ARC: mm: do_page_fault refactor #7: fold the various error handling

 - single up_read() call vs. 4
 - so much easier on eyes

Technically it seems like @bad_area label moved up, but even in old
regime, it was a special case of delivering SIGSEGV unconditionally
which we now do as well, although with checks.

Also note that @fault needs to be initialized since we can land in
@bad_area (which reads it) without setting it up with return value of
handle_mm_fault() - failing to do so did bite us although as a side
effect of different patch: see [1]

[1]: http://lists.infradead.org/pipermail/linux-snps-arc/2019-May/005803.html

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

diff --git a/arch/arc/mm/fault.c b/arch/arc/mm/fault.c
index 2672ce2..6a78a2d 100644 (file)
--- a/arch/arc/mm/fault.c
+++ b/arch/arc/mm/fault.c
@@ -63,9 +63,9 @@ void do_page_fault(unsigned long address, struct pt_regs *regs)
        struct vm_area_struct *vma = NULL;
        struct task_struct *tsk = current;
        struct mm_struct *mm = tsk->mm;
-       int si_code = SEGV_MAPERR;
+       int sig, si_code = SEGV_MAPERR;
        unsigned int write = 0, exec = 0, mask;
-       vm_fault_t fault;                       /* handle_mm_fault() output */
+       vm_fault_t fault = VM_FAULT_SIGSEGV;    /* handle_mm_fault() output */
        unsigned int flags;                     /* handle_mm_fault() input */
 
        /*
@@ -174,47 +174,27 @@ retry:
                return;
        }
 
-       if (fault & VM_FAULT_OOM)
-               goto out_of_memory;
-       else if (fault & VM_FAULT_SIGSEGV)
-               goto bad_area;
-       else if (fault & VM_FAULT_SIGBUS)
-               goto do_sigbus;
-
-       /* no man's land */
-       BUG();
-
-       /*
-        * 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);
 
        if (!user_mode(regs))
                goto no_context;
 
-       tsk->thread.fault_address = address;
-       force_sig_fault(SIGSEGV, si_code, (void __user *)address, tsk);
-       return;
-
-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);
+       if (fault & VM_FAULT_OOM) {
+               pagefault_out_of_memory();
+               return;
+       }
 
-       if (!user_mode(regs))
-               goto no_context;
+       if (fault & VM_FAULT_SIGBUS) {
+               sig = SIGBUS;
+               si_code = BUS_ADRERR;
+       }
+       else {
+               sig = SIGSEGV;
+       }
 
        tsk->thread.fault_address = address;
-       force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address, tsk);
+       force_sig_fault(sig, si_code, (void __user *)address, tsk);
        return;
 
 no_context: