[PATCH v2] arch: define weak abort

[PATCH v2] arch: define weak abort

[Alexey Brodkin]

Hi Sudip,

On Tue, 2017-12-12@22:49 +0000, Sudip Mukherjee wrote:
> gcc toggle -fisolate-erroneous-paths-dereference (default at -O2
> onwards) isolates faulty code paths such as null pointer access, divide
> by zero etc. If gcc port doesnt implement __builtin_trap, an abort() is
> generated which causes kernel link error.
> 
> In this case, gcc is generating abort due to 'divide by zero' in
> lib/mpi/mpih-div.c.
> 
> Currently 'frv' and 'arc' are failing. Previously other arch was also
> broken like m32r was fixed by d22e3d69ee1a ("m32r: fix build failure").
> 
> Lets define this weak function which is common for all arch and fix the
> problem permanently. We can even remove the arch specific 'abort' after
> this is done.
> 
> Cc: Alexey Brodkin <Alexey.Brodkin at synopsys.com>
> Signed-off-by: Sudip Mukherjee <sudipm.mukherjee at gmail.com>
> ---
> 
> Hi Alexey,
> I was thinking of sending the m32r revert patch in few days. My m32r
> builds are having a little problem and should be fixed by this weekend.
> I can not test m32r before that.

Understood, that's fine by me.

> We can also send a patch to remove the
> same code in arm and unicore32.

Sure that would be really great!

-Alexey

[PATCH v2] arch: define weak abort

[Vineet Gupta]

On 12/12/2017 02:49 PM, Sudip Mukherjee wrote:
> gcc toggle -fisolate-erroneous-paths-dereference (default at -O2
> onwards) isolates faulty code paths such as null pointer access, divide
> by zero etc. If gcc port doesnt implement __builtin_trap, an abort() is
> generated which causes kernel link error.
> 
> In this case, gcc is generating abort due to 'divide by zero' in
> lib/mpi/mpih-div.c.
> 
> Currently 'frv' and 'arc' are failing. Previously other arch was also
> broken like m32r was fixed by d22e3d69ee1a ("m32r: fix build failure").
> 
> Lets define this weak function which is common for all arch and fix the
> problem permanently. We can even remove the arch specific 'abort' after
> this is done.
> 
> Cc: Alexey Brodkin <Alexey.Brodkin at synopsys.com>
> Signed-off-by: Sudip Mukherjee <sudipm.mukherjee at gmail.com>
> ---
> 
> Hi Alexey,
> I was thinking of sending the m32r revert patch in few days. My m32r
> builds are having a little problem and should be fixed by this weekend.
> I can not test m32r before that. We can also send a patch to remove the
> same code in arm and unicore32.
> 
>   kernel/exit.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
> diff --git a/kernel/exit.c b/kernel/exit.c
> index af6c245..90c6869 100644
> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -1759,3 +1759,11 @@ long kernel_wait4(pid_t upid, int __user *stat_addr, int options,
>   	return -EFAULT;
>   }
>   #endif
> +
> +__weak void abort(void)
> +{
> +	BUG();
> +
> +	/* if that doesn't kill us, halt */
> +	panic("Oops failed to kill thread");
> +}

Hmm, I realize there's a small gotcha with this, when testing with a different 
patch from Arnd. This needs an EXPORT_SYMBOL() as well !

-Vineet

[PATCH v2] arch: define weak abort

[Andrew Morton]

On Tue, 19 Dec 2017 13:39:22 -0800 Vineet Gupta <Vineet.Gupta1@synopsys.com> wrote:

> > --- a/kernel/exit.c
> > +++ b/kernel/exit.c
> > @@ -1759,3 +1759,11 @@ long kernel_wait4(pid_t upid, int __user *stat_addr, int options,
> >   	return -EFAULT;
> >   }
> >   #endif
> > +
> > +__weak void abort(void)
> > +{
> > +	BUG();
> > +
> > +	/* if that doesn't kill us, halt */
> > +	panic("Oops failed to kill thread");
> > +}
> 
> Hmm, I realize there's a small gotcha with this, when testing with a different 
> patch from Arnd. This needs an EXPORT_SYMBOL() as well !

Yup.  This?

From: Andrew Morton <akpm@linux-foundation.org>
Subject: kernel/exit.c: export abort() to modules

gcc -fisolate-erroneous-paths-dereference can generate calls to abort()
from modular code too.

Reported-by: Vineet Gupta <Vineet.Gupta1 at synopsys.com>
Cc: Sudip Mukherjee <sudipm.mukherjee at gmail.com>
Cc: Arnd Bergmann <arnd at arndb.de>
Cc: "Alexey Brodkin" <Alexey.Brodkin at synopsys.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
---

 kernel/exit.c |    1 +
 1 file changed, 1 insertion(+)

diff -puN kernel/exit.c~a kernel/exit.c
--- a/kernel/exit.c~a
+++ a/kernel/exit.c
@@ -1763,3 +1763,4 @@ __weak void abort(void)
 	/* if that doesn't kill us, halt */
 	panic("Oops failed to kill thread");
 }
+EXPORT_SYMBOL(abort);
_

[PATCH v2] arch: define weak abort

[Sudip Mukherjee]

On Tue, Dec 19, 2017@01:55:59PM -0800, Andrew Morton wrote:
> On Tue, 19 Dec 2017 13:39:22 -0800 Vineet Gupta <Vineet.Gupta1@synopsys.com> wrote:
> 

<snip>

> > Hmm, I realize there's a small gotcha with this, when testing with a different 
> > patch from Arnd. This needs an EXPORT_SYMBOL() as well !
> 
> Yup.  This?

Yes, just faced this when I was testing with the reverted patch on m32r.

> 
> From: Andrew Morton <akpm at linux-foundation.org>
> Subject: kernel/exit.c: export abort() to modules
> 
> gcc -fisolate-erroneous-paths-dereference can generate calls to abort()
> from modular code too.
> 
> Reported-by: Vineet Gupta <Vineet.Gupta1 at synopsys.com>
> Cc: Sudip Mukherjee <sudipm.mukherjee at gmail.com>
> Cc: Arnd Bergmann <arnd at arndb.de>
> Cc: "Alexey Brodkin" <Alexey.Brodkin at synopsys.com>
> Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
> ---

Acked-by: Sudip Mukherjee <sudipm.mukherjee at gmail.com>

--
Regards
Sudip