On Thu, Jun 10, 2021 at 02:19:05PM +0100, Mark Brown wrote:
> On Wed, Jun 09, 2021 at 04:17:13PM +0100, Dave Martin wrote:
> > On Fri, Jun 04, 2021 at 12:24:49PM +0100, Mark Brown wrote:
>
> > > - if (system_supports_bti() && has_interp == is_interp &&
> > > - (*p & GNU_PROPERTY_AARCH64_FEATURE_1_BTI))
> > > - arch->flags |= ARM64_ELF_BTI;
> > > + if (system_supports_bti() &&
> > > + (*p & GNU_PROPERTY_AARCH64_FEATURE_1_BTI)) {
> > > + if (is_interp) {
> > > + arch->flags |= ARM64_ELF_INTERP_BTI;
> > > + } else {
> > > + arch->flags |= ARM64_ELF_EXEC_BTI;
> > > + }
>
> > Nit: surplus curlies? (coding-style.rst does actually say to drop them
> > when all branches of an if are single-statement one-liners -- I had
> > presumed I was just being pedantic...)
>
> I really think this hurts readability with the nested if inside
> another if with a multi-line condition.
So long as there is a reason rather than it being purely an accident of
editing, that's fine.
(Though if the nested if can be flattened so that this becomes a non-
issue, that's good too :)
> > > - if (prot & PROT_EXEC)
> > > - prot |= PROT_BTI;
> > > + if (state->flags & ARM64_ELF_EXEC_BTI && !is_interp)
> > > + prot |= PROT_BTI;
> > > + }
>
> > Is it worth adding () around the bitwise-& expressions? I'm always a
> > little uneasy about the operator precedence of binary &, although
> > without looking it up I think you're correct.
>
> Sure. I'm fairly sure the compiler would've complained about
> this case if it were ambiguous, I'm vaguely surprised it didn't
> already.
I was vaguely surprised too -- though I didn't try to compile this
myself yet. Anyway, not a huge deal. Adding a helper to generate the
appropriate mask would make this issue go away in any case, but so long
as you're confident this is being evaluated as intended I can take your
word for it.
> > Feel free to adopt if this appeals to you, otherwise I'm also fine with
> > your version.)
>
> I'll see what I think when I get back to looking at this
> properly.
Ack -- again, this was just a suggestion. I can also live with your
original code if you ultimately decide to stick with that.
Cheers
---Dave
