Re: [PATCH v5 19/30] arm64: add POE signal support
From: Kevin Brodsky <hidden>
Date: 2024-09-24 11:28:06
Also in:
kvmarm, linux-arm-kernel, linux-fsdevel, linux-kselftest, linux-mm
On 22/08/2024 17:11, Joey Gouly wrote:
quoted hunk ↗ jump to hunk
@@ -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). Kevin [1] https://lore.kernel.org/lkml/20240802061318.2140081-2-aruna.ramakrishna@oracle.com/ (local)
+ if (ka->sa.sa_flags & SA_RESTORER) sigtramp = ka->sa.sa_restorer; else