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

7 files changed, 11 insertions, 4 deletions

diff --git a/arch/powerpc/include/asm/asm-prototypes.h b/arch/powerpc/include/asm/asm-prototypes.h
index 49196d35e3bb..8561498e653c 100644
--- a/arch/powerpc/include/asm/asm-prototypes.h
+++ b/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);
diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
index 3dfb80b86561..f54a08a2cd70 100644
--- a/arch/powerpc/include/asm/ftrace.h
+++ b/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 */
diff --git a/arch/powerpc/kernel/stacktrace.c b/arch/powerpc/kernel/stacktrace.c
index 1e2276963f6d..e2a46cfed5fd 100644
--- a/arch/powerpc/kernel/stacktrace.c
+++ b/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
diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
index be1ca98fce5c..7ea0ca044b65 100644
--- a/arch/powerpc/kernel/trace/ftrace.c
+++ b/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;
diff --git a/arch/powerpc/kernel/trace/ftrace_32.S b/arch/powerpc/kernel/trace/ftrace_32.S
index 183f608efb81..e023ae59c429 100644
--- a/arch/powerpc/kernel/trace/ftrace_32.S
+++ b/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
diff --git a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
index 74acbf16a666..f9fd5f743eba 100644
--- a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
+++ b/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 */
diff --git a/arch/powerpc/kernel/trace/ftrace_64_pg.S b/arch/powerpc/kernel/trace/ftrace_64_pg.S
index e41a7d13c99c..6708e24db0ab 100644
--- a/arch/powerpc/kernel/trace/ftrace_64_pg.S
+++ b/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