[PATCH v4 26/57] ftrace: add return address pointer to ftrace_ret_stack

[Josh Poimboeuf]

Storing this value will help prevent unwinders from getting out of sync
with the function graph tracer ret_stack.  Now instead of needing a
stateful iterator, they can compare the return address pointer to find
the right ret_stack entry.

Note that an array of 50 ftrace_ret_stack structs is allocated for every
task.  So when an arch implements this, it will add either 200 or 400
bytes of memory usage per task (depending on whether it's a 32-bit or
64-bit platform).

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
 Documentation/trace/ftrace-design.txt | 11 +++++++++++
 arch/arm/kernel/ftrace.c              |  2 +-
 arch/arm64/kernel/ftrace.c            |  2 +-
 arch/blackfin/kernel/ftrace.c         |  2 +-
 arch/microblaze/kernel/ftrace.c       |  2 +-
 arch/mips/kernel/ftrace.c             |  4 ++--
 arch/parisc/kernel/ftrace.c           |  2 +-
 arch/powerpc/kernel/ftrace.c          |  3 ++-
 arch/s390/kernel/ftrace.c             |  3 ++-
 arch/sh/kernel/ftrace.c               |  2 +-
 arch/sparc/kernel/ftrace.c            |  2 +-
 arch/tile/kernel/ftrace.c             |  2 +-
 arch/x86/kernel/ftrace.c              |  2 +-
 include/linux/ftrace.h                |  5 ++++-
 kernel/trace/trace_functions_graph.c  |  5 ++++-
 15 files changed, 34 insertions(+), 15 deletions(-)

diff --git a/Documentation/trace/ftrace-design.txt b/Documentation/trace/ftrace-design.txt
index dd5f916..a273dd0 100644
--- a/Documentation/trace/ftrace-design.txt
+++ b/Documentation/trace/ftrace-design.txt
@@ -203,6 +203,17 @@ along to ftrace_push_return_trace() instead of a stub value of 0.
 
 Similarly, when you call ftrace_return_to_handler(), pass it the frame pointer.
 
+HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
+--------------------------------
+
+An arch may pass in a pointer to the return address on the stack.  This
+prevents potential stack unwinding issues where the unwinder gets out of
+sync with ret_stack and the wrong addresses are reported by
+ftrace_graph_ret_addr().
+
+Adding support for it is easy: just define the macro in asm/ftrace.h and
+pass the return address pointer as the 'retp' argument to
+ftrace_push_return_trace().
 
 HAVE_FTRACE_NMI_ENTER
 ---------------------
diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
index 709ee1d..3f17594 100644
--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -218,7 +218,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
 	}
 
 	err = ftrace_push_return_trace(old, self_addr, &trace.depth,
-				       frame_pointer);
+				       frame_pointer, NULL);
 	if (err == -EBUSY) {
 		*parent = old;
 		return;
diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
index ebecf9a..40ad08a 100644
--- a/arch/arm64/kernel/ftrace.c
+++ b/arch/arm64/kernel/ftrace.c
@@ -138,7 +138,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
 		return;
 
 	err = ftrace_push_return_trace(old, self_addr, &trace.depth,
-				       frame_pointer);
+				       frame_pointer, NULL);
 	if (err == -EBUSY)
 		return;
 	else
diff --git a/arch/blackfin/kernel/ftrace.c b/arch/blackfin/kernel/ftrace.c
index 095de0f..8dad758 100644
--- a/arch/blackfin/kernel/ftrace.c
+++ b/arch/blackfin/kernel/ftrace.c
@@ -107,7 +107,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
 		return;
 
 	if (ftrace_push_return_trace(*parent, self_addr, &trace.depth,
-	                             frame_pointer) == -EBUSY)
+				     frame_pointer, NULL) == -EBUSY)
 		return;
 
 	trace.func = self_addr;
diff --git a/arch/microblaze/kernel/ftrace.c b/arch/microblaze/kernel/ftrace.c
index fc7b48a..d57563c 100644
--- a/arch/microblaze/kernel/ftrace.c
+++ b/arch/microblaze/kernel/ftrace.c
@@ -63,7 +63,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
 		return;
 	}
 
-	err = ftrace_push_return_trace(old, self_addr, &trace.depth, 0);
+	err = ftrace_push_return_trace(old, self_addr, &trace.depth, 0, NULL);
 	if (err == -EBUSY) {
 		*parent = old;
 		return;
diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
index 937c54b..30a3b75 100644
--- a/arch/mips/kernel/ftrace.c
+++ b/arch/mips/kernel/ftrace.c
@@ -382,8 +382,8 @@ void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra,
 	if (unlikely(faulted))
 		goto out;
 
