powerpc/ftrace: Enable HAVE_FUNCTION_GRAPH_RET_ADDR_PTR

This associates entries in the ftrace_ret_stack with corresponding stack
frames, enabling more robust stack unwinding. Also update the only user
of ftrace_graph_ret_addr() to pass the stack pointer.
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/0224f2d0971b069c678e2ff678cfc2cd1e114cfe.1567707399.git.naveen.n.rao@linux.vnet.ibm.com

arch/powerpc/include/asm/asm-prototypes.h

@@ -134,7 +134,8 @@ extern int __ucmpdi2(u64, u64);
 
 /* tracing */
 void _mcount(void);
-unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip);
+unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip,
+						unsigned long sp);
 
 void pnv_power9_force_smt4_catch(void);
 void pnv_power9_force_smt4_release(void);

arch/powerpc/include/asm/ftrace.h

@@ -8,6 +8,8 @@
 #define MCOUNT_ADDR		((unsigned long)(_mcount))
 #define MCOUNT_INSN_SIZE	4 /* sizeof mcount call */
 
+#define HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
+
 #ifdef __ASSEMBLY__
 
 /* Based off of objdump optput from glibc */

arch/powerpc/kernel/stacktrace.c

@@ -182,7 +182,7 @@ static int __save_stack_trace_tsk_reliable(struct task_struct *tsk,
 		 * FIXME: IMHO these tests do not belong in
 		 * arch-dependent code, they are generic.
 		 */
-		ip = ftrace_graph_ret_addr(tsk, &graph_idx, ip, NULL);
+		ip = ftrace_graph_ret_addr(tsk, &graph_idx, ip, stack);
 #ifdef CONFIG_KPROBES
 		/*
 		 * Mark stacktraces with kretprobed functions on them

arch/powerpc/kernel/trace/ftrace.c

@@ -944,7 +944,8 @@ int ftrace_disable_ftrace_graph_caller(void)
  * Hook the return address and push it in the stack of return addrs
  * in current thread info. Return the address we want to divert to.
  */
-unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip)
+unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip,
+						unsigned long sp)
 {
 	unsigned long return_hooker;
 
@@ -956,7 +957,7 @@ unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip)
 
 	return_hooker = ppc_function_entry(return_to_handler);
 
-	if (!function_graph_enter(parent, ip, 0, NULL))
+	if (!function_graph_enter(parent, ip, 0, (unsigned long *)sp))
 		parent = return_hooker;
 out:
 	return parent;

arch/powerpc/kernel/trace/ftrace_32.S

@@ -50,6 +50,7 @@ _GLOBAL(ftrace_stub)
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 _GLOBAL(ftrace_graph_caller)
+	addi	r5, r1, 48
 	/* load r4 with local address */
 	lwz	r4, 44(r1)
 	subi	r4, r4, MCOUNT_INSN_SIZE

arch/powerpc/kernel/trace/ftrace_64_mprofile.S

@@ -294,6 +294,7 @@ _GLOBAL(ftrace_graph_caller)
 	std	r2, 24(r1)
 	ld	r2, PACATOC(r13)	/* get kernel TOC in r2 */
 
+	addi	r5, r1, 112
 	mfctr	r4		/* ftrace_caller has moved local addr here */
 	std	r4, 40(r1)
 	mflr	r3		/* ftrace_caller has restored LR from stack */

arch/powerpc/kernel/trace/ftrace_64_pg.S

@@ -41,6 +41,7 @@ _GLOBAL(ftrace_stub)
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 _GLOBAL(ftrace_graph_caller)
+	addi	r5, r1, 112
 	/* load r4 with local address */
 	ld	r4, 128(r1)
 	subi	r4, r4, MCOUNT_INSN_SIZE