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

Benjamin Herrenschmidt
2014-01-08T04:18:57Z

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.
> * 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 :-)

Olof: Can you try this totally untested patch ?

--- 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
+ }
}