domain builder: Fix sp_extents allocation

domain builder: Fix sp_extents allocation

We do not need more than count elements in the sp_extents array.

diff -r e355f9dce939 tools/libxc/xc_hvm_build.c

tools/libxc/xc_hvm_build.c Thu Jul 31 11:43:36 2008 +0100 renamed from tools/libxc/xc_hvm_build.c Wed Jul 30 17:20:25 2008 +0100 +1 -1

@@ -229,7 +229,7 @@ static int setup_guest(int xc_handle,
         if ( ((count | cur_pages) & (SUPERPAGE_NR_PFNS - 1)) == 0 )
         {
             long done;
-            xen_pfn_t sp_extents[2048 >> SUPERPAGE_PFN_SHIFT];
+            xen_pfn_t sp_extents[count >> SUPERPAGE_PFN_SHIFT];
             struct xen_memory_reservation sp_req = {
                 .nr_extents   = count >> SUPERPAGE_PFN_SHIFT,
                 .extent_order = SUPERPAGE_PFN_SHIFT,

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Doesn't this turn the array allocation into a dynamic allocation? I feel a bit dubious about that.

Quoted 5 lines

         {
             long done;

tools/libxc/xc_hvm_build.c +1 -1

-            xen_pfn_t sp_extents[2048 >> SUPERPAGE_PFN_SHIFT];
+            xen_pfn_t sp_extents[count >> SUPERPAGE_PFN_SHIFT];
             struct xen_memory_reservation sp_req = {

Quoted 8 lines · Keir Fraser, le Thu 31 Jul 2008 12:19:18 +0100, a écrit :

Doesn't this turn the array allocation into a dynamic allocation? I feel a bit dubious about that.

Quoted 5 lines

         {
             long done;

tools/libxc/xc_hvm_build.c +1 -1

-            xen_pfn_t sp_extents[2048 >> SUPERPAGE_PFN_SHIFT];
+            xen_pfn_t sp_extents[count >> SUPERPAGE_PFN_SHIFT];
             struct xen_memory_reservation sp_req = {

Err, I'd think that it just turns a

sub (2048>>SUPERPAGE_PFN_SHIFT) * sizeof(xen_pfn_t), %esp

into a

mov count, %eax
shr SUPERPAGE_PFN_SHIFT - log2(sizeof(xen_pfn_t)), %eax sub %eax, %esp