Add tests for rseq(2)

Add a decent set of syscall tests for rseq(2). These are a bit awkward because
of issues with library integration. libc may register rseq on thread start
(including before main on the initial thread), precluding much testing. Thus we
run tests in a libc-free subprocess.

Support for rseq(2) in gVisor will come in a later commit.

PiperOrigin-RevId: 284595994

1 files changed, 66 insertions, 0 deletions

diff --git a/test/syscalls/linux/rseq/critical.S b/test/syscalls/linux/rseq/critical.S
new file mode 100644
index 000000000..8c0687e6d
--- /dev/null
+++ b/test/syscalls/linux/rseq/critical.S
@@ -0,0 +1,66 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Restartable sequences critical sections.
+
+// Loops continuously until aborted.
+//
+// void rseq_loop(struct rseq* r, struct rseq_cs* cs)
+
+  .text
+  .globl  rseq_loop
+  .type   rseq_loop, @function
+
+rseq_loop:
+  jmp begin
+
+  // Abort block before the critical section.
+  // Abort signature is 4 nops for simplicity.
+  .byte 0x90, 0x90, 0x90, 0x90
+  .globl  rseq_loop_early_abort
+rseq_loop_early_abort:
+  ret
+
+begin:
+  // r->rseq_cs = cs
+  movq %rsi, 8(%rdi)
+
+  // N.B. rseq_cs will be cleared by any preempt, even outside the critical
+  // section. Thus it must be set in or immediately before the critical section
+  // to ensure it is not cleared before the section begins.
+  .globl  rseq_loop_start
+rseq_loop_start:
+  jmp rseq_loop_start
+
+  // "Pre-commit": extra instructions inside the critical section.  These are
+  // used as the abort point in TestAbortPreCommit, which is not valid.
+  .globl  rseq_loop_pre_commit
+rseq_loop_pre_commit:
+  // Extra abort signature + nop for TestAbortPostCommit.
+  .byte 0x90, 0x90, 0x90, 0x90
+  nop
+
+  // "Post-commit": never reached in this case.
+  .globl  rseq_loop_post_commit
+rseq_loop_post_commit:
+
+  // Abort signature is 4 nops for simplicity.
+  .byte 0x90, 0x90, 0x90, 0x90
+
+  .globl  rseq_loop_abort
+rseq_loop_abort:
+  ret
+
+  .size  rseq_loop,.-rseq_loop
+  .section  .note.GNU-stack,"",@progbits