ftrace: add stack tracing

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

3 files changed, 97 insertions, 18 deletions

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 3f73a1710242..eb1988ed84b7 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -10,6 +10,7 @@ config TRACER_MAX_TRACE
 config TRACING
         bool
         select DEBUG_FS
+        select STACKTRACE
 
 config FTRACE
         bool "Kernel Function Tracer"
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 192c1354a7e0..b4b1b4fe99fd 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -28,6 +28,8 @@
 #include <linux/gfp.h>
 #include <linux/fs.h>
 
+#include <linux/stacktrace.h>
+
 #include "trace.h"
 
 unsigned long __read_mostly     tracing_max_latency = (cycle_t)ULONG_MAX;
@@ -88,6 +90,7 @@ enum trace_type {
         TRACE_FN,
         TRACE_CTX,
         TRACE_WAKE,
+        TRACE_STACK,
         TRACE_SPECIAL,
 
         __TRACE_LAST_TYPE
@@ -109,6 +112,7 @@ enum trace_iterator_flags {
         TRACE_ITER_HEX                  = 0x20,
         TRACE_ITER_BIN                  = 0x40,
         TRACE_ITER_BLOCK                = 0x80,
+        TRACE_ITER_STACKTRACE           = 0x100,
 };
 
 #define TRACE_ITER_SYM_MASK \
@@ -124,10 +128,11 @@ static const char *trace_options[] = {
         "hex",
         "bin",
         "block",
+        "stacktrace",
         NULL
 };
 
-static unsigned trace_flags;
+static unsigned trace_flags = TRACE_ITER_PRINT_PARENT | TRACE_ITER_STACKTRACE;
 
 static DEFINE_SPINLOCK(ftrace_max_lock);
 
@@ -657,7 +662,7 @@ trace_function(struct trace_array *tr, struct trace_array_cpu *data,
         spin_unlock_irqrestore(&data->lock, irq_flags);
 
         if (!(trace_flags & TRACE_ITER_BLOCK))
-                wake_up (&trace_wait);
+                wake_up(&trace_wait);
 }
 
 void
@@ -685,13 +690,39 @@ trace_special(struct trace_array *tr, struct trace_array_cpu *data,
         spin_unlock_irqrestore(&data->lock, irq_flags);
 
         if (!(trace_flags & TRACE_ITER_BLOCK))
-                wake_up (&trace_wait);
+                wake_up(&trace_wait);
+}
+
+void __trace_stack(struct trace_array *tr,
+                   struct trace_array_cpu *data,
+                   unsigned long flags,
+                   int skip)
+{
+        struct trace_entry *entry;
+        struct stack_trace trace;
+
+        if (!(trace_flags & TRACE_ITER_STACKTRACE))
+                return;
+
+        entry                   = tracing_get_trace_entry(tr, data);
+        tracing_generic_entry_update(entry, flags);
+        entry->type             = TRACE_STACK;
+
+        memset(&entry->stack, 0, sizeof(entry->stack));
+
+        trace.nr_entries        = 0;
+        trace.max_entries       = FTRACE_STACK_ENTRIES;
+        trace.skip              = skip;
+        trace.entries           = entry->stack.caller;
+
+        save_stack_trace(&trace);
 }
 
 void
 tracing_sched_switch_trace(struct trace_array *tr,
                            struct trace_array_cpu *data,
-                           struct task_struct *prev, struct task_struct *next,
+                           struct task_struct *prev,
+                           struct task_struct *next,
                            unsigned long flags)
 {
         struct trace_entry *entry;
@@ -706,16 +737,18 @@ tracing_sched_switch_trace(struct trace_array *tr,
         entry->ctx.prev_state   = prev->state;
         entry->ctx.next_pid     = next->pid;
         entry->ctx.next_prio    = next->prio;
+        __trace_stack(tr, data, flags, 4);
         spin_unlock_irqrestore(&data->lock, irq_flags);
 
         if (!(trace_flags & TRACE_ITER_BLOCK))
-                wake_up (&trace_wait);
+                wake_up(&trace_wait);
 }
 
 void
 tracing_sched_wakeup_trace(struct trace_array *tr,
                            struct trace_array_cpu *data,
-                           struct task_struct *wakee, struct task_struct *curr,
+                           struct task_struct *wakee,
+                           struct task_struct *curr,
                            unsigned long flags)
 {
         struct trace_entry *entry;
@@ -730,6 +763,7 @@ tracing_sched_wakeup_trace(struct trace_array *tr,
         entry->ctx.prev_state   = curr->state;
         entry->ctx.next_pid     = wakee->pid;
         entry->ctx.next_prio    = wakee->prio;
+        __trace_stack(tr, data, flags, 5);
         spin_unlock_irqrestore(&data->lock, irq_flags);
 
         if (!(trace_flags & TRACE_ITER_BLOCK))
@@ -1179,6 +1213,7 @@ print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu)
         unsigned long rel_usecs;
         char *comm;
         int S;
+        int i;
 
