tracing: merge seq_print_sym_short() and seq_print_sym_offset()

PATCH In review Rasmus Villemoes 2 participants 9 messages Oct 26, 2018 – Oct 31, 2018 Tracing

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Rasmus Villemoes

author

2018-10-26 21:13 UTC #0 lore raw

PATCH v2 1/3 tracing: merge seq_print_sym_short() and seq_print_sym_offset()

These two functions are nearly identical, so we can avoid some code duplication by moving the conditional into a common implementation.

Signed-off-by Rasmus Villemoes <[email protected]>

---
 kernel/trace/trace_output.c | 34 +++++++---------------------------
 1 file changed, 7 insertions(+), 27 deletions(-)

kernel/trace/trace_output.c +7 ~~-27~~

index 6e6cc64faa38..501311dcfca6 100644
@@ -339,34 +339,17 @@ static inline const char *kretprobed(const char *name)
 #endif /* CONFIG_KRETPROBES */
 
 static void
-seq_print_sym_short(struct trace_seq *s, const char *fmt, unsigned long address)
+seq_print_sym(struct trace_seq *s, const char *fmt, unsigned long address,
+	      bool with_offset)
 {
 	char str[KSYM_SYMBOL_LEN];
 #ifdef CONFIG_KALLSYMS
 	const char *name;
 
-	kallsyms_lookup(address, NULL, NULL, NULL, str);
-
-	name = kretprobed(str);
-
-	if (name && strlen(name)) {
-		trace_seq_printf(s, fmt, name);
-		return;
-	}
-#endif
-	snprintf(str, KSYM_SYMBOL_LEN, "0x%08lx", address);
-	trace_seq_printf(s, fmt, str);
-}
-
-static void
-seq_print_sym_offset(struct trace_seq *s, const char *fmt,
-		     unsigned long address)
-{
-	char str[KSYM_SYMBOL_LEN];
-#ifdef CONFIG_KALLSYMS
-	const char *name;
-
-	sprint_symbol(str, address);
+	if (with_offset)
+		sprint_symbol(str, address);
+	else
+		kallsyms_lookup(address, NULL, NULL, NULL, str);
 	name = kretprobed(str);
 
 	if (name && strlen(name)) {

@@ -424,10 +407,7 @@ seq_print_ip_sym(struct trace_seq *s, unsigned long ip, unsigned long sym_flags)
 		goto out;
 	}
 
-	if (sym_flags & TRACE_ITER_SYM_OFFSET)
-		seq_print_sym_offset(s, "%s", ip);
-	else
-		seq_print_sym_short(s, "%s", ip);
+	seq_print_sym(s, "%s", ip, sym_flags & TRACE_ITER_SYM_OFFSET);
 
 	if (sym_flags & TRACE_ITER_SYM_ADDR)
 		trace_seq_printf(s, " <" IP_FMT ">", ip);

Signature · 1 line

2.19.1.6.gbde171bbf5

Rasmus Villemoes

author

2018-10-26 21:13 UTC #1 lore raw

PATCH v2 2/3 tracing: avoid -Wformat-nonliteral warning

Building with -Wformat-nonliteral, gcc complains

kernel/trace/trace_output.c: In function ‘seq_print_sym’:
kernel/trace/trace_output.c:356:3: warning: format not a string literal, argument types not checked [-Wformat-nonliteral]
trace_seq_printf(s, fmt, name);

But seq_print_sym only has a single caller which passes "%s" as fmt, so we might as well just use that directly. That also paves the way for further cleanups that will actually make that format string go away entirely.

Signed-off-by Rasmus Villemoes <[email protected]>

---
 kernel/trace/trace_output.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

kernel/trace/trace_output.c +4 -5

index 501311dcfca6..7417ce5fe4bb 100644
@@ -339,8 +339,7 @@ static inline const char *kretprobed(const char *name)
 #endif /* CONFIG_KRETPROBES */
 
 static void
-seq_print_sym(struct trace_seq *s, const char *fmt, unsigned long address,
-	      bool with_offset)
+seq_print_sym(struct trace_seq *s, unsigned long address, bool with_offset)
 {
 	char str[KSYM_SYMBOL_LEN];
 #ifdef CONFIG_KALLSYMS

@@ -353,12 +352,12 @@ seq_print_sym(struct trace_seq *s, const char *fmt, unsigned long address,
 	name = kretprobed(str);
 
 	if (name && strlen(name)) {
-		trace_seq_printf(s, fmt, name);
+		trace_seq_printf(s, "%s", name);
 		return;
 	}
 #endif
 	snprintf(str, KSYM_SYMBOL_LEN, "0x%08lx", address);
-	trace_seq_printf(s, fmt, str);
+	trace_seq_printf(s, "%s", str);
 }
 
 #ifndef CONFIG_64BIT

@@ -407,7 +406,7 @@ seq_print_ip_sym(struct trace_seq *s, unsigned long ip, unsigned long sym_flags)
 		goto out;
 	}
 
-	seq_print_sym(s, "%s", ip, sym_flags & TRACE_ITER_SYM_OFFSET);
+	seq_print_sym(s, ip, sym_flags & TRACE_ITER_SYM_OFFSET);
 
 	if (sym_flags & TRACE_ITER_SYM_ADDR)
 		trace_seq_printf(s, " <" IP_FMT ">", ip);

Signature · 1 line

2.19.1.6.gbde171bbf5

Rasmus Villemoes

author

2018-10-26 21:13 UTC #2 lore raw

PATCH v2 3/3 tracing: simplify printf'ing in seq_print_sym

In reply to Rasmus Villemoes

trace_seq_printf(..., "%s", ...) can be done with trace_seq_puts() instead, avoiding printf overhead. In the second instance, the string we're copying was just created from an snprintf() to a stack buffer, so we might as well do that printf directly. This naturally leads to moving the declaration of the str buffer inside the CONFIG_KALLSYMS guard, which in turn will make gcc inline the function for !CONFIG_KALLSYMS (it only has a single caller, but the huge stack frame seems to make gcc not inline it for CONFIG_KALLSYMS).

Signed-off-by Rasmus Villemoes <[email protected]>

---
 kernel/trace/trace_output.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

kernel/trace/trace_output.c +3 -4

index 7417ce5fe4bb..0f96262d23be 100644
@@ -341,8 +341,8 @@ static inline const char *kretprobed(const char *name)
 static void
 seq_print_sym(struct trace_seq *s, unsigned long address, bool with_offset)
 {
-	char str[KSYM_SYMBOL_LEN];
 #ifdef CONFIG_KALLSYMS
+	char str[KSYM_SYMBOL_LEN];
 	const char *name;
 
 	if (with_offset)

@@ -352,12 +352,11 @@ seq_print_sym(struct trace_seq *s, unsigned long address, bool with_offset)
 	name = kretprobed(str);
 
 	if (name && strlen(name)) {
-		trace_seq_printf(s, "%s", name);
+		trace_seq_puts(s, name);
 		return;
 	}
 #endif
-	snprintf(str, KSYM_SYMBOL_LEN, "0x%08lx", address);
-	trace_seq_printf(s, "%s", str);
+	trace_seq_printf(s, "0x%08lx", address);
 }
 
 #ifndef CONFIG_64BIT

Signature · 1 line

2.19.1.6.gbde171bbf5

Steven Rostedt

maintainer

2018-10-26 21:41 UTC #3 lore raw

In reply to Rasmus Villemoes

Hi Ramus,

Thanks for sending these patches. I have some small nits though.

First, please send a cover letter whenever sending more than one patch. It just groups them better in my inbox.

The second is embedded below.

Quoted 13 lines · On Fri, 26 Oct 2018 23:13:44 +0200 Rasmus Villemoes <[email protected]>…

These two functions are nearly identical, so we can avoid some code duplication by moving the conditional into a common implementation.
Signed-off-by Rasmus Villemoes <[email protected]>
---
 kernel/trace/trace_output.c | 34 +++++++---------------------------
 1 file changed, 7 insertions(+), 27 deletions(-)
kernel/trace/trace_output.c +0 -0
index 6e6cc64faa38..501311dcfca6 100644

kernel/trace/trace_output.c static inline const char *kretprobed(const char *name) · line 343

Quoted 6 lines

kernel/trace/trace_output.c +2 -1

@@ -339,34 +339,17 @@ static inline const char *kretprobed(const char *name)
 #endif /* CONFIG_KRETPROBES */
 
 static void
-seq_print_sym_short(struct trace_seq *s, const char *fmt, unsigned long address)
+seq_print_sym(struct trace_seq *s, const char *fmt, unsigned long address,
+	      bool with_offset)

Just call the variable "offset". It's rather obvious what that means.

The other patches look good, but can you send a v2 of the series, with these updates?

Thanks!

