[for-next][PATCH 0/7] ftrace: Updates for 6.13

[for-next][PATCH 0/7] ftrace: Updates for 6.13

[Steven Rostedt]

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

Head SHA1: 8b0cb3a4c5e85dda8957ba6a4c8c081a9aec6e80


Steven Rostedt (7):
      fgraph: Separate size of ret_stack from PAGE_SIZE
      fgraph: Give ret_stack its own kmem cache
      fgraph: Use guard(mutex)(&ftrace_lock) for unregister_ftrace_graph()
      ftrace: Use guard for match_records()
      ftrace: Use guard to lock ftrace_lock in cache_mod()
      ftrace: Use guard to take the ftrace_lock in release_probe()
      ftrace: Use guard to take ftrace_lock in ftrace_graph_set_hash()

----
 kernel/trace/fgraph.c | 45 +++++++++++++++++++++++++++++++------------
 kernel/trace/ftrace.c | 53 +++++++++++++++++----------------------------------
 2 files changed, 50 insertions(+), 48 deletions(-)

[for-next][PATCH 1/7] fgraph: Separate size of ret_stack from PAGE_SIZE

[Steven Rostedt]

From: Steven Rostedt <rostedt@goodmis.org>

The ret_stack (shadow stack used by function graph infrastructure) is
currently defined as PAGE_SIZE. But some architectures which have 64K
PAGE_SIZE, this is way overkill. Also there's an effort to allow the
PAGE_SIZE to be defined at boot up.

Hard code it for now to 4096. In the future, this size may change and even
be dependent on specific architectures.

Link: https://lore.kernel.org/all/e5067bb8-0fcd-4739-9bca-0e872037d5a1@arm.com/

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20241019152951.053f9646@rorschach.local.home
Suggested-by: Ryan Roberts <ryan.roberts@arm.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/fgraph.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
index 13fcc25d15a0..4ce87982966a 100644
--- a/kernel/trace/fgraph.c
+++ b/kernel/trace/fgraph.c
@@ -153,7 +153,7 @@ enum {
  * SHADOW_STACK_OFFSET:	The size in long words of the shadow stack
  * SHADOW_STACK_MAX_OFFSET: The max offset of the stack for a new frame to be added
  */
-#define SHADOW_STACK_SIZE	(PAGE_SIZE)
+#define SHADOW_STACK_SIZE	(4096)
 #define SHADOW_STACK_OFFSET	(SHADOW_STACK_SIZE / sizeof(long))
 /* Leave on a buffer at the end */
 #define SHADOW_STACK_MAX_OFFSET				\
-- 
2.45.2

[for-next][PATCH 2/7] fgraph: Give ret_stack its own kmem cache

[Steven Rostedt]

From: Steven Rostedt <rostedt@goodmis.org>

The ret_stack (shadow stack used by function graph infrastructure) is
created for every task on the system when function graph is enabled. Give
it its own kmem_cache. This will make it easier to see how much memory is
being used specifically for function graph shadow stacks.

In the future, this size may change and may not be a power of two. Having
its own cache can also keep it from fragmenting memory.

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Link: https://lore.kernel.org/20241026063210.7d4910a7@rorschach.local.home
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/fgraph.c | 33 ++++++++++++++++++++++++++++-----
 1 file changed, 28 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
index 4ce87982966a..001abf376c0c 100644
--- a/kernel/trace/fgraph.c
+++ b/kernel/trace/fgraph.c
@@ -172,6 +172,8 @@ enum {
 DEFINE_STATIC_KEY_FALSE(kill_ftrace_graph);
 int ftrace_graph_active;
 
+static struct kmem_cache *fgraph_stack_cachep;
+
 static struct fgraph_ops *fgraph_array[FGRAPH_ARRAY_SIZE];
 static unsigned long fgraph_array_bitmask;
 
@@ -1022,8 +1024,11 @@ static int alloc_retstack_tasklist(unsigned long **ret_stack_list)
 	int start = 0, end = FTRACE_RETSTACK_ALLOC_SIZE;
 	struct task_struct *g, *t;
 
+	if (WARN_ON_ONCE(!fgraph_stack_cachep))
+		return -ENOMEM;
+
 	for (i = 0; i < FTRACE_RETSTACK_ALLOC_SIZE; i++) {
-		ret_stack_list[i] = kmalloc(SHADOW_STACK_SIZE, GFP_KERNEL);
+		ret_stack_list[i] = kmem_cache_alloc(fgraph_stack_cachep, GFP_KERNEL);
 		if (!ret_stack_list[i]) {
 			start = 0;
 			end = i;
@@ -1054,7 +1059,7 @@ static int alloc_retstack_tasklist(unsigned long **ret_stack_list)
 	rcu_read_unlock();
 free:
 	for (i = start; i < end; i++)
-		kfree(ret_stack_list[i]);
+		kmem_cache_free(fgraph_stack_cachep, ret_stack_list[i]);
 	return ret;
 }
 
