Re: [PATCH?] uprobes: change uprobe_write_opcode() to modify the page directly

H. Peter Anvin
2013-12-04T16:55:52Z

On 12/04/2013 08:48 AM, Oleg Nesterov wrote:
> On 12/04, H. Peter Anvin wrote:
>>
>> On 12/04/2013 03:11 AM, Oleg Nesterov wrote:
>>>
>>> It is still not clear to me if we can simply change a single byte on
>>> x86 or not, but at least on powerpc we need to update 4 bytes. Perhaps
>>> we can conditionalize these pte games later.
>>>
>>
>> But 4 aligned bytes can be written as a single transaction.
>
> Ah yes, this is true.
>

That is why I talk about the atomic instruction word... most (but not
*all*) architectures have a fundamental minimum unit of instructions
which is aligned and can be atomically written. Typically this is 1, 2,
or 4 bytes.

-hpa