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>

15 files changed, 34 insertions, 15 deletions

diff --git a/Documentation/trace/ftrace-design.txt b/Documentation/trace/ftrace-design.txt
index dd5f916b351d..a273dd0bbaaa 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 709ee1d6d4df..3f1759411d51 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 ebecf9aa33d1..40ad08ac569a 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 095de0fa044d..8dad7589b843 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 fc7b48a52cd5..d57563c58a26 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 937c54bc8ccc..30a3b75e88eb 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 a828a0adf52c..5a5506a35395 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 cc52d9795f88..a95639b8d4ac 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 0f7bfeba6da6..60a8a4e207ed 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 38993e09ef03..95eccd49672f 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 0a2d2ddff543..6bcff698069b 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 4a572088b270..b827a418b155 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 d036cfb4495d..ae3b1fb2f582 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 4ad9ccc60e38..483e02a50d37 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 0e03ed0eac68..f7212ec643e2 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;