On Fri, Jun 23, 2023 at 06:28:12PM +0100, Catalin Marinas wrote: > On Thu, Jun 22, 2023 at 06:11:20PM +0100, Mark Brown wrote: > > TPIDR2 is intended to go along with the thread stack, it's intended to > > be used to allow lazy save of the (rather large) ZA register state when > > a called function needs it rather than forcing it to be caller saved. > > TPIDR2 is used to point to memory allocated for managing this process, > > something that provides a new value should be making a deliberate > > decision to do so and editing the stack frame. > OK, so if the signal handler invokes a function that touches the ZA > state, it may use TPIDR2 for lazy saving in any callee. In this case we > need to restore the original TPIDR2 of the interrupted context on > sigreturn. Yeah, or if something tries to sigreturn to a previously saved context which had live TPIDR2 state things might end up unfortunate. > So I convinced myself this is the only option that makes sense ;). I'll > queue the patches. Thanks.
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