Open source system call tests.

PiperOrigin-RevId: 224886231
Change-Id: I0fccb4d994601739d8b16b1d4e6b31f40297fb22

1 files changed, 105 insertions, 0 deletions

diff --git a/test/syscalls/linux/fpsig_fork.cc b/test/syscalls/linux/fpsig_fork.cc
new file mode 100644
index 000000000..e8f1dfa8a
--- /dev/null
+++ b/test/syscalls/linux/fpsig_fork.cc
@@ -0,0 +1,105 @@
+// Copyright 2018 Google LLC
+//
+// 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.
+
+// This test verifies that fork(2) in a signal handler will correctly
+// restore floating point state after the signal handler returns in both
+// the child and parent.
+#include <sys/time.h>
+
+#include "gtest/gtest.h"
+#include "test/util/logging.h"
+#include "test/util/test_util.h"
+#include "test/util/thread_util.h"
+
+namespace gvisor {
+namespace testing {
+
+namespace {
+
+#define GET_XMM(__var, __xmm) \
+  asm volatile("movq %%" #__xmm ", %0" : "=r"(__var))
+#define SET_XMM(__var, __xmm) asm volatile("movq %0, %%" #__xmm : : "r"(__var))
+
+int parent, child;
+
+void sigusr1(int s, siginfo_t* siginfo, void* _uc) {
+  // Fork and clobber %xmm0. The fpstate should be restored by sigreturn(2)
+  // in both parent and child.
+  child = fork();
+  TEST_CHECK_MSG(child >= 0, "fork failed");
+
+  uint64_t val = SIGUSR1;
+  SET_XMM(val, xmm0);
+}
+
+TEST(FPSigTest, Fork) {
+  parent = getpid();
+  pid_t parent_tid = gettid();
+
+  struct sigaction sa = {};
+  sigemptyset(&sa.sa_mask);
+  sa.sa_flags = SA_SIGINFO;
+  sa.sa_sigaction = sigusr1;
+  ASSERT_THAT(sigaction(SIGUSR1, &sa, nullptr), SyscallSucceeds());
+
+  // The amd64 ABI specifies that the XMM register set is caller-saved. This
+  // implies that if there is any function call between SET_XMM and GET_XMM the
+  // compiler might save/restore xmm0 implicitly. This defeats the entire
+  // purpose of the test which is to verify that fpstate is restored by
+  // sigreturn(2).
+  //
+  // This is the reason why 'tgkill(getpid(), gettid(), SIGUSR1)' is implemented
+  // in inline assembly below.
+  //
+  // If the OS is broken and registers are clobbered by the child, using tgkill
+  // to signal the current thread increases the likelihood that this thread will
+  // be the one clobbered.
+
+  uint64_t expected = 0xdeadbeeffacefeed;
+  SET_XMM(expected, xmm0);
+
+  asm volatile(
+      "movl %[killnr], %%eax;"
+      "movl %[parent], %%edi;"
+      "movl %[tid], %%esi;"
+      "movl %[sig], %%edx;"
+      "syscall;"
+      :
+      : [killnr] "i"(__NR_tgkill), [parent] "rm"(parent),
+        [tid] "rm"(parent_tid), [sig] "i"(SIGUSR1)
+      : "rax", "rdi", "rsi", "rdx",
+        // Clobbered by syscall.
+        "rcx", "r11");
+
+  uint64_t got;
+  GET_XMM(got, xmm0);
+
+  if (getpid() == parent) {  // Parent.
+    int status;
+    ASSERT_THAT(waitpid(child, &status, 0), SyscallSucceedsWithValue(child));
+    EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0);
+  }
+
+  // TEST_CHECK_MSG since this may run in the child.
+  TEST_CHECK_MSG(expected == got, "Bad xmm0 value");
+
+  if (getpid() != parent) {  // Child.
+    _exit(0);
+  }
+}
+
+}  // namespace
+
+}  // namespace testing
+}  // namespace gvisor