gvisor.dev/gvisor@v0.0.0-20240520182842-f9d4d51c7e0f/test/syscalls/linux/fpsig_mut_amd64.cc (about)

     1  // Copyright 2022 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  // This program verifies that application floating point state is visible in
    16  // signal frames, and that changes to said state is visible after the signal
    17  // handler returns.
    18  #include <sys/time.h>
    19  #include <sys/ucontext.h>
    20  
    21  #include "gtest/gtest.h"
    22  #include "test/util/test_util.h"
    23  #include "test/util/thread_util.h"
    24  
    25  namespace gvisor {
    26  namespace testing {
    27  
    28  namespace {
    29  
    30  #define GET_XMM(__var, __xmm) \
    31    asm volatile("movq %%" #__xmm ", %0" : "=r"(__var))
    32  #define SET_XMM(__var, __xmm) asm volatile("movq %0, %%" #__xmm : : "r"(__var))
    33  
    34  int pid;
    35  int tid;
    36  
    37  volatile uint64_t handlerxmm = ~0UL;
    38  volatile uint64_t framexmm = ~0UL;
    39  
    40  constexpr uint64_t kOldFPRegValue = 0xdeadbeeffacefeed;
    41  constexpr uint64_t kNewFPRegValue = 0xfacefeedbaad1dea;
    42  
    43  void sigusr1(int s, siginfo_t* siginfo, void* _uc) {
    44    uint64_t val = SIGUSR1;
    45  
    46    // Record the value of %xmm0 on entry and then clobber it.
    47    GET_XMM(handlerxmm, xmm0);
    48    SET_XMM(val, xmm0);
    49  
    50    // Record the value of %xmm0 stored in _uc and then replace it.
    51    ucontext_t* uc = reinterpret_cast<ucontext_t*>(_uc);
    52    auto* uc_xmm0 = &uc->uc_mcontext.fpregs->_xmm[0];
    53    framexmm = (static_cast<uint64_t>(uc_xmm0->element[1]) << 32) |
    54               static_cast<uint64_t>(uc_xmm0->element[0]);
    55    uc_xmm0->element[1] = static_cast<uint32_t>(kNewFPRegValue >> 32);
    56    uc_xmm0->element[0] = static_cast<uint32_t>(kNewFPRegValue);
    57  }
    58  
    59  TEST(FPSigTest, StateInFrame) {
    60    pid = getpid();
    61    tid = gettid();
    62  
    63    struct sigaction sa = {};
    64    sigemptyset(&sa.sa_mask);
    65    sa.sa_flags = SA_SIGINFO;
    66    sa.sa_sigaction = sigusr1;
    67    ASSERT_THAT(sigaction(SIGUSR1, &sa, nullptr), SyscallSucceeds());
    68  
    69    // The amd64 ABI specifies that the XMM register set is caller-saved. This
    70    // implies that if there is any function call between SET_XMM and GET_XMM the
    71    // compiler might save/restore xmm0 implicitly. This defeats the entire
    72    // purpose of the test which is to verify that fpstate is restored by
    73    // sigreturn(2).
    74    //
    75    // This is the reason why 'tgkill(getpid(), gettid(), SIGUSR1)' is implemented
    76    // in inline assembly below.
    77    //
    78    // If the OS is broken and registers are clobbered by the signal, using tgkill
    79    // to signal the current thread ensures that this is the clobbered thread.
    80    SET_XMM(kOldFPRegValue, xmm0);
    81  
    82    asm volatile(
    83        "movl %[killnr], %%eax;"
    84        "movl %[pid], %%edi;"
    85        "movl %[tid], %%esi;"
    86        "movl %[sig], %%edx;"
    87        "syscall;"
    88        :
    89        : [killnr] "i"(__NR_tgkill), [pid] "rm"(pid), [tid] "rm"(tid),
    90          [sig] "i"(SIGUSR1)
    91        : "rax", "rdi", "rsi", "rdx",
    92          // Clobbered by syscall.
    93          "rcx", "r11");
    94  
    95    uint64_t got;
    96    GET_XMM(got, xmm0);
    97  
    98    //
    99    // The checks below verifies the following:
   100    // - signal handlers must called with a clean fpu state.
   101    // - sigreturn(2) must restore fpstate of the interrupted context.
   102    //
   103    EXPECT_EQ(handlerxmm, 0);
   104    EXPECT_EQ(framexmm, kOldFPRegValue);
   105    EXPECT_EQ(got, kNewFPRegValue);
   106  }
   107  
   108  }  // namespace
   109  
   110  }  // namespace testing
   111  }  // namespace gvisor