[PATCH] 32on64 fixes (was Re: [Xen-devel] unmodified_drivers/linux-2.6/overrides.mk)

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

>>> Keir Fraser <keir@xxxxxxxxxxxxx> 24.01.07 16:58 >>>
>A quick question: how do we ensure that pointers ('guest handles') passed in
>a register to a hypercall have the high 32 bits cleared for a 32-bit-compat
>guest? I don't think the architecture guarantees anything about the upper 32
>bits of any register when running with CS.L==0, and I don't see anything
>that zaps those upper bits, or ignores them, for e.g., do_event_channel_op()
>(which isn't compat-ified).

Here is the promised patch, including two more fixes to the 32on64 additions.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

Index: 2007-01-08/xen/arch/x86/traps.c
===================================================================
--- 2007-01-08.orig/xen/arch/x86/traps.c        2007-01-25 10:37:39.000000000 
+0100
+++ 2007-01-08/xen/arch/x86/traps.c     2007-01-25 10:39:11.000000000 +0100
@@ -1146,7 +1146,9 @@ static int emulate_privileged_op(struct 
         goto fail;
     op_default = op_bytes = (ar & (_SEGMENT_L|_SEGMENT_DB)) ? 4 : 2;
     ad_default = ad_bytes = (ar & _SEGMENT_L) ? 8 : op_default;
-    if ( !(ar & (_SEGMENT_CODE|_SEGMENT_S|_SEGMENT_P)) )
+    if ( !(ar & _SEGMENT_S) ||
+         !(ar & _SEGMENT_P) ||
+         !(ar & _SEGMENT_CODE) )
         goto fail;
 
     /* emulating only opcodes not allowing SS to be default */
@@ -1234,7 +1236,8 @@ static int emulate_privileged_op(struct 
                                   &data_base, &data_limit, &ar,
                                   
_SEGMENT_WR|_SEGMENT_S|_SEGMENT_DPL|_SEGMENT_P) )
                 goto fail;
-            if ( !(ar & (_SEGMENT_S|_SEGMENT_P)) ||
+            if ( !(ar & _SEGMENT_S) ||
+                 !(ar & _SEGMENT_P) ||
                  (opcode & 2 ?
                   (ar & _SEGMENT_CODE) && !(ar & _SEGMENT_WR) :
                   (ar & _SEGMENT_CODE) || !(ar & _SEGMENT_WR)) )
Index: 2007-01-08/xen/arch/x86/x86_64/compat/entry.S
===================================================================
--- 2007-01-08.orig/xen/arch/x86/x86_64/compat/entry.S  2006-12-15 
15:39:13.000000000 +0100
+++ 2007-01-08/xen/arch/x86/x86_64/compat/entry.S       2007-01-25 
10:42:27.000000000 +0100
@@ -23,7 +23,9 @@ ENTRY(compat_hypercall)
         movq  %rsp,%rdi
         movl  $0xDEADBEEF,%eax
         rep   stosq
-        popq  %r9 ; popq  %r8 ; popq  %rcx; popq  %rdx; popq  %rsi; popq  %rdi
+        popq  %r8 ; popq  %r9 ; xchgl %r8d,%r9d
+        popq  %rdx; popq  %rcx; xchgl %edx,%ecx
+        popq  %rdi; popq  %rsi; xchgl %edi,%esi
         movl  UREGS_rax(%rsp),%eax
         pushq %rax
         pushq UREGS_rip+8(%rsp)
@@ -31,8 +33,9 @@ ENTRY(compat_hypercall)
         movl  %eax,%eax
         movl  %ebp,%r9d
         movl  %edi,%r8d
-        xchgl  %ecx,%esi
+        xchgl %ecx,%esi
         movl  UREGS_rbx(%rsp),%edi
+        movl  %edx,%edx
 #endif
         leaq  compat_hypercall_table(%rip),%r10
         PERFC_INCR(PERFC_hypercalls, %rax)


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