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authorRusty Russell <rusty@rustcorp.com.au>2008-03-11 09:35:56 -0500
committerRusty Russell <rusty@rustcorp.com.au>2008-03-11 09:35:56 +1100
commitf14ae652baa3d72ae378f0c06b89cc2c4ef15ff8 (patch)
tree65dfe2b310103bd6f2c981de2e1d0faecd05805c /drivers/lguest
parentf73d1e6ca6985b43a1871467463cba632fbc624d (diff)
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lguest: fix __get_vm_area usage.
Robert Bragg's 5dc331852848a38ca00a2817e5b98a1d0561b116 tightened (ie. fixed) the checking in __get_vm_area, and it broke lguest. lguest should pass the exact "end" it wants, not some random constant (it was possible previously that it would actually get an address different from SWITCHER_ADDR). Also, Fabio Checconi pointed out that we should make sure we're not hitting the fixmap area. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Cc: Robert Bragg <robert@sixbynine.org>
Diffstat (limited to 'drivers/lguest')
-rw-r--r--drivers/lguest/core.c15
1 files changed, 13 insertions, 2 deletions
diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c
index 7743d73..c632c08 100644
--- a/drivers/lguest/core.c
+++ b/drivers/lguest/core.c
@@ -69,11 +69,22 @@ static __init int map_switcher(void)
switcher_page[i] = virt_to_page(addr);
}
+ /* First we check that the Switcher won't overlap the fixmap area at
+ * the top of memory. It's currently nowhere near, but it could have
+ * very strange effects if it ever happened. */
+ if (SWITCHER_ADDR + (TOTAL_SWITCHER_PAGES+1)*PAGE_SIZE > FIXADDR_START){
+ err = -ENOMEM;
+ printk("lguest: mapping switcher would thwack fixmap\n");
+ goto free_pages;
+ }
+
/* Now we reserve the "virtual memory area" we want: 0xFFC00000
* (SWITCHER_ADDR). We might not get it in theory, but in practice
- * it's worked so far. */
+ * it's worked so far. The end address needs +1 because __get_vm_area
+ * allocates an extra guard page, so we need space for that. */
switcher_vma = __get_vm_area(TOTAL_SWITCHER_PAGES * PAGE_SIZE,
- VM_ALLOC, SWITCHER_ADDR, VMALLOC_END);
+ VM_ALLOC, SWITCHER_ADDR, SWITCHER_ADDR
+ + (TOTAL_SWITCHER_PAGES+1) * PAGE_SIZE);
if (!switcher_vma) {
err = -ENOMEM;
printk("lguest: could not map switcher pages high\n");