Re: [patch] i386, vdso=[0|1] boot option and /proc/sys/vm/vdso_enabled

Zachary Amsden
2006-05-20T09:43:56Z

Zachary Amsden wrote:
> Andrew Morton wrote:
>> vmm:/home/akpm# echo 1 > /proc/sys/vm/vdso_enabled vmm:/home/akpm#
>> vmm:/home/akpm> ls -l
>> zsh: segmentation fault ls -l
>>
>>
>>> That could tell us whether it's an init bug or a glibc bug.
>>>
>>
>> It tells us neither. This could be a new kernel bug which only
>> certain old
>> userspace setups are known to trigger. Until we know exactly why
>> this is
>> occurring, we don't know where the bug is.
>>
>> And once we've worked that thing out, and if we determine that the
>> bug is
>> in userspace then we might be able to craft the patch in such a fashion
>> that the old userspace continues to work, which would be a win.
>>
>
> Please try my patch - sent earlier, but attached again. It will tell
> you with 100% confidence if the problem is with userspace expecting
> the vsyscall page to be at a particular address.

I should rephrase. 100% confidence - engineer stupidity factor is more
appropriate. I can't guarantee an absolute. But it is my belief that
the only kernel space mapping that could ever have been relied on by
userspace on i386 is the vsyscall page.

Zach