On Wed, Nov 20, 2013 at 12:36 PM, H. Peter Anvin wrote:
>
> That being said, "lea (%rdx,%rcx,8),%ecx" (leal, as opposed to leaq) is
> a perfectly legitimate instruction and actually one byte shorter. The
> big question is if some broken version of gas will choke on it.
At least gcc-4.8.2 generat
On 11/20/2013 12:13 PM, Linus Torvalds wrote:
> On Wed, Nov 20, 2013 at 11:28 AM, H. Peter Anvin wrote:
>>>
>>> .section .fixup,"ax"
>>> 11: lea (%rdx,%rcx,8),%rcx
>>> 12: movl %ecx,%edx /* ecx is zerorest also */
>>
>> -> Even if %rdx+%rcx*8 > 2^32 we end up truncating at 12: -
On Wed, Nov 20, 2013 at 11:28 AM, H. Peter Anvin wrote:
>>
>> .section .fixup,"ax"
>> 11: lea (%rdx,%rcx,8),%rcx
>> 12: movl %ecx,%edx /* ecx is zerorest also */
>
> -> Even if %rdx+%rcx*8 > 2^32 we end up truncating at 12: -- not that it
> matters, since both arguments are prot
On 11/16/2013 10:44 PM, Linus Torvalds wrote:
> So this doesn't do the 32-bit truncation in the error path of the
> generic string copy. Oversight?
>
>Linus
I looked at the code again, and it turns out to be false alarm.
We *do* do 32-bit truncation in every path, still:
> ENTRY(copy_us
On 11/19/2013 11:38 AM, Linus Torvalds wrote:
> On Mon, Nov 18, 2013 at 8:37 PM, H. Peter Anvin wrote:
>>
>> Do you have a preference:
>>
>> 1. Considering the 32-bit truncation incidental (take it or leave it);
>> 2. Require the 32-bit truncation, or
>> 3. Get rid of it completely?
>
> I don't h
On Mon, Nov 18, 2013 at 8:37 PM, H. Peter Anvin wrote:
>
> Do you have a preference:
>
> 1. Considering the 32-bit truncation incidental (take it or leave it);
> 2. Require the 32-bit truncation, or
> 3. Get rid of it completely?
I don't have a huge preference, but I hate the current situation (w
On 11/16/2013 10:44 PM, Linus Torvalds wrote:
> So this doesn't do the 32-bit truncation in the error path of the generic
> string copy. Oversight?
>
>Linus
Hi Linus,
Do you have a preference:
1. Considering the 32-bit truncation incidental (take it or leave it);
2. Require the 32-bit t
On 11/16/2013 10:44 PM, Linus Torvalds wrote:
> So this doesn't do the 32-bit truncation in the error path of the generic
> string copy. Oversight?
>
>Linus
Indeed... although in the kernel it seems to be taken as an invariant
that copy lengths over 4G is simply prohibited. There are pla
Commit-ID: f4cb1cc18f364d761d5614eb62936647f259
Gitweb: http://git.kernel.org/tip/f4cb1cc18f364d761d5614eb62936647f259
Author: Fenghua Yu
AuthorDate: Sat, 16 Nov 2013 12:37:01 -0800
Committer: H. Peter Anvin
CommitDate: Sat, 16 Nov 2013 18:00:58 -0800
x86-64, copy_user: Remove
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