Hi, Le mardi 13 mai 2014 à 17:29 +0200, michi1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx a écrit : > On 21:46 Sat 10 May , net.study.sea@xxxxxxxxx wrote: > > > > Hi all : > > I want to know is it possible to hook SIGSEGV to restart the thread which the signal is sent to,without restart the whole process? And record the place where has caused this signal? > > > > Thanks! > > Yes, you can hook SIGSEGV like a normal signal. However, I have never tried to > do so... > I've played with this: in the segv signal handler, using SA_SIGINFO (see sigaction(3), I've retrieved the fault address and mmap() some anonymous memory page here, then leave the handler. At this point the kernel will resume the process/thread where it has triggered the fault. And voila. The process/thread will issue again the previously faulty instruction and succeed. This approach works when fault happen on a unmapped address. But if your process/thread is trying to read some values there and instead found a page full of 0, it might trigger more segfault. Especially if it's using the zero as a pointer: it's going to try to access to page 0, which, by default, is not map'able by userspace process to defeat kernel NULL pointer dereference vulns. For write access to a read only page, depending on the underlying mapping, you will not be able to recover from the error easily: You probably have to unmap the read-only page, map an anonymous page instead, and don't forget to restore the content the process was expected to find there. I've never tried the later, nor played with multiple threads triggering fault. So YMMV. Regards. -- Yann Droneaud OPTEYA _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
