[for-next][PATCH 0/4] tracing: Updates for v4.11

[for-next][PATCH 0/4] tracing: Updates for v4.11

[Steven Rostedt]

  git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git
for-next

Head SHA1: 068f530b3f274d313395663bf8d674798d4858c6


Kenny Yu (1):
      uprobe: Find last occurrence of ':' when parsing uprobe PATH:OFFSET

Steven Rostedt (VMware) (3):
      tracing: Process constants for (un)likely() profiler
      tracing: Show number of constants profiled in likely profiler
      tracing: Add the constant count for branch tracer

----
 include/linux/compiler.h     | 27 ++++++++------
 kernel/trace/trace_branch.c  | 83 ++++++++++++++++++++++++++++++++++----------
 kernel/trace/trace_entries.h |  6 ++--
 kernel/trace/trace_uprobe.c  |  3 +-
 4 files changed, 88 insertions(+), 31 deletions(-)

[for-next][PATCH 1/4] uprobe: Find last occurrence of : when parsing uprobe PATH:OFFSET

[Steven Rostedt]

[-- Attachment #1: 0001-uprobe-Find-last-occurrence-of-when-parsing-uprobe-P.patch --]
[-- Type: text/plain, Size: 2385 bytes --]

From: Kenny Yu <kennyyu@fb.com>

Previously, `create_trace_uprobe` found the *first* occurence
of the ':' character when parsing `PATH:OFFSET` for a uprobe.
However, if the path contains a ':' character, then the function
would parse the path incorrectly. Even worse, if the path does not
exist, the subsequent call to `kern_path()` would set `ret` to
`ENOENT`, leading to very cryptic errno values in user space.

The fix is to find the *last* occurence of ':'.

How to repro:: The write fails with "No such file or directory", suggesting
incorrectly that the `uprobe_events` file does not exist.

  $ mkdir testing && cd testing
  $ cp /bin/bash .
  $ cp /bin/bash ./bash:with:colon
  $ echo "p:uprobes/p__root_testing_bash_0x6 /root/testing/bash:0x6" > /sys/kernel/debug/tracing/uprobe_events     # this works
  $ echo "p:uprobes/p__root_testing_bash_with_colon_0x6 /root/testing/bash:with:colon:0x6" >> /sys/kernel/debug/tracing/uprobe_events     # this doesn't
  -bash: echo: write error: No such file or directory

With the patch:

  $ echo "p:uprobes/p__root_testing_bash_0x6 /root/testing/bash:0x6" > /sys/kernel/debug/tracing/uprobe_events     # this still works
  $ echo "p:uprobes/p__root_testing_bash_with_colon_0x6 /root/testing/bash:with:colon:0x6" >> /sys/kernel/debug/tracing/uprobe_events     # this works now too!
  $ cat /sys/kernel/debug/tracing/uprobe_events
  p:uprobes/p__root_testing_bash_0x6 /root/testing/bash:0x0000000000000006
  p:uprobes/p__root_testing_bash_with_colon_0x6 /root/testing/bash:with:colon:0x0000000000000006

Link: http://lkml.kernel.org/r/20170113165834.4081016-1-kennyyu@fb.com

Signed-off-by: Kenny Yu <kennyyu@fb.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/trace_uprobe.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 0913693caf6e..4f2ba2bb11e0 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -431,7 +431,8 @@ static int create_trace_uprobe(int argc, char **argv)
 		pr_info("Probe point is not specified.\n");
 		return -EINVAL;
 	}
-	arg = strchr(argv[1], ':');
+	/* Find the last occurrence, in case the path contains ':' too. */
+	arg = strrchr(argv[1], ':');
 	if (!arg) {
 		ret = -EINVAL;
 		goto fail_address_parse;
-- 
2.10.2

[for-next][PATCH 2/4] tracing: Process constants for (un)likely() profiler

[Steven Rostedt]

[-- Attachment #1: 0002-tracing-Process-constants-for-un-likely-profiler.patch --]
[-- Type: text/plain, Size: 3827 bytes --]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

When running the likely/unlikely profiler, one of the results did not look
accurate. It noted that the unlikely() in link_path_walk() was 100%
incorrect. When I added a trace_printk() to see what was happening there, it
became 80% correct! Looking deeper into what whas happening, I found that
gcc split that if statement into two paths. One where the if statement
became a constant, the other path a variable. The other path had the if
statement always hit (making the unlikely there, always false), but since
the #define unlikely() has:

  #define unlikely() (__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 0))

Where constants are ignored by the branch profiler, the "constant" path
made by the compiler was ignored, even though it was hit 80% of the time.

