[PATCH] powerpc: Fix audit crash due to save/restore PPR changes

[Haren Myneni]

On 04/14/2013 06:44 PM, Alistair Popple wrote:
> The current mainline crashes when hitting userspace with the following:
> 
> kernel BUG at /home/alistair/Source/linux-stable/kernel/auditsc.c:1769!
> cpu 0x1: Vector: 700 (Program Check) at [c000000023883a60]
>     pc: c0000000001047a8: .__audit_syscall_entry+0x38/0x130
>     lr: c00000000000ed64: .do_syscall_trace_enter+0xc4/0x270
>     sp: c000000023883ce0
>    msr: 8000000000029032
>   current = 0xc000000023800000
>   paca    = 0xc00000000f080380   softe: 0        irq_happened: 0x01
>     pid   = 1629, comm = start_udev
> kernel BUG at /home/alistair/Source/linux-stable/kernel/auditsc.c:1769!
> enter ? for help
> [c000000023883d80] c00000000000ed64 .do_syscall_trace_enter+0xc4/0x270
> [c000000023883e30] c000000000009b08 syscall_dotrace+0xc/0x38
> --- Exception: c00 (System Call) at 0000008010ec50dc
> 
> Bisecting found the following patch caused it:
> 
> commit 44e9309f1f357794b7ae93d5f3e3e6f11d2b8a7f
> Author: Haren Myneni <haren at linux.vnet.ibm.com>
> powerpc: Implement PPR save/restore
> 
> It was found this patch corrupted r9 when calling
> SET_DEFAULT_THREAD_PPR()
> 
> Using r10 as a scratch register instead of r9 solved the problem.

Thanks for fixing. Sorry I missed it

Acked-by: Haren Myneni <haren at us.ibm.com>

> 
> Signed-off-by: Alistair Popple <alistair at popple.id.au>
> Acked-by: Michael Neuling <mikey at neuling.org>
> ---
> 
> diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
> index 256c5bf..3acb1a0 100644
> --- a/arch/powerpc/kernel/entry_64.S
> +++ b/arch/powerpc/kernel/entry_64.S
> @@ -304,7 +304,7 @@ syscall_exit_work:
>  	subi	r12,r12,TI_FLAGS
> 
>  4:	/* Anything else left to do? */
> -	SET_DEFAULT_THREAD_PPR(r3, r9)		/* Set thread.ppr = 3 */
> +	SET_DEFAULT_THREAD_PPR(r3, r10)		/* Set thread.ppr = 3 */
>  	andi.	r0,r9,(_TIF_SYSCALL_T_OR_A|_TIF_SINGLESTEP)
>  	beq	.ret_from_except_lite
> 
> 
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