powerpc/mm: Rework mm_fault_error()

First, handle the normal retry failure in do_page_fault itself,
since it's a simple return statement. That allows us to remove
the "continue" special return code from mm_fault_error().

Once that's done, we can have an implementation much closer to
x86 where we only call mm_fault_error() if VM_FAULT_ERROR is set
and directly return.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 3903b55fccf89fba2f25fbc633a66972236991d0..0b217947d34fe0b11c4e72865602062cae32d504 100644 (file)
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -147,10 +147,6 @@ static noinline int bad_area(struct pt_regs *regs, unsigned long address)
        return __bad_area(regs, address, SEGV_MAPERR);
 }
 
-#define MM_FAULT_RETURN                0
-#define MM_FAULT_CONTINUE      -1
-#define MM_FAULT_ERR(sig)      (sig)
-
 static int do_sigbus(struct pt_regs *regs, unsigned long address,
                     unsigned int fault)
 {
@@ -158,7 +154,7 @@ static int do_sigbus(struct pt_regs *regs, unsigned long address,
        unsigned int lsb = 0;
 
        if (!user_mode(regs))
-               return MM_FAULT_ERR(SIGBUS);
+               return SIGBUS;
 
        current->thread.trap_nr = BUS_ADRERR;
        info.si_signo = SIGBUS;
@@ -179,25 +175,17 @@ static int do_sigbus(struct pt_regs *regs, unsigned long address,
 #endif
        info.si_addr_lsb = lsb;
        force_sig_info(SIGBUS, &info, current);
-       return MM_FAULT_RETURN;
+       return 0;
 }
 
 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.
+        * Kernel page fault interrupted by SIGKILL. We have no reason to
+        * continue processing.
         */
-       if (fatal_signal_pending(current)) {
-               /* 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;
+       if (fatal_signal_pending(current) && !user_mode(regs))
+               return SIGKILL;
 
        /* Out of memory */
        if (fault & VM_FAULT_OOM) {
@@ -206,17 +194,18 @@ static int mm_fault_error(struct pt_regs *regs, unsigned long addr, int fault)
                 * made us unable to handle the page fault gracefully.
                 */
                if (!user_mode(regs))
-                       return MM_FAULT_ERR(SIGKILL);
+                       return SIGSEGV;
                pagefault_out_of_memory();
-               return MM_FAULT_RETURN;
+       } else {
+               if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
+                            VM_FAULT_HWPOISON_LARGE))
+                       return do_sigbus(regs, addr, fault);
+               else if (fault & VM_FAULT_SIGSEGV)
+                       return bad_area_nosemaphore(regs, addr);
+               else
+                       BUG();
        }
-
-       if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE))
-               return do_sigbus(regs, addr, fault);
-
-       /* We don't understand the fault code, this is fatal */
-       BUG();
-       return MM_FAULT_CONTINUE;
+       return 0;
 }
 
 /* Is this a bad kernel fault ? */
@@ -274,7 +263,7 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address,
        int is_user = user_mode(regs);
        int is_write = page_fault_is_write(error_code);
        int fault;
-       int rc = 0, store_update_sp = 0;
+       int store_update_sp = 0;
 
 #ifdef CONFIG_PPC_ICSWX
        /*
@@ -283,7 +272,7 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address,
         * look at it
         */
        if (error_code & ICSWX_DSI_UCT) {
-               rc = acop_handle_fault(regs, address, error_code);
+               int rc = acop_handle_fault(regs, address, error_code);
                if (rc)
                        return rc;
        }
@@ -492,18 +481,19 @@ good_area:
                        if (!fatal_signal_pending(current))
                                goto retry;
                }
-               /* We will enter mm_fault_error() below */
-       } else
-               up_read(&current->mm->mmap_sem);
 
-       if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
-               if (fault & VM_FAULT_SIGSEGV)
-                       return bad_area_nosemaphore(regs, address);
-               rc = mm_fault_error(regs, address, fault);
-               if (rc >= MM_FAULT_RETURN)
-                       return rc;
+               /*
+                * User mode? Just return to handle the fatal exception otherwise
+                * return to bad_page_fault
+                */
+               return is_user ? 0 : SIGBUS;
        }
 
+       up_read(&current->mm->mmap_sem);
+
+       if (unlikely(fault & VM_FAULT_ERROR))
+               return mm_fault_error(regs, address, fault);
+
        /*
         * Major/minor page fault accounting.
         */