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279 lines
8.8 KiB
279 lines
8.8 KiB
commit e3e589829d16af9f7e73c7b70f74f3c5d5003e45
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Author: Florian Weimer <fweimer@redhat.com>
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Date: Thu Dec 9 09:49:32 2021 +0100
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nptl: Add glibc.pthread.rseq tunable to control rseq registration
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This tunable allows applications to register the rseq area instead
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of glibc.
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Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
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Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
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diff --git a/manual/tunables.texi b/manual/tunables.texi
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index 658547c6137bf177..1f5c410288eeecec 100644
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--- a/manual/tunables.texi
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+++ b/manual/tunables.texi
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@@ -413,6 +413,16 @@ The value is measured in bytes. The default is @samp{41943040}
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(fourty mibibytes).
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@end deftp
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+@deftp Tunable glibc.pthread.rseq
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+The @code{glibc.pthread.rseq} tunable can be set to @samp{0}, to disable
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+restartable sequences support in @theglibc{}. This enables applications
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+to perform direct restartable sequence registration with the kernel.
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+The default is @samp{1}, which means that @theglibc{} performs
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+registration on behalf of the application.
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+
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+Restartable sequences are a Linux-specific extension.
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+@end deftp
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+
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@node Hardware Capability Tunables
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@section Hardware Capability Tunables
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@cindex hardware capability tunables
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diff --git a/nptl/pthread_create.c b/nptl/pthread_create.c
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index d2b40924dafad316..f405fa356c2955ce 100644
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--- a/nptl/pthread_create.c
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+++ b/nptl/pthread_create.c
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@@ -369,7 +369,10 @@ start_thread (void *arg)
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__ctype_init ();
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/* Register rseq TLS to the kernel. */
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- rseq_register_current_thread (pd);
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+ {
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+ bool do_rseq = THREAD_GETMEM (pd, flags) & ATTR_FLAG_DO_RSEQ;
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+ rseq_register_current_thread (pd, do_rseq);
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+ }
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#ifndef __ASSUME_SET_ROBUST_LIST
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if (__nptl_set_robust_list_avail)
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@@ -678,6 +681,11 @@ __pthread_create_2_1 (pthread_t *newthread, const pthread_attr_t *attr,
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pd->flags = ((iattr->flags & ~(ATTR_FLAG_SCHED_SET | ATTR_FLAG_POLICY_SET))
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| (self->flags & (ATTR_FLAG_SCHED_SET | ATTR_FLAG_POLICY_SET)));
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+ /* Inherit rseq registration state. Without seccomp filters, rseq
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+ registration will either always fail or always succeed. */
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+ if ((int) THREAD_GETMEM_VOLATILE (self, rseq_area.cpu_id) >= 0)
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+ pd->flags |= ATTR_FLAG_DO_RSEQ;
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+
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/* Initialize the field for the ID of the thread which is waiting
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for us. This is a self-reference in case the thread is created
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detached. */
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diff --git a/sysdeps/nptl/dl-tls_init_tp.c b/sysdeps/nptl/dl-tls_init_tp.c
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index fedb876fdb2642d2..b39dfbff2c6678d5 100644
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--- a/sysdeps/nptl/dl-tls_init_tp.c
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+++ b/sysdeps/nptl/dl-tls_init_tp.c
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@@ -23,6 +23,9 @@
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#include <tls.h>
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#include <rseq-internal.h>
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+#define TUNABLE_NAMESPACE pthread
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+#include <dl-tunables.h>
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+
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#ifndef __ASSUME_SET_ROBUST_LIST
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bool __nptl_set_robust_list_avail;
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rtld_hidden_data_def (__nptl_set_robust_list_avail)
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@@ -92,7 +95,13 @@ __tls_init_tp (void)
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}
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}
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- rseq_register_current_thread (pd);
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+ {
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+ bool do_rseq = true;
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+#if HAVE_TUNABLES
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+ do_rseq = TUNABLE_GET (rseq, int, NULL);
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+#endif
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+ rseq_register_current_thread (pd, do_rseq);
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+ }
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/* Set initial thread's stack block from 0 up to __libc_stack_end.
