linux-kernel - Re: [PATCH v3] powerpc/uprobes: Validation for prefixed instruction

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Message-ID: <b2b25299-ca5a-1d43-5532-5a489d4de789@linux.ibm.com>
Date:   Thu, 4 Mar 2021 13:09:56 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
To:     "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
Cc:     mpe@...erman.id.au, oleg@...hat.com, rostedt@...dmis.org,
        paulus@...ba.org, jniethe5@...il.com, naveen.n.rao@...ux.ibm.com,
        sandipan@...ux.ibm.com, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
Subject: Re: [PATCH v3] powerpc/uprobes: Validation for prefixed instruction


>> @@ -41,6 +41,14 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe,
>>   	if (addr & 0x03)
>>   		return -EINVAL;
>>   
>> +	if (!IS_ENABLED(CONFIG_PPC64) || !cpu_has_feature(CPU_FTR_ARCH_31))
>> +		return 0;
> 
> Sorry, I missed this last time, but I think we can drop the above
> checks. ppc_inst_prefixed() already factors in the dependency on
> CONFIG_PPC64,

Yeah, makes sense. I initially added CONFIG_PPC64 check because
I was using ppc_inst_prefix(x, y) macro which is not available
for !CONFIG_PPC64.

> and I don't think we need to confirm if we're running on a
> ISA V3.1 for the below check.

Prefixed instructions would be supported only when ARCH_31 is set.
(Ignoring insane scenario where user probes on prefixed instruction
on p10 predecessors). So I guess I still need ARCH_31 check?

Ravi