test/004-SignalTest/signaltest.cc

/*
 * Copyright (C) 2014 The Android Open Source Project
 *
 * 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.
 */

#include <android-base/logging.h>

#include <jni.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ucontext.h>
#include <unistd.h>

#include "base/macros.h"

static int signal_count;
static const int kMaxSignal = 1;

#if defined(__i386__) || defined(__x86_64__)
#if defined(__APPLE__)
#define ucontext __darwin_ucontext

#if defined(__x86_64__)
// 64 bit mac build.
#define CTX_EIP uc_mcontext->__ss.__rip
#else
// 32 bit mac build.
#define CTX_EIP uc_mcontext->__ss.__eip
#endif

#elif defined(__x86_64__)
// 64 bit linux build.
#define CTX_EIP uc_mcontext.gregs[REG_RIP]
#else
// 32 bit linux build.
#define CTX_EIP uc_mcontext.gregs[REG_EIP]
#endif
#endif

#define BLOCKED_SIGNAL SIGUSR1
#define UNBLOCKED_SIGNAL SIGUSR2

static void blocked_signal([[maybe_unused]] int sig) {
  printf("blocked signal received\n");
}

static void unblocked_signal([[maybe_unused]] int sig) {
  printf("unblocked signal received\n");
}

static void signalhandler([[maybe_unused]] int sig, [[maybe_unused]] siginfo_t* info,
                          void* context) {
  printf("signal caught\n");
  ++signal_count;
  if (signal_count > kMaxSignal) {
     abort();
  }

  raise(UNBLOCKED_SIGNAL);
  raise(BLOCKED_SIGNAL);
  printf("unblocking blocked signal\n");

  sigset_t mask;
  sigemptyset(&mask);
  sigaddset(&mask, BLOCKED_SIGNAL);
  sigprocmask(SIG_UNBLOCK, &mask, nullptr);

#if defined(__arm__)
  ucontext_t* uc = reinterpret_cast<ucontext_t*>(context);
  mcontext_t* mc = reinterpret_cast<mcontext_t*>(&uc->uc_mcontext);
  mc->arm_pc += 2;  // Skip instruction causing segv.
#elif defined(__aarch64__)
  ucontext_t* uc = reinterpret_cast<ucontext_t*>(context);
  mcontext_t* mc = reinterpret_cast<mcontext_t*>(&uc->uc_mcontext);
  mc->pc += 4;  // Skip instruction causing segv.
#elif defined(__riscv)
  ucontext_t* uc = reinterpret_cast<ucontext_t*>(context);
  mcontext_t* mc = reinterpret_cast<mcontext_t*>(&uc->uc_mcontext);
  mc->__gregs[REG_PC] += 4;  // Skip instruction causing segv.
#elif defined(__i386__)
  ucontext_t* uc = reinterpret_cast<ucontext_t*>(context);
  uc->CTX_EIP += 3;
#elif defined(__x86_64__)
  ucontext_t* uc = reinterpret_cast<ucontext_t*>(context);
  uc->CTX_EIP += 2;
#else
  UNUSED(context);
  UNIMPLEMENTED(FATAL) << "Unsupported architecture";
#endif

  printf("signal handler done\n");
}

static struct sigaction oldaction;

bool compare_sigaction(const struct sigaction* lhs, const struct sigaction* rhs) {
  // bionic's definition of `struct sigaction` has internal padding bytes, so we can't just do a
  // naive memcmp of the entire struct.
#if defined(SA_RESTORER)
  if (lhs->sa_restorer != rhs->sa_restorer) {
    return false;
  }
#endif
  return memcmp(&lhs->sa_mask, &rhs->sa_mask, sizeof(lhs->sa_mask)) == 0 &&
         lhs->sa_sigaction == rhs->sa_sigaction &&
         lhs->sa_flags == rhs->sa_flags;
}

extern "C" JNIEXPORT void JNICALL Java_Main_initSignalTest(JNIEnv*, jclass) {
  struct sigaction action;
  action.sa_sigaction = signalhandler;
  sigfillset(&action.sa_mask);
  sigdelset(&action.sa_mask, UNBLOCKED_SIGNAL);
  action.sa_flags = SA_SIGINFO | SA_ONSTACK;
#if !defined(__APPLE__)
  action.sa_restorer = nullptr;
#endif

  sigaction(SIGSEGV, &action, &oldaction);
  struct sigaction check;
  sigaction(SIGSEGV, nullptr, &check);
  if (!compare_sigaction(&check, &action)) {
    printf("sigaction returned different value\n");
    printf("action.sa_mask = %p, check.sa_mask = %p\n",
           *reinterpret_cast<void**>(&action.sa_mask),
           *reinterpret_cast<void**>(&check.sa_mask));
    printf("action.sa_sigaction = %p, check.sa_sigaction = %p\n",
           action.sa_sigaction, check.sa_sigaction);
    printf("action.sa_flags = %x, check.sa_flags = %x\n",
           action.sa_flags, check.sa_flags);
  }
  signal(BLOCKED_SIGNAL, blocked_signal);
  signal(UNBLOCKED_SIGNAL, unblocked_signal);
}

extern "C" JNIEXPORT void JNICALL Java_Main_terminateSignalTest(JNIEnv*, jclass) {
  sigaction(SIGSEGV, &oldaction, nullptr);
}

// Prevent the compiler being a smart-alec and optimizing out the assignment
// to null.
char *go_away_compiler = nullptr;

extern "C" JNIEXPORT jint JNICALL Java_Main_testSignal(JNIEnv*, jclass) {
  // Unblock UNBLOCKED_SIGNAL.
  sigset_t mask;
  memset(&mask, 0, sizeof(mask));
  sigaddset(&mask, UNBLOCKED_SIGNAL);
  sigprocmask(SIG_UNBLOCK, &mask, nullptr);

#if defined(__arm__) || defined(__i386__) || defined(__aarch64__)
  // On supported architectures we cause a real SEGV.
  *go_away_compiler = 'a';
#elif defined(__riscv)
  // Cause a SEGV using an instruction known to be 4 bytes long to account for hardcoded jump
  // in the signal handler
  asm volatile("ld zero, (zero);" : : :);
#elif defined(__x86_64__)
  // Cause a SEGV using an instruction known to be 2 bytes long to account for hardcoded jump
  // in the signal handler
  asm volatile("movl $0, %%eax;" "movb %%ah, (%%rax);" : : : "%eax");
#else
  // On other architectures we simulate SEGV.
  kill(getpid(), SIGSEGV);
#endif
  return 1234;
}