@@ -1117,9 +1122,12 @@ void ftrace_graph_init_idle_task(struct task_struct *t, int cpu)
 	if (ftrace_graph_active) {
 		unsigned long *ret_stack;
 
+		if (WARN_ON_ONCE(!fgraph_stack_cachep))
+			return;
+
 		ret_stack = per_cpu(idle_ret_stack, cpu);
 		if (!ret_stack) {
-			ret_stack = kmalloc(SHADOW_STACK_SIZE, GFP_KERNEL);
+			ret_stack = kmem_cache_alloc(fgraph_stack_cachep, GFP_KERNEL);
 			if (!ret_stack)
 				return;
 			per_cpu(idle_ret_stack, cpu) = ret_stack;
@@ -1139,7 +1147,10 @@ void ftrace_graph_init_task(struct task_struct *t)
 	if (ftrace_graph_active) {
 		unsigned long *ret_stack;
 
-		ret_stack = kmalloc(SHADOW_STACK_SIZE, GFP_KERNEL);
+		if (WARN_ON_ONCE(!fgraph_stack_cachep))
+			return;
+
+		ret_stack = kmem_cache_alloc(fgraph_stack_cachep, GFP_KERNEL);
 		if (!ret_stack)
 			return;
 		graph_init_task(t, ret_stack);
@@ -1154,7 +1165,11 @@ void ftrace_graph_exit_task(struct task_struct *t)
 	/* NULL must become visible to IRQs before we free it: */
 	barrier();
 
-	kfree(ret_stack);
+	if (ret_stack) {
+		if (WARN_ON_ONCE(!fgraph_stack_cachep))
+			return;
+		kmem_cache_free(fgraph_stack_cachep, ret_stack);
+	}
 }
 
 #ifdef CONFIG_DYNAMIC_FTRACE
@@ -1294,6 +1309,14 @@ int register_ftrace_graph(struct fgraph_ops *gops)
 
 	guard(mutex)(&ftrace_lock);
 
+	if (!fgraph_stack_cachep) {
+		fgraph_stack_cachep = kmem_cache_create("fgraph_stack",
+							SHADOW_STACK_SIZE,
+							SHADOW_STACK_SIZE, 0, NULL);
+		if (!fgraph_stack_cachep)
+			return -ENOMEM;
+	}
+
 	if (!fgraph_initialized) {
 		ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "fgraph:online",
 					fgraph_cpu_init, NULL);
-- 
2.45.2

[for-next][PATCH 3/7] fgraph: Use guard(mutex)(&ftrace_lock) for unregister_ftrace_graph()

[Steven Rostedt]

From: Steven Rostedt <rostedt@goodmis.org>

The ftrace_lock is held throughout unregister_ftrace_graph(), use a guard
to simplify the error paths.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/20241028071307.770550792@goodmis.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/fgraph.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
index 001abf376c0c..0bf78517b5d4 100644
--- a/kernel/trace/fgraph.c
+++ b/kernel/trace/fgraph.c
@@ -1381,17 +1381,17 @@ void unregister_ftrace_graph(struct fgraph_ops *gops)
 {
 	int command = 0;
 
-	mutex_lock(&ftrace_lock);
+	guard(mutex)(&ftrace_lock);
 
 	if (unlikely(!ftrace_graph_active))
-		goto out;
+		return;
 
 	if (unlikely(gops->idx < 0 || gops->idx >= FGRAPH_ARRAY_SIZE ||
 		     fgraph_array[gops->idx] != gops))
-		goto out;
+		return;
 
 	if (fgraph_lru_release_index(gops->idx) < 0)
-		goto out;
+		return;
 
 	fgraph_array[gops->idx] = &fgraph_stub;
 
@@ -1413,7 +1413,5 @@ void unregister_ftrace_graph(struct fgraph_ops *gops)
 		unregister_pm_notifier(&ftrace_suspend_notifier);
 		unregister_trace_sched_switch(ftrace_graph_probe_sched_switch, NULL);
 	}
- out:
 	gops->saved_func = NULL;
-	mutex_unlock(&ftrace_lock);
 }
-- 
2.45.2

[for-next][PATCH 4/7] ftrace: Use guard for match_records()

[Steven Rostedt]

From: Steven Rostedt <rostedt@goodmis.org>

The ftrace_lock is held for most of match_records() until the end of the
function. Use guard to make error paths simpler.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/20241028071307.927146604@goodmis.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/ftrace.c | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index e9fd4fb2769e..44adc34643c9 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -4829,15 +4829,13 @@ match_records(struct ftrace_hash *hash, char *func, int len, char *mod)
 		mod_g.len = strlen(mod_g.search);
 	}
 
-	mutex_lock(&ftrace_lock);
+	guard(mutex)(&ftrace_lock);
 
 	if (unlikely(ftrace_disabled))
-		goto out_unlock;
+		return 0;
 
