ftrace: Expose call graph depth as unsigned int

PATCH New Ilya Leoshkevich 1 participant 3 messages Apr 12, 2025 Tracing

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Ilya Leoshkevich

author

2025-04-12 22:19 UTC #1 lore raw

PATCH v2 1/2 ftrace: Fix type of ftrace_graph_ent_entry.depth

In reply to Ilya Leoshkevich

ftrace_graph_ent.depth is int, but ftrace_graph_ent_entry.depth is unsigned long. This confuses trace-cmd on 64-bit big-endian systems and makes it print a huge amount of spaces. Fix this by using unsigned int, which has a matching size, instead.

Fixes ff5c9c576e75 ("ftrace: Add support for function argument to graph tracer")

Signed-off-by Ilya Leoshkevich <[email protected]>

---
 kernel/trace/trace_entries.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

kernel/trace/trace_entries.h +2 -2

index ee40d4e6ad1c..4ef4df6623a8 100644
@@ -80,11 +80,11 @@ FTRACE_ENTRY(funcgraph_entry, ftrace_graph_ent_entry,
 	F_STRUCT(
 		__field_struct(	struct ftrace_graph_ent,	graph_ent	)
 		__field_packed(	unsigned long,	graph_ent,	func		)
-		__field_packed(	unsigned long,	graph_ent,	depth		)
+		__field_packed(	unsigned int,	graph_ent,	depth		)
 		__dynamic_array(unsigned long,	args				)
 	),
 
-	F_printk("--> %ps (%lu)", (void *)__entry->func, __entry->depth)
+	F_printk("--> %ps (%u)", (void *)__entry->func, __entry->depth)
 );
 
 #ifdef CONFIG_FUNCTION_GRAPH_RETADDR

Signature · 1 line

2.49.0

Ilya Leoshkevich

author

2025-04-12 22:19 UTC #2 lore raw

PATCH v2 2/2 ftrace: Expose call graph depth as unsigned int

In reply to Ilya Leoshkevich

Depth is stored as int because the code uses negative values to break out of iterations. But what is recorded is always zero or positive. So expose it as unsigned int instead of int.

Signed-off-by Ilya Leoshkevich <[email protected]>

---
 kernel/trace/trace_entries.h | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

kernel/trace/trace_entries.h +6 -6

index 4ef4df6623a8..de294ae2c5c5 100644
@@ -97,11 +97,11 @@ FTRACE_ENTRY_PACKED(fgraph_retaddr_entry, fgraph_retaddr_ent_entry,
 	F_STRUCT(
 		__field_struct(	struct fgraph_retaddr_ent,	graph_ent	)
 		__field_packed(	unsigned long,	graph_ent,	func		)
-		__field_packed(	int,		graph_ent,	depth		)
+		__field_packed(	unsigned int,	graph_ent,	depth		)
 		__field_packed(	unsigned long,	graph_ent,	retaddr		)
 	),
 
-	F_printk("--> %ps (%d) <- %ps", (void *)__entry->func, __entry->depth,
+	F_printk("--> %ps (%u) <- %ps", (void *)__entry->func, __entry->depth,
 		(void *)__entry->retaddr)
 );

@@ -124,13 +124,13 @@ FTRACE_ENTRY_PACKED(funcgraph_exit, ftrace_graph_ret_entry,
 		__field_struct(	struct ftrace_graph_ret,	ret	)
 		__field_packed(	unsigned long,	ret,		func	)
 		__field_packed(	unsigned long,	ret,		retval	)
-		__field_packed(	int,		ret,		depth	)
+		__field_packed(	unsigned int,	ret,		depth	)
 		__field_packed(	unsigned int,	ret,		overrun	)
 		__field(unsigned long long,	calltime		)
 		__field(unsigned long long,	rettime			)
 	),
 
-	F_printk("<-- %ps (%d) (start: %llx  end: %llx) over: %d retval: %lx",
+	F_printk("<-- %ps (%u) (start: %llx  end: %llx) over: %u retval: %lx",
 		 (void *)__entry->func, __entry->depth,
 		 __entry->calltime, __entry->rettime,
 		 __entry->depth, __entry->retval)

@@ -146,13 +146,13 @@ FTRACE_ENTRY_PACKED(funcgraph_exit, ftrace_graph_ret_entry,
 	F_STRUCT(
 		__field_struct(	struct ftrace_graph_ret,	ret	)
 		__field_packed(	unsigned long,	ret,		func	)
-		__field_packed(	int,		ret,		depth	)
+		__field_packed(	unsigned int,	ret,		depth	)
 		__field_packed(	unsigned int,	ret,		overrun	)
 		__field(unsigned long long,	calltime		)
 		__field(unsigned long long,	rettime			)
 	),
 
-	F_printk("<-- %ps (%d) (start: %llx  end: %llx) over: %d",
+	F_printk("<-- %ps (%u) (start: %llx  end: %llx) over: %u",
 		 (void *)__entry->func, __entry->depth,
 		 __entry->calltime, __entry->rettime,
 		 __entry->depth)

Signature · 1 line

2.49.0

Ilya Leoshkevich

author

2025-04-12 22:19 UTC #0 lore raw

v2 cover ftrace: Expose call graph depth as unsigned int

v1: https://lore.kernel.org/lkml/[email protected]/
v1 -> v2: Use unsigned int instead of int.
Add a follow-up patch that changes depth to unsigned int in all events.

Hi,

This series changes the type of depth in all call graph events to unsigned int.

Patch 1 fixes a size mismatch issue in ftrace_graph_ent_entry, which causes trace-cmd on 64-bit big-endian systems to output a lot of bogus spaces, rendering it unusable.

Patch 2 changes type of depth in all other events to unsigned int in order to better reflect its semantics: it can only be negative internally, but recorded values are always non-negative.

Best regards,
Ilya

Ilya Leoshkevich (2):
ftrace: Fix type of ftrace_graph_ent_entry.depth
ftrace: Expose call graph depth as unsigned int

 kernel/trace/trace_entries.h | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

Signature · 1 line

2.49.0