VServer 1.9.2 (patch-2.6.8.1-vs1.9.2.diff)

[linux-2.6.git] / arch / ppc64 / mm / fault.c

diff --git a/arch/ppc64/mm/fault.c b/arch/ppc64/mm/fault.c
index ca2b86d..b78e7f4 100644 (file)
--- a/arch/ppc64/mm/fault.c
+++ b/arch/ppc64/mm/fault.c
@@ -80,37 +80,69 @@ static int store_updates_sp(struct pt_regs *regs)
  *  - DSISR for a non-SLB data access fault,
  *  - SRR1 & 0x08000000 for a non-SLB instruction access fault
  *  - 0 any SLB fault.
+ * The return value is 0 if the fault was handled, or the signal
+ * number if this is a kernel fault that can't be handled here.
  */
-void do_page_fault(struct pt_regs *regs, unsigned long address,
-                  unsigned long error_code)
+int do_page_fault(struct pt_regs *regs, unsigned long address,
+                 unsigned long error_code)
 {
        struct vm_area_struct * vma;
        struct mm_struct *mm = current->mm;
        siginfo_t info;
        unsigned long code = SEGV_MAPERR;
        unsigned long is_write = error_code & 0x02000000;
+       unsigned long trap = TRAP(regs);
 
-       if (regs->trap == 0x300 || regs->trap == 0x380) {
+       BUG_ON((trap == 0x380) || (trap == 0x480));
+
+       if (trap == 0x300) {
                if (debugger_fault_handler(regs))
-                       return;
+                       return 0;
        }
 
        /* On a kernel SLB miss we can only check for a valid exception entry */
-       if (!user_mode(regs) && (regs->trap == 0x380)) {
-               bad_page_fault(regs, address, SIGSEGV);
-               return;
-       }
+       if (!user_mode(regs) && (address >= TASK_SIZE))
+               return SIGSEGV;
 
        if (error_code & 0x00400000) {
                if (debugger_dabr_match(regs))
-                       return;
+                       return 0;
        }
 
        if (in_atomic() || mm == NULL) {
-               bad_page_fault(regs, address, SIGSEGV);
-               return;
+               if (!user_mode(regs))
+                       return SIGSEGV;
+               /* in_atomic() in user mode is really bad,
+                  as is current->mm == NULL. */
+               printk(KERN_EMERG "Page fault in user mode with"
+                      "in_atomic() = %d mm = %p\n", in_atomic(), mm);
+               printk(KERN_EMERG "NIP = %lx  MSR = %lx\n",
+                      regs->nip, regs->msr);
+               die("Weird page fault", regs, SIGSEGV);
+       }
+
+       /* When running in the kernel we expect faults to occur only to
+        * addresses in user space.  All other faults represent errors in the
+        * kernel and should generate an OOPS.  Unfortunatly, in the case of an
+        * erroneous fault occuring in a code path which already holds mmap_sem
+        * we will deadlock attempting to validate the fault against the
+        * address space.  Luckily the kernel only validly references user
+        * space from well defined areas of code, which are listed in the
+        * exceptions table.
+        *
+        * As the vast majority of faults will be valid we will only perform
+        * the source reference check when there is a possibilty of a deadlock.
+        * Attempt to lock the address space, if we cannot we then validate the
+        * source.  If this is invalid we can skip the address space check,
+        * thus avoiding the deadlock.
+        */
+       if (!down_read_trylock(&mm->mmap_sem)) {
+               if (!user_mode(regs) && !search_exception_tables(regs->nip))
+                       goto bad_area_nosemaphore;
+
+               down_read(&mm->mmap_sem);
        }
-       down_read(&mm->mmap_sem);
+
        vma = find_vma(mm, address);
        if (!vma)
                goto bad_area;
@@ -195,23 +227,23 @@ good_area:
        }
 
        up_read(&mm->mmap_sem);
-       return;
+       return 0;
 
 bad_area:
        up_read(&mm->mmap_sem);
 
+bad_area_nosemaphore:
        /* User mode accesses cause a SIGSEGV */
        if (user_mode(regs)) {
                info.si_signo = SIGSEGV;
                info.si_errno = 0;
                info.si_code = code;
-               info.si_addr = (void *) address;
+               info.si_addr = (void __user *) address;
                force_sig_info(SIGSEGV, &info, current);
-               return;
+               return 0;
        }
 
-       bad_page_fault(regs, address, SIGSEGV);
-       return;
+       return SIGSEGV;
 
 /*
  * We ran out of memory, or some other thing happened to us that made
@@ -227,18 +259,19 @@ out_of_memory:
        printk("VM: killing process %s\n", current->comm);
        if (user_mode(regs))
                do_exit(SIGKILL);
-       bad_page_fault(regs, address, SIGKILL);
-       return;
+       return SIGKILL;
 
 do_sigbus:
        up_read(&mm->mmap_sem);
-       info.si_signo = SIGBUS;
-       info.si_errno = 0;
-       info.si_code = BUS_ADRERR;
-       info.si_addr = (void *)address;
-       force_sig_info (SIGBUS, &info, current);
-       if (!user_mode(regs))
-               bad_page_fault(regs, address, SIGBUS);
+       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;
 }
 
 /*