nptl: clear the whole rseq area before registration

Due to the extensible nature of the rseq area we can't explictly
initialize fields that are not part of the ABI yet. It was agreed with
upstream that all new fields will be documented as zero initialized by
userspace. Future kernels configured with CONFIG_DEBUG_RSEQ will
validate the content of all fields during registration.

Replace the explicit field initialization with a memset of the whole
rseq area which will cover fields as they are added to future kernels.

Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Reviewed-by: Florian Weimer <fweimer@redhat.com>
(cherry picked from commit 689a62a4217fae78b9ce0db781dc2a421f2b1ab4)

diff --git a/sysdeps/nptl/dl-tls_init_tp.c b/sysdeps/nptl/dl-tls_init_tp.c
index 7803e19fd16ad803d778b415740874197908f9a3..ed10185e3708f4b685355d1b251763111235455f 100644 (file)
--- a/sysdeps/nptl/dl-tls_init_tp.c
+++ b/sysdeps/nptl/dl-tls_init_tp.c
@@ -23,6 +23,7 @@
 #include <tls.h>
 #include <rseq-internal.h>
 #include <thread_pointer.h>
+#include <dl-symbol-redir-ifunc.h>
 
 #define TUNABLE_NAMESPACE pthread
 #include <dl-tunables.h>

diff --git a/sysdeps/unix/sysv/linux/rseq-internal.h b/sysdeps/unix/sysv/linux/rseq-internal.h
index ef3eab1fefd4d90dc23bae54caf082beaec2e213..76de2b7ff079eb0f36ecc0cba0964d10da08aa50 100644 (file)
--- a/sysdeps/unix/sysv/linux/rseq-internal.h
+++ b/sysdeps/unix/sysv/linux/rseq-internal.h
@@ -52,13 +52,12 @@ rseq_register_current_thread (struct pthread *self, bool do_rseq)
            but still expected size 32.  */
         size = RSEQ_AREA_SIZE_INITIAL;
 
-      /* Initialize the rseq fields that are read by the kernel on
-         registration, there is no guarantee that struct pthread is
-         cleared on all architectures.  */
+      /* Initialize the whole rseq area to zero prior to registration.  */
+      memset (&self->rseq_area, 0, size);
+
+      /* Set the cpu_id field to RSEQ_CPU_ID_UNINITIALIZED, this is checked by
+         the kernel at registration when CONFIG_DEBUG_RSEQ is enabled.  */
       THREAD_SETMEM (self, rseq_area.cpu_id, RSEQ_CPU_ID_UNINITIALIZED);
-      THREAD_SETMEM (self, rseq_area.cpu_id_start, 0);
-      THREAD_SETMEM (self, rseq_area.rseq_cs, 0);
-      THREAD_SETMEM (self, rseq_area.flags, 0);
 
       int ret = INTERNAL_SYSCALL_CALL (rseq, &self->rseq_area,
                                        size, 0, RSEQ_SIG);