s390/mm: Dump fault info in case of low address protection fault

hcahca · Vasily Gorbik · commit af6bfcd1698d · 2025-03-31T12:20:39.000+02:00
In case of an unexpected low address protection fault in user mode dump
fault info to make debugging a bit easier. At least the teid is valid,
while dumping the page table is racy, since no lock is held.
But it might still give some hints.

Acked-by: Vasily Gorbik &lt;gor@linux.ibm.com&gt;
Signed-off-by: Heiko Carstens &lt;hca@linux.ibm.com&gt;
Signed-off-by: Vasily Gorbik &lt;gor@linux.ibm.com&gt;
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
@@ -376,6 +376,7 @@ void do_protection_exception(struct pt_regs *regs)
 	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");
 		}
 		/*

Original file line number	Diff line number	Diff line change
`@@ -376,6 +376,7 @@ void do_protection_exception(struct pt_regs *regs)`
`376`	`376`	`if (unlikely(!teid.b61)) {`
`377`	`377`	`if (user_mode(regs)) {`
`378`	`378`	`/* Low-address protection in user mode: cannot happen */`
	`379`	`+ dump_fault_info(regs);`
`379`	`380`	`die(regs, "Low-address protection");`
`380`	`381`	`}`
`381`	`382`	`/*`