-- Steve

Quoted 46 lines

kernel/trace/trace_output.c +5 ~~-26~~

 {
 	char str[KSYM_SYMBOL_LEN];
 #ifdef CONFIG_KALLSYMS
 	const char *name;
 
-	kallsyms_lookup(address, NULL, NULL, NULL, str);
-
-	name = kretprobed(str);
-
-	if (name && strlen(name)) {
-		trace_seq_printf(s, fmt, name);
-		return;
-	}
-#endif
-	snprintf(str, KSYM_SYMBOL_LEN, "0x%08lx", address);
-	trace_seq_printf(s, fmt, str);
-}
-
-static void
-seq_print_sym_offset(struct trace_seq *s, const char *fmt,
-		     unsigned long address)
-{
-	char str[KSYM_SYMBOL_LEN];
-#ifdef CONFIG_KALLSYMS
-	const char *name;
-
-	sprint_symbol(str, address);
+	if (with_offset)
+		sprint_symbol(str, address);
+	else
+		kallsyms_lookup(address, NULL, NULL, NULL, str);
 	name = kretprobed(str);
 
 	if (name && strlen(name)) {

@@ -424,10 +407,7 @@ seq_print_ip_sym(struct trace_seq *s, unsigned long ip, unsigned long sym_flags)
 		goto out;
 	}
 
-	if (sym_flags & TRACE_ITER_SYM_OFFSET)
-		seq_print_sym_offset(s, "%s", ip);
-	else
-		seq_print_sym_short(s, "%s", ip);
+	seq_print_sym(s, "%s", ip, sym_flags & TRACE_ITER_SYM_OFFSET);
 
 	if (sym_flags & TRACE_ITER_SYM_ADDR)
 		trace_seq_printf(s, " <" IP_FMT ">", ip);

Rasmus Villemoes

author

2018-10-29 22:35 UTC #4 lore raw

v2 cover tracing: a few simplifying patches

In reply to Rasmus Villemoes

Playing around with -Wformat-nonliteral, I stumbled on two instances in trace_output.c. Looking at the code a bit, turns out one can remove the use of the non-constant format string and eliminate some code duplication at the same time.

v2: Include cover letter, rename argument with_offset -> offset.

Rasmus Villemoes (3):
tracing: merge seq_print_sym_short() and seq_print_sym_offset()
tracing: avoid -Wformat-nonliteral warning
tracing: simplify printf'ing in seq_print_sym

 kernel/trace/trace_output.c | 38 ++++++++-----------------------------
 1 file changed, 8 insertions(+), 30 deletions(-)

Signature · 1 line

2.19.1.6.gbde171bbf5

Rasmus Villemoes

author

2018-10-29 22:35 UTC #5 lore raw

PATCH v2 1/3 tracing: merge seq_print_sym_short() and seq_print_sym_offset()

These two functions are nearly identical, so we can avoid some code duplication by moving the conditional into a common implementation.

Signed-off-by Rasmus Villemoes <[email protected]>

---
 kernel/trace/trace_output.c | 34 +++++++---------------------------
 1 file changed, 7 insertions(+), 27 deletions(-)

kernel/trace/trace_output.c +7 ~~-27~~

index 6e6cc64faa38..85ecd061c7be 100644
@@ -339,34 +339,17 @@ static inline const char *kretprobed(const char *name)
 #endif /* CONFIG_KRETPROBES */
 
 static void
-seq_print_sym_short(struct trace_seq *s, const char *fmt, unsigned long address)
+seq_print_sym(struct trace_seq *s, const char *fmt, unsigned long address,
+	      bool offset)
 {
 	char str[KSYM_SYMBOL_LEN];
 #ifdef CONFIG_KALLSYMS
 	const char *name;
 
-	kallsyms_lookup(address, NULL, NULL, NULL, str);
-
-	name = kretprobed(str);
-
-	if (name && strlen(name)) {
-		trace_seq_printf(s, fmt, name);
-		return;
-	}
-#endif
-	snprintf(str, KSYM_SYMBOL_LEN, "0x%08lx", address);
-	trace_seq_printf(s, fmt, str);
-}
-
-static void
-seq_print_sym_offset(struct trace_seq *s, const char *fmt,
-		     unsigned long address)
-{
-	char str[KSYM_SYMBOL_LEN];
-#ifdef CONFIG_KALLSYMS
-	const char *name;
-
-	sprint_symbol(str, address);
+	if (offset)
+		sprint_symbol(str, address);
+	else
+		kallsyms_lookup(address, NULL, NULL, NULL, str);
 	name = kretprobed(str);
 
 	if (name && strlen(name)) {

@@ -424,10 +407,7 @@ seq_print_ip_sym(struct trace_seq *s, unsigned long ip, unsigned long sym_flags)
 		goto out;
 	}
 
-	if (sym_flags & TRACE_ITER_SYM_OFFSET)
-		seq_print_sym_offset(s, "%s", ip);
-	else
-		seq_print_sym_short(s, "%s", ip);
+	seq_print_sym(s, "%s", ip, sym_flags & TRACE_ITER_SYM_OFFSET);
 
 	if (sym_flags & TRACE_ITER_SYM_ADDR)
 		trace_seq_printf(s, " <" IP_FMT ">", ip);

