[XenPPC] [linux-ppc-2.6] [powerpc] Use new method to detect NULL xencomm handle

[Xen patchbot-linux-ppc-2.6 <patchbot-linux-ppc-2.6@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Jimi Xenidis <jimix@xxxxxxxxxxxxxx>
# Node ID 17aa29a18b080bd96286b29e7b5918701a330eff
# Parent  e30fba67c38de4e6a769f0b57bb8613d79a23f16
[powerpc] Use new method to detect NULL xencomm handle

old method wasted cycles and could give false positive.

Signed-off-by: Jimi Xenidis <jimix@xxxxxxxxxxxxxx>
---
 arch/powerpc/platforms/xen/hcall.c |    5 +---
 drivers/xen/core/xencomm.c         |   45 +++++++++++++++++++------------------
 2 files changed, 26 insertions(+), 24 deletions(-)

diff -r e30fba67c38d -r 17aa29a18b08 arch/powerpc/platforms/xen/hcall.c
--- a/arch/powerpc/platforms/xen/hcall.c        Wed Jul 26 15:00:06 2006 -0400
+++ b/arch/powerpc/platforms/xen/hcall.c        Thu Jul 27 18:57:20 2006 -0400
@@ -93,9 +93,8 @@ int HYPERVISOR_xen_version(int cmd, void
                argsize = sizeof(xen_platform_parameters_t);
                break;
        case XENVER_pagesize:
-               argsize = sizeof(void *);
-               break;
-
+               argsize = (arg == NULL) ? 0 : sizeof(void *);
+               break;
        default:
                printk("%s: unknown version cmd %d\n", __func__, cmd);
                return -ENOSYS;
diff -r e30fba67c38d -r 17aa29a18b08 drivers/xen/core/xencomm.c
--- a/drivers/xen/core/xencomm.c        Wed Jul 26 15:00:06 2006 -0400
+++ b/drivers/xen/core/xencomm.c        Thu Jul 27 18:57:20 2006 -0400
@@ -59,33 +59,36 @@ static int __xencomm_init(struct xencomm
        unsigned long recorded = 0;
        int i = 0;
 
+       BUG_ON((buffer == NULL) && (bytes > 0));
+
        /* record the physical pages used */
-       if (buffer) {
-               while ((recorded < bytes) && (i < desc->nr_addrs)) {
-                       unsigned long vaddr = (unsigned long)buffer + recorded;
-                       unsigned long paddr;
-                       int offset;
-                       int chunksz;
+       if (buffer == NULL)
+               desc->nr_addrs = 0;
 
-                       offset = vaddr % PAGE_SIZE; /* handle partial pages */
-                       chunksz = min(PAGE_SIZE - offset, bytes - recorded);
+       while ((recorded < bytes) && (i < desc->nr_addrs)) {
+               unsigned long vaddr = (unsigned long)buffer + recorded;
+               unsigned long paddr;
+               int offset;
+               int chunksz;
 
-                       paddr = to_phys(vaddr);
-                       if (paddr == ~0UL) {
-                               printk("%s: couldn't translate vaddr %lx\n",
-                                      __func__, vaddr);
-                               return -EINVAL;
-                       }
+               offset = vaddr % PAGE_SIZE; /* handle partial pages */
+               chunksz = min(PAGE_SIZE - offset, bytes - recorded);
 
-                       desc->address[i++] = paddr;
-                       recorded += chunksz;
+               paddr = to_phys(vaddr);
+               if (paddr == ~0UL) {
+                       printk("%s: couldn't translate vaddr %lx\n",
+                              __func__, vaddr);
+                       return -EINVAL;
                }
 
-               if (recorded < bytes) {
-                       printk("%s: could only translate %ld of %ld bytes\n",
-                              __func__, recorded, bytes);
-                       return -ENOSPC;
-               }
+               desc->address[i++] = paddr;
+               recorded += chunksz;
+       }
+
+       if (recorded < bytes) {
+               printk("%s: could only translate %ld of %ld bytes\n",
+                      __func__, recorded, bytes);
+               return -ENOSPC;
        }
 
        /* mark remaining addresses invalid (just for safety) */

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