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

[Pratyush Anand]

Hi Oleg,

How can I generate a scenario to test:

a) arch_uprobe_xol_was_trapped
b) arch_uprobe_abort_xol

~Pratyush

On Monday 12 January 2015 10:34 AM, Pratyush Anand wrote:
> 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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