On 29.04.2025 03:27, Stefano Stabellini wrote:
> On Mon, 28 Apr 2025, Jan Beulich wrote:
>> On 26.04.2025 01:42, victorm.l...@amd.com wrote:
>>> From: Nicola Vetrini <nicola.vetr...@bugseng.com>
>>>
>>> Rule 19.1 states: "An object shall not be assigned or copied
>>> to an overlapping object". Since the "call" and "compat_call" are
>>
>> Was this taken from patch 2 without editing?
>>
>>> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
>>> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
>>> @@ -526,9 +526,19 @@ static inline void put_loop_count(
>>> */ \
>>> if ( !amd_like(ctxt) && mode_64bit() && ad_bytes == 4 ) \
>>> { \
>>> + uint64_t tmp; \
>>> + \
>>> _regs.r(cx) = 0; \
>>> - if ( extend_si ) _regs.r(si) = _regs.esi; \
>>> - if ( extend_di ) _regs.r(di) = _regs.edi; \
>>> + if ( extend_si ) \
>>> + { \
>>> + tmp = _regs.esi; \
>>> + _regs.r(si) = tmp; \
>>> + } \
>>> + if ( extend_di ) \
>>> + { \
>>> + tmp = _regs.edi; \
>>> + _regs.r(di) = tmp; \
>>> + } \
>>
>> See commit 7225f13aef03 for how we chose to address similar issues elsewhere
>> in the emulator. I think we want to be consistent there. This will then also
>> eliminate ...
>>
>>> @@ -2029,7 +2039,12 @@ x86_emulate(
>>> switch ( op_bytes )
>>> {
>>> case 2: _regs.ax = (int8_t)_regs.ax; break; /* cbw */
>>> - case 4: _regs.r(ax) = (uint32_t)(int16_t)_regs.ax; break; /* cwde
>>> */
>>> + case 4:
>>> + {
>>> + uint32_t tmp = (uint32_t)(int16_t)_regs.ax;
>>> + _regs.r(ax) = tmp;
>>> + break; /* cwde */
>>> + }
>>
>> ... the odd brace placement here, as well as the inconsistency in the types
>> you used for the temporary variables (both really could have been unsigned
>> int; no need for a fixed-width type).
>
> Is this what you have in mind?
No, and that's also not what the referenced commit did in a similar situation.
> --- a/xen/arch/x86/x86_emulate/x86_emulate.c
> +++ b/xen/arch/x86/x86_emulate/x86_emulate.c
> @@ -527,8 +527,8 @@ static inline void put_loop_count(
> if ( !amd_like(ctxt) && mode_64bit() && ad_bytes == 4 ) \
> { \
> _regs.r(cx) = 0; \
> - if ( extend_si ) _regs.r(si) = _regs.esi; \
> - if ( extend_di ) _regs.r(di) = _regs.edi; \
> + if ( extend_si ) _regs.r(si) = (uint64_t)_regs.esi; \
> + if ( extend_di ) _regs.r(di) = (uint64_t)_regs.edi; \
if ( extend_si ) _regs.r(si) = (uint32_t)_regs.r(si); \
if ( extend_di ) _regs.r(di) = (uint32_t)_regs.r(di); \
After all what the rule requires is that we use _the same_ field on both sides.
Jan
