Add "gfp_t" support in synthetic_events, then the "gfp_t" type
parameter in some functions can be traced.

Prints the gfp flags as hex in addition to the human-readable flag
string.  Example output:

  whoopsie-630 [000] ...1 78.969452: testevent: bar=b20 (GFP_ATOMIC|__GFP_ZERO)
    rcuc/0-11  [000] ...1 81.097555: testevent: bar=a20 (GFP_ATOMIC)
    rcuc/0-11  [000] ...1 81.583123: testevent: bar=a20 (GFP_ATOMIC)

Signed-off-by: Tom Zanussi <zanu...@kernel.org>
Signed-off-by: Zhengjun Xing <zhengjun.x...@linux.intel.com>
---
 kernel/trace/trace_events_hist.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index ca6b0dff60c5..30f0f32aca62 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -13,6 +13,10 @@
 #include <linux/rculist.h>
 #include <linux/tracefs.h>
 
+/* for gfp flag names */
+#include <linux/trace_events.h>
+#include <trace/events/mmflags.h>
+
 #include "tracing_map.h"
 #include "trace.h"
 #include "trace_dynevent.h"
@@ -752,6 +756,8 @@ static int synth_field_size(char *type)
                size = sizeof(unsigned long);
        else if (strcmp(type, "pid_t") == 0)
                size = sizeof(pid_t);
+       else if (strcmp(type, "gfp_t") == 0)
+               size = sizeof(gfp_t);
        else if (synth_field_is_string(type))
                size = synth_field_string_size(type);
 
@@ -792,6 +798,8 @@ static const char *synth_field_fmt(char *type)
                fmt = "%lu";
        else if (strcmp(type, "pid_t") == 0)
                fmt = "%d";
+       else if (strcmp(type, "gfp_t") == 0)
+               fmt = "%x";
        else if (synth_field_is_string(type))
                fmt = "%s";
 
@@ -834,9 +842,20 @@ static enum print_line_t print_synth_event(struct 
trace_iterator *iter,
                                         i == se->n_fields - 1 ? "" : " ");
                        n_u64 += STR_VAR_LEN_MAX / sizeof(u64);
                } else {
+                       struct trace_print_flags __flags[] = {
+                           __def_gfpflag_names, {-1, NULL} };
+
                        trace_seq_printf(s, print_fmt, se->fields[i]->name,
                                         entry->fields[n_u64],
                                         i == se->n_fields - 1 ? "" : " ");
+
+                       if (strcmp(se->fields[i]->type, "gfp_t") == 0) {
+                               trace_seq_puts(s, " (");
+                               trace_print_flags_seq(s, "|",
+                                                     entry->fields[n_u64],
+                                                     __flags);
+                               trace_seq_putc(s, ')');
+                       }
                        n_u64++;
                }
        }
-- 
2.14.1

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