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It will be bigger than it actually is, but for unwind.c/pt-longjmp.c
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diff --git a/sysdeps/nptl/dl-tunables.list b/sysdeps/nptl/dl-tunables.list
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index ac5d053298725468..d24f4be0d08ba407 100644
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--- a/sysdeps/nptl/dl-tunables.list
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+++ b/sysdeps/nptl/dl-tunables.list
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@@ -27,5 +27,11 @@ glibc {
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type: SIZE_T
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default: 41943040
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}
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+ rseq {
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+ type: INT_32
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+ minval: 0
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+ maxval: 1
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+ default: 1
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+ }
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}
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}
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diff --git a/sysdeps/nptl/internaltypes.h b/sysdeps/nptl/internaltypes.h
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index 50a2ad19ae7210ae..8205c6d15a918952 100644
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--- a/sysdeps/nptl/internaltypes.h
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+++ b/sysdeps/nptl/internaltypes.h
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@@ -49,6 +49,7 @@ struct pthread_attr
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#define ATTR_FLAG_OLDATTR 0x0010
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#define ATTR_FLAG_SCHED_SET 0x0020
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#define ATTR_FLAG_POLICY_SET 0x0040
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+#define ATTR_FLAG_DO_RSEQ 0x0080
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/* Used to allocate a pthread_attr_t object which is also accessed
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internally. */
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diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
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index f84ccd6bbb3b16ad..d30d21898b402d1e 100644
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--- a/sysdeps/unix/sysv/linux/Makefile
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+++ b/sysdeps/unix/sysv/linux/Makefile
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@@ -135,6 +135,12 @@ tests-internal += \
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tst-sigcontext-get_pc \
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# tests-internal
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+ifneq (no,$(have-tunables))
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+tests-internal += \
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+ tst-rseq-disable \
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+ # tests-internal $(have-tunables)
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+endif
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+
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tests-time64 += \
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tst-adjtimex-time64 \
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tst-clock_adjtime-time64 \
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@@ -226,6 +232,8 @@ $(objpfx)tst-mman-consts.out: ../sysdeps/unix/sysv/linux/tst-mman-consts.py
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< /dev/null > $@ 2>&1; $(evaluate-test)
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$(objpfx)tst-mman-consts.out: $(sysdeps-linux-python-deps)
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+tst-rseq-disable-ENV = GLIBC_TUNABLES=glibc.pthread.rseq=0
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+
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endif # $(subdir) == misc
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ifeq ($(subdir),time)
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diff --git a/sysdeps/unix/sysv/linux/rseq-internal.h b/sysdeps/unix/sysv/linux/rseq-internal.h
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index 909f5478251d3d13..15bc7ffd6eda632d 100644
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--- a/sysdeps/unix/sysv/linux/rseq-internal.h
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+++ b/sysdeps/unix/sysv/linux/rseq-internal.h
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@@ -21,22 +21,27 @@
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#include <sysdep.h>
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#include <errno.h>
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#include <kernel-features.h>
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+#include <stdbool.h>
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#include <stdio.h>
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#include <sys/rseq.h>
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#ifdef RSEQ_SIG
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static inline void
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-rseq_register_current_thread (struct pthread *self)
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+rseq_register_current_thread (struct pthread *self, bool do_rseq)
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{
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- int ret = INTERNAL_SYSCALL_CALL (rseq,
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- &self->rseq_area, sizeof (self->rseq_area),
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- 0, RSEQ_SIG);
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- if (INTERNAL_SYSCALL_ERROR_P (ret))
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- THREAD_SETMEM (self, rseq_area.cpu_id, RSEQ_CPU_ID_REGISTRATION_FAILED);
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+ if (do_rseq)
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+ {
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+ int ret = INTERNAL_SYSCALL_CALL (rseq, &self->rseq_area,
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+ sizeof (self->rseq_area),
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+ 0, RSEQ_SIG);
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+ if (!INTERNAL_SYSCALL_ERROR_P (ret))
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+ return;
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+ }
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+ THREAD_SETMEM (self, rseq_area.cpu_id, RSEQ_CPU_ID_REGISTRATION_FAILED);
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}
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#else /* RSEQ_SIG */
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static inline void
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-rseq_register_current_thread (struct pthread *self)
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+rseq_register_current_thread (struct pthread *self, bool do_rseq)
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{
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THREAD_SETMEM (self, rseq_area.cpu_id, RSEQ_CPU_ID_REGISTRATION_FAILED);
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}
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diff --git a/sysdeps/unix/sysv/linux/tst-rseq-disable.c b/sysdeps/unix/sysv/linux/tst-rseq-disable.c
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new file mode 100644
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index 0000000000000000..000e351872fc2f76
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--- /dev/null
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+++ b/sysdeps/unix/sysv/linux/tst-rseq-disable.c
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@@ -0,0 +1,89 @@
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+/* Test disabling of rseq registration via tunable.
