Cross-Referenced Linux and Device Driver Code

   /*
    * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
    * Licensed under the GPL
    */
   
   #include <linux/module.h>
   #include <linux/ptrace.h>
   #include <linux/sched.h>
   #include <asm/siginfo.h>
  #include <asm/signal.h>
  #include <asm/unistd.h>
  #include "frame_kern.h"
  #include "kern_util.h"
  #include <sysdep/sigcontext.h>
  
  EXPORT_SYMBOL(block_signals);
  EXPORT_SYMBOL(unblock_signals);
  
  #define _S(nr) (1<<((nr)-1))
  
  #define _BLOCKABLE (~(_S(SIGKILL) | _S(SIGSTOP)))
  
  /*
   * OK, we're invoking a handler
   */
  static int handle_signal(struct pt_regs *regs, unsigned long signr,
                           struct k_sigaction *ka, siginfo_t *info,
                           sigset_t *oldset)
  {
          unsigned long sp;
          int err;
  
          /* Always make any pending restarted system calls return -EINTR */
          current_thread_info()->restart_block.fn = do_no_restart_syscall;
  
          /* Did we come from a system call? */
          if (PT_REGS_SYSCALL_NR(regs) >= 0) {
                  /* If so, check system call restarting.. */
                  switch (PT_REGS_SYSCALL_RET(regs)) {
                  case -ERESTART_RESTARTBLOCK:
                  case -ERESTARTNOHAND:
                          PT_REGS_SYSCALL_RET(regs) = -EINTR;
                          break;
  
                  case -ERESTARTSYS:
                          if (!(ka->sa.sa_flags & SA_RESTART)) {
                                  PT_REGS_SYSCALL_RET(regs) = -EINTR;
                                  break;
                          }
                  /* fallthrough */
                  case -ERESTARTNOINTR:
                          PT_REGS_RESTART_SYSCALL(regs);
                          PT_REGS_ORIG_SYSCALL(regs) = PT_REGS_SYSCALL_NR(regs);
                          break;
                  }
          }
  
          sp = PT_REGS_SP(regs);
          if ((ka->sa.sa_flags & SA_ONSTACK) && (sas_ss_flags(sp) == 0))
                  sp = current->sas_ss_sp + current->sas_ss_size;
  
  #ifdef CONFIG_ARCH_HAS_SC_SIGNALS
          if (!(ka->sa.sa_flags & SA_SIGINFO))
                  err = setup_signal_stack_sc(sp, signr, ka, regs, oldset);
          else
  #endif
                  err = setup_signal_stack_si(sp, signr, ka, regs, info, oldset);
  
          if (err) {
                  spin_lock_irq(&current->sighand->siglock);
                  current->blocked = *oldset;
                  recalc_sigpending();
                  spin_unlock_irq(&current->sighand->siglock);
                  force_sigsegv(signr, current);
          } else {
                  spin_lock_irq(&current->sighand->siglock);
                  sigorsets(&current->blocked, &current->blocked,
                            &ka->sa.sa_mask);
                  if (!(ka->sa.sa_flags & SA_NODEFER))
                          sigaddset(&current->blocked, signr);
                  recalc_sigpending();
                  spin_unlock_irq(&current->sighand->siglock);
          }
  
          return err;
  }
  
  static int kern_do_signal(struct pt_regs *regs)
  {
          struct k_sigaction ka_copy;
          siginfo_t info;
          sigset_t *oldset;
          int sig, handled_sig = 0;
  
          if (test_thread_flag(TIF_RESTORE_SIGMASK))
                  oldset = &current->saved_sigmask;
          else
                  oldset = &current->blocked;
  
         while ((sig = get_signal_to_deliver(&info, &ka_copy, regs, NULL)) > 0) {
                 handled_sig = 1;
                 /* Whee!  Actually deliver the signal.  */
                 if (!handle_signal(regs, sig, &ka_copy, &info, oldset)) {
                         /*
                          * a signal was successfully delivered; the saved
                          * sigmask will have been stored in the signal frame,
                          * and will be restored by sigreturn, so we can simply
                          * clear the TIF_RESTORE_SIGMASK flag
                          */
                         if (test_thread_flag(TIF_RESTORE_SIGMASK))
                                 clear_thread_flag(TIF_RESTORE_SIGMASK);
                         break;
                 }
         }
 
         /* Did we come from a system call? */
         if (!handled_sig && (PT_REGS_SYSCALL_NR(regs) >= 0)) {
                 /* Restart the system call - no handlers present */
                 switch (PT_REGS_SYSCALL_RET(regs)) {
                 case -ERESTARTNOHAND:
                 case -ERESTARTSYS:
                 case -ERESTARTNOINTR:
                         PT_REGS_ORIG_SYSCALL(regs) = PT_REGS_SYSCALL_NR(regs);
                         PT_REGS_RESTART_SYSCALL(regs);
                         break;
                 case -ERESTART_RESTARTBLOCK:
                         PT_REGS_ORIG_SYSCALL(regs) = __NR_restart_syscall;
                         PT_REGS_RESTART_SYSCALL(regs);
                         break;
                 }
         }
 
         /*
          * This closes a way to execute a system call on the host.  If
          * you set a breakpoint on a system call instruction and singlestep
          * from it, the tracing thread used to PTRACE_SINGLESTEP the process
          * rather than PTRACE_SYSCALL it, allowing the system call to execute
          * on the host.  The tracing thread will check this flag and
          * PTRACE_SYSCALL if necessary.
          */
         if (current->ptrace & PT_DTRACE)
                 current->thread.singlestep_syscall =
                         is_syscall(PT_REGS_IP(&current->thread.regs));
 
         /*
          * if there's no signal to deliver, we just put the saved sigmask
          * back
          */
         if (!handled_sig && test_thread_flag(TIF_RESTORE_SIGMASK)) {
                 clear_thread_flag(TIF_RESTORE_SIGMASK);
                 sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
         }
         return handled_sig;
 }
 
 int do_signal(void)
 {
         return kern_do_signal(&current->thread.regs);
 }
 
 /*
  * Atomically swap in the new signal mask, and wait for a signal.
  */
 long sys_sigsuspend(int history0, int history1, old_sigset_t mask)
 {
         mask &= _BLOCKABLE;
         spin_lock_irq(&current->sighand->siglock);
         current->saved_sigmask = current->blocked;
         siginitset(&current->blocked, mask);
         recalc_sigpending();
         spin_unlock_irq(&current->sighand->siglock);
 
         current->state = TASK_INTERRUPTIBLE;
         schedule();
         set_thread_flag(TIF_RESTORE_SIGMASK);
         return -ERESTARTNOHAND;
 }
 
 long sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss)
 {
         return do_sigaltstack(uss, uoss, PT_REGS_SP(&current->thread.regs));
 }