By just passing the constant value to the __branch_check__() function and
tracing it out of line (as always correct, as likely/unlikely isn't a factor
for constants), then we get back the accurate readings of branches that were
optimized by gcc causing part of the execution to become constant.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 include/linux/compiler.h    | 14 ++++++++------
 kernel/trace/trace_branch.c |  6 +++++-
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index cf0fa5d86059..bbbe1570de1c 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -107,12 +107,13 @@ struct ftrace_branch_data {
  */
 #if defined(CONFIG_TRACE_BRANCH_PROFILING) \
     && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__)
-void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
+void ftrace_likely_update(struct ftrace_branch_data *f, int val,
+			  int expect, int is_constant);
 
 #define likely_notrace(x)	__builtin_expect(!!(x), 1)
 #define unlikely_notrace(x)	__builtin_expect(!!(x), 0)
 
-#define __branch_check__(x, expect) ({					\
+#define __branch_check__(x, expect, is_constant) ({			\
 			int ______r;					\
 			static struct ftrace_branch_data		\
 				__attribute__((__aligned__(4)))		\
@@ -122,8 +123,9 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
 				.file = __FILE__,			\
 				.line = __LINE__,			\
 			};						\
-			______r = likely_notrace(x);			\
-			ftrace_likely_update(&______f, ______r, expect); \
+			______r = __builtin_expect(!!(x), expect);	\
+			ftrace_likely_update(&______f, ______r,		\
+					     expect, is_constant);	\
 			______r;					\
 		})
 
@@ -133,10 +135,10 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
  * written by Daniel Walker.
  */
 # ifndef likely
-#  define likely(x)	(__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 1))
+#  define likely(x)	(__branch_check__(x, 1, __builtin_constant_p(x)))
 # endif
 # ifndef unlikely
-#  define unlikely(x)	(__builtin_constant_p(x) ? !!(x) : __branch_check__(x, 0))
+#  define unlikely(x)	(__branch_check__(x, 0, __builtin_constant_p(x)))
 # endif
 
 #ifdef CONFIG_PROFILE_ALL_BRANCHES
diff --git a/kernel/trace/trace_branch.c b/kernel/trace/trace_branch.c
index 75489de546b6..7afe426ea528 100644
--- a/kernel/trace/trace_branch.c
+++ b/kernel/trace/trace_branch.c
@@ -200,8 +200,12 @@ void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
 }
 #endif /* CONFIG_BRANCH_TRACER */
 
-void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect)
+void ftrace_likely_update(struct ftrace_branch_data *f, int val,
+			  int expect, int is_constant)
 {
+	/* A constant is always correct */
+	if (is_constant)
+		val = expect;
 	/*
 	 * I would love to have a trace point here instead, but the
 	 * trace point code is so inundated with unlikely and likely
-- 
2.10.2

[for-next][PATCH 3/4] tracing: Show number of constants profiled in likely profiler

[Steven Rostedt]

[-- Attachment #1: 0003-tracing-Show-number-of-constants-profiled-in-likely-.patch --]
[-- Type: text/plain, Size: 5950 bytes --]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

Now that constants are traced, it is useful to see the number of constants
that are traced in the likely/unlikely profiler in order to know if they
should be ignored or not.

The likely/unlikely will display a number after the "correct" number if a
"constant" count exists.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 include/linux/compiler.h    | 15 ++++++----
 kernel/trace/trace_branch.c | 68 ++++++++++++++++++++++++++++++++++++---------
 2 files changed, 65 insertions(+), 18 deletions(-)

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index bbbe1570de1c..a73cc9afa784 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -101,13 +101,18 @@ struct ftrace_branch_data {
 	};
 };
 
+struct ftrace_likely_data {
+	struct ftrace_branch_data	data;
+	unsigned long			constant;
+};
+
 /*
  * Note: DISABLE_BRANCH_PROFILING can be used by special lowlevel code
  * to disable branch tracing on a per file basis.
  */
 #if defined(CONFIG_TRACE_BRANCH_PROFILING) \
     && !defined(DISABLE_BRANCH_PROFILING) && !defined(__CHECKER__)
-void ftrace_likely_update(struct ftrace_branch_data *f, int val,
+void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 			  int expect, int is_constant);
 
 #define likely_notrace(x)	__builtin_expect(!!(x), 1)
@@ -115,13 +120,13 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val,
 