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+ Copyright (C) 2021 Free Software Foundation, Inc.
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+
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+ The GNU C Library is free software; you can redistribute it and/or
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+ modify it under the terms of the GNU Lesser General Public
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+ License as published by the Free Software Foundation; either
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+ version 2.1 of the License, or (at your option) any later version.
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+
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+ The GNU C Library is distributed in the hope that it will be useful,
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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+ Lesser General Public License for more details.
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+
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+ You should have received a copy of the GNU Lesser General Public
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+ License along with the GNU C Library; if not, see
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+ <https://www.gnu.org/licenses/>. */
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+
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+#include <errno.h>
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+#include <stdio.h>
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+#include <support/check.h>
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+#include <support/namespace.h>
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+#include <support/xthread.h>
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+#include <sysdep.h>
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+#include <unistd.h>
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+
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+#ifdef RSEQ_SIG
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+
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+/* Check that rseq can be registered and has not been taken by glibc. */
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+static void
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+check_rseq_disabled (void)
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+{
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+ struct pthread *pd = THREAD_SELF;
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+ TEST_COMPARE ((int) pd->rseq_area.cpu_id, RSEQ_CPU_ID_REGISTRATION_FAILED);
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+
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+ int ret = syscall (__NR_rseq, &pd->rseq_area, sizeof (pd->rseq_area),
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+ 0, RSEQ_SIG);
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+ if (ret == 0)
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+ {
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+ ret = syscall (__NR_rseq, &pd->rseq_area, sizeof (pd->rseq_area),
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+ RSEQ_FLAG_UNREGISTER, RSEQ_SIG);
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+ TEST_COMPARE (ret, 0);
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+ pd->rseq_area.cpu_id = RSEQ_CPU_ID_REGISTRATION_FAILED;
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+ }
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+ else
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+ {
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+ TEST_VERIFY (errno != -EINVAL);
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+ TEST_VERIFY (errno != -EBUSY);
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+ }
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+}
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+
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+static void *
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+thread_func (void *ignored)
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+{
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+ check_rseq_disabled ();
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+ return NULL;
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+}
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+
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+static void
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+proc_func (void *ignored)
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+{
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+ check_rseq_disabled ();
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+}
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+
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+static int
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+do_test (void)
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+{
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+ puts ("info: checking main thread");
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+ check_rseq_disabled ();
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+
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+ puts ("info: checking main thread (2)");
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+ check_rseq_disabled ();
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+
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+ puts ("info: checking new thread");
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+ xpthread_join (xpthread_create (NULL, thread_func, NULL));
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+
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+ puts ("info: checking subprocess");
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+ support_isolate_in_subprocess (proc_func, NULL);
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+
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+ return 0;
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+}
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+#else /* !RSEQ_SIG */
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+static int
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+do_test (void)
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+{
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+ FAIL_UNSUPPORTED ("glibc does not define RSEQ_SIG, skipping test");
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+}
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+#endif
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+
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+#include <support/test-driver.c>
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