Re: [Xen-devel] [PATCH v3 09/24] x86/emul: Provide a wrapper to x86_emulate() to ASSERT() certain behaviour

[Jan Beulich]

>>> On 01.12.16 at 11:58,  wrote:
> On 01/12/16 10:40, Jan Beulich wrote:
>>
>>> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
>>> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
>>> @@ -2404,6 +2404,11 @@ x86_decode(
>>>  #undef insn_fetch_bytes
>>>  #undef insn_fetch_type
>>>  
>>> +/* Undo DEBUG wrapper. */
>>> +#ifdef x86_emulate
>>> +#undef x86_emulate
>>> +#endif
>> I don't see the need for the #ifdef here.
> 
> It will break the non-debug build if removed, as x86_emulate wouldn't be
> a define.

#undef for something that isn't a #define is well defined to do
nothing.

Jan


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Re: [Xen-devel] [PATCH v3 09/24] x86/emul: Provide a wrapper to x86_emulate() to ASSERT() certain behaviour

[Andrew Cooper]

On 01/12/16 10:40, Jan Beulich wrote:
>
>> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
>> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
>> @@ -2404,6 +2404,11 @@ x86_decode(
>>  #undef insn_fetch_bytes
>>  #undef insn_fetch_type
>>  
>> +/* Undo DEBUG wrapper. */
>> +#ifdef x86_emulate
>> +#undef x86_emulate
>> +#endif
> I don't see the need for the #ifdef here.

It will break the non-debug build if removed, as x86_emulate wouldn't be
a define.

>
>> --- a/xen/arch/x86/x86_emulate/x86_emulate.h
>> +++ b/xen/arch/x86/x86_emulate/x86_emulate.h
>> @@ -23,6 +23,10 @@
>>  #ifndef __X86_EMULATE_H__
>>  #define __X86_EMULATE_H__
>>  
>> +#ifndef ASSERT
>> +#define ASSERT assert
>> +#endif
> This doesn't seem to belong here (as there's nothing making sure
> assert is defined), and duplicates an existing #define in the test
> harness'es x86_emulate.c. I could agree to deleting that other one
> and wrapping the one here with #ifndef __XEN__.

Ok.

>
>> @@ -554,6 +558,27 @@ x86_emulate(
>>  const struct x86_emulate_ops *ops);
>>  
>>  /*
>> + * In debug builds, wrap x86_emulate() with some assertions about its 
>> expected
>> + * behaviour.
>> + */
>> +#ifndef NDEBUG
> Mind swapping the order of comment and #ifndef, to make it more
> reasonable to possibly add further things into this guarded block?

Ok.

~Andrew

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Re: [Xen-devel] [PATCH v3 09/24] x86/emul: Provide a wrapper to x86_emulate() to ASSERT() certain behaviour

[Jan Beulich]

>>> On 30.11.16 at 14:50,  wrote:
> In debug builds, confirm that some properties of x86_emulate()'s behaviour
> actually hold.  The first property, fixed in a previous change, is that retire
> flags are only ever set in the X86EMUL_OKAY case.
> 
> While adjusting the userspace test harness to cope with ASSERT() in
> x86_emulate.h, fix a build problem introduced in c/s 122dd9575c7 "x86emul:
> in_longmode() should not ignore ->read_msr() errors" by providing an
> implementation of likely()/unlikely().

Oh, I'm sorry for that one. When moving that patch ahead of about
50 other ones touching the emulator, I didn't notice I should have
pulled that addition out from another patch.

> --- a/tools/tests/x86_emulator/x86_emulate.c
> +++ b/tools/tests/x86_emulator/x86_emulate.c
> @@ -50,4 +50,7 @@ typedef bool bool_t;
>  #define __init
>  #define __maybe_unused __attribute__((__unused__))
>  
> +#define likely(x) __builtin_expect(!!(x),1)
> +#define unlikely(x)   __builtin_expect(!!(x),0)

Please use true/false here and add blanks after the commas.

> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
> @@ -2404,6 +2404,11 @@ x86_decode(
>  #undef insn_fetch_bytes
>  #undef insn_fetch_type
>  
> +/* Undo DEBUG wrapper. */
> +#ifdef x86_emulate
> +#undef x86_emulate
> +#endif

I don't see the need for the #ifdef here.

> --- a/xen/arch/x86/x86_emulate/x86_emulate.h
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.h
> @@ -23,6 +23,10 @@
>  #ifndef __X86_EMULATE_H__
>  #define __X86_EMULATE_H__
>  
> +#ifndef ASSERT
> +#define ASSERT assert
> +#endif

This doesn't seem to belong here (as there's nothing making sure
assert is defined), and duplicates an existing #define in the test
harness'es x86_emulate.c. I could agree to deleting that other one
and wrapping the one here with #ifndef __XEN__.

