+/*
+ * do_page_fault error handling helpers
+ */
+
+#define MM_FAULT_RETURN 0
+#define MM_FAULT_CONTINUE -1
+#define MM_FAULT_ERR(sig) (sig)
+
+static int out_of_memory(struct pt_regs *regs)
+{
+ /*
+ * We ran out of memory, or some other thing happened to us that made
+ * us unable to handle the page fault gracefully.
+ */
+ up_read(¤t->mm->mmap_sem);
+ if (!user_mode(regs))
+ return MM_FAULT_ERR(SIGKILL);
+ pagefault_out_of_memory();
+ return MM_FAULT_RETURN;
+}
+
+static int do_sigbus(struct pt_regs *regs, unsigned long address)
+{
+ siginfo_t info;
+
+ up_read(¤t->mm->mmap_sem);
+
+ if (user_mode(regs)) {
+ info.si_signo = SIGBUS;
+ info.si_errno = 0;
+ info.si_code = BUS_ADRERR;
+ info.si_addr = (void __user *)address;
+ force_sig_info(SIGBUS, &info, current);
+ return MM_FAULT_RETURN;
+ }
+ return MM_FAULT_ERR(SIGBUS);
+}
+
+static int mm_fault_error(struct pt_regs *regs, unsigned long addr, int fault)
+{
+ /*
+ * Pagefault was interrupted by SIGKILL. We have no reason to
+ * continue the pagefault.
+ */
+ if (fatal_signal_pending(current)) {
+ /*
+ * If we have retry set, the mmap semaphore will have
+ * alrady been released in __lock_page_or_retry(). Else
+ * we release it now.
+ */
+ if (!(fault & VM_FAULT_RETRY))
+ up_read(¤t->mm->mmap_sem);
+ /* Coming from kernel, we need to deal with uaccess fixups */
+ if (user_mode(regs))
+ return MM_FAULT_RETURN;
+ return MM_FAULT_ERR(SIGKILL);
+ }
+
+ /* No fault: be happy */
+ if (!(fault & VM_FAULT_ERROR))
+ return MM_FAULT_CONTINUE;
+
+ /* Out of memory */
+ if (fault & VM_FAULT_OOM)
+ return out_of_memory(regs);
+
+ /* Bus error. x86 handles HWPOISON here, we'll add this if/when
+ * we support the feature in HW
+ */
+ if (fault & VM_FAULT_SIGBUS)
+ return do_sigbus(regs, addr);
+
+ /* We don't understand the fault code, this is fatal */
+ BUG();
+ return MM_FAULT_CONTINUE;
+}