[PATCH 0/8] ftrace/x86: function_graph stack dump fixes

[PATCH 0/8] ftrace/x86: function_graph stack dump fixes

[Josh Poimboeuf]

Some stack dump fixes related to function_graph tracing.

Josh Poimboeuf (8):
  ftrace: remove CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST from config
  ftrace: only allocate the ret_stack 'fp' field when needed
  ftrace: add return address pointer to ftrace_ret_stack
  ftrace: add ftrace_graph_ret_addr() stack unwinding helpers
  x86/dumpstack/ftrace: convert dump_trace() callbacks to use
    ftrace_graph_ret_addr()
  ftrace/x86: implement HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
  x86/dumpstack/ftrace: mark function graph handler function as
    unreliable
  x86/dumpstack/ftrace: don't print unreliable addresses in
    print_context_stack_bp()

 Documentation/trace/ftrace-design.txt | 11 ++++++
 arch/arm/kernel/ftrace.c              |  2 +-
 arch/arm64/kernel/entry-ftrace.S      |  2 +-
 arch/arm64/kernel/ftrace.c            |  2 +-
 arch/blackfin/kernel/ftrace-entry.S   |  4 +-
 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/Kconfig                    |  1 -
 arch/sparc/include/asm/ftrace.h       |  4 ++
 arch/sparc/kernel/ftrace.c            |  2 +-
 arch/tile/kernel/ftrace.c             |  2 +-
 arch/x86/Kconfig                      |  1 -
 arch/x86/include/asm/ftrace.h         |  3 ++
 arch/x86/kernel/dumpstack.c           | 73 ++++++++++++++---------------------
 arch/x86/kernel/ftrace.c              |  2 +-
 include/linux/ftrace.h                | 17 +++++++-
 kernel/trace/Kconfig                  |  5 ---
 kernel/trace/trace_functions_graph.c  | 67 +++++++++++++++++++++++++++++++-
 23 files changed, 146 insertions(+), 70 deletions(-)

-- 
2.7.4

[PATCH 1/8] ftrace: remove CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST from config

[Josh Poimboeuf]

Make HAVE_FUNCTION_GRAPH_FP_TEST a normal define, independent from
kconfig.  This removes some config file pollution and simplifies the
checking for the fp test.

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 arch/arm64/kernel/entry-ftrace.S     | 2 +-
 arch/blackfin/kernel/ftrace-entry.S  | 4 ++--
 arch/sparc/Kconfig                   | 1 -
 arch/sparc/include/asm/ftrace.h      | 4 ++++
 arch/x86/Kconfig                     | 1 -
 arch/x86/include/asm/ftrace.h        | 1 +
 kernel/trace/Kconfig                 | 5 -----
 kernel/trace/trace_functions_graph.c | 2 +-
 8 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S
index 0f03a8f..aef02d2 100644
--- a/arch/arm64/kernel/entry-ftrace.S
+++ b/arch/arm64/kernel/entry-ftrace.S
@@ -219,7 +219,7 @@ ENDPROC(ftrace_graph_caller)
  *
  * Run ftrace_return_to_handler() before going back to parent.
  * @fp is checked against the value passed by ftrace_graph_caller()
- * only when CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST is enabled.
+ * only when HAVE_FUNCTION_GRAPH_FP_TEST is enabled.
  */
 ENTRY(return_to_handler)
 	save_return_regs
diff --git a/arch/blackfin/kernel/ftrace-entry.S b/arch/blackfin/kernel/ftrace-entry.S
index 28d0595..3b8bdcb 100644
--- a/arch/blackfin/kernel/ftrace-entry.S
+++ b/arch/blackfin/kernel/ftrace-entry.S
@@ -169,7 +169,7 @@ ENTRY(_ftrace_graph_caller)
 	r0 = sp;	/* unsigned long *parent */
 	r1 = [sp];	/* unsigned long self_addr */
 # endif
-# ifdef CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST
+# ifdef HAVE_FUNCTION_GRAPH_FP_TEST
 	r2 = fp;	/* unsigned long frame_pointer */
 # endif
 	r0 += 16;	/* skip the 4 local regs on stack */
@@ -190,7 +190,7 @@ ENTRY(_return_to_handler)
 	[--sp] = r1;
 
 	/* get original return address */
-# ifdef CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST
+# ifdef HAVE_FUNCTION_GRAPH_FP_TEST
 	r0 = fp;	/* Blackfin is sane, so omit this */
 # endif
 	call _ftrace_return_to_handler;
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index 59b0960..f5d60f1 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -56,7 +56,6 @@ config SPARC64
 	def_bool 64BIT
 	select HAVE_FUNCTION_TRACER
 	select HAVE_FUNCTION_GRAPH_TRACER
-	select HAVE_FUNCTION_GRAPH_FP_TEST
 	select HAVE_KRETPROBES
 	select HAVE_KPROBES
 	select HAVE_RCU_TABLE_FREE if SMP
diff --git a/arch/sparc/include/asm/ftrace.h b/arch/sparc/include/asm/ftrace.h
index 3192a8e..62755a3 100644
--- a/arch/sparc/include/asm/ftrace.h
+++ b/arch/sparc/include/asm/ftrace.h
@@ -9,6 +9,10 @@
 void _mcount(void);
 #endif
 
+#endif /* CONFIG_MCOUNT */
+
+#if defined(CONFIG_SPARC64) && !defined(CC_USE_FENTRY)
+#define HAVE_FUNCTION_GRAPH_FP_TEST
 #endif
 
 #ifdef CONFIG_DYNAMIC_FTRACE
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index c580d8c..acf85ae 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -110,7 +110,6 @@ config X86
 	select HAVE_EXIT_THREAD
 	select HAVE_FENTRY			if X86_64
 	select HAVE_FTRACE_MCOUNT_RECORD
-	select HAVE_FUNCTION_GRAPH_FP_TEST
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_FUNCTION_TRACER
 	select HAVE_GCC_PLUGINS
diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
index a4820d4..37f67cb 100644
--- a/arch/x86/include/asm/ftrace.h
+++ b/arch/x86/include/asm/ftrace.h
@@ -6,6 +6,7 @@
 # define MCOUNT_ADDR		((unsigned long)(__fentry__))
 #else
 # define MCOUNT_ADDR		((unsigned long)(mcount))
+# define HAVE_FUNCTION_GRAPH_FP_TEST
 #endif
 #define MCOUNT_INSN_SIZE	5 /* sizeof mcount call */
 