> @@ -554,6 +558,27 @@ x86_emulate(
>  const struct x86_emulate_ops *ops);
>  
>  /*
> + * In debug builds, wrap x86_emulate() with some assertions about its 
> expected
> + * behaviour.
> + */
> +#ifndef NDEBUG

Mind swapping the order of comment and #ifndef, to make it more
reasonable to possibly add further things into this guarded block?

Jan


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[Xen-devel] [PATCH v3 09/24] x86/emul: Provide a wrapper to x86_emulate() to ASSERT() certain behaviour

[Andrew Cooper]

In debug builds, confirm that some properties of x86_emulate()'s behaviour
actually hold.  The first property, fixed in a previous change, is that retire
flags are only ever set in the X86EMUL_OKAY case.

While adjusting the userspace test harness to cope with ASSERT() in
x86_emulate.h, fix a build problem introduced in c/s 122dd9575c7 "x86emul:
in_longmode() should not ignore ->read_msr() errors" by providing an
implementation of likely()/unlikely().

Signed-off-by: Andrew Cooper 
---
CC: Jan Beulich 

v3:
 * New
---
 tools/tests/x86_emulator/test_x86_emulator.c |  1 +
 tools/tests/x86_emulator/x86_emulate.c   |  3 +++
 xen/arch/x86/x86_emulate/x86_emulate.c   |  5 +
 xen/arch/x86/x86_emulate/x86_emulate.h   | 25 +
 4 files changed, 34 insertions(+)

diff --git a/tools/tests/x86_emulator/test_x86_emulator.c 
b/tools/tests/x86_emulator/test_x86_emulator.c
index f255fef..b54fd11 100644
--- a/tools/tests/x86_emulator/test_x86_emulator.c
+++ b/tools/tests/x86_emulator/test_x86_emulator.c
@@ -1,3 +1,4 @@
+#include 
 #include 
 #include 
 #include 
diff --git a/tools/tests/x86_emulator/x86_emulate.c 
b/tools/tests/x86_emulator/x86_emulate.c
index c46b7fc..3272867 100644
--- a/tools/tests/x86_emulator/x86_emulate.c
+++ b/tools/tests/x86_emulator/x86_emulate.c
@@ -50,4 +50,7 @@ typedef bool bool_t;
 #define __init
 #define __maybe_unused __attribute__((__unused__))
 
+#define likely(x) __builtin_expect(!!(x),1)
+#define unlikely(x)   __builtin_expect(!!(x),0)
+
 #include "x86_emulate/x86_emulate.c"
diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c 
b/xen/arch/x86/x86_emulate/x86_emulate.c
index bacdee6..e4643a3 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -2404,6 +2404,11 @@ x86_decode(
 #undef insn_fetch_bytes
 #undef insn_fetch_type
 
+/* Undo DEBUG wrapper. */
+#ifdef x86_emulate
+#undef x86_emulate
+#endif
+
 int
 x86_emulate(
 struct x86_emulate_ctxt *ctxt,
diff --git a/xen/arch/x86/x86_emulate/x86_emulate.h 
b/xen/arch/x86/x86_emulate/x86_emulate.h
index ef39601..f84ced2 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.h
+++ b/xen/arch/x86/x86_emulate/x86_emulate.h
@@ -23,6 +23,10 @@
 #ifndef __X86_EMULATE_H__
 #define __X86_EMULATE_H__
 
+#ifndef ASSERT
+#define ASSERT assert
+#endif
+
 #define MAX_INST_LEN 15
 
 struct x86_emulate_ctxt;
@@ -554,6 +558,27 @@ x86_emulate(
 const struct x86_emulate_ops *ops);
 
 /*
+ * In debug builds, wrap x86_emulate() with some assertions about its expected
+ * behaviour.
+ */
+#ifndef NDEBUG
+static inline int x86_emulate_wrapper(
+struct x86_emulate_ctxt *ctxt,
+const struct x86_emulate_ops *ops)
+{
+int rc = x86_emulate(ctxt, ops);
+
+/* Retire flags should only be set for successful instruction emulation. */
+if ( rc != X86EMUL_OKAY )
+ASSERT(ctxt->retire.raw == 0);
+
+return rc;
+}
+
+#define x86_emulate x86_emulate_wrapper
+#endif
+
+/*
  * Given the 'reg' portion of a ModRM byte, and a register block, return a
  * pointer into the block that addresses the relevant register.
  * @highbyte_regs specifies whether to decode AH,CH,DH,BH.
-- 
2.1.4


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