s390/ftrace: use HAVE_FUNCTION_GRAPH_RET_ADDR_PTR

Make the call chain more reliable by tagging the ftrace stack entries
with the stack pointer that is associated with the return address.

Signed-off-by: Martin Schwidefsky <[e-mail]>

arch/s390/include/asm/ftrace.h

···
 #define MCOUNT_RETURN_FIXUP	18
 #endif
 
+#define HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
+
 #ifndef __ASSEMBLY__
 
 #ifdef CONFIG_CC_IS_CLANG

arch/s390/kernel/entry.h

···
 void __init time_init(void);
 int pfn_is_nosave(unsigned long);
 void s390_early_resume(void);
-unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip);
+unsigned long prepare_ftrace_return(unsigned long parent, unsigned long sp, unsigned long ip);
 
 struct s390_mmap_arg_struct;
 struct fadvise64_64_args;

arch/s390/kernel/ftrace.c

···
  * Hook the return address and push it in the stack of return addresses
  * in current thread info.
  */
-unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip)
+unsigned long prepare_ftrace_return(unsigned long ra, unsigned long sp,
+				    unsigned long ip)
 {
 	if (unlikely(ftrace_graph_is_dead()))
 		goto out;
 	if (unlikely(atomic_read(&current->tracing_graph_pause)))
 		goto out;
 	ip -= MCOUNT_INSN_SIZE;
-	if (!function_graph_enter(parent, ip, 0, NULL))
-		parent = (unsigned long) return_to_handler;
+	if (!function_graph_enter(ra, ip, 0, (void *) sp))
+		ra = (unsigned long) return_to_handler;
 out:
-	return parent;
+	return ra;
 }
 NOKPROBE_SYMBOL(prepare_ftrace_return);
 

arch/s390/kernel/mcount.S

···
 	.globl ftrace_graph_caller
 ftrace_graph_caller:
 	j	ftrace_graph_caller_end
-	lg	%r2,(STACK_PTREGS_GPRS+14*8)(%r15)
-	lg	%r3,(STACK_PTREGS_PSW+8)(%r15)
+	lmg	%r2,%r3,(STACK_PTREGS_GPRS+14*8)(%r15)
+	lg	%r4,(STACK_PTREGS_PSW+8)(%r15)
 	brasl	%r14,prepare_ftrace_return
 	stg	%r2,(STACK_PTREGS_GPRS+14*8)(%r15)
 ftrace_graph_caller_end:

arch/s390/kernel/unwind_bc.c

···
 	/* Decode any ftrace redirection */
 	if (ip == (unsigned long) return_to_handler)
 		ip = ftrace_graph_ret_addr(state->task, &state->graph_idx,
-					   ip, NULL);
+					   ip, (void *) sp);
 #endif
 
 	/* Update unwind state */