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index f4b86e8..ba33267 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -24,11 +24,6 @@ config HAVE_FUNCTION_GRAPH_TRACER
 	help
 	  See Documentation/trace/ftrace-design.txt
 
-config HAVE_FUNCTION_GRAPH_FP_TEST
-	bool
-	help
-	  See Documentation/trace/ftrace-design.txt
-
 config HAVE_DYNAMIC_FTRACE
 	bool
 	help
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 7363ccf..fc173cd 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -204,7 +204,7 @@ ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret,
 		return;
 	}
 
-#if defined(CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST) && !defined(CC_USING_FENTRY)
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
 	/*
 	 * The arch may choose to record the frame pointer used
 	 * and check it here to make sure that it is what we expect it
-- 
2.7.4

[PATCH 2/8] ftrace: only allocate the ret_stack 'fp' field when needed

[Josh Poimboeuf]

This saves some memory when HAVE_FUNCTION_GRAPH_FP_TEST isn't defined.
On x86_64 with newer versions of gcc which have -mfentry, it saves 400
bytes per task.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 include/linux/ftrace.h               | 2 ++
 kernel/trace/trace_functions_graph.c | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 7d565af..4ad9ccc 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -795,7 +795,9 @@ struct ftrace_ret_stack {
 	unsigned long func;
 	unsigned long long calltime;
 	unsigned long long subtime;
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
 	unsigned long fp;
+#endif
 };
 
 /*
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index fc173cd..0e03ed0 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -171,7 +171,9 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth,
 	current->ret_stack[index].func = func;
 	current->ret_stack[index].calltime = calltime;
 	current->ret_stack[index].subtime = 0;
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
 	current->ret_stack[index].fp = frame_pointer;
+#endif
 	*depth = current->curr_ret_stack;
 
 	return 0;
-- 
2.7.4

[PATCH 3/8] 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@redhat.com>
---
 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

[PATCH 4/8] ftrace: add ftrace_graph_ret_addr() stack unwinding helpers

[Josh Poimboeuf]

When function graph tracing is enabled for a function, ftrace modifies
the stack by replacing the original return address with the address of a
hook function (return_to_handler).

Stack unwinders need a way to get the original return address.  Add an
arch-independent helper function for that named ftrace_graph_ret_addr().

This adds two variations of the function: one depends on
HAVE_FUNCTION_GRAPH_RET_ADDR_PTR, and the other relies on an index state
variable.

The former is recommended because, in some cases, the latter can cause
problems when the unwinder skips stack frames.  It can get out of sync
with the ret_stack index and wrong addresses can be reported for the
stack trace.

Once all arches have been ported to use
HAVE_FUNCTION_GRAPH_RET_ADDR_PTR, we can get rid of the distinction.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 include/linux/ftrace.h               | 10 +++++++
 kernel/trace/trace_functions_graph.c | 58 ++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 483e02a..6f93ac4 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -814,6 +814,9 @@ extern int
 ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth,
 			 unsigned long frame_pointer, unsigned long *retp);
 
+unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
+				    unsigned long ret, unsigned long *retp);
+
 /*
  * Sometimes we don't want to trace a function with the function
  * graph tracer but we want them to keep traced by the usual function
@@ -875,6 +878,13 @@ static inline int task_curr_ret_stack(struct task_struct *tsk)
 	return -1;
 }
 
+static inline unsigned long
+ftrace_graph_ret_addr(struct task_struct *task, int *idx, unsigned long ret,
+		      unsigned long *retp)
+{
+	return ret;
+}
+
 static inline void pause_graph_tracing(void) { }
 static inline void unpause_graph_tracing(void) { }
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index f7212ec..0cbe38a 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -284,6 +284,64 @@ unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
 	return ret;
 }
 
+/**
+ * ftrace_graph_ret_addr - convert a potentially modified stack return address
+ *			   to its original value
+ *
+ * This function can be called by stack unwinding code to convert a found stack
+ * return address ('ret') to its original value, in case the function graph
+ * tracer has modified it to be 'return_to_handler'.  If the address hasn't
+ * been modified, the unchanged value of 'ret' is returned.
+ *
+ * 'idx' is a state variable which should be initialized by the caller to zero
+ * before the first call.
+ *
+ * 'retp' is a pointer to the return address on the stack.  It's ignored if
+ * the arch doesn't have HAVE_FUNCTION_GRAPH_RET_ADDR_PTR defined.
+ */
+#ifdef HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
+unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
+				    unsigned long ret, unsigned long *retp)
+{
+	int index = task->curr_ret_stack;
+	int i;
+
+	if (ret != (unsigned long)return_to_handler)
+		return ret;
+
+	if (index < -1)
+		index += FTRACE_NOTRACE_DEPTH;
+
+	if (index < 0)
+		return ret;
+
+	for (i = 0; i <= index; i++)
+		if (task->ret_stack[i].retp == retp)
+			return task->ret_stack[i].ret;
+
+	return ret;
+}
+#else /* !HAVE_FUNCTION_GRAPH_RET_ADDR_PTR */
+unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
+				    unsigned long ret, unsigned long *retp)
+{
+	int task_idx;
+
+	if (ret != (unsigned long)return_to_handler)
+		return ret;
+
+	task_idx = task->curr_ret_stack;
+
+	if (!task->ret_stack || task_idx < *idx)
+		return ret;
+
+	task_idx -= *idx;
+	(*idx)++;
+
+	return task->ret_stack[task_idx].ret;
+}
+#endif /* HAVE_FUNCTION_GRAPH_RET_ADDR_PTR */
+
 int __trace_graph_entry(struct trace_array *tr,
 				struct ftrace_graph_ent *trace,
 				unsigned long flags,
-- 
2.7.4

[PATCH 5/8] x86/dumpstack/ftrace: convert dump_trace() callbacks to use ftrace_graph_ret_addr()

[Josh Poimboeuf]

Convert print_context_stack() and print_context_stack_bp() to use the
arch-independent ftrace_graph_ret_addr() helper.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 arch/x86/kernel/dumpstack.c | 65 +++++++++++++++------------------------------
 1 file changed, 22 insertions(+), 43 deletions(-)

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 5f49c04..9bf3d02 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -38,38 +38,6 @@ void printk_address(unsigned long address)
 	pr_cont(" [<%p>] %pS\n", (void *)address, (void *)address);
 }
 
