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Re: RELEASE BLOCKER: Linux doesn't follow x86/x86-64 ABI wrt direction flag
Chris Lattner a écrit :
>>>> Richard Guenther wrote:
>>>>> We didn't yet run into this issue and build openSUSE with 4.3 since
>>>>> more
>>>>> than
>>>>> three month.
>>>>
>>>> Well, how often do you take a trap inside an overlapping memmove()?
>>>
>>> How hard is it to change the kernel signal entry path from "pushf" to
>>> "pushf;cld"? Problem solved, no?
>>
>> The problem is with old kernels, which by definition stay unfixed.
>
> My impression was that the problem occurs in GCC compiled code in the
> kernel itself, not in user space:
>
> 1. User space has direction flag set.
> 2. signal occurs
> 3. kernel code is entered
> 4. kernel code does string operation <boom>
Wrong. Except maybe for the Hurd kernel. For other kernels:
4. signal handler is called
5. signal handler does string operation <boom>
The GCC used to compile the kernel doesn't matter. Using gcc 4.3 to
compile the user code triggers the bug.
--
.''`. Aurelien Jarno | GPG: 1024D/F1BCDB73
: :' : Debian developer | Electrical Engineer
`. `' aurel32@debian.org | aurelien@aurel32.net
`- people.debian.org/~aurel32 | www.aurel32.net