On 09/26/18 11:34, Ni, Ruiyu wrote:
> On 9/26/2018 5:05 PM, Laszlo Ersek wrote:
>> Hi,
>>
>> On 09/25/18 21:48, Laszlo Ersek wrote:
>>> Currently, "gcc-4.8.5-28.el7_5.1.x86_64" generates the following code
>>> for
>>> me, from the XADD inline assembly added to "X64/GccInline.c" in commit
>>> 17634d026f96:
>>>
>>>> 0000000000004383 <InternalSyncIncrement>:
>>>> UINT32
>>>> EFIAPI
>>>> InternalSyncIncrement (
>>>> IN volatile UINT32 *Value
>>>> )
>>>> {
>>>> 4383: 55 push %rbp
>>>> 4384: 48 89 e5 mov %rsp,%rbp
>>>> 4387: 48 83 ec 10 sub $0x10,%rsp
>>>> 438b: 48 89 4d 10 mov %rcx,0x10(%rbp)
>>>> UINT32 Result;
>>>>
>>>> __asm__ __volatile__ (
>>>> 438f: 48 8b 55 10 mov 0x10(%rbp),%rdx
>>>> 4393: 48 8b 45 10 mov 0x10(%rbp),%rax
>>>> 4397: b8 01 00 00 00 mov $0x1,%eax
>>>> 439c: f0 0f c1 00 lock xadd %eax,(%rax)
>>>> 43a0: ff c0 inc %eax
>>>> 43a2: 89 45 fc mov %eax,-0x4(%rbp)
>>>> : "m" (*Value) // %2
>>>> : "memory",
>>>> "cc"
>>>> );
>>>>
>>>> return Result;
>>>> 43a5: 8b 45 fc mov -0x4(%rbp),%eax
>>>> }
>>>> 43a8: c9 leaveq
>>>> 43a9: c3 retq
>>>>
>>>
>>> The MOV $0X1,%EAX instruction corrupts the address of Value in %RAX
>>> before
>>> we reach the XADD instruction. In fact, it makes no sense for XADD to
>>> use
>>> %EAX as source operand and (%RAX) as destination operand at the same
>>> time.
>>
>> may I get a fast review for this patch, please? The regression from
>> commit 17634d026f96 prevents OVMF from booting.
>
> Sure. Reviewed-by: Ruiyu Ni <[email protected]>
Thanks, Ray! Commit 8a94eb9283fa.
Laszlo
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