-#ifdef CONFIG_FUNCTION_GRAPH_TRACER
-static void
-print_ftrace_graph_addr(unsigned long addr, void *data,
-			const struct stacktrace_ops *ops,
-			struct task_struct *task, int *graph)
-{
-	unsigned long ret_addr;
-	int index;
-
-	if (addr != (unsigned long)return_to_handler)
-		return;
-
-	index = task->curr_ret_stack;
-
-	if (!task->ret_stack || index < *graph)
-		return;
-
-	index -= *graph;
-	ret_addr = task->ret_stack[index].ret;
-
-	ops->address(data, ret_addr, 1);
-
-	(*graph)++;
-}
-#else
-static inline void
-print_ftrace_graph_addr(unsigned long addr, void *data,
-			const struct stacktrace_ops *ops,
-			struct task_struct *task, int *graph)
-{ }
-#endif
-
 /*
  * x86-64 can have up to three kernel stacks:
  * process stack
@@ -107,18 +75,24 @@ print_context_stack(struct task_struct *task,
 		stack = (unsigned long *)task_stack_page(task);
 
 	while (valid_stack_ptr(task, stack, sizeof(*stack), end)) {
-		unsigned long addr;
+		unsigned long addr = *stack;
 
-		addr = *stack;
 		if (__kernel_text_address(addr)) {
+			unsigned long real_addr;
+			int reliable = 0;
+
 			if ((unsigned long) stack == bp + sizeof(long)) {
-				ops->address(data, addr, 1);
+				reliable = 1;
 				frame = frame->next_frame;
 				bp = (unsigned long) frame;
-			} else {
-				ops->address(data, addr, 0);
 			}
-			print_ftrace_graph_addr(addr, data, ops, task, graph);
+
+			ops->address(data, addr, reliable);
+
+			real_addr = ftrace_graph_ret_addr(task, graph, addr,
+							  stack);
+			if (real_addr != addr)
+				ops->address(data, real_addr, 1);
 		}
 		stack++;
 	}
@@ -133,19 +107,24 @@ print_context_stack_bp(struct task_struct *task,
 		       unsigned long *end, int *graph)
 {
 	struct stack_frame *frame = (struct stack_frame *)bp;
-	unsigned long *ret_addr = &frame->return_address;
+	unsigned long *retp = &frame->return_address;
 
-	while (valid_stack_ptr(task, ret_addr, sizeof(*ret_addr), end)) {
-		unsigned long addr = *ret_addr;
+	while (valid_stack_ptr(task, retp, sizeof(*retp), end)) {
+		unsigned long addr = *retp;
+		unsigned long real_addr;
 
 		if (!__kernel_text_address(addr))
 			break;
 
 		if (ops->address(data, addr, 1))
 			break;
+
+		real_addr = ftrace_graph_ret_addr(task, graph, addr, retp);
+		if (real_addr != addr)
+			ops->address(data, real_addr, 1);
+
 		frame = frame->next_frame;
-		ret_addr = &frame->return_address;
-		print_ftrace_graph_addr(addr, data, ops, task, graph);
+		retp = &frame->return_address;
 	}
 
 	return (unsigned long)frame;
-- 
2.7.4

[PATCH 6/8] ftrace/x86: implement HAVE_FUNCTION_GRAPH_RET_ADDR_PTR

[Josh Poimboeuf]

Use the more reliable version of ftrace_graph_ret_addr() so we no longer
have to worry about the unwinder getting out of sync with the function
graph ret_stack index, which can happen if the unwinder skips any frames
before calling ftrace_graph_ret_addr().

This fixes this issue (and several others like it):

  $ cat /proc/self/stack
  [<ffffffff810489a2>] save_stack_trace_tsk+0x22/0x40
  [<ffffffff81311a89>] proc_pid_stack+0xb9/0x110
  [<ffffffff813127c4>] proc_single_show+0x54/0x80
  [<ffffffff812be088>] seq_read+0x108/0x3e0
  [<ffffffff812923d7>] __vfs_read+0x37/0x140
  [<ffffffff812929d9>] vfs_read+0x99/0x140
  [<ffffffff81293f28>] SyS_read+0x58/0xc0
  [<ffffffff818af97c>] entry_SYSCALL_64_fastpath+0x1f/0xbd
  [<ffffffffffffffff>] 0xffffffffffffffff

  $ echo function_graph > /sys/kernel/debug/tracing/current_tracer

  $ cat /proc/self/stack
  [<ffffffff818b2428>] return_to_handler+0x0/0x27
  [<ffffffff810394cc>] print_context_stack+0xfc/0x100
  [<ffffffff818b2428>] return_to_handler+0x0/0x27
  [<ffffffff8103891b>] dump_trace+0x12b/0x350
  [<ffffffff818b2428>] return_to_handler+0x0/0x27
  [<ffffffff810489a2>] save_stack_trace_tsk+0x22/0x40
  [<ffffffff818b2428>] return_to_handler+0x0/0x27
  [<ffffffff81311a89>] proc_pid_stack+0xb9/0x110
  [<ffffffff818b2428>] return_to_handler+0x0/0x27
  [<ffffffff813127c4>] proc_single_show+0x54/0x80
  [<ffffffff818b2428>] return_to_handler+0x0/0x27
  [<ffffffff812be088>] seq_read+0x108/0x3e0
  [<ffffffff818b2428>] return_to_handler+0x0/0x27
  [<ffffffff812923d7>] __vfs_read+0x37/0x140
  [<ffffffff818b2428>] return_to_handler+0x0/0x27
  [<ffffffff812929d9>] vfs_read+0x99/0x140
  [<ffffffffffffffff>] 0xffffffffffffffff

Enabling function graph tracing causes the stack trace to change in two
ways:

First, the real call addresses are confusingly interspersed with
'return_to_handler' addresses.  This issue will be fixed by the next
patch.

