Re: [LTP] ltp_clone alignment issues.

Carmelo AMOROSO
2010-09-30T10:43:16Z

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On 9/30/2010 3:31 PM, Hannu Heikkinen wrote:
> On 29/09/10 15:34 +0200, ext Carmelo AMOROSO wrote:
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> > On 9/27/2010 3:34 PM, Carmelo AMOROSO wrote:
> > > Folks,
> > > I want to reopen an old discussion on ltp_clone and stack alignment
> > > issue (see
> > >
> http://sourceforge.net/mailarchive/message.php?msg_name=4B421480.1040400%40petalogix.com).
> > > Indeed recently a commit has partially fixed a problem on ARM
> > > (0056e395170eb8fc3ffbb22d7bd364fe47c2013e), but I think this should be
> > > extended to all archs that have stack that grows downwards.
> > >
> > > Indeed, as Jiri replied in that old thread, the value passed to clone as
> > > child stack should be never accessed, because it is the topmost address
> > > of the memory allocated for the child process (it's the previous stack
> > > pointer).
> > >
> > > So, in archs that do not like unaligned stack, using (stack - size - 1 )
> > > will cause the process to be killed by a SIGBUS, on other archs, we are
> > > just wasting one byte of the malloc-ed stack.
> > >
> > > On my SH4 arch, the stack must be 4byte aligned (as in ARM).
> > >
> > > Please, find attached a patch against master branch
> > >
> > > Best regards,
> > > Carmelo
> >
> > Hi,
> > any feedback on this ?
> >
> > Cheers,
> > Carmelo
>
> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
> Signed-off-by: Carmelo Amoroso <carmelo.amoroso@st.com>
> ---
> lib/cloner.c | 9 +++------
> 1 files changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/lib/cloner.c b/lib/cloner.c
> index 6ad4a00..e53c9cf 100644
> --- a/lib/cloner.c
> +++ b/lib/cloner.c
> @@ -59,16 +59,13 @@ ltp_clone(unsigned long clone_flags, int (*fn)(void
> *arg), void *arg,
> ret = clone(fn, stack, clone_flags, arg);
> #elif defined(__ia64__)
> ret = clone2(fn, stack, stack_size, clone_flags, arg, NULL, NULL,
> NULL);
> -#elif defined(__arm__)
> +#else
> /*
> - * Stack size should be a multiple of 32 bit words
> - * & stack limit must be aligned to a 32 bit boundary
> + * For archs where stack grows downwards, stack points to the topmost
> address
> + * of the memory space set up for the child stack.
> */
> ret = clone(fn, (stack ? stack + stack_size : NULL),
> clone_flags, arg);
> -#else
> - ret = clone(fn, (stack ? stack + stack_size - 1 : NULL),
> - clone_flags, arg);
> #endif
>
> return ret;
> --
> <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
>
> Hi,
>
> Acked-by Hannu Heikkinen <ext-hannu.m.heikkinen@nokia.com>
>
> Br,
> Hannu
>
> --
> Hannu Heikkinen
> http://www.nixu.com
>

Thanks, Hannu
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