_size} is at least 32 (the +initial size of @code{struct rseq}). +@end deftypevar + +@deftypevar {unsigned int} __rseq_flags +@standards{Linux, sys/rseq.h} +The flags used during restartable sequence registration with the kernel. +Currently zero. +@end deftypevar + +@deftypevr Macro int RSEQ_SIG +@standards{Linux, sys/rseq.h} +Each supported architecture provides a @code{RSEQ_SIG} macro in +@file{sys/rseq.h} which contains a signature. That signature is +expected to be present in the code before each restartable sequences +abort handler. Failure to provide the expected signature may terminate +the process with a segmentation fault. +@end deftypevr + @c FIXME these are undocumented: @c pthread_atfork @c pthread_attr_destroy diff --git a/sysdeps/nptl/dl-tls_init_tp.c b/sysdeps/nptl/dl-tls_init_tp.c index b39dfbff2c..4a73927f80 100644 --- a/sysdeps/nptl/dl-tls_init_tp.c +++ b/sysdeps/nptl/dl-tls_init_tp.c @@ -22,6 +22,7 @@ #include <pthreadP.h> #include <tls.h> #include <rseq-internal.h> +#include <thread_pointer.h> #define TUNABLE_NAMESPACE pthread #include <dl-tunables.h> @@ -43,6 +44,10 @@ rtld_mutex_dummy (pthread_mutex_t *lock) } #endif +const unsigned int __rseq_flags; +const unsigned int __rseq_size attribute_relro; +const int __rseq_offset attribute_relro; + void __tls_pre_init_tp (void) { @@ -100,7 +105,23 @@ __tls_init_tp (void) #if HAVE_TUNABLES do_rseq = TUNABLE_GET (rseq, int, NULL); #endif - rseq_register_current_thread (pd, do_rseq); + if (rseq_register_current_thread (pd, do_rseq)) + { + /* We need a writable view of the variables. They are in + .data.relro and are not yet write-protected. */ + extern unsigned int size __asm__ ("__rseq_size"); + size = sizeof (pd->rseq_area); + } + +#ifdef RSEQ_SIG + /* This should be a compile-time constant, but the current + infrastructure makes it difficult to determine its value. Not + all targets support __thread_pointer, so set __rseq_offset only + if thre rseq registration may have happened because RSEQ_SIG is + defined. */ + extern int offset __asm__ ("__rseq_offset"); + offset = (char *) &pd->rseq_area - (char *) __thread_pointer (); +#endif } /* Set initial thread's stack block from 0 up to __libc_stack_end. diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile index 62a796f214..61acc1987d 100644 --- a/sysdeps/unix/sysv/linux/Makefile +++ b/sysdeps/unix/sysv/linux/Makefile @@ -112,7 +112,8 @@ sysdep_headers += sys/mount.h sys/acct.h \ bits/types/struct_semid64_ds_helper.h \ bits/types/struct_shmid64_ds.h \ bits/types/struct_shmid64_ds_helper.h \ - bits/pthread_stack_min.h bits/pthread_stack_min-dynamic.h + bits/pthread_stack_min.h bits/pthread_stack_min-dynamic.h \ + sys/rseq.h bits/rseq.h tests += tst-clone tst-clone2 tst-clone3 tst-fanotify tst-personality \ tst-quota tst-sync_file_range tst-sysconf-iov_max tst-ttyname \ diff --git a/sysdeps/unix/sysv/linux/Versions b/sysdeps/unix/sysv/linux/Versions index 26452f3f17..3f8809a158 100644 --- a/sysdeps/unix/sysv/linux/Versions +++ b/sysdeps/unix/sysv/linux/Versions @@ -316,6 +316,11 @@ librt { } ld { + GLIBC_2.35 { + __rseq_flags; + __rseq_offset; + __rseq_size; + } GLIBC_PRIVATE { __nptl_change_stack_perm; } diff --git a/sysdeps/unix/sysv/linux/aarch64/ld.abilist b/sysdeps/unix/sysv/linux/aarch64/ld.abilist index 80b2fe6725..717a35f242 100644 --- a/sysdeps/unix/sysv/linux/aarch64/ld.abilist +++ b/sysdeps/unix/sysv/linux/aarch64/ld.abilist @@ -3,3 +3,6 @@ GLIBC_2.17 __stack_chk_guard D 0x8 GLIBC_2.17 __tls_get_addr F GLIBC_2.17 _dl_mcount F GLIBC_2.17 _r_debug D 0x28 +GLIBC_2.35 __rseq_flags D 0x4 +GLIBC_2.35 __rseq_offset D 0x4 +GLIBC_2.35 __rseq_size D 0x4 diff --git a/sysdeps/unix/sysv/linux/alpha/ld.abilist b/sysdeps/unix/sysv/linux/alpha/ld.abilist index 98a03f611f..76911bd7f8 100644 --- a/sysdeps/unix/sysv/linux/alpha/ld.abilist +++ b/sysdeps/unix/sysv/linux/alpha/ld.abilist @@ -2,4 +2,7 @@ GLIBC_2.0 _r_debug D 0x28 GLIBC_2.1 __libc_stack_end D 0x8 GLIBC_2.1 _dl_mcount F GLIBC_2.3 __tls_get_addr F +GLIBC_2.35 __rseq_flags D 0x4 +GLIBC_2.35 __rseq_offset D 0x4 +GLIBC_2.35 __rseq_size D 0x4 GLIBC_2.4 __stack_chk_guard D 0x8 diff --git a/sysdeps/unix/sysv/linux/arc/ld.abilist b/sysdeps/unix/sysv/linux/arc/ld.abilist index 048f17c848..71c67f9803 100644 --- a/sysdeps/unix/sysv/linux/arc/ld.abilist +++ b/sysdeps/unix/sysv/linux/arc/ld.abilist @@ -3,3 +3,6 @@ GLIBC_2.32 __stack_chk_guard D 0x4 GLIBC_2.32 __tls_get_addr F GLIBC_2.32 _dl_mcount F GLIBC_2.32 _r_debug D 0x14 +GLIBC_2.35 __rseq_flags D 0x4 +GLIBC_2.35 __rseq_offset D 0x4 +GLIBC_2.35 __rseq_size D 0x4 diff --git a/sysdeps/unix/sysv/linux/arm/be/ld.abilist b/sysdeps/unix/sysv/linux/arm/be/ld.abilist index cc8825c3bc..3859433b21 100644 --- a/sysdeps/unix/sysv/linux/arm/be/ld.abilist +++ b/sysdeps/unix/sysv/linux/arm/be/ld.abilist @@ -1,3 +1,6 @@ +GLIBC_2.35 __rseq_flags D 0x4 +GLIBC_2.35 __rseq_offset D 0x4 +GLIBC_2.35 __rseq_size D 0x4 GLIBC_2.4 __libc_stack_end D 0x4 GLIBC_2.4 __stack_chk_guard D 0x4 GLIBC_2.4 __tls_get_addr F diff --git a/sysdeps/unix/sysv/linux/arm/le/ld.abilist b/sysdeps/unix/sysv/linux/arm/le/ld.abilist index cc8825c3bc..3859433b21 100644 --- a/sysdeps/unix/sysv/linux/arm/le/ld.abilist +++ b/sysdeps/unix/sysv/linux/arm/le/ld.abilist @@ -1,3 +1,6 @@ +GLIBC_2.35 __rseq_flags D 0x4 +GLIBC_2.35 __rseq_offset D 0x4 +GLIBC_2.35 __rseq_size D 0x4 GLIBC_2.4 __libc_stack_end D 0x4 GLIBC_2.4 __stack_chk_guard D 0x4 GLIBC_2.4 __tls_get_addr F diff --git a/sysdeps/unix/sysv/linux/csky/ld.abilist b/sysdeps/unix/sysv/linux/csky/ld.abilist index 564ac09737..6bfc582b73 100644 --- a/sysdeps/unix/sysv/linux/csky/ld.abilist +++ b/sysdeps/unix/sysv/linux/csky/ld.abilist @@ -3,3 +3,6 @@ GLIBC_2.29 __stack_chk_guard D 0x4 GLIBC_2.29 __tls_get_addr F GLIBC_2.29 _dl_mcount F GLIBC_2.29 _r_debug D 0x14 +GLIBC_2.35 __rseq_flags D 0x4 +GLIBC_2.35 __rseq_offset D 0x4 +GLIBC_2.35 __rseq_size D 0x4 diff --git a/sysdeps/unix/sysv/linux/hppa/ld.abilist b/sysdeps/unix/sysv/linux/hppa/ld.abilist