Second, the stack trace is offset by two frames, because the unwinder
skipped the first two frames and got out of sync with the ret_stack
index.  This patch fixes this issue.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 arch/x86/include/asm/ftrace.h | 2 ++
 arch/x86/kernel/ftrace.c      | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
index 37f67cb..eccd0ac 100644
--- a/arch/x86/include/asm/ftrace.h
+++ b/arch/x86/include/asm/ftrace.h
@@ -14,6 +14,8 @@
 #define ARCH_SUPPORTS_FTRACE_OPS 1
 #endif
 
+#define HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
+
 #ifndef __ASSEMBLY__
 extern void mcount(void);
 extern atomic_t modifying_ftrace_code;
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index ae3b1fb..8639bb2 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, NULL) == -EBUSY) {
+				     frame_pointer, parent) == -EBUSY) {
 		*parent = old;
 		return;
 	}
-- 
2.7.4

[PATCH 7/8] x86/dumpstack/ftrace: mark function graph handler function as unreliable

[Josh Poimboeuf]

When function graph tracing is enabled for a function, its return
address on the stack is replaced with the address of an ftrace handler
(return_to_handler).

Currently 'return_to_handler' can be reported as reliable.  That's not
ideal, and can actually be misleading.  When saving or dumping the
stack, you normally only care about what led up to that point (the call
path), rather than what will happen in the future (the return path).

That's especially true in the non-oops stack trace case, which isn't
used for debugging.  For example, in a perf profiling operation,
reporting return_to_handler() in the trace would just be confusing.

And in the oops case, where debugging is important, "unreliable" is also
more appropriate there because it serves as a hint that graph tracing
was involved, instead of trying to imply that return_to_handler() was
the real caller.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 arch/x86/kernel/dumpstack.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 9bf3d02..6aad8d4 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -87,12 +87,21 @@ print_context_stack(struct task_struct *task,
 				bp = (unsigned long) frame;
 			}
 
-			ops->address(data, addr, reliable);
-
+			/*
+			 * When function graph tracing is enabled for a
+			 * function, its return address on the stack is
+			 * replaced with the address of an ftrace handler
+			 * (return_to_handler).  In that case, before printing
+			 * the "real" address, we want to print the handler
+			 * address as an "unreliable" hint that function graph
+			 * tracing was involved.
+			 */
 			real_addr = ftrace_graph_ret_addr(task, graph, addr,
 							  stack);
 			if (real_addr != addr)
-				ops->address(data, real_addr, 1);
+				ops->address(data, addr, 0);
+
+			ops->address(data, real_addr, reliable);
 		}
 		stack++;
 	}
@@ -116,12 +125,11 @@ print_context_stack_bp(struct task_struct *task,
 		if (!__kernel_text_address(addr))
 			break;
 
-		if (ops->address(data, addr, 1))
-			break;
-
 		real_addr = ftrace_graph_ret_addr(task, graph, addr, retp);
-		if (real_addr != addr)
-			ops->address(data, real_addr, 1);
+		if (real_addr != addr && ops->address(data, addr, 0))
+			break;
+		if (ops->address(data, real_addr, 1))
+			break;
 
 		frame = frame->next_frame;
 		retp = &frame->return_address;
-- 
2.7.4

[PATCH 8/8] x86/dumpstack/ftrace: don't print unreliable addresses in print_context_stack_bp()

[Josh Poimboeuf]

When function graph tracing is enabled, print_context_stack_bp() can
report return_to_handler() as an unreliable address, which is confusing
and misleading: return_to_handler() is really only useful as a hint for
debugging, whereas print_context_stack_bp() users only care about the
actual 'reliable' call path.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
---
 arch/x86/kernel/dumpstack.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 6aad8d4..01072e9 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -126,8 +126,6 @@ print_context_stack_bp(struct task_struct *task,
 			break;
 
 		real_addr = ftrace_graph_ret_addr(task, graph, addr, retp);
-		if (real_addr != addr && ops->address(data, addr, 0))
-			break;
 		if (ops->address(data, real_addr, 1))
 			break;
 
-- 
2.7.4

Re: [PATCH 0/8] ftrace/x86: function_graph stack dump fixes

[Steven Rostedt]

On Fri, 19 Aug 2016 06:52:54 -0500
Josh Poimboeuf <jpoimboe@redhat.com> wrote:

> Some stack dump fixes related to function_graph tracing.
> 
> Josh Poimboeuf (8):
>   ftrace: remove CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST from config
>   ftrace: only allocate the ret_stack 'fp' field when needed
>   ftrace: add return address pointer to ftrace_ret_stack
>   ftrace: add ftrace_graph_ret_addr() stack unwinding helpers
>   x86/dumpstack/ftrace: convert dump_trace() callbacks to use
>     ftrace_graph_ret_addr()
>   ftrace/x86: implement HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
>   x86/dumpstack/ftrace: mark function graph handler function as
>     unreliable
>   x86/dumpstack/ftrace: don't print unreliable addresses in
>     print_context_stack_bp()

For the series..

Acked-by: Steven Rostedt <rostedt@goodmis.org>

Ingo,

If you want, please take it through tip.

Thanks!

-- Steve

> 
>  Documentation/trace/ftrace-design.txt | 11 ++++++
>  arch/arm/kernel/ftrace.c              |  2 +-
>  arch/arm64/kernel/entry-ftrace.S      |  2 +-
>  arch/arm64/kernel/ftrace.c            |  2 +-
>  arch/blackfin/kernel/ftrace-entry.S   |  4 +-
>  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/Kconfig                    |  1 -
>  arch/sparc/include/asm/ftrace.h       |  4 ++
>  arch/sparc/kernel/ftrace.c            |  2 +-
>  arch/tile/kernel/ftrace.c             |  2 +-
>  arch/x86/Kconfig                      |  1 -
>  arch/x86/include/asm/ftrace.h         |  3 ++
>  arch/x86/kernel/dumpstack.c           | 73 ++++++++++++++---------------------
>  arch/x86/kernel/ftrace.c              |  2 +-
>  include/linux/ftrace.h                | 17 +++++++-
>  kernel/trace/Kconfig                  |  5 ---
>  kernel/trace/trace_functions_graph.c  | 67 +++++++++++++++++++++++++++++++-
>  23 files changed, 146 insertions(+), 70 deletions(-)
> 

Re: [PATCH 0/8] ftrace/x86: function_graph stack dump fixes

[Ingo Molnar]

* Steven Rostedt <rostedt@goodmis.org> wrote:

> On Fri, 19 Aug 2016 06:52:54 -0500
> Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> 
> > Some stack dump fixes related to function_graph tracing.
> > 
> > Josh Poimboeuf (8):
> >   ftrace: remove CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST from config
> >   ftrace: only allocate the ret_stack 'fp' field when needed
> >   ftrace: add return address pointer to ftrace_ret_stack
> >   ftrace: add ftrace_graph_ret_addr() stack unwinding helpers
> >   x86/dumpstack/ftrace: convert dump_trace() callbacks to use
> >     ftrace_graph_ret_addr()
> >   ftrace/x86: implement HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
> >   x86/dumpstack/ftrace: mark function graph handler function as
> >     unreliable
> >   x86/dumpstack/ftrace: don't print unreliable addresses in
> >     print_context_stack_bp()
> 
> For the series..
> 
> Acked-by: Steven Rostedt <rostedt@goodmis.org>
> 
> Ingo,
> 
> If you want, please take it through tip.