Signature · 1 line

2.19.1.6.gbde171bbf5

Rasmus Villemoes

author

2018-10-29 22:35 UTC #6 lore raw

PATCH v2 2/3 tracing: avoid -Wformat-nonliteral warning

In reply to Rasmus Villemoes

Building with -Wformat-nonliteral, gcc complains

Signed-off-by Rasmus Villemoes <[email protected]>

---
 kernel/trace/trace_output.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

kernel/trace/trace_output.c +4 -5

index 85ecd061c7be..f06fb899b746 100644
@@ -339,8 +339,7 @@ static inline const char *kretprobed(const char *name)
 #endif /* CONFIG_KRETPROBES */
 
 static void
-seq_print_sym(struct trace_seq *s, const char *fmt, unsigned long address,
-	      bool offset)
+seq_print_sym(struct trace_seq *s, unsigned long address, bool offset)
 {
 	char str[KSYM_SYMBOL_LEN];
 #ifdef CONFIG_KALLSYMS

@@ -353,12 +352,12 @@ seq_print_sym(struct trace_seq *s, const char *fmt, unsigned long address,
 	name = kretprobed(str);
 
 	if (name && strlen(name)) {
-		trace_seq_printf(s, fmt, name);
+		trace_seq_printf(s, "%s", name);
 		return;
 	}
 #endif
 	snprintf(str, KSYM_SYMBOL_LEN, "0x%08lx", address);
-	trace_seq_printf(s, fmt, str);
+	trace_seq_printf(s, "%s", str);
 }
 
 #ifndef CONFIG_64BIT

@@ -407,7 +406,7 @@ seq_print_ip_sym(struct trace_seq *s, unsigned long ip, unsigned long sym_flags)
 		goto out;
 	}
 
-	seq_print_sym(s, "%s", ip, sym_flags & TRACE_ITER_SYM_OFFSET);
+	seq_print_sym(s, ip, sym_flags & TRACE_ITER_SYM_OFFSET);
 
 	if (sym_flags & TRACE_ITER_SYM_ADDR)
 		trace_seq_printf(s, " <" IP_FMT ">", ip);

Signature · 1 line

2.19.1.6.gbde171bbf5

Rasmus Villemoes

author

2018-10-29 22:35 UTC #7 lore raw

PATCH v2 3/3 tracing: simplify printf'ing in seq_print_sym

In reply to Rasmus Villemoes

Signed-off-by Rasmus Villemoes <[email protected]>

---
 kernel/trace/trace_output.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

kernel/trace/trace_output.c +3 -4

index f06fb899b746..54373d93e251 100644
@@ -341,8 +341,8 @@ static inline const char *kretprobed(const char *name)
 static void
 seq_print_sym(struct trace_seq *s, unsigned long address, bool offset)
 {
-	char str[KSYM_SYMBOL_LEN];
 #ifdef CONFIG_KALLSYMS
+	char str[KSYM_SYMBOL_LEN];
 	const char *name;
 
 	if (offset)

@@ -352,12 +352,11 @@ seq_print_sym(struct trace_seq *s, unsigned long address, bool offset)
 	name = kretprobed(str);
 
 	if (name && strlen(name)) {
-		trace_seq_printf(s, "%s", name);
+		trace_seq_puts(s, name);
 		return;
 	}
 #endif
-	snprintf(str, KSYM_SYMBOL_LEN, "0x%08lx", address);
-	trace_seq_printf(s, "%s", str);
+	trace_seq_printf(s, "0x%08lx", address);
 }
 
 #ifndef CONFIG_64BIT

Signature · 1 line

2.19.1.6.gbde171bbf5

Steven Rostedt

maintainer

2018-10-31 11:45 UTC #8 lore raw

Re: [PATCH v2 0/3] tracing: a few simplifying patches

In reply to Rasmus Villemoes

On Mon, 29 Oct 2018 23:35:39 +0100
Rasmus Villemoes <[email protected]> wrote:

Hi Rasmus,

I'm currently traveling. I'll try to take a look at these later. If you don't hear from me by next week, feel free to send me a gentle reminder ;-)

-- Steve

Quoted 15 lines

Playing around with -Wformat-nonliteral, I stumbled on two instances in trace_output.c. Looking at the code a bit, turns out one can remove the use of the non-constant format string and eliminate some code duplication at the same time.
v2: Include cover letter, rename argument with_offset -> offset.
Rasmus Villemoes (3):
tracing: merge seq_print_sym_short() and seq_print_sym_offset()
tracing: avoid -Wformat-nonliteral warning
tracing: simplify printf'ing in seq_print_sym
 kernel/trace/trace_output.c | 38 ++++++++-----------------------------
 1 file changed, 8 insertions(+), 30 deletions(-)