sh: Tidy up and generalize page fault error paths.

This follows the x86 changes for tidying up the page fault error paths.
We'll build on top of this for _32/_64 unification.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 220 insertions, 105 deletions

diff --git a/arch/sh/mm/fault_32.c b/arch/sh/mm/fault_32.c
index 8ce856d1572d..889e83b5ff22 100644
--- a/arch/sh/mm/fault_32.c
+++ b/arch/sh/mm/fault_32.c
@@ -2,7 +2,7 @@
  * Page fault handler for SH with an MMU.
  *
  *  Copyright (C) 1999  Niibe Yutaka
- *  Copyright (C) 2003 - 2009  Paul Mundt
+ *  Copyright (C) 2003 - 2012  Paul Mundt
  *
  *  Based on linux/arch/i386/mm/fault.c:
  *   Copyright (C) 1995  Linus Torvalds
@@ -16,6 +16,7 @@
 #include <linux/hardirq.h>
 #include <linux/kprobes.h>
 #include <linux/perf_event.h>
+#include <linux/kdebug.h>
 #include <asm/io_trapped.h>
 #include <asm/mmu_context.h>
 #include <asm/tlbflush.h>
@@ -35,6 +36,20 @@ static inline int notify_page_fault(struct pt_regs *regs, int trap)
         return ret;
 }
 
+static void
+force_sig_info_fault(int si_signo, int si_code, unsigned long address,
+                     struct task_struct *tsk)
+{
+        siginfo_t info;
+
+        info.si_signo   = si_signo;
+        info.si_errno   = 0;
+        info.si_code    = si_code;
+        info.si_addr    = (void __user *)address;
+
+        force_sig_info(si_signo, &info, tsk);
+}
+
 /*
  * This is useful to dump out the page tables associated with
  * 'addr' in mm 'mm'.
@@ -176,6 +191,185 @@ static noinline int vmalloc_fault(unsigned long address)
         return 0;
 }
 
