[Xen-devel] [PATCH] x86/entry: Fix passing 6th argument for compat hypercalls

[Jason Andryuk <jandryuk@xxxxxxxxx>]

Commit ec05090403ef4d760fbe701e31afd0f0edc414d5 ("x86/entry: Erase guest
GPR state on entry to Xen") zero-ed %rbp, compat arg 6, but it is not
restored before passing to hypercalls.  We need to pass the saved compat
arg 6 to the hypercall in r9, the 6th function argument.

Signed-off-by: Jason Andryuk <jandryuk@xxxxxxxxx>
---
This is against Xen 4.6.  I believe it is also applicable to 4.7.

 xen/arch/x86/x86_64/compat/entry.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/x86/x86_64/compat/entry.S 
b/xen/arch/x86/x86_64/compat/entry.S
index bc1f509672..b99b142e45 100644
--- a/xen/arch/x86/x86_64/compat/entry.S
+++ b/xen/arch/x86/x86_64/compat/entry.S
@@ -56,7 +56,7 @@ UNLIKELY_END(msi_check)
         xchgl %ecx,%esi              /* Arg 2, Arg 4 */
         movl  %edx,%edx              /* Arg 3        */
         movl  %edi,%r8d              /* Arg 5        */
-        movl  %ebp,%r9d              /* Arg 6        */
+        movl  UREGS_rbp(%rsp),%r9d   /* Arg 6        */
         movl  UREGS_rbx(%rsp),%edi   /* Arg 1        */
 #define SHADOW_BYTES 0  /* No on-stack shadow state */
 #endif
-- 
2.14.3


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