Merge tag 'arc-5.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc

Pull ARC updates from Vineet Gupta:

 - long due rewrite of do_page_fault

 - refactoring of entry/exit code to utilize the double load/store
   instructions

 - hsdk platform updates

* tag 'arc-5.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc:
  ARC: [plat-hsdk]: Enable AXI DW DMAC in defconfig
  ARC: [plat-hsdk]: enable DW SPI controller
  ARC: hide unused function unw_hdr_alloc
  ARC: [haps] Add Virtio support
  ARCv2: entry: simplify return to Delay Slot via interrupt
  ARC: entry: EV_Trap expects r10 (vs. r9) to have exception cause
  ARCv2: entry: rewrite to enable use of double load/stores LDD/STD
  ARCv2: entry: avoid a branch
  ARCv2: entry: push out the Z flag unclobber from common EXCEPTION_PROLOGUE
  ARCv2: entry: comments about hardware auto-save on taken interrupts
  ARC: mm: do_page_fault refactor #8: release mmap_sem sooner
  ARC: mm: do_page_fault refactor #7: fold the various error handling
  ARC: mm: do_page_fault refactor #6: error handlers to use same pattern
  ARC: mm: do_page_fault refactor #5: scoot no_context to end
  ARC: mm: do_page_fault refactor #4: consolidate retry related logic
  ARC: mm: do_page_fault refactor #3: tidyup vma access permission code
  ARC: mm: do_page_fault refactor #2: remove short lived variable
  ARC: mm: do_page_fault refactor #1: remove label @good_area

1 files changed, 77 insertions, 108 deletions

diff --git a/arch/arc/mm/fault.c b/arch/arc/mm/fault.c
index 81e84426fe21..3861543b66a0 100644
--- a/arch/arc/mm/fault.c
+++ b/arch/arc/mm/fault.c
@@ -63,24 +63,19 @@ 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 ret;
-        vm_fault_t fault;
-        int write = regs->ecr_cause & ECR_C_PROTV_STORE;  /* ST/EX */
-        unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
+        int sig, si_code = SEGV_MAPERR;
+        unsigned int write = 0, exec = 0, mask;
+        vm_fault_t fault = VM_FAULT_SIGSEGV;    /* handle_mm_fault() output */
+        unsigned int flags;                     /* handle_mm_fault() input */
 
         /*
-         * We fault-in kernel-space virtual memory on-demand. The
-         * 'reference' page table is init_mm.pgd.
-         *
          * NOTE! We MUST NOT take any locks for this case. We may
          * be in an interrupt or a critical region, and should
          * only copy the information from the master page table,
          * nothing more.
          */
         if (address >= VMALLOC_START && !user_mode(regs)) {
-                ret = handle_kernel_vaddr_fault(address);
-                if (unlikely(ret))
+                if (unlikely(handle_kernel_vaddr_fault(address)))
                         goto no_context;
                 else
                         return;
@@ -93,143 +88,117 @@ void do_page_fault(unsigned long address, struct pt_regs *regs)
         if (faulthandler_disabled() || !mm)
                 goto no_context;
 
+        if (regs->ecr_cause & ECR_C_PROTV_STORE)        /* ST/EX */
+                write = 1;
+        else if ((regs->ecr_vec == ECR_V_PROTV) &&
+                 (regs->ecr_cause == ECR_C_PROTV_INST_FETCH))
+                exec = 1;
+
+        flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
         if (user_mode(regs))
                 flags |= FAULT_FLAG_USER;
+        if (write)
+                flags |= FAULT_FLAG_WRITE;
+
 retry:
         down_read(&mm->mmap_sem);
+
         vma = find_vma(mm, address);
         if (!vma)
                 goto bad_area;
-        if (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(address < vma->vm_start)) {
+                if (!(vma->vm_flags & VM_GROWSDOWN) || expand_stack(vma, address))
+                        goto bad_area;
+        }
 
         /*
-         * Ok, we have a good vm_area for this memory access, so
-         * we can handle it..
+         * vm_area is good, now check permissions for this memory access
          */
-good_area:
-        si_code = SEGV_ACCERR;
-
-        /* Handle protection violation, execute on heap or stack */
-
-        if ((regs->ecr_vec == ECR_V_PROTV) &&
-            (regs->ecr_cause == ECR_C_PROTV_INST_FETCH))
+        mask = VM_READ;
+        if (write)
+                mask = VM_WRITE;
+        if (exec)
+                mask = VM_EXEC;
+
+        if (!(vma->vm_flags & mask)) {
+                si_code = SEGV_ACCERR;
                 goto bad_area;
-
-        if (write) {
-                if (!(vma->vm_flags & VM_WRITE))
-                        goto bad_area;
-                flags |= FAULT_FLAG_WRITE;
-        } else {
-                if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
-                        goto bad_area;
         }
 
