Hi Kevin, On Tue, Sep 24, 2024 at 01:27:58PM +0200, Kevin Brodsky wrote: > On 22/08/2024 17:11, Joey Gouly wrote: > > @@ -1178,6 +1237,9 @@ static void setup_return(struct pt_regs *regs, struct k_sigaction *ka, > > sme_smstop(); > > } > > > > + if (system_supports_poe()) > > + write_sysreg_s(POR_EL0_INIT, SYS_POR_EL0); > > At the point where setup_return() is called, the signal frame has > already been written to the user stack. In other words, we write to the > user stack first, and then reset POR_EL0. This may be problematic, > especially if we are using the alternate signal stack, which the > interrupted POR_EL0 may not grant access to. In that situation uaccess > will fail and we'll end up with a SIGSEGV. > > This issue has already been discussed on the x86 side, and as it happens > patches to reset PKRU early [1] have just landed. I don't think this is > a blocker for getting this series landed, but we should try and align > with x86. If there's no objection, I'm planning to work on a counterpart > to the x86 series (resetting POR_EL0 early during signal delivery). Did you get a chance to work on that? It would be great to land the fixes for 6.12, if possible, so that the first kernel release with POE support doesn't land with known issues. Cheers, Will
