Re: [LTP] mmstress[1309]: segfault at 7f3d71a36ee8 ip 00007f3d77132bdf sp 00007f3d71a36ee8 error 4 in libc-2.27.so[7f3d77058000+1aa000]

[Song Liu]

On Fri, Oct 23, 2020 at 10:51 AM Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Fri, Oct 23, 2020 at 10:00 AM Naresh Kamboju
> <naresh.kamboju@xxxxxxxxxx> wrote:
> >
> > [Old patch from yesterday]
> >
> > After applying your patch on top on linux next tag 20201015
> > there are two observations,
> >   1) i386 build failed. please find build error build
>
> Yes, this was expected. That patch explicitly only works on x86-64,
> because 32-bit needs the double register handling for 64-bit values
> (mainly loff_t).
>
> >   2) x86_64 kasan test PASS and the reported error not found.
>
> Ok, good. That confirms that the problem you reported is indeed the
> register allocation.
>
> The patch I sent an hour ago (the one based on Rasmus' one from
> yesterday) should fix things too, and - unlike yesterday's - work on
> 32-bit.
>
> But I'll wait for confirmation (and hopefully a sign-off from Rasmus
> so that I can give him authorship) before actually committing it.
>
>               Linus

My test vm failed to boot since

commit d55564cfc222326e944893eff0c4118353e349ec
x86: Make __put_user() generate an out-of-line call

The patch also fixed it.

Thanks!
Song