On Sun, 2023-07-16 at 22:50 +0100, Mark Brown wrote:
On arm64 and x86 the kernel can control if there is write access to the shadow stack via specific instructions defined for the purpose, useful for things like userspace threading at the expense of some security. Add a flag to allow this to be selected when changing the shadow stack status.
On arm64 the kernel can separately control if userspace is able to pop and push values directly onto the shadow stack via GCS push and pop instructions, supporting many scenarios where userspace needs to write to the stack with less security exposure than full write access. Add a flag to allow this to be selected when changing the shadow stack status.
Is this correct? I thought Szabolcs was saying pop was always supported, but push was optional.