+static void
+show_fault_oops(struct pt_regs *regs, unsigned long address)
+{
+        if (!oops_may_print())
+                return;
+
+        printk(KERN_ALERT "BUG: unable to handle kernel ");
+        if (address < PAGE_SIZE)
+                printk(KERN_CONT "NULL pointer dereference");
+        else
+                printk(KERN_CONT "paging request");
+
+        printk(KERN_CONT " at %08lx\n", address);
+        printk(KERN_ALERT "PC:");
+        printk_address(regs->pc, 1);
+
+        show_pte(NULL, address);
+}
+
+static noinline void
+no_context(struct pt_regs *regs, unsigned long writeaccess,
+           unsigned long address)
+{
+        /* Are we prepared to handle this kernel fault?  */
+        if (fixup_exception(regs))
+                return;
+
+        if (handle_trapped_io(regs, address))
+                return;
+
+        /*
+         * Oops. The kernel tried to access some bad page. We'll have to
+         * terminate things with extreme prejudice.
+         */
+        bust_spinlocks(1);
+
+        show_fault_oops(regs, address);
+
+        die("Oops", regs, writeaccess);
+        bust_spinlocks(0);
+        do_exit(SIGKILL);
+}
+
+static void
+__bad_area_nosemaphore(struct pt_regs *regs, unsigned long writeaccess,
+                       unsigned long address, int si_code)
+{
+        struct task_struct *tsk = current;
+
+        /* User mode accesses just cause a SIGSEGV */
+        if (user_mode(regs)) {
+                /*
+                 * It's possible to have interrupts off here:
+                 */
+                local_irq_enable();
+
+                force_sig_info_fault(SIGSEGV, si_code, address, tsk);
+
+                return;
+        }
+
+        no_context(regs, writeaccess, address);
+}
+
+static noinline void
+bad_area_nosemaphore(struct pt_regs *regs, unsigned long writeaccess,
+                     unsigned long address)
+{
+        __bad_area_nosemaphore(regs, writeaccess, address, SEGV_MAPERR);
+}
+
+static void
+__bad_area(struct pt_regs *regs, unsigned long writeaccess,
+           unsigned long address, int si_code)
+{
+        struct mm_struct *mm = current->mm;
+
+        /*
+         * Something tried to access memory that isn't in our memory map..
+         * Fix it, but check if it's kernel or user first..
+         */
+        up_read(&mm->mmap_sem);
+
+        __bad_area_nosemaphore(regs, writeaccess, address, si_code);
+}
+
+static noinline void
+bad_area(struct pt_regs *regs, unsigned long writeaccess, unsigned long address)
+{
+        __bad_area(regs, writeaccess, address, SEGV_MAPERR);
+}
+
+static noinline void
+bad_area_access_error(struct pt_regs *regs, unsigned long writeaccess,
+                      unsigned long address)
+{
+        __bad_area(regs, writeaccess, address, SEGV_ACCERR);
+}
+
+static void out_of_memory(void)
+{
+        /*
+         * We ran out of memory, call the OOM killer, and return the userspace
+         * (which will retry the fault, or kill us if we got oom-killed):
+         */
+        up_read(&current->mm->mmap_sem);
+
+        pagefault_out_of_memory();
+}
+
+static void
+do_sigbus(struct pt_regs *regs, unsigned long writeaccess, unsigned long address)
+{
+        struct task_struct *tsk = current;
+        struct mm_struct *mm = tsk->mm;
+
+        up_read(&mm->mmap_sem);
+
+        /* Kernel mode? Handle exceptions or die: */
+        if (!user_mode(regs))
+                no_context(regs, writeaccess, address);
+
+        force_sig_info_fault(SIGBUS, BUS_ADRERR, address, tsk);
+}
+
+static noinline int
+mm_fault_error(struct pt_regs *regs, unsigned long writeaccess,
+               unsigned long address, unsigned int fault)
+{
+        /*
+         * Pagefault was interrupted by SIGKILL. We have no reason to
+         * continue pagefault.
+         */
+        if (fatal_signal_pending(current)) {
+                if (!(fault & VM_FAULT_RETRY))
+                        up_read(&current->mm->mmap_sem);
+                if (!user_mode(regs))
+                        no_context(regs, writeaccess, address);
+                return 1;
+        }
+
+        if (!(fault & VM_FAULT_ERROR))
+                return 0;
+
+        if (fault & VM_FAULT_OOM) {
+                /* Kernel mode? Handle exceptions or die: */
+                if (!user_mode(regs)) {
+                        up_read(&current->mm->mmap_sem);
+                        no_context(regs, writeaccess, address);
+                        return 1;
+                }
+
+                out_of_memory();
+        } else {
+                if (fault & VM_FAULT_SIGBUS)
+                        do_sigbus(regs, writeaccess, address);
+                else
+                        BUG();
+        }
+
+        return 1;
+}
+
+static inline int access_error(int write, struct vm_area_struct *vma)
+{
+        if (write) {
+                /* write, present and write, not present: */
+                if (unlikely(!(vma->vm_flags & VM_WRITE)))
+                        return 1;
+                return 0;
+        }
+
+        /* read, not present: */
+        if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
+                return 1;
+
+        return 0;
+}
+
 static int fault_in_kernel_space(unsigned long address)
 {
         return address >= TASK_SIZE;
@@ -194,15 +388,12 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
         struct task_struct *tsk;
         struct mm_struct *mm;
         struct vm_area_struct * vma;
-        int si_code;
         int fault;
-        siginfo_t info;
         unsigned int flags = (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
                               (writeaccess ? FAULT_FLAG_WRITE : 0));
 
         tsk = current;
         mm = tsk->mm;
-        si_code = SEGV_MAPERR;
         vec = lookup_exception_vector();
 
         /*
@@ -220,7 +411,8 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
                 if (notify_page_fault(regs, vec))
                         return;
 