Thanks Steve!

	Ingo

[tip:x86/asm] ftrace: Remove CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST from config

[tip-bot for Josh Poimboeuf]

Commit-ID:  e4a744ef2fef5c803348b650a3a2d01da7797a9b
Gitweb:     http://git.kernel.org/tip/e4a744ef2fef5c803348b650a3a2d01da7797a9b
Author:     Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Fri, 19 Aug 2016 06:52:55 -0500
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 24 Aug 2016 12:15:13 +0200

ftrace: Remove CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST from config

Make HAVE_FUNCTION_GRAPH_FP_TEST a normal define, independent from
kconfig.  This removes some config file pollution and simplifies the
checking for the fp test.

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/2c4e5f05054d6d367f702fd153af7a0109dd5c81.1471607358.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/arm64/kernel/entry-ftrace.S     | 2 +-
 arch/blackfin/kernel/ftrace-entry.S  | 4 ++--
 arch/sparc/Kconfig                   | 1 -
 arch/sparc/include/asm/ftrace.h      | 4 ++++
 arch/x86/Kconfig                     | 1 -
 arch/x86/include/asm/ftrace.h        | 1 +
 kernel/trace/Kconfig                 | 5 -----
 kernel/trace/trace_functions_graph.c | 2 +-
 8 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S
index 0f03a8f..aef02d2 100644
--- a/arch/arm64/kernel/entry-ftrace.S
+++ b/arch/arm64/kernel/entry-ftrace.S
@@ -219,7 +219,7 @@ ENDPROC(ftrace_graph_caller)
  *
  * Run ftrace_return_to_handler() before going back to parent.
  * @fp is checked against the value passed by ftrace_graph_caller()
- * only when CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST is enabled.
+ * only when HAVE_FUNCTION_GRAPH_FP_TEST is enabled.
  */
 ENTRY(return_to_handler)
 	save_return_regs
diff --git a/arch/blackfin/kernel/ftrace-entry.S b/arch/blackfin/kernel/ftrace-entry.S
index 28d0595..3b8bdcb 100644
--- a/arch/blackfin/kernel/ftrace-entry.S
+++ b/arch/blackfin/kernel/ftrace-entry.S
@@ -169,7 +169,7 @@ ENTRY(_ftrace_graph_caller)
 	r0 = sp;	/* unsigned long *parent */
 	r1 = [sp];	/* unsigned long self_addr */
 # endif
-# ifdef CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST
+# ifdef HAVE_FUNCTION_GRAPH_FP_TEST
 	r2 = fp;	/* unsigned long frame_pointer */
 # endif
 	r0 += 16;	/* skip the 4 local regs on stack */
@@ -190,7 +190,7 @@ ENTRY(_return_to_handler)
 	[--sp] = r1;
 
 	/* get original return address */
-# ifdef CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST
+# ifdef HAVE_FUNCTION_GRAPH_FP_TEST
 	r0 = fp;	/* Blackfin is sane, so omit this */
 # endif
 	call _ftrace_return_to_handler;
diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index 59b0960..f5d60f1 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -56,7 +56,6 @@ config SPARC64
 	def_bool 64BIT
 	select HAVE_FUNCTION_TRACER
 	select HAVE_FUNCTION_GRAPH_TRACER
-	select HAVE_FUNCTION_GRAPH_FP_TEST
 	select HAVE_KRETPROBES
 	select HAVE_KPROBES
 	select HAVE_RCU_TABLE_FREE if SMP
diff --git a/arch/sparc/include/asm/ftrace.h b/arch/sparc/include/asm/ftrace.h
index 3192a8e..62755a3 100644
--- a/arch/sparc/include/asm/ftrace.h
+++ b/arch/sparc/include/asm/ftrace.h
@@ -9,6 +9,10 @@
 void _mcount(void);
 #endif
 
+#endif /* CONFIG_MCOUNT */
+
+#if defined(CONFIG_SPARC64) && !defined(CC_USE_FENTRY)
+#define HAVE_FUNCTION_GRAPH_FP_TEST
 #endif
 
 #ifdef CONFIG_DYNAMIC_FTRACE
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 21a6d0e..ce8860c 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -111,7 +111,6 @@ config X86
 	select HAVE_EXIT_THREAD
 	select HAVE_FENTRY			if X86_64
 	select HAVE_FTRACE_MCOUNT_RECORD
-	select HAVE_FUNCTION_GRAPH_FP_TEST
 	select HAVE_FUNCTION_GRAPH_TRACER
 	select HAVE_FUNCTION_TRACER
 	select HAVE_GCC_PLUGINS
diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
index a4820d4..37f67cb 100644
--- a/arch/x86/include/asm/ftrace.h
+++ b/arch/x86/include/asm/ftrace.h
@@ -6,6 +6,7 @@
 # define MCOUNT_ADDR		((unsigned long)(__fentry__))
 #else
 # define MCOUNT_ADDR		((unsigned long)(mcount))
+# define HAVE_FUNCTION_GRAPH_FP_TEST
 #endif
 #define MCOUNT_INSN_SIZE	5 /* sizeof mcount call */
 
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index f4b86e8..ba33267 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -24,11 +24,6 @@ config HAVE_FUNCTION_GRAPH_TRACER
 	help
 	  See Documentation/trace/ftrace-design.txt
 
-config HAVE_FUNCTION_GRAPH_FP_TEST
-	bool
-	help
-	  See Documentation/trace/ftrace-design.txt
-
 config HAVE_DYNAMIC_FTRACE
 	bool
 	help
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 7363ccf..fc173cd 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -204,7 +204,7 @@ ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret,
 		return;
 	}
 
-#if defined(CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST) && !defined(CC_USING_FENTRY)
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
 	/*
 	 * The arch may choose to record the frame pointer used
 	 * and check it here to make sure that it is what we expect it

