而 return si_addr 与 sigwaitinfo 函数的偏移导致分段错误

Question

我正在研究 signal handler 来处理收割信号，当我调用 sigwaitinfo 函数时，我随机得到带有偏移量的信号。除了 info.si_addr 之外，所有信号属性都是正确的。 info.si_addr 中的此偏移量导致分段错误。

这个偏移量似乎是相同的 - 我已经尝试删除偏移量并且有效，但我需要一个正确的解决方案才能继续。

static void *signalHandler(void *vptr_args __attribute__((unused)))
  {
      sigset_t signal_set;
      siginfo_t info;

      sigemptyset(&signal_set);
      sigaddset(&signal_set, SIG_REAP);
      sigaddset(&signal_set, SIG_ISOC_CANCEL);
      sigaddset(&signal_set, SIGTERM);
      sigaddset(&signal_set, SIGPIPE);

      while (true) {
          int rc = sigwaitinfo(&signal_set, &info);
          //...
          if (rc > 0) 
{
            if(info.si_signo == SIG_REAP) 
               {
                 // Reap URBs after some simple checks
                 if ((info.si_code != SI_ASYNCIO) &&
                     (info.si_code != SI_KERNEL)) {
                      printf("Bad si_code %d in SIG_REAP", info.si_code);                      
                      continue;
                 } 
                   else {
                      printf("OK si_code %d in SIG_REAP", info.si_code);
                 }
                   struct usbdevfs_urb *ioctl_urb = (struct usbdevfs_urb*)info.si_addres
                  if (!ioctl_urb) {
                     printf("SIG_REAP gave NULL ioctl_urb");
                      continue;
                  }
                  UrbInfo *urbInfo = ioctl_urb->usercontext;
                  if (!urbInfo) {
                     printf("SIG_REAP gave NULL urbInfo");
                      continue;
}

Answer 1

您在滥用 si_addr。它仅适用于有限数量的信号，并且不包括任何 real-time 信号。

Per POSIX、si_addr不适用于SIGILL、SIGFPE、SIGSEGV和SIGBUS以外的信号。 Linux 还为 SIGTRAP:

提供 si_addr 数据

SIGILL, SIGFPE, SIGSEGV, SIGBUS, and SIGTRAP fill in si_addr with the address of the fault.

没有其他信号提供 si_addr 的值。

填写si_addr的

The source code linux/kernel/signal.c清楚地表明si_addr不用于列出的信号以外的任何信号。

请注意，根据 the Linux signal(7) man page:

Real-time signals are distinguished by the following:

Multiple instances of real-time signals can be queued. By contrast, if multiple instances of a standard signal are delivered while that signal is currently blocked, then only one instance is queued.

If the signal is sent using sigqueue(3), an accompanying value (either an integer or a pointer) can be sent with the signal. If the receiving process establishes a handler for this signal using the SA_SIGINFO flag to sigaction(2), then it can obtain this data via the si_value field of the siginfo_t structure passed as the second argument to the handler. Furthermore, the si_pid and si_uid fields of this structure can be used to obtain the PID and real user ID of the process sending the signal.

...

而 return si_addr 与 sigwaitinfo 函数的偏移导致分段错误

While return si_addr with offset from sigwaitinfo function causing segmentation fault

c

linux

multithreading

signals

linux-kernel