1 files changed, 131 insertions, 50 deletions

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 2f0d1b032a89..19f2f9498b27 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -105,6 +105,82 @@ static int store_updates_sp(struct pt_regs *regs)
         }
         return 0;
 }
+/*
+ * 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(&current->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(&current->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(&current->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;
+}
 
 /*
  * For 600- and 800-family processors, the error_code parameter is DSISR
@@ -124,11 +200,12 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
 {
         struct vm_area_struct * vma;
         struct mm_struct *mm = current->mm;
-        siginfo_t info;
+        unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
         int code = SEGV_MAPERR;
-        int is_write = 0, ret;
+        int is_write = 0;
         int trap = TRAP(regs);
         int is_exec = trap == 0x400;
+        int fault;
 
 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
         /*
@@ -145,6 +222,9 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
         is_write = error_code & ESR_DST;
 #endif /* CONFIG_4xx || CONFIG_BOOKE */
 
+        if (is_write)
+                flags |= FAULT_FLAG_WRITE;
+
 #ifdef CONFIG_PPC_ICSWX
         /*
          * we need to do this early because this "data storage
@@ -152,13 +232,11 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
          * look at it
          */
         if (error_code & ICSWX_DSI_UCT) {
-                int ret;
-
-                ret = acop_handle_fault(regs, address, error_code);
-                if (ret)
-                        return ret;
+                int rc = acop_handle_fault(regs, address, error_code);
+                if (rc)
+                        return rc;
         }
-#endif
+#endif /* CONFIG_PPC_ICSWX */
 
         if (notify_page_fault(regs))
                 return 0;
@@ -179,6 +257,10 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
         }
 #endif
 
+        /* We restore the interrupt state now */
+        if (!arch_irq_disabled_regs(regs))
+                local_irq_enable();
+
         if (in_atomic() || mm == NULL) {
                 if (!user_mode(regs))
                         return SIGSEGV;
@@ -212,7 +294,15 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
                 if (!user_mode(regs) && !search_exception_tables(regs->nip))
                         goto bad_area_nosemaphore;
 
+retry:
                 down_read(&mm->mmap_sem);
+        } else {
+                /*
+                 * The above down_read_trylock() might have succeeded in
+                 * which case we'll have missed the might_sleep() from
+                 * down_read():
+                 */
+                might_sleep();
         }
 
         vma = find_vma(mm, address);
@@ -327,30 +417,43 @@ good_area:
          * make sure we exit gracefully rather than endlessly redo
          * the fault.
          */
-        ret = handle_mm_fault(mm, vma, address, is_write ? FAULT_FLAG_WRITE : 0);
-        if (unlikely(ret & VM_FAULT_ERROR)) {
-                if (ret & VM_FAULT_OOM)
-                        goto out_of_memory;
-                else if (ret & VM_FAULT_SIGBUS)
-                        goto do_sigbus;
-                BUG();
+        fault = handle_mm_fault(mm, vma, address, flags);
+        if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
+                int rc = mm_fault_error(regs, address, fault);
+                if (rc >= MM_FAULT_RETURN)
+                        return rc;
         }
-        if (ret & VM_FAULT_MAJOR) {
-                current->maj_flt++;
-                perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
-                                     regs, address);
+
+        /*
+         * Major/minor page fault accounting is only done on the
+         * initial attempt. If we go through a retry, it is extremely
+         * likely that the page will be found in page cache at that point.
+         */
+        if (flags & FAULT_FLAG_ALLOW_RETRY) {
+                if (fault & VM_FAULT_MAJOR) {
+                        current->maj_flt++;
+                        perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
+                                      regs, address);
 #ifdef CONFIG_PPC_SMLPAR
-                if (firmware_has_feature(FW_FEATURE_CMO)) {
-                        preempt_disable();
-                        get_lppaca()->page_ins += (1 << PAGE_FACTOR);
-                        preempt_enable();
+                        if (firmware_has_feature(FW_FEATURE_CMO)) {
+                                preempt_disable();
+                                get_lppaca()->page_ins += (1 << PAGE_FACTOR);
+                                preempt_enable();
+                        }
+#endif /* CONFIG_PPC_SMLPAR */
+                } else {
+                        current->min_flt++;
+                        perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
+                                      regs, address);
+                }
+                if (fault & VM_FAULT_RETRY) {
+                        /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
+                         * of starvation. */
+                        flags &= ~FAULT_FLAG_ALLOW_RETRY;
+                        goto retry;
                 }
-#endif
-        } else {
-                current->min_flt++;
-                perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
-                                     regs, address);
         }
+
         up_read(&mm->mmap_sem);
         return 0;
 
@@ -371,28 +474,6 @@ bad_area_nosemaphore:
 
         return SIGSEGV;
 
-/*
- * We ran out of memory, or some other thing happened to us that made
- * us unable to handle the page fault gracefully.
- */
-out_of_memory:
-        up_read(&mm->mmap_sem);
-        if (!user_mode(regs))
-                return SIGKILL;
-        pagefault_out_of_memory();
-        return 0;
-
-do_sigbus:
-        up_read(&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 0;
-        }
-        return SIGBUS;
 }
 
 /*