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:

quoted

-		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.

quoted

-	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.

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.