ARC: mm: preps ahead of HIGHMEM support

Before we plug in highmem support, some of code needs to be ready for it
 - copy_user_highpage() needs to be using the kmap_atomic API
 - mk_pte() can't assume page_address()
 - do_page_fault() can't assume VMALLOC_END is end of kernel vaddr space

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

1 files changed, 10 insertions, 3 deletions

diff --git a/arch/arc/mm/fault.c b/arch/arc/mm/fault.c
index d948e4e9d89c..af63f4a13e60 100644
--- a/arch/arc/mm/fault.c
+++ b/arch/arc/mm/fault.c
@@ -18,7 +18,14 @@
 #include <asm/pgalloc.h>
 #include <asm/mmu.h>
 
-static int handle_vmalloc_fault(unsigned long address)
+/*
+ * kernel virtual address is required to implement vmalloc/pkmap/fixmap
+ * Refer to asm/processor.h for System Memory Map
+ *
+ * It simply copies the PMD entry (pointer to 2nd level page table or hugepage)
+ * from swapper pgdir to task pgdir. The 2nd level table/page is thus shared
+ */
+noinline static int handle_kernel_vaddr_fault(unsigned long address)
 {
         /*
          * Synchronize this task's top level page-table
@@ -72,8 +79,8 @@ void do_page_fault(unsigned long address, struct pt_regs *regs)
          * only copy the information from the master page table,
          * nothing more.
          */
-        if (address >= VMALLOC_START && address <= VMALLOC_END) {
-                ret = handle_vmalloc_fault(address);
+        if (address >= VMALLOC_START) {
+                ret = handle_kernel_vaddr_fault(address);
                 if (unlikely(ret))
                         goto bad_area_nosemaphore;
                 else