-                goto bad_area_nosemaphore;
+                bad_area_nosemaphore(regs, writeaccess, address);
+                return;
         }
 
         if (unlikely(notify_page_fault(regs, vec)))
@@ -236,34 +428,38 @@ asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
          * If we're in an interrupt, have no user context or are running
          * in an atomic region then we must not take the fault:
          */
-        if (in_atomic() || !mm)
-                goto no_context;
+        if (unlikely(in_atomic() || !mm)) {
+                bad_area_nosemaphore(regs, writeaccess, address);
+                return;
+        }
 
 retry:
         down_read(&mm->mmap_sem);
 
         vma = find_vma(mm, address);
-        if (!vma)
-                goto bad_area;
-        if (vma->vm_start <= address)
+        if (unlikely(!vma)) {
+                bad_area(regs, writeaccess, address);
+                return;
+        }
+        if (likely(vma->vm_start <= address))
                 goto good_area;
-        if (!(vma->vm_flags & VM_GROWSDOWN))
-                goto bad_area;
-        if (expand_stack(vma, address))
-                goto bad_area;
+        if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
+                bad_area(regs, writeaccess, address);
+                return;
+        }
+        if (unlikely(expand_stack(vma, address))) {
+                bad_area(regs, writeaccess, address);
+                return;
+        }
 
         /*
          * Ok, we have a good vm_area for this memory access, so
          * we can handle it..
          */
 good_area:
-        si_code = SEGV_ACCERR;
-        if (writeaccess) {
-                if (!(vma->vm_flags & VM_WRITE))
-                        goto bad_area;
-        } else {
-                if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
-                        goto bad_area;
+        if (unlikely(access_error(writeaccess, vma))) {
+                bad_area_access_error(regs, writeaccess, address);
+                return;
         }
 
         /*
@@ -273,16 +469,9 @@ good_area:
          */
         fault = handle_mm_fault(mm, vma, address, flags);
 
-        if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
-                return;
-
-        if (unlikely(fault & VM_FAULT_ERROR)) {
-                if (fault & VM_FAULT_OOM)
-                        goto out_of_memory;
-                else if (fault & VM_FAULT_SIGBUS)
-                        goto do_sigbus;
-                BUG();
-        }
+        if (unlikely(fault & (VM_FAULT_RETRY | VM_FAULT_ERROR)))
+                if (mm_fault_error(regs, writeaccess, address, fault))
+                        return;
 
         if (flags & FAULT_FLAG_ALLOW_RETRY) {
                 if (fault & VM_FAULT_MAJOR) {
@@ -307,80 +496,6 @@ good_area:
         }
 
         up_read(&mm->mmap_sem);
-        return;
-
-        /*
-         * Something tried to access memory that isn't in our memory map..
-         * Fix it, but check if it's kernel or user first..
-         */
-bad_area:
-        up_read(&mm->mmap_sem);
-
-bad_area_nosemaphore:
-        if (user_mode(regs)) {
-                info.si_signo = SIGSEGV;
-                info.si_errno = 0;
-                info.si_code = si_code;
-                info.si_addr = (void *) address;
-                force_sig_info(SIGSEGV, &info, tsk);
-                return;
-        }
-
-no_context:
-        /* Are we prepared to handle this kernel fault?  */
-        if (fixup_exception(regs))
-                return;
-
-        if (handle_trapped_io(regs, address))
-                return;
-/*
- * Oops. The kernel tried to access some bad page. We'll have to
- * terminate things with extreme prejudice.
- *
- */
-
-        bust_spinlocks(1);
-
-        if (oops_may_print()) {
-                printk(KERN_ALERT
-                       "Unable to handle kernel %s at virtual address %08lx\n",
-                       (address < PAGE_SIZE) ? "NULL pointer dereference" :
-                       "paging request", address);
-
-                show_pte(mm, address);
-        }
-
-        die("Oops", regs, writeaccess);
-        bust_spinlocks(0);
-        do_exit(SIGKILL);
-
-/*
- * 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))
-                goto no_context;
-        pagefault_out_of_memory();
-        return;
-
-do_sigbus:
-        up_read(&mm->mmap_sem);
-
-        /*
-         * Send a sigbus, regardless of whether we were in kernel
-         * or user mode.
-         */
-        info.si_signo = SIGBUS;
-        info.si_errno = 0;
-        info.si_code = BUS_ADRERR;
-        info.si_addr = (void *)address;
-        force_sig_info(SIGBUS, &info, tsk);
-
-        /* Kernel mode? Handle exceptions or die */
-        if (!user_mode(regs))
-                goto no_context;
 }
 
 /*