>>> 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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