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
* 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
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
#include <pthreadP.h>
#include <tls.h>
#include <rseq-internal.h>
+#include <thread_pointer.h>
#define TUNABLE_NAMESPACE pthread
#include <dl-tunables.h>
}
#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)
{
#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.
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 \
}
ld {
+ GLIBC_2.35 {
+ __rseq_flags;
+ __rseq_offset;
+ __rseq_size;
+ }
GLIBC_PRIVATE {
__nptl_change_stack_perm;
}
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
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
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
+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
+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
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
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
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
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
+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
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
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
GLIBC_2.2 __libc_stack_end D 0x4
GLIBC_2.2 _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
GLIBC_2.2 __libc_stack_end D 0x4
GLIBC_2.2 _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
GLIBC_2.2 __libc_stack_end D 0x8
GLIBC_2.2 _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
GLIBC_2.21 __tls_get_addr F
GLIBC_2.21 _dl_mcount F
GLIBC_2.21 _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
GLIBC_2.22 __tls_get_addr_opt F
GLIBC_2.23 __parse_hwcap_and_convert_at_platform 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_2.3 __tls_get_addr F
GLIBC_2.3 _dl_mcount F
GLIBC_2.3 _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
GLIBC_2.17 _r_debug D 0x28
GLIBC_2.22 __tls_get_addr_opt F
GLIBC_2.23 __parse_hwcap_and_convert_at_platform F
+GLIBC_2.35 __rseq_flags D 0x4
+GLIBC_2.35 __rseq_offset D 0x4
+GLIBC_2.35 __rseq_size D 0x4
GLIBC_2.33 __tls_get_addr F
GLIBC_2.33 _dl_mcount F
GLIBC_2.33 _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
GLIBC_2.27 __tls_get_addr F
GLIBC_2.27 _dl_mcount F
GLIBC_2.27 _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
#include <sys/rseq.h>
#ifdef RSEQ_SIG
-static inline void
+static inline bool
rseq_register_current_thread (struct pthread *self, bool do_rseq)
{
if (do_rseq)
sizeof (self->rseq_area),
0, RSEQ_SIG);
if (!INTERNAL_SYSCALL_ERROR_P (ret))
- return;
+ return true;
}
THREAD_SETMEM (self, rseq_area.cpu_id, RSEQ_CPU_ID_REGISTRATION_FAILED);
+ return false;
}
#else /* RSEQ_SIG */
-static inline void
+static inline bool
rseq_register_current_thread (struct pthread *self, bool do_rseq)
{
THREAD_SETMEM (self, rseq_area.cpu_id, RSEQ_CPU_ID_REGISTRATION_FAILED);
+ return false;
}
#endif /* RSEQ_SIG */
GLIBC_2.1 __libc_stack_end D 0x4
GLIBC_2.1 _dl_mcount F
GLIBC_2.3 __tls_get_offset F
+GLIBC_2.35 __rseq_flags D 0x4
+GLIBC_2.35 __rseq_offset D 0x4
+GLIBC_2.35 __rseq_size D 0x4
GLIBC_2.2 _dl_mcount F
GLIBC_2.2 _r_debug D 0x28
GLIBC_2.3 __tls_get_offset F
+GLIBC_2.35 __rseq_flags D 0x4
+GLIBC_2.35 __rseq_offset D 0x4
+GLIBC_2.35 __rseq_size 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
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
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_2.2 _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
#endif /* __GLIBC_HAVE_KERNEL_RSEQ */
+/* Offset from the thread pointer to the rseq area. */
+extern const int __rseq_offset;
+
+/* Size of the registered rseq area. 0 if the registration was
+ unsuccessful. */
+extern const unsigned int __rseq_size;
+
+/* Flags used during rseq registration. */
+extern const unsigned int __rseq_flags;
+
#endif /* sys/rseq.h */
#include <support/namespace.h>
#include <support/xthread.h>
#include <sysdep.h>
+#include <thread_pointer.h>
#include <unistd.h>
#ifdef RSEQ_SIG
check_rseq_disabled (void)
{
struct pthread *pd = THREAD_SELF;
+
+ TEST_COMPARE (__rseq_flags, 0);
+ TEST_VERIFY ((char *) __thread_pointer () + __rseq_offset
+ == (char *) &pd->rseq_area);
+ TEST_COMPARE (__rseq_size, 0);
TEST_COMPARE ((int) pd->rseq_area.cpu_id, RSEQ_CPU_ID_REGISTRATION_FAILED);
int ret = syscall (__NR_rseq, &pd->rseq_area, sizeof (pd->rseq_area),
# include <stdlib.h>
# include <string.h>
# include <syscall.h>
+# include <thread_pointer.h>
+# include <tls.h>
# include "tst-rseq.h"
static void
do_rseq_main_test (void)
{
+ struct pthread *pd = THREAD_SELF;
+
TEST_VERIFY_EXIT (rseq_thread_registered ());
+ TEST_COMPARE (__rseq_flags, 0);
+ TEST_VERIFY ((char *) __thread_pointer () + __rseq_offset
+ == (char *) &pd->rseq_area);
+ TEST_COMPARE (__rseq_size, sizeof (pd->rseq_area));
}
static void
GLIBC_2.2.5 _dl_mcount F
GLIBC_2.2.5 _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
GLIBC_2.16 __tls_get_addr F
GLIBC_2.16 _dl_mcount F
GLIBC_2.16 _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
projects / thirdparty / glibc.git / commitdiff
