[Blackfin] arch: try to remove condition that causes double fault, by checking current before it gets dereferenced

Signed-off-by: Robin Getz <rgetz@blackfin.uclinux.org>
Signed-off-by: Bryan Wu <cooloney@kernel.org>

1 files changed, 24 insertions, 10 deletions

diff --git a/arch/blackfin/kernel/traps.c b/arch/blackfin/kernel/traps.c
index de249d6fdd9c..d0f675422074 100644
--- a/arch/blackfin/kernel/traps.c
+++ b/arch/blackfin/kernel/traps.c
@@ -137,17 +137,30 @@ static void decode_address(char *buf, unsigned long address)
                                 /* FLAT does not have its text aligned to the start of
                                  * the map while FDPIC ELF does ...
                                  */
-                                if (current->mm &&
-                                    (address > current->mm->start_code) &&
-                                    (address < current->mm->end_code))
-                                        offset = address - current->mm->start_code;
-                                else
-                                        offset = (address - vma->vm_start) + (vma->vm_pgoff << PAGE_SHIFT);
-
-                                sprintf(buf, "<0x%p> [ %s + 0x%lx ]",
-                                        (void *)address, name, offset);
+
+                                /* before we can check flat/fdpic, we need to
+                                 * make sure current is valid
+                                 */
+                                if ((unsigned long)current >= FIXED_CODE_START &&
+                                    !((unsigned long)current & 0x3)) {
+                                        if (current->mm &&
+                                            (address > current->mm->start_code) &&
+                                            (address < current->mm->end_code))
+                                                offset = address - current->mm->start_code;
+                                        else
+                                                offset = (address - vma->vm_start) +
+                                                         (vma->vm_pgoff << PAGE_SHIFT);
+
+                                        sprintf(buf, "<0x%p> [ %s + 0x%lx ]",
+                                                (void *)address, name, offset);
+                                } else
+                                        sprintf(buf, "<0x%p> [ %s vma:0x%lx-0x%lx]",
+                                                (void *)address, name,
+                                                vma->vm_start, vma->vm_end);
+
                                 if (!in_atomic)
                                         mmput(mm);
+
                                 goto done;
                         }
 
@@ -658,7 +671,8 @@ void dump_bfin_process(struct pt_regs *fp)
         /* Because we are crashing, and pointers could be bad, we check things
          * pretty closely before we use them
          */
-        if (!((unsigned long)current & 0x3) && current->pid) {
+        if ((unsigned long)current >= FIXED_CODE_START &&
+            !((unsigned long)current & 0x3) && current->pid) {
                 printk(KERN_NOTICE "CURRENT PROCESS:\n");
                 if (current->comm >= (char *)FIXED_CODE_START)
                         printk(KERN_NOTICE "COMM=%s PID=%d\n",