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Subject[PATCH] tracing/ftrace: add the printk-msg-only option
Impact: display ftrace_printk messages "as is"

By default, ftrace_printk() messages find their output with some other
informations like pid, caller, ...
Sometimes a developer just want to have the ftrace_printk left "as is", without
other information.

This is done by providing a default-off option called printk-msg-only.
To enable it, just do `echo printk-msg-only > /debugfs/tracing/trace_options`

Before the patch:

<...>-2739 [000] 145.692153: __might_sleep: I'm an ftrace_printk msg in __might_sleep
<...>-2739 [000] 145.692155: __might_sleep: I'm another ftrace_printk msg in __might_sleep

After the patch and the printk-msg-only option enabled:

I'm an ftrace_printk msg in __might_sleep
I'm another ftrace_printk msg in __might_sleep

Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8fd3c5a..cd4dbf2 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -287,6 +287,7 @@ static const char *trace_options[] = {
"annotate",
"userstacktrace",
"sym-userobj",
+ "printk-msg-only",
NULL
};

@@ -2265,6 +2266,25 @@ static enum print_line_t print_hex_fmt(struct trace_iterator *iter)
return TRACE_TYPE_HANDLED;
}

+static enum print_line_t print_printk_msg_only(struct trace_iterator *iter)
+{
+ struct trace_seq *s = &iter->seq;
+ struct trace_entry *entry = iter->ent;
+ struct print_entry *field;
+ int ret;
+
+ trace_assign_type(field, entry);
+
+ ret = trace_seq_printf(s, field->buf);
+ if (!ret)
+ return TRACE_TYPE_PARTIAL_LINE;
+
+ if (entry->flags & TRACE_FLAG_CONT)
+ trace_seq_print_cont(s, iter);
+
+ return TRACE_TYPE_HANDLED;
+}
+
static enum print_line_t print_bin_fmt(struct trace_iterator *iter)
{
struct trace_seq *s = &iter->seq;
@@ -2345,6 +2365,11 @@ static enum print_line_t print_trace_line(struct trace_iterator *iter)
return ret;
}

+ if (iter->ent->type == TRACE_PRINT &&
+ trace_flags & TRACE_ITER_PRINTK &&
+ trace_flags & TRACE_ITER_PRINTK_MSGONLY)
+ return print_printk_msg_only(iter);
+
if (trace_flags & TRACE_ITER_BIN)
return print_bin_fmt(iter);

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index f07c246..fc75dce 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -578,7 +578,8 @@ enum trace_iterator_flags {
TRACE_ITER_BRANCH = 0x1000,
TRACE_ITER_ANNOTATE = 0x2000,
TRACE_ITER_USERSTACKTRACE = 0x4000,
- TRACE_ITER_SYM_USEROBJ = 0x8000
+ TRACE_ITER_SYM_USEROBJ = 0x8000,
+ TRACE_ITER_PRINTK_MSGONLY = 0x10000
};

/*
--
1.6.0.4


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