[Xen-changelog] [xen master] x86/compat: correct SMEP/SMAP NOPs patching

[patchbot@xxxxxxx]

commit f5610009529628314c9d1d52b00715fe855fcf06
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu May 26 17:26:24 2016 +0100
Commit:     Wei Liu <wei.liu2@xxxxxxxxxx>
CommitDate: Thu May 26 17:26:24 2016 +0100

    x86/compat: correct SMEP/SMAP NOPs patching
    
    Correct the number of single byte NOPs we want to be replaced in case
    neither SMEP nor SMAP are available.
    
    Also simplify the expression adding these NOPs - at that location .
    equals .Lcr4_orig, and removing that part of the expression fixes a
    bogus ".space or fill with negative value, ignored" warning by very old
    gas (which actually is what made me look at those constructs again).
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Wei Liu <wei.liu2@xxxxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Release-acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 xen/arch/x86/x86_64/compat/entry.S | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/x86_64/compat/entry.S 
b/xen/arch/x86/x86_64/compat/entry.S
index e7a2686..7f02afd 100644
--- a/xen/arch/x86/x86_64/compat/entry.S
+++ b/xen/arch/x86/x86_64/compat/entry.S
@@ -175,7 +175,7 @@ compat_bad_hypercall:
 ENTRY(compat_restore_all_guest)
         ASSERT_INTERRUPTS_DISABLED
 .Lcr4_orig:
-        .skip (.Lcr4_alt_end - .Lcr4_alt) - (. - .Lcr4_orig), 0x90
+        .skip .Lcr4_alt_end - .Lcr4_alt, 0x90
 .Lcr4_orig_end:
         .pushsection .altinstr_replacement, "ax"
 .Lcr4_alt:
@@ -200,7 +200,8 @@ ENTRY(compat_restore_all_guest)
         jne   1b
 .Lcr4_alt_end:
         .section .altinstructions, "a"
-        altinstruction_entry .Lcr4_orig, .Lcr4_orig, X86_FEATURE_ALWAYS, 12, 0
+        altinstruction_entry .Lcr4_orig, .Lcr4_orig, X86_FEATURE_ALWAYS, \
+                             (.Lcr4_orig_end - .Lcr4_orig), 0
         altinstruction_entry .Lcr4_orig, .Lcr4_alt, X86_FEATURE_SMEP, \
                              (.Lcr4_orig_end - .Lcr4_orig), \
                              (.Lcr4_alt_end - .Lcr4_alt)
--
generated by git-patchbot for /home/xen/git/xen.git#master

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