106 lines
3.1 KiB
C++
106 lines
3.1 KiB
C++
// Copyright 2018 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// This test verifies that fork(2) in a signal handler will correctly
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// restore floating point state after the signal handler returns in both
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// the child and parent.
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#include <sys/time.h>
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#include "gtest/gtest.h"
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#include "test/util/logging.h"
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#include "test/util/test_util.h"
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#include "test/util/thread_util.h"
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namespace gvisor {
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namespace testing {
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namespace {
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#define GET_XMM(__var, __xmm) \
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asm volatile("movq %%" #__xmm ", %0" : "=r"(__var))
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#define SET_XMM(__var, __xmm) asm volatile("movq %0, %%" #__xmm : : "r"(__var))
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int parent, child;
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void sigusr1(int s, siginfo_t* siginfo, void* _uc) {
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// Fork and clobber %xmm0. The fpstate should be restored by sigreturn(2)
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// in both parent and child.
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child = fork();
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TEST_CHECK_MSG(child >= 0, "fork failed");
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uint64_t val = SIGUSR1;
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SET_XMM(val, xmm0);
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}
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TEST(FPSigTest, Fork) {
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parent = getpid();
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pid_t parent_tid = gettid();
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struct sigaction sa = {};
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sigemptyset(&sa.sa_mask);
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sa.sa_flags = SA_SIGINFO;
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sa.sa_sigaction = sigusr1;
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ASSERT_THAT(sigaction(SIGUSR1, &sa, nullptr), SyscallSucceeds());
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// The amd64 ABI specifies that the XMM register set is caller-saved. This
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// implies that if there is any function call between SET_XMM and GET_XMM the
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// compiler might save/restore xmm0 implicitly. This defeats the entire
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// purpose of the test which is to verify that fpstate is restored by
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// sigreturn(2).
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//
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// This is the reason why 'tgkill(getpid(), gettid(), SIGUSR1)' is implemented
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// in inline assembly below.
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//
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// If the OS is broken and registers are clobbered by the child, using tgkill
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// to signal the current thread increases the likelihood that this thread will
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// be the one clobbered.
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uint64_t expected = 0xdeadbeeffacefeed;
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SET_XMM(expected, xmm0);
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asm volatile(
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"movl %[killnr], %%eax;"
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"movl %[parent], %%edi;"
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"movl %[tid], %%esi;"
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"movl %[sig], %%edx;"
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"syscall;"
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:
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: [killnr] "i"(__NR_tgkill), [parent] "rm"(parent),
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[tid] "rm"(parent_tid), [sig] "i"(SIGUSR1)
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: "rax", "rdi", "rsi", "rdx",
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// Clobbered by syscall.
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"rcx", "r11");
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uint64_t got;
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GET_XMM(got, xmm0);
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if (getpid() == parent) { // Parent.
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int status;
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ASSERT_THAT(waitpid(child, &status, 0), SyscallSucceedsWithValue(child));
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EXPECT_TRUE(WIFEXITED(status) && WEXITSTATUS(status) == 0);
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}
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// TEST_CHECK_MSG since this may run in the child.
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TEST_CHECK_MSG(expected == got, "Bad xmm0 value");
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if (getpid() != parent) { // Child.
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_exit(0);
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}
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}
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} // namespace
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} // namespace testing
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} // namespace gvisor
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