Re: [RFC 8/8] ARM64: Add uprobe support

[Pratyush Anand]

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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