[SPARC64]: Top-down address space allocation for 32-bit tasks.

Currently allocations are very constrained for 32-bit processes.
It grows down-up from 0x70000000 to 0xf0000000 which gives about
2GB of stack + dynamic mmap() space.

So support the top-down method, and we need to override the
generic helper function in order to deal with D-cache coloring.

With these changes I was able to squeeze out a mmap() just over
3.6GB in size in a 32-bit process.

Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 6 insertions, 1 deletions

diff --git a/include/asm-sparc64/pgtable.h b/include/asm-sparc64/pgtable.h
index d427ce649214..ed4124edf837 100644
--- a/include/asm-sparc64/pgtable.h
+++ b/include/asm-sparc64/pgtable.h
@@ -752,8 +752,11 @@ extern int io_remap_pfn_range(struct vm_area_struct *vma, unsigned long from,
 
 #include <asm-generic/pgtable.h>
 
-/* We provide our own get_unmapped_area to cope with VA holes for userland */
+/* We provide our own get_unmapped_area to cope with VA holes and
+ * SHM area cache aliasing for userland.
+ */
 #define HAVE_ARCH_UNMAPPED_AREA
+#define HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
 
 /* We provide a special get_unmapped_area for framebuffer mmaps to try and use
  * the largest alignment possible such that larget PTEs can be used.
diff --git a/include/asm-sparc64/processor.h b/include/asm-sparc64/processor.h
index 685479fb4364..c6896b88283e 100644
--- a/include/asm-sparc64/processor.h
+++ b/include/asm-sparc64/processor.h
@@ -217,6 +217,8 @@ static inline void prefetchw(const void *x)
 
 #define spin_lock_prefetch(x)   prefetchw(x)
 
+#define HAVE_ARCH_PICK_MMAP_LAYOUT
+
 #endif /* !(__ASSEMBLY__) */
 
 #endif /* !(__ASM_SPARC64_PROCESSOR_H) */