[PATCH] powerpc: Make hugepage mappings respect hint addresses

Currently, the powerpc version of hugetlb_get_unmapped_area() entirely
ignores the hint address.  The only way to get a hugepage mapping at a
specified address is with MAP_FIXED, in which case there's no way
(short of parsing /proc/self/maps) for userspace to tell if it will
clobber an existing mapping.  This is inconvenient, so the patch below
makes hugepage mappings use the given hint address if possible.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 39 insertions, 4 deletions

diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index 54131b877da3..f6fe3eaf87a3 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -549,6 +549,17 @@ fail:
         return addr;
 }
 
+static int htlb_check_hinted_area(unsigned long addr, unsigned long len)
+{
+        struct vm_area_struct *vma;
+
+        vma = find_vma(current->mm, addr);
+        if (!vma || ((addr + len) <= vma->vm_start))
+                return 0;
+
+        return -ENOMEM;
+}
+
 static unsigned long htlb_get_low_area(unsigned long len, u16 segmask)
 {
         unsigned long addr = 0;
@@ -609,6 +620,7 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
 {
         int lastshift;
         u16 areamask, curareas;
+        struct vm_area_struct *vma;
 
         if (HPAGE_SHIFT == 0)
                 return -EINVAL;
@@ -618,15 +630,28 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
         if (!cpu_has_feature(CPU_FTR_16M_PAGE))
                 return -EINVAL;
 
+        /* Paranoia, caller should have dealt with this */
+        BUG_ON((addr + len)  < addr);
+
         if (test_thread_flag(TIF_32BIT)) {
+                /* Paranoia, caller should have dealt with this */
+                BUG_ON((addr + len) > 0x100000000UL);
+
                 curareas = current->mm->context.low_htlb_areas;
 
-                /* First see if we can do the mapping in the existing
-                 * low areas */
+                /* First see if we can use the hint address */
+                if (addr && (htlb_check_hinted_area(addr, len) == 0)) {
+                        areamask = LOW_ESID_MASK(addr, len);
+                        if (open_low_hpage_areas(current->mm, areamask) == 0)
+                                return addr;
+                }
+
+                /* Next see if we can map in the existing low areas */
                 addr = htlb_get_low_area(len, curareas);
                 if (addr != -ENOMEM)
                         return addr;
 
+                /* Finally go looking for areas to open */
                 lastshift = 0;
                 for (areamask = LOW_ESID_MASK(0x100000000UL-len, len);
                      ! lastshift; areamask >>=1) {
@@ -641,12 +666,22 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
         } else {
                 curareas = current->mm->context.high_htlb_areas;
 
-                /* First see if we can do the mapping in the existing
-                 * high areas */
+                /* First see if we can use the hint address */
+                /* We discourage 64-bit processes from doing hugepage
+                 * mappings below 4GB (must use MAP_FIXED) */
+                if ((addr >= 0x100000000UL)
+                    && (htlb_check_hinted_area(addr, len) == 0)) {
+                        areamask = HTLB_AREA_MASK(addr, len);
+                        if (open_high_hpage_areas(current->mm, areamask) == 0)
+                                return addr;
+                }
+
+                /* Next see if we can map in the existing high areas */
                 addr = htlb_get_high_area(len, curareas);
                 if (addr != -ENOMEM)
                         return addr;
 
+                /* Finally go looking for areas to open */
                 lastshift = 0;
                 for (areamask = HTLB_AREA_MASK(TASK_SIZE_USER64-len, len);
                      ! lastshift; areamask >>=1) {