[PATCH 2/2] powerpc/64s/interrupt: Check and fix srr_valid without crashing

[Christophe Leroy]

Le 22/06/2021 à 10:54, Nicholas Piggin a écrit :
> Excerpts from Christophe Leroy's message of June 22, 2021 4:47 pm:
>>
>>
>> Le 22/06/2021 à 08:04, Nicholas Piggin a écrit :
>>> The PPC_RFI_SRR_DEBUG check added by patch "powerpc/64s: avoid reloading
>>> (H)SRR registers if they are still valid" has a few deficiencies. It
>>> does not fix the actual problem, it's not enabled by default, and it
>>> causes a program check interrupt which can cause more difficulties.
>>>
>>> However there are a lot of paths which may clobber SRRs or change return
>>> regs, and difficult to have a high confidence that all paths are covered
>>> without wider testing.
>>>
>>> Add a relatively low overhead always-enabled check that catches most
>>> such cases, reports once, and fixes it so the kernel can continue.
>>>
>>> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
>>> ---
>>>    arch/powerpc/kernel/interrupt.c | 58 +++++++++++++++++++++++++++++++++
>>>    1 file changed, 58 insertions(+)
>>>
>>> diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
>>> index 05fa3ae56e25..5920a3e8d1d5 100644
>>> --- a/arch/powerpc/kernel/interrupt.c
>>> +++ b/arch/powerpc/kernel/interrupt.c
>>> @@ -231,6 +231,56 @@ static notrace void booke_load_dbcr0(void)
>>>    #endif
>>>    }
>>>    
>>> +#include <linux/sched/debug.h> /* for show_regs */
>>> +static void check_return_regs_valid(struct pt_regs *regs)
>>> +{
>>> +#ifdef CONFIG_PPC_BOOK3S_64
>>> +	static bool warned = false;
>>> +
>>> +	if (regs->trap == 0x980 || regs->trap == 0xe00 || regs->trap == 0xe20 ||
>>> +	    regs->trap == 0xe40 || regs->trap == 0xe60 || regs->trap == 0xe80 ||
>>> +	    regs->trap == 0xea0 || regs->trap == 0xf80 || regs->trap == 0x1200 ||
>>> +	    regs->trap == 0x1500 || regs->trap == 0x1600 || regs->trap == 0x1800) {
>>
>> Can you use names defined in asm/interrupt.h instead of raw values ?
>> Some are already there, others can be added.
> 
> Good idea. Could go into a helper too actually.
> 
> I wanted to clean up the KVM definitions and unify them with interrupt.h
> defs but that's a bit of churn. Can I get to that in the next merge or
> so?
> 


Sure

Christophe