-	if (ftrace_push_return_trace(old_parent_ra, self_ra, &trace.depth, fp)
-	    == -EBUSY) {
+	if (ftrace_push_return_trace(old_parent_ra, self_ra, &trace.depth, fp,
+				     NULL) == -EBUSY) {
 		*parent_ra_addr = old_parent_ra;
 		return;
 	}
diff --git a/arch/parisc/kernel/ftrace.c b/arch/parisc/kernel/ftrace.c
index a828a0a..5a5506a 100644
--- a/arch/parisc/kernel/ftrace.c
+++ b/arch/parisc/kernel/ftrace.c
@@ -48,7 +48,7 @@ static void __hot prepare_ftrace_return(unsigned long *parent,
 		return;
 
         if (ftrace_push_return_trace(old, self_addr, &trace.depth,
-			0 ) == -EBUSY)
+				     0, NULL) == -EBUSY)
                 return;
 
 	/* activate parisc_return_to_handler() as return point */
diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index cc52d97..a95639b 100644
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c
@@ -593,7 +593,8 @@ unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip)
 	if (!ftrace_graph_entry(&trace))
 		goto out;
 
-	if (ftrace_push_return_trace(parent, ip, &trace.depth, 0) == -EBUSY)
+	if (ftrace_push_return_trace(parent, ip, &trace.depth, 0,
+				     NULL) == -EBUSY)
 		goto out;
 
 	parent = return_hooker;
diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
index 0f7bfeb..60a8a4e 100644
--- a/arch/s390/kernel/ftrace.c
+++ b/arch/s390/kernel/ftrace.c
@@ -209,7 +209,8 @@ unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip)
 	/* Only trace if the calling function expects to. */
 	if (!ftrace_graph_entry(&trace))
 		goto out;
-	if (ftrace_push_return_trace(parent, ip, &trace.depth, 0) == -EBUSY)
+	if (ftrace_push_return_trace(parent, ip, &trace.depth, 0,
+				     NULL) == -EBUSY)
 		goto out;
 	parent = (unsigned long) return_to_handler;
 out:
diff --git a/arch/sh/kernel/ftrace.c b/arch/sh/kernel/ftrace.c
index 38993e0..95eccd4 100644
--- a/arch/sh/kernel/ftrace.c
+++ b/arch/sh/kernel/ftrace.c
@@ -382,7 +382,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
 		return;
 	}
 
-	err = ftrace_push_return_trace(old, self_addr, &trace.depth, 0);
+	err = ftrace_push_return_trace(old, self_addr, &trace.depth, 0, NULL);
 	if (err == -EBUSY) {
 		__raw_writel(old, parent);
 		return;
diff --git a/arch/sparc/kernel/ftrace.c b/arch/sparc/kernel/ftrace.c
index 0a2d2dd..6bcff69 100644
--- a/arch/sparc/kernel/ftrace.c
+++ b/arch/sparc/kernel/ftrace.c
@@ -131,7 +131,7 @@ unsigned long prepare_ftrace_return(unsigned long parent,
 		return parent + 8UL;
 
 	if (ftrace_push_return_trace(parent, self_addr, &trace.depth,
-				     frame_pointer) == -EBUSY)
+				     frame_pointer, NULL) == -EBUSY)
 		return parent + 8UL;
 
 	trace.func = self_addr;
diff --git a/arch/tile/kernel/ftrace.c b/arch/tile/kernel/ftrace.c
index 4a57208..b827a41 100644
--- a/arch/tile/kernel/ftrace.c
+++ b/arch/tile/kernel/ftrace.c
@@ -184,7 +184,7 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
 	*parent = return_hooker;
 
 	err = ftrace_push_return_trace(old, self_addr, &trace.depth,
-				       frame_pointer);
+				       frame_pointer, NULL);
 	if (err == -EBUSY) {
 		*parent = old;
 		return;
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index d036cfb..ae3b1fb 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -1029,7 +1029,7 @@ void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent,
 	}
 
 	if (ftrace_push_return_trace(old, self_addr, &trace.depth,
-		    frame_pointer) == -EBUSY) {
+				     frame_pointer, NULL) == -EBUSY) {
 		*parent = old;
 		return;
 	}
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 4ad9ccc..483e02a 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -798,6 +798,9 @@ struct ftrace_ret_stack {
 #ifdef HAVE_FUNCTION_GRAPH_FP_TEST
 	unsigned long fp;
 #endif
+#ifdef HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
+	unsigned long *retp;
+#endif
 };
 
 /*
@@ -809,7 +812,7 @@ extern void return_to_handler(void);
 
 extern int
 ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth,
-			 unsigned long frame_pointer);
+			 unsigned long frame_pointer, unsigned long *retp);
 
 /*
  * Sometimes we don't want to trace a function with the function
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 0e03ed0..f7212ec 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -119,7 +119,7 @@ print_graph_duration(struct trace_array *tr, unsigned long long duration,
 /* Add a function return address to the trace stack on thread info.*/
 int
 ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth,
-			 unsigned long frame_pointer)
+			 unsigned long frame_pointer, unsigned long *retp)
 {
 	unsigned long long calltime;
 	int index;
@@ -174,6 +174,9 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth,
 #ifdef HAVE_FUNCTION_GRAPH_FP_TEST
 	current->ret_stack[index].fp = frame_pointer;
 #endif
+#ifdef HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
+	current->ret_stack[index].retp = retp;
+#endif
 	*depth = current->curr_ret_stack;
 
 	return 0;
-- 
2.7.4