On Tue, May 19, 2020 at 05:28:20PM +0100, Will Deacon wrote:
> For better or worse, GDB relies on the exact instruction sequence in the
> VDSO sigreturn trampoline in order to unwind from signals correctly.
> Commit c91db232da48 ("arm64: vdso: Convert to modern assembler annotations")
> unfortunately added a BTI C instruction to the start of __kernel_rt_sigreturn,
> which breaks this check. Thankfully, it's also not required, since the
> trampoline is called from a RET instruction when returning from the signal
> handler

Reviwed-by: Mark Brown <broonie@kernel.org>