Re: [PATCH -next] openrisc: Define __ro_after_init to avoid crash

[Guenter Roeck]

On 09/27/2016 07:15 AM, Stafford Horne wrote:
> On Sat, 24 Sep 2016, Guenter Roeck wrote:
>
> > openrisc qemu tests fail with the following crash.
> >
> > Unable to handle kernel access at virtual address 0xc0300c34
> >
> > Oops#: 0001
> > CPU #: 0
> >   PC: c016c710    SR: 0000ae67    SP: c1017e04
> >   GPR00: 00000000 GPR01: c1017e04 GPR02: c0300c34 GPR03: c0300c34
> >   GPR04: 00000000 GPR05: c0300cb0 GPR06: c0300c34 GPR07: 000000ff
> >   GPR08: c107f074 GPR09: c0199ef4 GPR10: c1016000 GPR11: 00000000
> >   GPR12: 00000000 GPR13: c107f044 GPR14: c0473774 GPR15: 07ce0000
> >   GPR16: 00000000 GPR17: c107ed8a GPR18: 00009600 GPR19: c107f044
> >   GPR20: c107ee74 GPR21: 00000003 GPR22: c0473770 GPR23: 00000033
> >   GPR24: 000000bf GPR25: 00000019 GPR26: c046400c GPR27: 00000001
> >   GPR28: c0464028 GPR29: c1018000 GPR30: 00000006 GPR31: ccf37483
> >     RES: 00000000 oGPR11: ffffffff
> >     Process swapper (pid: 1, stackpage=c1001960)
> >
> >     Stack: Stack dump [0xc1017cf8]:
> >     sp + 00: 0xc1017e04
> >     sp + 04: 0xc0300c34
> >     sp + 08: 0xc0300c34
> >     sp + 12: 0x00000000
> > ...
> >
> > Bisect points to commit d2ec3f77de8e ("pty: make ptmx file ops read-only
> > after init"). Fix by defining __ro_after_init for the openrisc
> > architecture, similar to parisc.
>
> Thanks for finding this one.
> Just for clatify __read_mostly falls back to default blank in openrisc, so it gets no special section treatment.

Yes, I understand. It falls back to the pre-_ro_after_init behavior, which should be
perfectly fine here.

Guenter


> Acked-by: Stafford Horne <shorne@xxxxxxxxx>
>
>
> > Fixes: d2ec3f77de8e ("pty: make ptmx file ops read-only after init")
> > Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> > Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> > ---
> > arch/openrisc/include/asm/cache.h | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/arch/openrisc/include/asm/cache.h b/arch/openrisc/include/asm/cache.h
> > index 4ce7a01a252d..5f55da9cbfd5 100644
> > --- a/arch/openrisc/include/asm/cache.h
> > +++ b/arch/openrisc/include/asm/cache.h
> > @@ -23,6 +23,8 @@
> >  * they shouldn't be hard-coded!
> >  */
> >
> > +#define __ro_after_init __read_mostly
> > +
> > #define L1_CACHE_BYTES 16
> > #define L1_CACHE_SHIFT 4
> >
> > --
> > 2.5.0