On Mon, Mar 23, 2020 at 02:39:55PM +0000, Catalin Marinas wrote:

On Mon, Mar 23, 2020 at 01:57:22PM +0000, Mark Rutland wrote:

quoted

On Mon, Mar 23, 2020 at 01:24:12PM +0000, Mark Brown wrote:

quoted

On Mon, Mar 23, 2020 at 12:21:44PM +0000, Catalin Marinas wrote:

quoted

On Fri, Mar 20, 2020 at 05:39:46PM +0000, Szabolcs Nagy wrote:

quoted

+int arch_elf_adjust_prot(int prot, const struct arch_elf_state *state,
+                        bool has_interp, bool is_interp)
+{
+       if (is_interp != has_interp)
+               return prot;
+
+       if (!(state->flags & ARM64_ELF_BTI))
+               return prot;
+
+       if (prot & PROT_EXEC)
+               prot |= PROT_BTI;
+
+       return prot;
+}

quoted

I think it would be best to document the current behaviour, as it's a
simple ABI that we can guarantee, and the dynamic linker will have to be
aware of BTI in order to do the right thing anyhow.

That's a valid point. If we have an old dynamic linker and the kernel
enabled BTI automatically for the main executable, could things go wrong
(e.g. does the PLT need to be BTI-aware)?

Also worth noting that an old dynamic linker won't have ARM64_ELF_BTI
set, so the kernel will not enable BTI for this.

Mark.

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