From: Heiko Carstens Date: Mon, 3 Nov 2025 15:25:32 +0000 (+0100) Subject: s390/mm: Change comment and die() message if teid.b61 is zero X-Git-Tag: v6.19-rc1~206^2~19 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=76502abca219fc8579353458a12744587b7a281f;p=thirdparty%2Flinux.git s390/mm: Change comment and die() message if teid.b61 is zero The comments in do_protection() give the impression that a TEID, where bit 61 is zero, indicates a low address protection exception. This is not necessarily true, and it depends on the type of Suppression-on-Protection facility of the machine (see Princples of Operation) what this means. Rework the comments and the die() message to reflect this. This may also help to avoid confusion. Reviewed-by: Alexander Gordeev Signed-off-by: Heiko Carstens --- diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c index e1ad05bfd28ad..639c4f610fdd7 100644 --- a/arch/s390/mm/fault.c +++ b/arch/s390/mm/fault.c @@ -368,20 +368,15 @@ void do_protection_exception(struct pt_regs *regs) if (!(regs->int_code & 0x200)) regs->psw.addr = __rewind_psw(regs->psw, regs->int_code >> 16); /* - * Check for low-address protection. This needs to be treated - * as a special case because the translation exception code - * field is not guaranteed to contain valid data in this case. + * If bit 61 if the TEID is not set, the remainder of the + * TEID is unpredictable. Special handling is required. */ if (unlikely(!teid.b61)) { if (user_mode(regs)) { - /* Low-address protection in user mode: cannot happen */ dump_fault_info(regs); - die(regs, "Low-address protection"); + die(regs, "Unexpected TEID"); } - /* - * Low-address protection in kernel mode means - * NULL pointer write access in kernel mode. - */ + /* Assume low-address protection in kernel mode. */ return handle_fault_error_nolock(regs, 0); } if (unlikely(cpu_has_nx() && teid.b56)) {