seccomp: allow rseq syscall

Starting with v4.18, the Linux kernel provides the rseq
syscall which is a mechanism for fast userspace task
synchronization.

Starting with v2.35 glibc uses the new syscall, if it
exists, to gain some performance improvements, so we
need to update the policy files to allow it.

Even on older kernels where rseq is not supported,
glibc will still probe for its existence by expecting
an -ENOSYS response.

BUG=b:235960683
TEST=Local builds against glibc 2.35

Change-Id: I704f2fbf2b058c3a4c3269c7441c3a7324012f8a
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/3763901
Commit-Queue: Manoj Gupta <manojgupta@chromium.org>
Owners-Override: Dominick Ng <dominickn@google.com>
Reviewed-by: Allen Webb <allenwebb@google.com>
Reviewed-by: Dennis Kempin <denniskempin@google.com>
Tested-by: Manoj Gupta <manojgupta@chromium.org>

seccomp/aarch64/common_device.policy

@@ -2,6 +2,9 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+# rseq should be first due to frequency and purpose to decrease nptl latency
+rseq: 1
+
 brk: 1
 clock_gettime: 1
 clone: arg0 & CLONE_THREAD

seccomp/aarch64/gpu_common.policy

@@ -4,6 +4,10 @@
 
 # Rules from common_device.policy with some rules removed because they block certain flags needed
 # for gpu.
+
+# rseq should be first due to frequency and purpose to decrease nptl latency
+rseq: 1
+
 brk: 1
 clock_gettime: 1
 close: 1

seccomp/arm/common_device.policy

@@ -2,6 +2,9 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+# rseq should be first due to frequency and purpose to decrease nptl latency
+rseq: 1
+
 brk: 1
 clock_gettime: 1
 clock_gettime64: 1

seccomp/arm/gpu_common.policy

@@ -4,6 +4,10 @@
 
 # Rules from common_device.policy with some rules removed because they block certain flags needed
 # for gpu.
+
+# rseq should be first due to frequency and purpose to decrease nptl latency
+rseq: 1
+
 brk: 1
 close: 1
 dup2: 1

seccomp/x86_64/common_device.policy

@@ -3,6 +3,10 @@
 # found in the LICENSE file.
 
 @frequency ./common_device.frequency
+
+# rseq should be first due to frequency and purpose to decrease nptl latency
+rseq: 1
+
 brk: 1
 clock_gettime: 1
 clone: arg0 & CLONE_THREAD

seccomp/x86_64/gpu_common.policy

@@ -4,6 +4,10 @@
 
 # Rules from common_device.policy with some rules removed because they block certain flags needed
 # for gpu.
+
+# rseq should be first due to frequency and purpose to decrease nptl latency
+rseq: 1
+
 brk: 1
 clock_gettime: 1
 close: 1