[Xen-changelog] [xen stable-4.2] Revert "x86/percpu: Force INVALID_PERCPU_AREA into the non-canonical address region"

[patchbot@xxxxxxx]

commit b2be780f326f7e36c844d17ad94dda2e240ca11a
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Mon Oct 28 11:03:54 2013 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Oct 28 11:03:54 2013 +0100

    Revert "x86/percpu: Force INVALID_PERCPU_AREA into the non-canonical 
address region"
    
    This reverts commit 707aec94c54127ebfda7d0f8455ecbb332ee49f0.
    It needs the 32-bit case to be taken into account.
---
 xen/arch/x86/percpu.c |    9 +--------
 1 files changed, 1 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/percpu.c b/xen/arch/x86/percpu.c
index 1c1dad9..e545024 100644
--- a/xen/arch/x86/percpu.c
+++ b/xen/arch/x86/percpu.c
@@ -6,14 +6,7 @@
 #include <xen/rcupdate.h>
 
 unsigned long __per_cpu_offset[NR_CPUS];
-
-/*
- * Force uses of per_cpu() with an invalid area to attempt to access the
- * middle of the non-canonical address space resulting in a #GP, rather than a
- * possible #PF at (NULL + a little) which has security implications in the
- * context of PV guests.
- */
-#define INVALID_PERCPU_AREA (0x8000000000000000L - (long)__per_cpu_start)
+#define INVALID_PERCPU_AREA (-(long)__per_cpu_start)
 #define PERCPU_ORDER (get_order_from_bytes(__per_cpu_data_end-__per_cpu_start))
 
 void __init percpu_init_areas(void)
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.2

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