[S390] debug: enable exception-trace debug facility

The exception-trace facility on x86 and other architectures prints
traces to dmesg whenever a user space application crashes.
s390 has such a feature since ages however it is called
userprocess_debug and is enabled differently.
This patch makes sure that whenever one of the two procfs files

/proc/sys/kernel/userprocess_debug
/proc/sys/debug/exception-trace

is modified the contents of the second one changes as well.
That way we keep backwards compatibilty but also support the same
interface like other architectures do.
Besides that the output of the traces is improved since it will now
also contain the corresponding filename of the vma (when available)
where the process caused a fault or trap.
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/Kconfig

@@ -444,13 +444,6 @@ config FORCE_MAX_ZONEORDER
 	int
 	default "9"
 
-config PROCESS_DEBUG
-	bool "Show crashed user process info"
-	help
-	  Say Y to print all process fault locations to the console.  This is
-	  a debugging option; you probably do not want to set it unless you
-	  are an S390 port maintainer.
-
 config PFAULT
 	bool "Pseudo page fault support"
 	help

arch/s390/kernel/traps.c

@@ -46,13 +46,7 @@
 
 pgm_check_handler_t *pgm_check_table[128];
 
-#ifdef CONFIG_SYSCTL
-#ifdef CONFIG_PROCESS_DEBUG
-int sysctl_userprocess_debug = 1;
-#else
-int sysctl_userprocess_debug = 0;
-#endif
-#endif
+int show_unhandled_signals;
 
 extern pgm_check_handler_t do_protection_exception;
 extern pgm_check_handler_t do_dat_exception;
@@ -315,18 +309,19 @@ void die(const char * str, struct pt_regs * regs, long err)
 	do_exit(SIGSEGV);
 }
 
-static void inline
-report_user_fault(long interruption_code, struct pt_regs *regs)
+static void inline report_user_fault(struct pt_regs *regs, long int_code,
+				     int signr)
 {
-#if defined(CONFIG_SYSCTL)
-	if (!sysctl_userprocess_debug)
+	if ((task_pid_nr(current) > 1) && !show_unhandled_signals)
 		return;
-#endif
-#if defined(CONFIG_SYSCTL) || defined(CONFIG_PROCESS_DEBUG)
-	printk("User process fault: interruption code 0x%lX\n",
-	       interruption_code);
+	if (!unhandled_signal(current, signr))
+		return;
+	if (!printk_ratelimit())
+		return;
+	printk("User process fault: interruption code 0x%lX ", int_code);
+	print_vma_addr("in ", regs->psw.addr & PSW_ADDR_INSN);
+	printk("\n");
 	show_regs(regs);
-#endif
 }
 
 int is_valid_bugaddr(unsigned long addr)
@@ -354,7 +349,7 @@ static void __kprobes inline do_trap(long interruption_code, int signr,
 
                 tsk->thread.trap_no = interruption_code & 0xffff;
 		force_sig_info(signr, info, tsk);
-		report_user_fault(interruption_code, regs);
+		report_user_fault(regs, interruption_code, signr);
         } else {
                 const struct exception_table_entry *fixup;
                 fixup = search_exception_tables(regs->psw.addr & PSW_ADDR_INSN);
@@ -390,7 +385,7 @@ static void default_trap_handler(struct pt_regs * regs, long interruption_code)
 {
         if (regs->psw.mask & PSW_MASK_PSTATE) {
 		local_irq_enable();
-		report_user_fault(interruption_code, regs);
+		report_user_fault(regs, interruption_code, SIGSEGV);
 		do_exit(SIGSEGV);
 	} else
 		die("Unknown program exception", regs, interruption_code);

arch/s390/mm/fault.c

@@ -48,10 +48,6 @@
 #define __PF_RES_FIELD 0x8000000000000000ULL
 #endif /* CONFIG_64BIT */
 
-#ifdef CONFIG_SYSCTL
-extern int sysctl_userprocess_debug;
-#endif
-
 #define VM_FAULT_BADCONTEXT	0x010000
 #define VM_FAULT_BADMAP		0x020000
 #define VM_FAULT_BADACCESS	0x040000
@@ -120,6 +116,22 @@ static inline int user_space_fault(unsigned long trans_exc_code)
 	return trans_exc_code != 3;
 }
 
+static inline void report_user_fault(struct pt_regs *regs, long int_code,
+				     int signr, unsigned long address)
+{
+	if ((task_pid_nr(current) > 1) && !show_unhandled_signals)
+		return;
+	if (!unhandled_signal(current, signr))
+		return;
+	if (!printk_ratelimit())
+		return;
+	printk("User process fault: interruption code 0x%lX ", int_code);
+	print_vma_addr(KERN_CONT "in ", regs->psw.addr & PSW_ADDR_INSN);
+	printk("\n");
+	printk("failing address: %lX\n", address);
+	show_regs(regs);
+}
+
 /*
  * Send SIGSEGV to task.  This is an external routine
  * to keep the stack usage of do_page_fault small.
@@ -133,17 +145,7 @@ static noinline void do_sigsegv(struct pt_regs *regs, long int_code,
 	address = trans_exc_code & __FAIL_ADDR_MASK;
 	current->thread.prot_addr = address;
 	current->thread.trap_no = int_code;
-#if defined(CONFIG_SYSCTL) || defined(CONFIG_PROCESS_DEBUG)
-#if defined(CONFIG_SYSCTL)
-	if (sysctl_userprocess_debug)
-#endif
-	{
-		printk("User process fault: interruption code 0x%lX\n",
-		       int_code);
-		printk("failing address: %lX\n", address);
-		show_regs(regs);
-	}
-#endif
+	report_user_fault(regs, int_code, SIGSEGV, address);
 	si.si_signo = SIGSEGV;
 	si.si_code = si_code;
 	si.si_addr = (void __user *) address;

kernel/sysctl.c

@@ -621,7 +621,7 @@ static struct ctl_table kern_table[] = {
 #endif
 	{
 		.procname	= "userprocess_debug",
-		.data		= &sysctl_userprocess_debug,
+		.data		= &show_unhandled_signals,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec,
@@ -1431,7 +1431,8 @@ static struct ctl_table fs_table[] = {
 };
 
 static struct ctl_table debug_table[] = {
-#if defined(CONFIG_X86) || defined(CONFIG_PPC) || defined(CONFIG_SPARC)
+#if defined(CONFIG_X86) || defined(CONFIG_PPC) || defined(CONFIG_SPARC) || \
+    defined(CONFIG_S390)
 	{
 		.procname	= "exception-trace",
 		.data		= &show_unhandled_signals,