-        /*
-         * If for any reason at all we couldn't handle the fault,
-         * make sure we exit gracefully rather than endlessly redo
-         * the fault.
-         */
         fault = handle_mm_fault(vma, address, flags);
 
-        if (fatal_signal_pending(current)) {
+        /*
+         * Fault retry nuances
+         */
+        if (unlikely(fault & VM_FAULT_RETRY)) {
 
                 /*
-                 * if fault retry, mmap_sem already relinquished by core mm
-                 * so OK to return to user mode (with signal handled first)
+                 * If fault needs to be retried, handle any pending signals
+                 * first (by returning to user mode).
+                 * mmap_sem already relinquished by core mm for RETRY case
                  */
-                if (fault & VM_FAULT_RETRY) {
+                if (fatal_signal_pending(current)) {
                         if (!user_mode(regs))
                                 goto no_context;
                         return;
                 }
-        }
-
-        perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
-
-        if (likely(!(fault & VM_FAULT_ERROR))) {
+                /*
+                 * retry state machine
+                 */
                 if (flags & FAULT_FLAG_ALLOW_RETRY) {
-                        /* To avoid updating stats twice for retry case */
-                        if (fault & VM_FAULT_MAJOR) {
-                                tsk->maj_flt++;
-                                perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
-                                              regs, address);
-                        } else {
-                                tsk->min_flt++;
-                                perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
-                                              regs, address);
-                        }
-
-                        if (fault & VM_FAULT_RETRY) {
-                                flags &= ~FAULT_FLAG_ALLOW_RETRY;
-                                flags |= FAULT_FLAG_TRIED;
-                                goto retry;
-                        }
+                        flags &= ~FAULT_FLAG_ALLOW_RETRY;
+                        flags |= FAULT_FLAG_TRIED;
+                        goto retry;
                 }
-
-                /* Fault Handled Gracefully */
-                up_read(&mm->mmap_sem);
-                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();
+bad_area:
+        up_read(&mm->mmap_sem);
 
         /*
-         * Something tried to access memory that isn't in our memory map..
-         * Fix it, but check if it's kernel or user first..
+         * Major/minor page fault accounting
+         * (in case of retry we only land here once)
          */
-bad_area:
-        up_read(&mm->mmap_sem);
+        perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 
-        /* User mode accesses just cause a SIGSEGV */
-        if (user_mode(regs)) {
-                tsk->thread.fault_address = address;
-                force_sig_fault(SIGSEGV, si_code, (void __user *)address);
-                return;
-        }
+        if (likely(!(fault & VM_FAULT_ERROR))) {
+                if (fault & VM_FAULT_MAJOR) {
+                        tsk->maj_flt++;
+                        perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
+                                      regs, address);
+                } else {
+                        tsk->min_flt++;
+                        perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
+                                      regs, address);
+                }
 
-no_context:
-        /* Are we prepared to handle this kernel fault?
-         *
-         * (The kernel has valid exception-points in the source
-         *  when it accesses user-memory. When it fails in one
-         *  of those points, we find it in a table and do a jump
-         *  to some fixup code that loads an appropriate error
-         *  code)
-         */
-        if (fixup_exception(regs))
+                /* Normal return path: fault Handled Gracefully */
                 return;
+        }
 
-        die("Oops", regs, address);
-
-out_of_memory:
-        up_read(&mm->mmap_sem);
+        if (!user_mode(regs))
+                goto no_context;
 
-        if (user_mode(regs)) {
+        if (fault & VM_FAULT_OOM) {
                 pagefault_out_of_memory();
                 return;
         }
 
-        goto no_context;
+        if (fault & VM_FAULT_SIGBUS) {
+                sig = SIGBUS;
+                si_code = BUS_ADRERR;
+        }
+        else {
+                sig = SIGSEGV;
+        }
 
-do_sigbus:
-        up_read(&mm->mmap_sem);
+        tsk->thread.fault_address = address;
+        force_sig_fault(sig, si_code, (void __user *)address);
+        return;
 
-        if (!user_mode(regs))
-                goto no_context;
+no_context:
+        if (fixup_exception(regs))
+                return;
 
-        tsk->thread.fault_address = address;
-        force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
+        die("Oops", regs, address);
 }