 #define __branch_check__(x, expect, is_constant) ({			\
 			int ______r;					\
-			static struct ftrace_branch_data		\
+			static struct ftrace_likely_data		\
 				__attribute__((__aligned__(4)))		\
 				__attribute__((section("_ftrace_annotated_branch"))) \
 				______f = {				\
-				.func = __func__,			\
-				.file = __FILE__,			\
-				.line = __LINE__,			\
+				.data.func = __func__,			\
+				.data.file = __FILE__,			\
+				.data.line = __LINE__,			\
 			};						\
 			______r = __builtin_expect(!!(x), expect);	\
 			ftrace_likely_update(&______f, ______r,		\
diff --git a/kernel/trace/trace_branch.c b/kernel/trace/trace_branch.c
index 7afe426ea528..fd483d74f8e1 100644
--- a/kernel/trace/trace_branch.c
+++ b/kernel/trace/trace_branch.c
@@ -200,25 +200,27 @@ void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
 }
 #endif /* CONFIG_BRANCH_TRACER */
 
-void ftrace_likely_update(struct ftrace_branch_data *f, int val,
+void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 			  int expect, int is_constant)
 {
 	/* A constant is always correct */
-	if (is_constant)
+	if (is_constant) {
+		f->constant++;
 		val = expect;
+	}
 	/*
 	 * I would love to have a trace point here instead, but the
 	 * trace point code is so inundated with unlikely and likely
 	 * conditions that the recursive nightmare that exists is too
 	 * much to try to get working. At least for now.
 	 */
-	trace_likely_condition(f, val, expect);
+	trace_likely_condition(&f->data, val, expect);
 
 	/* FIXME: Make this atomic! */
 	if (val == expect)
-		f->correct++;
+		f->data.correct++;
 	else
-		f->incorrect++;
+		f->data.incorrect++;
 }
 EXPORT_SYMBOL(ftrace_likely_update);
 
@@ -249,29 +251,60 @@ static inline long get_incorrect_percent(struct ftrace_branch_data *p)
 	return percent;
 }
 
-static int branch_stat_show(struct seq_file *m, void *v)
+static const char *branch_stat_process_file(struct ftrace_branch_data *p)
 {
-	struct ftrace_branch_data *p = v;
 	const char *f;
-	long percent;
 
 	/* Only print the file, not the path */
 	f = p->file + strlen(p->file);
 	while (f >= p->file && *f != '/')
 		f--;
-	f++;
+	return ++f;
+}
+
+static void branch_stat_show(struct seq_file *m,
+			     struct ftrace_branch_data *p, const char *f)
+{
+	long percent;
 
 	/*
 	 * The miss is overlayed on correct, and hit on incorrect.
 	 */
 	percent = get_incorrect_percent(p);
 
-	seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
 	if (percent < 0)
 		seq_puts(m, "  X ");
 	else
 		seq_printf(m, "%3ld ", percent);
+
 	seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
+}
+
+static int branch_stat_show_normal(struct seq_file *m,
+				   struct ftrace_branch_data *p, const char *f)
+{
+	seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
+	branch_stat_show(m, p, f);
+	return 0;
+}
+
+static int annotate_branch_stat_show(struct seq_file *m, void *v)
+{
+	struct ftrace_likely_data *p = v;
+	const char *f;
+	int l;
+
+	f = branch_stat_process_file(&p->data);
+
+	if (!p->constant)
+		return branch_stat_show_normal(m, &p->data, f);
+
+	l = snprintf(NULL, 0, "/%lu", p->constant);
+	l = l > 8 ? 0 : 8 - l;
+
+	seq_printf(m, "%8lu/%lu %*lu ",
+		   p->data.correct, p->constant, l, p->data.incorrect);
+	branch_stat_show(m, &p->data, f);
 	return 0;
 }
 
@@ -283,7 +316,7 @@ static void *annotated_branch_stat_start(struct tracer_stat *trace)
 static void *
 annotated_branch_stat_next(void *v, int idx)
 {
-	struct ftrace_branch_data *p = v;
+	struct ftrace_likely_data *p = v;
 
 	++p;
 
@@ -332,7 +365,7 @@ static struct tracer_stat annotated_branch_stats = {
 	.stat_next = annotated_branch_stat_next,
 	.stat_cmp = annotated_branch_stat_cmp,
 	.stat_headers = annotated_branch_stat_headers,
-	.stat_show = branch_stat_show
+	.stat_show = annotate_branch_stat_show
 };
 
 __init static int init_annotated_branch_stats(void)
@@ -383,12 +416,21 @@ all_branch_stat_next(void *v, int idx)
 	return p;
 }
 
+static int all_branch_stat_show(struct seq_file *m, void *v)
+{
+	struct ftrace_branch_data *p = v;
+	const char *f;
+
+	f = branch_stat_process_file(p);
+	return branch_stat_show_normal(m, p, f);
+}
+
 static struct tracer_stat all_branch_stats = {
 	.name = "branch_all",
 	.stat_start = all_branch_stat_start,
 	.stat_next = all_branch_stat_next,
 	.stat_headers = all_branch_stat_headers,
-	.stat_show = branch_stat_show
+	.stat_show = all_branch_stat_show
 };
 
 __init static int all_annotated_branch_stats(void)
-- 
2.10.2

[for-next][PATCH 4/4] tracing: Add the constant count for branch tracer

[Steven Rostedt]

[-- Attachment #1: 0004-tracing-Add-the-constant-count-for-branch-tracer.patch --]
[-- Type: text/plain, Size: 3387 bytes --]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

The unlikely/likely branch profiler now gets called even if the if statement
is a constant (always goes in one direction without a compare). Add a value
to denote this in the likely/unlikely tracer as well.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/trace_branch.c  | 17 +++++++++--------
 kernel/trace/trace_entries.h |  6 ++++--
 2 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/kernel/trace/trace_branch.c b/kernel/trace/trace_branch.c
index fd483d74f8e1..4d8fdf3184dc 100644
--- a/kernel/trace/trace_branch.c
+++ b/kernel/trace/trace_branch.c
@@ -27,7 +27,7 @@ static DEFINE_MUTEX(branch_tracing_mutex);
 static struct trace_array *branch_tracer;
 
 static void
-probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
+probe_likely_condition(struct ftrace_likely_data *f, int val, int expect)
 {
 	struct trace_event_call *call = &event_branch;
 	struct trace_array *tr = branch_tracer;
@@ -68,16 +68,17 @@ probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
 	entry	= ring_buffer_event_data(event);
 
 	/* Strip off the path, only save the file */
-	p = f->file + strlen(f->file);
-	while (p >= f->file && *p != '/')
+	p = f->data.file + strlen(f->data.file);
+	while (p >= f->data.file && *p != '/')
 		p--;
 	p++;
 
-	strncpy(entry->func, f->func, TRACE_FUNC_SIZE);
+	strncpy(entry->func, f->data.func, TRACE_FUNC_SIZE);
 	strncpy(entry->file, p, TRACE_FILE_SIZE);
 	entry->func[TRACE_FUNC_SIZE] = 0;
 	entry->file[TRACE_FILE_SIZE] = 0;
-	entry->line = f->line;
+	entry->constant = f->constant;
+	entry->line = f->data.line;
 	entry->correct = val == expect;
 
 	if (!call_filter_check_discard(call, entry, buffer, event))
@@ -89,7 +90,7 @@ probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
 }
 
 static inline
-void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
+void trace_likely_condition(struct ftrace_likely_data *f, int val, int expect)
 {
 	if (!branch_tracing_enabled)
 		return;
@@ -195,7 +196,7 @@ core_initcall(init_branch_tracer);
 
 #else
 static inline
-void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
+void trace_likely_condition(struct ftrace_likely_data *f, int val, int expect)
 {
 }
 #endif /* CONFIG_BRANCH_TRACER */
@@ -214,7 +215,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 	 * conditions that the recursive nightmare that exists is too
 	 * much to try to get working. At least for now.
 	 */
-	trace_likely_condition(&f->data, val, expect);
+	trace_likely_condition(f, val, expect);
 
 	/* FIXME: Make this atomic! */
 	if (val == expect)
diff --git a/kernel/trace/trace_entries.h b/kernel/trace/trace_entries.h
index eb7396b7e7c3..c203ac4df791 100644
--- a/kernel/trace/trace_entries.h
+++ b/kernel/trace/trace_entries.h
@@ -328,11 +328,13 @@ FTRACE_ENTRY(branch, trace_branch,
 		__array(	char,		func,	TRACE_FUNC_SIZE+1	)
 		__array(	char,		file,	TRACE_FILE_SIZE+1	)
 		__field(	char,		correct				)
+		__field(	char,		constant			)
 	),
 
-	F_printk("%u:%s:%s (%u)",
+	F_printk("%u:%s:%s (%u)%s",
 		 __entry->line,
-		 __entry->func, __entry->file, __entry->correct),
+		 __entry->func, __entry->file, __entry->correct,
+		 __entry->constant ? " CONSTANT" : ""),
 
 	FILTER_OTHER
 );
-- 
2.10.2