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Message-ID: <54B355FA.60702@redhat.com>
Date: Mon, 12 Jan 2015 10:34:58 +0530
From: Pratyush Anand <panand@...hat.com>
To: Oleg Nesterov <oleg@...hat.com>
CC: tixy@...aro.org, linux@....linux.org.uk, ananth@...ibm.com,
sandeepa.prabhu@...aro.org, catalin.marinas@....com,
will.deacon@....com, linux-kernel@...r.kernel.org,
anil.s.keshavamurthy@...el.com, masami.hiramatsu.pt@...achi.com,
wcohen@...hat.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC 8/8] ARM64: Add uprobe support
On Friday 09 January 2015 11:29 PM, Oleg Nesterov wrote:
> On 12/31, Pratyush Anand wrote:
>>
>> +int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
>> + unsigned long addr)
>> +{
>> + probe_opcode_t insn;
>> +
>> + insn = *(probe_opcode_t *)(&auprobe->insn[0]);
>> +
>> + switch (arm_probe_decode_insn(insn, &auprobe->ainsn)) {
>> + case INSN_REJECTED:
>> + return -EINVAL;
>> +
>> + case INSN_GOOD_NO_SLOT:
>> + auprobe->simulate = true;
>> + if (auprobe->ainsn.prepare)
>> + auprobe->ainsn.prepare(insn, &auprobe->ainsn);
>> + break;
>> +
>> + case INSN_GOOD:
>> + default:
>> + break;
>> + }
>> +
>> + return 0;
>> +}
>
> forgot to mention... shouldn't it also check IS_ALIGNED(addr, AARCH64_INSN_SIZE) ?
>
> I do not know if unaligned insn address is valid on arm64 or not, but please
AARCH64 instructions are always of fixed lenght ie 4 bytes. I do not see
possibility of addr being unaligned. Please let me know, if I am missing
something.
> note that at least it should not cross the page boundary, set_swbp() needs to
> write AARCH64_INSN_SIZE == UPROBE_SWBP_INSN bytes and it assumes that this
> should fit the single page.
So, again I do not see the possibility of crossing of page boundary for
any instruction address.
~Pratyush
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