         if (!next_entry)
                 next_entry = entry;
@@ -1197,8 +1232,10 @@ print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu)
                                  abs_usecs % 1000, rel_usecs/1000,
                                  rel_usecs % 1000);
         } else {
-                lat_print_generic(s, entry, cpu);
-                lat_print_timestamp(s, abs_usecs, rel_usecs);
+                if (entry->type != TRACE_STACK) {
+                        lat_print_generic(s, entry, cpu);
+                        lat_print_timestamp(s, abs_usecs, rel_usecs);
+                }
         }
         switch (entry->type) {
         case TRACE_FN:
@@ -1226,6 +1263,14 @@ print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu)
                                  entry->special.arg2,
                                  entry->special.arg3);
                 break;
+        case TRACE_STACK:
+                for (i = 0; i < FTRACE_STACK_ENTRIES; i++) {
+                        if (i)
+                                trace_seq_puts(s, " <= ");
+                        seq_print_ip_sym(s, entry->stack.caller[i], sym_flags);
+                }
+                trace_seq_puts(s, "\n");
+                break;
         default:
                 trace_seq_printf(s, "Unknown type %d\n", entry->type);
         }
@@ -1241,8 +1286,9 @@ static int print_trace_fmt(struct trace_iterator *iter)
         unsigned long long t;
         unsigned long secs;
         char *comm;
-        int S;
         int ret;
+        int S;
+        int i;
 
         entry = iter->ent;
 
@@ -1252,15 +1298,17 @@ static int print_trace_fmt(struct trace_iterator *iter)
         usec_rem = do_div(t, 1000000ULL);
         secs = (unsigned long)t;
 
-        ret = trace_seq_printf(s, "%16s-%-5d ", comm, entry->pid);
-        if (!ret)
-                return 0;
-        ret = trace_seq_printf(s, "[%02d] ", iter->cpu);
-        if (!ret)
-                return 0;
-        ret = trace_seq_printf(s, "%5lu.%06lu: ", secs, usec_rem);
-        if (!ret)
-                return 0;
+        if (entry->type != TRACE_STACK) {
+                ret = trace_seq_printf(s, "%16s-%-5d ", comm, entry->pid);
+                if (!ret)
+                        return 0;
+                ret = trace_seq_printf(s, "[%02d] ", iter->cpu);
+                if (!ret)
+                        return 0;
+                ret = trace_seq_printf(s, "%5lu.%06lu: ", secs, usec_rem);
+                if (!ret)
+                        return 0;
+        }
 
         switch (entry->type) {
         case TRACE_FN:
@@ -1303,6 +1351,22 @@ static int print_trace_fmt(struct trace_iterator *iter)
                 if (!ret)
                         return 0;
                 break;
+        case TRACE_STACK:
+                for (i = 0; i < FTRACE_STACK_ENTRIES; i++) {
+                        if (i) {
+                                ret = trace_seq_puts(s, " <= ");
+                                if (!ret)
+                                        return 0;
+                        }
+                        ret = seq_print_ip_sym(s, entry->stack.caller[i],
+                                               sym_flags);
+                        if (!ret)
+                                return 0;
+                }
+                ret = trace_seq_puts(s, "\n");
+                if (!ret)
+                        return 0;
+                break;
         }
         return 1;
 }
@@ -1344,6 +1408,7 @@ static int print_raw_fmt(struct trace_iterator *iter)
                         return 0;
                 break;
         case TRACE_SPECIAL:
+        case TRACE_STACK:
                 ret = trace_seq_printf(s, " %lx %lx %lx\n",
                                  entry->special.arg1,
                                  entry->special.arg2,
@@ -1399,6 +1464,7 @@ static int print_hex_fmt(struct trace_iterator *iter)
                 SEQ_PUT_HEX_FIELD_RET(s, entry->fn.parent_ip);
                 break;
         case TRACE_SPECIAL:
+        case TRACE_STACK:
                 SEQ_PUT_HEX_FIELD_RET(s, entry->special.arg1);
                 SEQ_PUT_HEX_FIELD_RET(s, entry->special.arg2);
                 SEQ_PUT_HEX_FIELD_RET(s, entry->special.arg3);
@@ -1433,6 +1499,7 @@ static int print_bin_fmt(struct trace_iterator *iter)
                 SEQ_PUT_FIELD_RET(s, entry->ctx.next_prio);
                 break;
         case TRACE_SPECIAL:
+        case TRACE_STACK:
                 SEQ_PUT_FIELD_RET(s, entry->special.arg1);
                 SEQ_PUT_FIELD_RET(s, entry->special.arg2);
                 SEQ_PUT_FIELD_RET(s, entry->special.arg3);
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 90e0ba0f6eba..387bdcf45e28 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -35,6 +35,16 @@ struct special_entry {
 };
 
 /*
+ * Stack-trace entry:
+ */
+
+#define FTRACE_STACK_ENTRIES    5
+
+struct stack_entry {
+        unsigned long           caller[FTRACE_STACK_ENTRIES];
+};
+
+/*
  * The trace entry - the most basic unit of tracing. This is what
  * is printed in the end as a single line in the trace output, such as:
  *
@@ -51,6 +61,7 @@ struct trace_entry {
                 struct ftrace_entry             fn;
                 struct ctx_switch_entry         ctx;
                 struct special_entry            special;
+                struct stack_entry              stack;
         };
 };