[tip:x86/asm] ftrace: Only allocate the ret_stack 'fp' field when needed

[tip-bot for Josh Poimboeuf]

Commit-ID:  daa460a88c09b26b68e8b017de589c217e901afb
Gitweb:     http://git.kernel.org/tip/daa460a88c09b26b68e8b017de589c217e901afb
Author:     Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Fri, 19 Aug 2016 06:52:56 -0500
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 24 Aug 2016 12:15:14 +0200

ftrace: Only allocate the ret_stack 'fp' field when needed

This saves some memory when HAVE_FUNCTION_GRAPH_FP_TEST isn't defined.
On x86_64 with newer versions of gcc which have -mfentry, it saves 400
bytes per task.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/5c7747d9ea7b5cb47ef0a8ce8a6cea6bf7aa94bf.1471607358.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 include/linux/ftrace.h               | 2 ++
 kernel/trace/trace_functions_graph.c | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 7d565af..4ad9ccc 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -795,7 +795,9 @@ struct ftrace_ret_stack {
 	unsigned long func;
 	unsigned long long calltime;
 	unsigned long long subtime;
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
 	unsigned long fp;
+#endif
 };
 
 /*
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index fc173cd..0e03ed0 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -171,7 +171,9 @@ ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth,
 	current->ret_stack[index].func = func;
 	current->ret_stack[index].calltime = calltime;
 	current->ret_stack[index].subtime = 0;
+#ifdef HAVE_FUNCTION_GRAPH_FP_TEST
 	current->ret_stack[index].fp = frame_pointer;
+#endif
 	*depth = current->curr_ret_stack;
 
 	return 0;

[tip:x86/asm] ftrace: Add return address pointer to ftrace_ret_stack

[tip-bot for Josh Poimboeuf]

Commit-ID:  9a7c348ba6a46f6270d4fe49577649dad5664fe7
Gitweb:     http://git.kernel.org/tip/9a7c348ba6a46f6270d4fe49577649dad5664fe7
Author:     Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Fri, 19 Aug 2016 06:52:57 -0500
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 24 Aug 2016 12:15:14 +0200

ftrace: Add return address pointer to ftrace_ret_stack

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@redhat.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/a95cfcc39e8f26b89a430c56926af0bb217bc0a1.1471607358.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 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;

[tip:x86/asm] ftrace: Add ftrace_graph_ret_addr() stack unwinding helpers

[tip-bot for Josh Poimboeuf]

Commit-ID:  223918e32a87c79ac55ca4aa513ba405ba4d57cd
Gitweb:     http://git.kernel.org/tip/223918e32a87c79ac55ca4aa513ba405ba4d57cd
Author:     Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Fri, 19 Aug 2016 06:52:58 -0500
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 24 Aug 2016 12:15:14 +0200

ftrace: Add ftrace_graph_ret_addr() stack unwinding helpers

When function graph tracing is enabled for a function, ftrace modifies
the stack by replacing the original return address with the address of a
hook function (return_to_handler).

Stack unwinders need a way to get the original return address.  Add an
arch-independent helper function for that named ftrace_graph_ret_addr().

This adds two variations of the function: one depends on
HAVE_FUNCTION_GRAPH_RET_ADDR_PTR, and the other relies on an index state
variable.

The former is recommended because, in some cases, the latter can cause
problems when the unwinder skips stack frames.  It can get out of sync
with the ret_stack index and wrong addresses can be reported for the
stack trace.

Once all arches have been ported to use
HAVE_FUNCTION_GRAPH_RET_ADDR_PTR, we can get rid of the distinction.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/36bd90f762fc5e5af3929e3797a68a64906421cf.1471607358.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 include/linux/ftrace.h               | 10 +++++++
 kernel/trace/trace_functions_graph.c | 58 ++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 483e02a..6f93ac4 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -814,6 +814,9 @@ extern int
 ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth,
 			 unsigned long frame_pointer, unsigned long *retp);
 
+unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
+				    unsigned long ret, unsigned long *retp);
+
 /*
  * Sometimes we don't want to trace a function with the function
  * graph tracer but we want them to keep traced by the usual function
@@ -875,6 +878,13 @@ static inline int task_curr_ret_stack(struct task_struct *tsk)
 	return -1;
 }
 
+static inline unsigned long
+ftrace_graph_ret_addr(struct task_struct *task, int *idx, unsigned long ret,
+		      unsigned long *retp)
+{
+	return ret;
+}
+
 static inline void pause_graph_tracing(void) { }
 static inline void unpause_graph_tracing(void) { }
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index f7212ec..0cbe38a 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -284,6 +284,64 @@ unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
 	return ret;
 }
 
+/**
+ * ftrace_graph_ret_addr - convert a potentially modified stack return address
+ *			   to its original value
+ *
+ * This function can be called by stack unwinding code to convert a found stack
+ * return address ('ret') to its original value, in case the function graph
+ * tracer has modified it to be 'return_to_handler'.  If the address hasn't
+ * been modified, the unchanged value of 'ret' is returned.
+ *
+ * 'idx' is a state variable which should be initialized by the caller to zero
+ * before the first call.
+ *
+ * 'retp' is a pointer to the return address on the stack.  It's ignored if
+ * the arch doesn't have HAVE_FUNCTION_GRAPH_RET_ADDR_PTR defined.
+ */
+#ifdef HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
+unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
+				    unsigned long ret, unsigned long *retp)
+{
+	int index = task->curr_ret_stack;
+	int i;
+
+	if (ret != (unsigned long)return_to_handler)
+		return ret;
+
+	if (index < -1)
+		index += FTRACE_NOTRACE_DEPTH;
+
+	if (index < 0)
+		return ret;
+
+	for (i = 0; i <= index; i++)
+		if (task->ret_stack[i].retp == retp)
+			return task->ret_stack[i].ret;
+
+	return ret;
+}
+#else /* !HAVE_FUNCTION_GRAPH_RET_ADDR_PTR */
+unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
+				    unsigned long ret, unsigned long *retp)
+{
+	int task_idx;
+
+	if (ret != (unsigned long)return_to_handler)
+		return ret;
+
+	task_idx = task->curr_ret_stack;
+
+	if (!task->ret_stack || task_idx < *idx)
+		return ret;
+
+	task_idx -= *idx;
+	(*idx)++;
+
+	return task->ret_stack[task_idx].ret;
+}
+#endif /* HAVE_FUNCTION_GRAPH_RET_ADDR_PTR */
+
 int __trace_graph_entry(struct trace_array *tr,
 				struct ftrace_graph_ent *trace,
 				unsigned long flags,