index d155a59843..efccd6a023 100644 --- a/sysdeps/unix/sysv/linux/hppa/ld.abilist +++ b/sysdeps/unix/sysv/linux/hppa/ld.abilist @@ -2,4 +2,7 @@ GLIBC_2.2 __libc_stack_end D 0x4 GLIBC_2.2 _dl_mcount F GLIBC_2.2 _r_debug D 0x14 GLIBC_2.3 __tls_get_addr F +GLIBC_2.35 __rseq_flags D 0x4 +GLIBC_2.35 __rseq_offset D 0x4 +GLIBC_2.35 __rseq_size D 0x4 GLIBC_2.4 __stack_chk_guard D 0x4 diff --git a/sysdeps/unix/sysv/linux/i386/ld.abilist b/sysdeps/unix/sysv/linux/i386/ld.abilist index 0478e22071..1eb94ae75f 100644 --- a/sysdeps/unix/sysv/linux/i386/ld.abilist +++ b/sysdeps/unix/sysv/linux/i386/ld.abilist @@ -3,3 +3,6 @@ GLIBC_2.1 __libc_stack_end D 0x4 GLIBC_2.1 _dl_mcount F GLIBC_2.3 ___tls_get_addr F GLIBC_2.3 __tls_get_addr F +GLIBC_2.35 __rseq_flags D 0x4 +GLIBC_2.35 __rseq_offset D 0x4 +GLIBC_2.35 __rseq_size D 0x4 diff --git a/sysdeps/unix/sysv/linux/ia64/ld.abilist b/sysdeps/unix/sysv/linux/ia64/ld.abilist index 33f91199bf..2cc68bcf7b 100644 --- a/sysdeps/unix/sysv/linux/ia64/ld.abilist +++ b/sysdeps/unix/sysv/linux/ia64/ld.abilist @@ -2,3 +2,6 @@ GLIBC_2.2 __libc_stack_end D 0x8 GLIBC_2.2 _dl_mcount F GLIBC_2.2 _r_debug D 0x28 GLIBC_2.3 __tls_get_addr F +GLIBC_2.35 __rseq_flags D 0x4 +GLIBC_2.35 __rseq_offset D 0x4 +GLIBC_2.35 __rseq_size D 0x4 diff --git a/sysdeps/unix/sysv/linux/m68k/coldfire/ld.abilist b/sysdeps/unix/sysv/linux/m68k/coldfire/ld.abilist index cc8825c3bc..3859433b21 100644 --- a/sysdeps/unix/sysv/linux/m68k/coldfire/ld.abilist +++ b/sysdeps/unix/sysv/linux/m68k/coldfire/ld.abilist @@ -1,3 +1,6 @@ +GLIBC_2.35 __rseq_flags D 0x4 +GLIBC_2.35 __rseq_offset D 0x4 +GLIBC_2.35 __rseq_size D 0x4 GLIBC_2.4 __libc_stack_end D 0x4 GLIBC_2.4 __stack_chk_guard D 0x4 GLIBC_2.4 __tls_get_addr F diff --git a/sysdeps/unix/sysv/linux/m68k/m680x0/ld.abilist b/sysdeps/unix/sysv/linux/m68k/m680x0/ld.abilist index 3ba474c27f..e62b2742af 100644 --- a/sysdeps/unix/sysv/linux/m68k/m680x0/ld.abilist +++ b/sysdeps/unix/sysv/linux/m68k/m680x0/ld.abilist @@ -2,4 +2,7 @@ GLIBC_2.0 _r_debug D 0x14 GLIBC_2.1 __libc_stack_end D 0x4 GLIBC_2.1 _dl_mcount F GLIBC_2.3 __tls_get_addr F +GLIBC_2.35 __rseq_flags D 0x4 +GLIBC_2.35 __rseq_offset D 0x4 +GLIBC_2.35 __rseq_size D 0x4 GLIBC_2.4 __stack_chk_guard D 0x4 diff --git a/sysdeps/unix/sysv/linux/microblaze/ld.abilist b/sysdeps/unix/sysv/linux/microblaze/ld.abilist index a4933c3541..5d63d74e8f 100644 --- a/sysdeps/unix/sysv/linux/microblaze/ld.abilist +++ b/sysdeps/unix/sysv/linux/microblaze/ld.abilist @@ -3,3 +3,6 @@ GLIBC_2.18 __stack_chk_guard D 0x4 GLIBC_2.18 __tls_get_addr F GLIBC_2.18 _dl_mcount F GLIBC_2.18 _r_debug D 0x14 +GLIBC_2.35 __rseq_flags D 0x4 +GLIBC_2.35 __rseq_offset D 0x4 +GLIBC_2.35 __rseq_size D 0x4 diff --git a/sysdeps/unix/sysv/linux/mips/mips32/ld.abilist b/sysdeps/unix/sysv/linux/mips/mips32/ld.abilist index be09641a48..53ca22de2f 100644 --- a/sysdeps/unix/sysv/linux/mips/mips32/ld.abilist +++ b/sysdeps/unix/sysv/linux/mips/mips32/ld.abilist @@ -2,4 +2,7 @@ GLIBC_2.0 _r_debu |