Re: [PATCH] powerpc: Fix alignment of secondary cpu spin vars

Olof Johansson
2014-01-08T17:50:32Z

On Wed, Jan 08, 2014 at 03:18:26PM +1100, Benjamin Herrenschmidt wrote:
> On Wed, 2014-01-08 at 15:09 +1100, Michael Ellerman wrote:
> > > Of course, main worry is that this is just hiding some latent NULL
> > deref in
> > > the kernel now... :-/
> >
> > Wow, that would have to come close to winning the
> > grossest-hack-in-arch-powerpc
> > award :)
> >
> > Have you tried changing the value at 8 to point to a reserved page?
> >
> > Some other possibilities:
> >
> > * Change the #define so FIXUP_ENDIAN is empty for PASEMI, that would
> > mean
> > you'd only be able to boot pasemi_defconfig.

No thanks -- this went uncaught because that used to be all I booted
(and for some random reason it didn't trigger in that case).

> > * Move the hack into FIXUP_ENDIAN
>
> We actually found the root cause on irc the other day, I was waiting for
> Olof to send a fix :-)

Yeah, I'm low on spare time these days, in particular spare time to spend on
ppc stuff. :-(

> Olof: Can you try this totally untested patch ?

With one fixup below:

Tested-by: Olof Johansson <olof@lixom.net>

> --- a/arch/powerpc/kernel/prom_init.c
> +++ b/arch/powerpc/kernel/prom_init.c
> @@ -1986,8 +1986,6 @@ static void __init prom_init_stdout(void)
> /* Get the full OF pathname of the stdout device */
> memset(path, 0, 256);
> call_prom("instance-to-path", 3, 1, prom.stdout, path, 255);
> - stdout_node = call_prom("instance-to-package", 1, 1, prom.stdout);
> - val = cpu_to_be32(stdout_node);
> prom_setprop(prom.chosen, "/chosen", "linux,stdout-package",
> &val, sizeof(val));
> prom_printf("OF stdout device is: %s\n", of_stdout_device);
> @@ -1995,10 +1993,14 @@ static void __init prom_init_stdout(void)
> path, strlen(path) + 1);
>
> /* If it's a display, note it */
> - memset(type, 0, sizeof(type));
> - prom_getprop(stdout_node, "device_type", type, sizeof(type));
> - if (strcmp(type, "display") == 0)
> - prom_setprop(stdout_node, path, "linux,boot-display", NULL, 0);
> + stdout_node = call_prom("instance-to-package", 1, 1, prom.stdout);
> + if (stdout_node != PROM_ERROR) {
> + val = cpu_to_be32(stdout_node);
> + memset(type, 0, sizeof(type));
> + prom_getprop(stdout_node, "device_type", type, sizeof(type));
> + if (strcmp(type, "display") == 0)
> + prom_setprop(stdout_node, path, "linux,boot-display", NU

Line is cut off, this needs "NULL, 0);" at the end.

-Olof