[tip:x86/asm] x86/dumpstack/ftrace: Convert dump_trace() callbacks to use ftrace_graph_ret_addr()

[tip-bot for Josh Poimboeuf]

Commit-ID:  408fe5de2f2767059a9561e0ae6d4385d1b39dac
Gitweb:     http://git.kernel.org/tip/408fe5de2f2767059a9561e0ae6d4385d1b39dac
Author:     Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Fri, 19 Aug 2016 06:52:59 -0500
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 24 Aug 2016 12:15:14 +0200

x86/dumpstack/ftrace: Convert dump_trace() callbacks to use ftrace_graph_ret_addr()

Convert print_context_stack() and print_context_stack_bp() to use the
arch-independent ftrace_graph_ret_addr() helper.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/56ec97cafc1bf2e34d1119e6443d897db406da86.1471607358.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/kernel/dumpstack.c | 65 +++++++++++++++------------------------------
 1 file changed, 22 insertions(+), 43 deletions(-)

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 5f49c04..9bf3d02 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -38,38 +38,6 @@ void printk_address(unsigned long address)
 	pr_cont(" [<%p>] %pS\n", (void *)address, (void *)address);
 }
 
-#ifdef CONFIG_FUNCTION_GRAPH_TRACER
-static void
-print_ftrace_graph_addr(unsigned long addr, void *data,
-			const struct stacktrace_ops *ops,
-			struct task_struct *task, int *graph)
-{
-	unsigned long ret_addr;
-	int index;
-
-	if (addr != (unsigned long)return_to_handler)
-		return;
-
-	index = task->curr_ret_stack;
-
-	if (!task->ret_stack || index < *graph)
-		return;
-
-	index -= *graph;
-	ret_addr = task->ret_stack[index].ret;
-
-	ops->address(data, ret_addr, 1);
-
-	(*graph)++;
-}
-#else
-static inline void
-print_ftrace_graph_addr(unsigned long addr, void *data,
-			const struct stacktrace_ops *ops,
-			struct task_struct *task, int *graph)
-{ }
-#endif
-
 /*
  * x86-64 can have up to three kernel stacks:
  * process stack
@@ -107,18 +75,24 @@ print_context_stack(struct task_struct *task,
 		stack = (unsigned long *)task_stack_page(task);
 
 	while (valid_stack_ptr(task, stack, sizeof(*stack), end)) {
-		unsigned long addr;
+		unsigned long addr = *stack;
 
-		addr = *stack;
 		if (__kernel_text_address(addr)) {
+			unsigned long real_addr;
+			int reliable = 0;
+
 			if ((unsigned long) stack == bp + sizeof(long)) {
-				ops->address(data, addr, 1);
+				reliable = 1;
 				frame = frame->next_frame;
 				bp = (unsigned long) frame;
-			} else {
-				ops->address(data, addr, 0);
 			}
-			print_ftrace_graph_addr(addr, data, ops, task, graph);
+
+			ops->address(data, addr, reliable);
+
+			real_addr = ftrace_graph_ret_addr(task, graph, addr,
+							  stack);
+			if (real_addr != addr)
+				ops->address(data, real_addr, 1);
 		}
 		stack++;
 	}
@@ -133,19 +107,24 @@ print_context_stack_bp(struct task_struct *task,
 		       unsigned long *end, int *graph)
 {
 	struct stack_frame *frame = (struct stack_frame *)bp;
-	unsigned long *ret_addr = &frame->return_address;
+	unsigned long *retp = &frame->return_address;
 
-	while (valid_stack_ptr(task, ret_addr, sizeof(*ret_addr), end)) {
-		unsigned long addr = *ret_addr;
+	while (valid_stack_ptr(task, retp, sizeof(*retp), end)) {
+		unsigned long addr = *retp;
+		unsigned long real_addr;
 
 		if (!__kernel_text_address(addr))
 			break;
 
 		if (ops->address(data, addr, 1))
 			break;
+
+		real_addr = ftrace_graph_ret_addr(task, graph, addr, retp);
+		if (real_addr != addr)
+			ops->address(data, real_addr, 1);
+
 		frame = frame->next_frame;
-		ret_addr = &frame->return_address;
-		print_ftrace_graph_addr(addr, data, ops, task, graph);
+		retp = &frame->return_address;
 	}
 
 	return (unsigned long)frame;

[tip:x86/asm] ftrace/x86: Implement HAVE_FUNCTION_GRAPH_RET_ADDR_PTR

[tip-bot for Josh Poimboeuf]

Commit-ID:  471bd10f5e2880bd91a2627d887f6062494cfe9c
Gitweb:     http://git.kernel.org/tip/471bd10f5e2880bd91a2627d887f6062494cfe9c
Author:     Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Fri, 19 Aug 2016 06:53:00 -0500
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 24 Aug 2016 12:15:15 +0200

ftrace/x86: Implement HAVE_FUNCTION_GRAPH_RET_ADDR_PTR

Use the more reliable version of ftrace_graph_ret_addr() so we no longer
have to worry about the unwinder getting out of sync with the function
graph ret_stack index, which can happen if the unwinder skips any frames
before calling ftrace_graph_ret_addr().

This fixes this issue (and several others like it):

  $ cat /proc/self/stack
  [<ffffffff810489a2>] save_stack_trace_tsk+0x22/0x40
  [<ffffffff81311a89>] proc_pid_stack+0xb9/0x110
  [<ffffffff813127c4>] proc_single_show+0x54/0x80
  [<ffffffff812be088>] seq_read+0x108/0x3e0
  [<ffffffff812923d7>] __vfs_read+0x37/0x140
  [<ffffffff812929d9>] vfs_read+0x99/0x140
  [<ffffffff81293f28>] SyS_read+0x58/0xc0
  [<ffffffff818af97c>] entry_SYSCALL_64_fastpath+0x1f/0xbd
  [<ffffffffffffffff>] 0xffffffffffffffff

