s390/stacktrace: Merge perf_callchain_user() and arch_stack_walk_user()

The two functions perf_callchain_user() and arch_stack_walk_user() are
nearly identical. Reduce code duplication and add a common helper which can
be called by both functions.

Fixes: aa44433ac4 ("s390: add USER_STACKTRACE support")
Reviewed-by: Jens Remus <jremus@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

arch/s390/include/asm/stacktrace.h

@@ -2,6 +2,7 @@
 #ifndef _ASM_S390_STACKTRACE_H
 #define _ASM_S390_STACKTRACE_H
 
+#include <linux/stacktrace.h>
 #include <linux/uaccess.h>
 #include <linux/ptrace.h>
 
@@ -12,6 +13,12 @@ struct stack_frame_user {
 	unsigned long empty2[4];
 };
 
+struct perf_callchain_entry_ctx;
+
+void arch_stack_walk_user_common(stack_trace_consume_fn consume_entry, void *cookie,
+				 struct perf_callchain_entry_ctx *entry,
+				 const struct pt_regs *regs, bool perf);
+
 enum stack_type {
 	STACK_TYPE_UNKNOWN,
 	STACK_TYPE_TASK,

arch/s390/kernel/perf_event.c

@@ -218,39 +218,7 @@ void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
 void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
 			 struct pt_regs *regs)
 {
-	struct stack_frame_user __user *sf;
+	arch_stack_walk_user_common(NULL, NULL, entry, regs, true);
-	unsigned long ip, sp;
-	bool first = true;
-
-	if (is_compat_task())
-		return;
-	perf_callchain_store(entry, instruction_pointer(regs));
-	sf = (void __user *)user_stack_pointer(regs);
-	pagefault_disable();
-	while (entry->nr < entry->max_stack) {
-		if (__get_user(sp, &sf->back_chain))
-			break;
-		if (__get_user(ip, &sf->gprs[8]))
-			break;
-		if (ip & 0x1) {
-			/*
-			 * If the instruction address is invalid, and this
-			 * is the first stack frame, assume r14 has not
-			 * been written to the stack yet. Otherwise exit.
-			 */
-			if (first && !(regs->gprs[14] & 0x1))
-				ip = regs->gprs[14];
-			else
-				break;
-		}
-		perf_callchain_store(entry, ip);
-		/* Sanity check: ABI requires SP to be aligned 8 bytes. */
-		if (!sp || sp & 0x7)
-			break;
-		sf = (void __user *)sp;
-		first = false;
-	}
-	pagefault_enable();
 }
 
 /* Perf definitions for PMU event attributes in sysfs */

arch/s390/kernel/stacktrace.c

@@ -5,6 +5,7 @@
  *  Copyright IBM Corp. 2006
  */
 
+#include <linux/perf_event.h>
 #include <linux/stacktrace.h>
 #include <linux/uaccess.h>
 #include <linux/compat.h>
@@ -62,8 +63,23 @@ int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry,
 	return 0;
 }
 
-void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
+static inline bool store_ip(stack_trace_consume_fn consume_entry, void *cookie,
-			  const struct pt_regs *regs)
+			    struct perf_callchain_entry_ctx *entry, bool perf,
+			    unsigned long ip)
+{
+#ifdef CONFIG_PERF_EVENTS
+	if (perf) {
+		if (perf_callchain_store(entry, ip))
+			return false;
+		return true;
+	}
+#endif
+	return consume_entry(cookie, ip);
+}
+
+void arch_stack_walk_user_common(stack_trace_consume_fn consume_entry, void *cookie,
+				 struct perf_callchain_entry_ctx *entry,
+				 const struct pt_regs *regs, bool perf)
 {
 	struct stack_frame_user __user *sf;
 	unsigned long ip, sp;
@@ -71,7 +87,8 @@ void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
 
 	if (is_compat_task())
 		return;
-	if (!consume_entry(cookie, instruction_pointer(regs)))
+	ip = instruction_pointer(regs);
+	if (!store_ip(consume_entry, cookie, entry, perf, ip))
 		return;
 	sf = (void __user *)user_stack_pointer(regs);
 	pagefault_disable();
@@ -91,8 +108,8 @@ void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
 			else
 				break;
 		}
-		if (!consume_entry(cookie, ip))
+		if (!store_ip(consume_entry, cookie, entry, perf, ip))
-			break;
+			return;
 		/* Sanity check: ABI requires SP to be aligned 8 bytes. */
 		if (!sp || sp & 0x7)
 			break;
@@ -102,6 +119,12 @@ void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
 	pagefault_enable();
 }
 
+void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
+			  const struct pt_regs *regs)
+{
+	arch_stack_walk_user_common(consume_entry, cookie, NULL, regs, false);
+}
+
 unsigned long return_address(unsigned int n)
 {
 	struct unwind_state state;