-	if (func_g.type == MATCH_INDEX) {
-		found = add_rec_by_index(hash, &func_g, clear_filter);
-		goto out_unlock;
-	}
+	if (func_g.type == MATCH_INDEX)
+		return add_rec_by_index(hash, &func_g, clear_filter);
 
 	do_for_each_ftrace_rec(pg, rec) {
 
@@ -4846,16 +4844,12 @@ match_records(struct ftrace_hash *hash, char *func, int len, char *mod)
 
 		if (ftrace_match_record(rec, &func_g, mod_match, exclude_mod)) {
 			ret = enter_record(hash, rec, clear_filter);
-			if (ret < 0) {
-				found = ret;
-				goto out_unlock;
-			}
+			if (ret < 0)
+				return ret;
 			found = 1;
 		}
 		cond_resched();
 	} while_for_each_ftrace_rec();
- out_unlock:
-	mutex_unlock(&ftrace_lock);
 
 	return found;
 }
-- 
2.45.2

[for-next][PATCH 5/7] ftrace: Use guard to lock ftrace_lock in cache_mod()

[Steven Rostedt]

From: Steven Rostedt <rostedt@goodmis.org>

The ftrace_lock is held throughout cache_mod(), use guard to simplify the
error paths.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/20241028071308.088458856@goodmis.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/ftrace.c | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 44adc34643c9..64997416415e 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -4947,14 +4947,14 @@ static int cache_mod(struct trace_array *tr,
 {
 	struct ftrace_mod_load *ftrace_mod, *n;
 	struct list_head *head = enable ? &tr->mod_trace : &tr->mod_notrace;
-	int ret;
 
-	mutex_lock(&ftrace_lock);
+	guard(mutex)(&ftrace_lock);
 
 	/* We do not cache inverse filters */
 	if (func[0] == '!') {
+		int ret = -EINVAL;
+
 		func++;
-		ret = -EINVAL;
 
 		/* Look to remove this hash */
 		list_for_each_entry_safe(ftrace_mod, n, head, list) {
@@ -4970,20 +4970,15 @@ static int cache_mod(struct trace_array *tr,
 				continue;
 			}
 		}
-		goto out;
+		return ret;
 	}
 
-	ret = -EINVAL;
 	/* We only care about modules that have not been loaded yet */
 	if (module_exists(module))
-		goto out;
+		return -EINVAL;
 
 	/* Save this string off, and execute it when the module is loaded */
-	ret = ftrace_add_mod(tr, func, module, enable);
- out:
-	mutex_unlock(&ftrace_lock);
-
-	return ret;
+	return ftrace_add_mod(tr, func, module, enable);
 }
 
 static int
-- 
2.45.2

[for-next][PATCH 6/7] ftrace: Use guard to take the ftrace_lock in release_probe()

[Steven Rostedt]

From: Steven Rostedt <rostedt@goodmis.org>

The ftrace_lock is held throughout the entire release_probe() function.
Use guard to simplify any exit paths.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/20241028071308.250787901@goodmis.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/ftrace.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 64997416415e..c0fabd7da5b2 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -5288,7 +5288,7 @@ static void release_probe(struct ftrace_func_probe *probe)
 {
 	struct ftrace_probe_ops *probe_ops;
 
-	mutex_lock(&ftrace_lock);
+	guard(mutex)(&ftrace_lock);
 
 	WARN_ON(probe->ref <= 0);
 
@@ -5306,7 +5306,6 @@ static void release_probe(struct ftrace_func_probe *probe)
 		list_del(&probe->list);
 		kfree(probe);
 	}
-	mutex_unlock(&ftrace_lock);
 }
 
 static void acquire_probe_locked(struct ftrace_func_probe *probe)
-- 
2.45.2

[for-next][PATCH 7/7] ftrace: Use guard to take ftrace_lock in ftrace_graph_set_hash()

[Steven Rostedt]

From: Steven Rostedt <rostedt@goodmis.org>

The ftrace_lock is taken for most of the ftrace_graph_set_hash() function
throughout the end. Use guard to take the ftrace_lock to simplify the exit
paths.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/20241028071308.406073025@goodmis.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/ftrace.c | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index c0fabd7da5b2..b4ef469f4fd2 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6816,12 +6816,10 @@ ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer)
 
 	func_g.len = strlen(func_g.search);
 
-	mutex_lock(&ftrace_lock);
+	guard(mutex)(&ftrace_lock);
 
-	if (unlikely(ftrace_disabled)) {
-		mutex_unlock(&ftrace_lock);
+	if (unlikely(ftrace_disabled))
 		return -ENODEV;
-	}
 
 	do_for_each_ftrace_rec(pg, rec) {
 
@@ -6837,7 +6835,7 @@ ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer)
 				if (entry)
 					continue;
 				if (add_hash_entry(hash, rec->ip) == NULL)
-					goto out;
+					return 0;
 			} else {
 				if (entry) {
 					free_hash_entry(hash, entry);
@@ -6846,13 +6844,8 @@ ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer)
 			}
 		}
 	} while_for_each_ftrace_rec();
-out:
-	mutex_unlock(&ftrace_lock);
 
-	if (fail)
-		return -EINVAL;
-
-	return 0;
+	return fail ? -EINVAL : 0;
 }
 
 static ssize_t
-- 
2.45.2