diff options
| author | Jan Beulich <JBeulich@novell.com> | 2011-08-16 15:07:41 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2011-08-29 13:29:12 -0700 |
| commit | 1561007953be5267725fca1223d79b133e48113a (patch) | |
| tree | 9beaca02a00fa2ee45b815558229c7bb810012e2 /arch/x86/xen/enlighten.c | |
| parent | b3120702bfb40e3689c2a6ae3944d9886201b753 (diff) | |
xen/x86: replace order-based range checking of M2P table by linear one
commit ccbcdf7cf1b5f6c6db30d84095b9c6c53043af55 upstream.
The order-based approach is not only less efficient (requiring a shift
and a compare, typical generated code looking like this
mov eax, [machine_to_phys_order]
mov ecx, eax
shr ebx, cl
test ebx, ebx
jnz ...
whereas a direct check requires just a compare, like in
cmp ebx, [machine_to_phys_nr]
jae ...
), but also slightly dangerous in the 32-on-64 case - the element
address calculation can wrap if the next power of two boundary is
sufficiently far away from the actual upper limit of the table, and
hence can result in user space addresses being accessed (with it being
unknown what may actually be mapped there).
Additionally, the elimination of the mistaken use of fls() here (should
have been __fls()) fixes a latent issue on x86-64 that would trigger
if the code was run on a system with memory extending beyond the 44-bit
boundary.
Signed-off-by: Jan Beulich <jbeulich@novell.com>
[v1: Based on Jeremy's feedback]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'arch/x86/xen/enlighten.c')
| -rw-r--r-- | arch/x86/xen/enlighten.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index 53257421082b..67d69f1e2b73 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -77,8 +77,8 @@ EXPORT_SYMBOL_GPL(xen_domain_type); unsigned long *machine_to_phys_mapping = (void *)MACH2PHYS_VIRT_START; EXPORT_SYMBOL(machine_to_phys_mapping); -unsigned int machine_to_phys_order; -EXPORT_SYMBOL(machine_to_phys_order); +unsigned long machine_to_phys_nr; +EXPORT_SYMBOL(machine_to_phys_nr); struct start_info *xen_start_info; EXPORT_SYMBOL_GPL(xen_start_info); |