  $ echo function_graph > /sys/kernel/debug/tracing/current_tracer

  $ cat /proc/self/stack
  [<ffffffff818b2428>] return_to_handler+0x0/0x27
  [<ffffffff810394cc>] print_context_stack+0xfc/0x100
  [<ffffffff818b2428>] return_to_handler+0x0/0x27
  [<ffffffff8103891b>] dump_trace+0x12b/0x350
  [<ffffffff818b2428>] return_to_handler+0x0/0x27
  [<ffffffff810489a2>] save_stack_trace_tsk+0x22/0x40
  [<ffffffff818b2428>] return_to_handler+0x0/0x27
  [<ffffffff81311a89>] proc_pid_stack+0xb9/0x110
  [<ffffffff818b2428>] return_to_handler+0x0/0x27
  [<ffffffff813127c4>] proc_single_show+0x54/0x80
  [<ffffffff818b2428>] return_to_handler+0x0/0x27
  [<ffffffff812be088>] seq_read+0x108/0x3e0
  [<ffffffff818b2428>] return_to_handler+0x0/0x27
  [<ffffffff812923d7>] __vfs_read+0x37/0x140
  [<ffffffff818b2428>] return_to_handler+0x0/0x27
  [<ffffffff812929d9>] vfs_read+0x99/0x140
  [<ffffffffffffffff>] 0xffffffffffffffff

Enabling function graph tracing causes the stack trace to change in two
ways:

First, the real call addresses are confusingly interspersed with
'return_to_handler' addresses.  This issue will be fixed by the next
patch.

Second, the stack trace is offset by two frames, because the unwinder
skipped the first two frames and got out of sync with the ret_stack
index.  This patch fixes this issue.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/a6d623e36f8d08f9a17bd74d804d201177a23afd.1471607358.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/include/asm/ftrace.h | 2 ++
 arch/x86/kernel/ftrace.c      | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
index 37f67cb..eccd0ac 100644
--- a/arch/x86/include/asm/ftrace.h
+++ b/arch/x86/include/asm/ftrace.h
@@ -14,6 +14,8 @@
 #define ARCH_SUPPORTS_FTRACE_OPS 1
 #endif
 
+#define HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
+
 #ifndef __ASSEMBLY__
 extern void mcount(void);
 extern atomic_t modifying_ftrace_code;
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index ae3b1fb..8639bb2 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, NULL) == -EBUSY) {
+				     frame_pointer, parent) == -EBUSY) {
 		*parent = old;
 		return;
 	}

[tip:x86/asm] x86/dumpstack/ftrace: Mark function graph handler function as unreliable

[tip-bot for Josh Poimboeuf]

Commit-ID:  6f727b84e23421721025f4eb1b4f6cea1d4d723a
Gitweb:     http://git.kernel.org/tip/6f727b84e23421721025f4eb1b4f6cea1d4d723a
Author:     Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Fri, 19 Aug 2016 06:53:01 -0500
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 24 Aug 2016 12:15:15 +0200

x86/dumpstack/ftrace: Mark function graph handler function as unreliable

When function graph tracing is enabled for a function, its return
address on the stack is replaced with the address of an ftrace handler
(return_to_handler).

Currently 'return_to_handler' can be reported as reliable.  That's not
ideal, and can actually be misleading.  When saving or dumping the
stack, you normally only care about what led up to that point (the call
path), rather than what will happen in the future (the return path).

That's especially true in the non-oops stack trace case, which isn't
used for debugging.  For example, in a perf profiling operation,
reporting return_to_handler() in the trace would just be confusing.

And in the oops case, where debugging is important, "unreliable" is also
more appropriate there because it serves as a hint that graph tracing
was involved, instead of trying to imply that return_to_handler() was
the real caller.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/f8af15749c7d632d3e7f815995831d5b7f82950d.1471607358.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/kernel/dumpstack.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 9bf3d02..6aad8d4 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -87,12 +87,21 @@ print_context_stack(struct task_struct *task,
 				bp = (unsigned long) frame;
 			}
 
-			ops->address(data, addr, reliable);
-
+			/*
+			 * When function graph tracing is enabled for a
+			 * function, its return address on the stack is
+			 * replaced with the address of an ftrace handler
+			 * (return_to_handler).  In that case, before printing
+			 * the "real" address, we want to print the handler
+			 * address as an "unreliable" hint that function graph
+			 * tracing was involved.
+			 */
 			real_addr = ftrace_graph_ret_addr(task, graph, addr,
 							  stack);
 			if (real_addr != addr)
-				ops->address(data, real_addr, 1);
+				ops->address(data, addr, 0);
+
+			ops->address(data, real_addr, reliable);
 		}
 		stack++;
 	}
@@ -116,12 +125,11 @@ print_context_stack_bp(struct task_struct *task,
 		if (!__kernel_text_address(addr))
 			break;
 
-		if (ops->address(data, addr, 1))
-			break;
-
 		real_addr = ftrace_graph_ret_addr(task, graph, addr, retp);
-		if (real_addr != addr)
-			ops->address(data, real_addr, 1);
+		if (real_addr != addr && ops->address(data, addr, 0))
+			break;
+		if (ops->address(data, real_addr, 1))
+			break;
 
 		frame = frame->next_frame;
 		retp = &frame->return_address;

[tip:x86/asm] x86/dumpstack/ftrace: Don't print unreliable addresses in print_context_stack_bp()

[tip-bot for Josh Poimboeuf]

Commit-ID:  13e25bab7e51bdd4ba7df1ef2388961294bb565e
Gitweb:     http://git.kernel.org/tip/13e25bab7e51bdd4ba7df1ef2388961294bb565e
Author:     Josh Poimboeuf <jpoimboe@redhat.com>
AuthorDate: Fri, 19 Aug 2016 06:53:02 -0500
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 24 Aug 2016 12:15:15 +0200

x86/dumpstack/ftrace: Don't print unreliable addresses in print_context_stack_bp()

When function graph tracing is enabled, print_context_stack_bp() can
report return_to_handler() as an unreliable address, which is confusing
and misleading: return_to_handler() is really only useful as a hint for
debugging, whereas print_context_stack_bp() users only care about the
actual 'reliable' call path.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/c51aef578d8027791b38d2ad9bac0c7f499fde91.1471607358.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/kernel/dumpstack.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index 6aad8d4..01072e9 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -126,8 +126,6 @@ print_context_stack_bp(struct task_struct *task,
 			break;
 
 		real_addr = ftrace_graph_ret_addr(task, graph, addr, retp);
-		if (real_addr != addr && ops->address(data, addr, 0))
-			break;
 		if (ops->address(data, real_addr, 1))
 			break;