[for-next][PATCH 05/11] tracing: Move saved_cmdline code into trace_sched_switch.c

Steven Rostedt
2024-02-21T14:06:40Z

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

The code that handles saved_cmdlines is split between the trace.c file and
the trace_sched_switch.c. There's some history to this. The
trace_sched_switch.c was originally created to handle the sched_switch
tracer that was deprecated due to sched_switch trace event making it
obsolete. But that file did not get deleted as it had some code to help
with saved_cmdlines. But trace.c has grown tremendously since then. Just
move all the saved_cmdlines code into trace_sched_switch.c as that's the
only reason that file still exists, and trace.c has gotten too big.

No functional changes.

Link: https://lore.kernel.org/linux-trace-kernel/20240220140703.497966629@goodmis.org

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: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Mete Durlu <meted@linux.ibm.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
kernel/trace/trace.c | 515 +-----------------------------
kernel/trace/trace.h | 10 +
kernel/trace/trace_sched_switch.c | 515 ++++++++++++++++++++++++++++++
3 files changed, 528 insertions(+), 512 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 06c593fc93d0..50fab999e72e 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -39,7 +39,6 @@
#include <linux/ctype.h>
#include <linux/init.h>
#include <linux/panic_notifier.h>
-#include <linux/kmemleak.h>
#include <linux/poll.h>
#include <linux/nmi.h>
#include <linux/fs.h>
@@ -105,7 +104,7 @@ dummy_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
* tracing is active, only save the comm when a trace event
* occurred.
*/
-static DEFINE_PER_CPU(bool, trace_taskinfo_save);
+DEFINE_PER_CPU(bool, trace_taskinfo_save);

/*
* Kill all tracing for good (never come back).
@@ -2299,96 +2298,6 @@ void tracing_reset_all_online_cpus(void)
mutex_unlock(&trace_types_lock);
}

-/*
- * The tgid_map array maps from pid to tgid; i.e. the value stored at index i
- * is the tgid last observed corresponding to pid=i.
- */
-static int *tgid_map;
-
-/* The maximum valid index into tgid_map. */
-static size_t tgid_map_max;
-
-#define SAVED_CMDLINES_DEFAULT 128
-#define NO_CMDLINE_MAP UINT_MAX
-/*
- * Preemption must be disabled before acquiring trace_cmdline_lock.
- * The various trace_arrays' max_lock must be acquired in a context
- * where interrupt is disabled.
- */
-static arch_spinlock_t trace_cmdline_lock = __ARCH_SPIN_LOCK_UNLOCKED;
-struct saved_cmdlines_buffer {
- unsigned map_pid_to_cmdline[PID_MAX_DEFAULT+1];
- unsigned *map_cmdline_to_pid;
- unsigned cmdline_num;
- int cmdline_idx;
- char saved_cmdlines[];
-};
-static struct saved_cmdlines_buffer *savedcmd;
-
-/* Holds the size of a cmdline and pid element */
-#define SAVED_CMDLINE_MAP_ELEMENT_SIZE(s) \
- (TASK_COMM_LEN + sizeof((s)->map_cmdline_to_pid[0]))
-
-static inline char *get_saved_cmdlines(int idx)
-{
- return &savedcmd->saved_cmdlines[idx * TASK_COMM_LEN];
-}
-
-static inline void set_cmdline(int idx, const char *cmdline)
-{
- strncpy(get_saved_cmdlines(idx), cmdline, TASK_COMM_LEN);
-}
-
-static void free_saved_cmdlines_buffer(struct saved_cmdlines_buffer *s)
-{
- int order = get_order(sizeof(*s) + s->cmdline_num * TASK_COMM_LEN);
-
- kmemleak_free(s);
- free_pages((unsigned long)s, order);
-}
-
-static struct saved_cmdlines_buffer *allocate_cmdlines_buffer(unsigned int val)
-{
- struct saved_cmdlines_buffer *s;
- struct page *page;
- int orig_size, size;
- int order;
-
- /* Figure out how much is needed to hold the given number of cmdlines */
- orig_size = sizeof(*s) + val * SAVED_CMDLINE_MAP_ELEMENT_SIZE(s);
- order = get_order(orig_size);
- size = 1 << (order + PAGE_SHIFT);
- page = alloc_pages(GFP_KERNEL, order);
- if (!page)
- return NULL;
-
- s = page_address(page);
- kmemleak_alloc(s, size, 1, GFP_KERNEL);
- memset(s, 0, sizeof(*s));
-
- /* Round up to actual allocation */
- val = (size - sizeof(*s)) / SAVED_CMDLINE_MAP_ELEMENT_SIZE(s);
- s->cmdline_num = val;
-
- /* Place map_cmdline_to_pid array right after saved_cmdlines */
- s->map_cmdline_to_pid = (unsigned *)&s->saved_cmdlines[val * TASK_COMM_LEN];
-
- s->cmdline_idx = 0;
- memset(&s->map_pid_to_cmdline, NO_CMDLINE_MAP,
- sizeof(s->map_pid_to_cmdline));
- memset(s->map_cmdline_to_pid, NO_CMDLINE_MAP,
- val * sizeof(*s->map_cmdline_to_pid));
-
- return s;
-}
-
-static int trace_create_savedcmd(void)
-{
- savedcmd = allocate_cmdlines_buffer(SAVED_CMDLINES_DEFAULT);
-
- return savedcmd ? 0 : -ENOMEM;
-}
-
int is_tracing_stopped(void)
{
return global_trace.stop_count;
@@ -2481,201 +2390,6 @@ void tracing_stop(void)
return tracing_stop_tr(&global_trace);
}

-static int trace_save_cmdline(struct task_struct *tsk)
-{
- unsigned tpid, idx;
-
- /* treat recording of idle task as a success */
- if (!tsk->pid)
- return 1;
-
- tpid = tsk->pid & (PID_MAX_DEFAULT - 1);
-
- /*
- * It's not the end of the world if we don't get
- * the lock, but we also don't want to spin
- * nor do we want to disable interrupts,
- * so if we miss here, then better luck next time.
- *
- * This is called within the scheduler and wake up, so interrupts
- * had better been disabled and run queue lock been held.
- */
- lockdep_assert_preemption_disabled();
- if (!arch_spin_trylock(&trace_cmdline_lock))
- return 0;
-
- idx = savedcmd->map_pid_to_cmdline[tpid];
- if (idx == NO_CMDLINE_MAP) {
- idx = (savedcmd->cmdline_idx + 1) % savedcmd->cmdline_num;
-
- savedcmd->map_pid_to_cmdline[tpid] = idx;
- savedcmd->cmdline_idx = idx;
- }
-
- savedcmd->map_cmdline_to_pid[idx] = tsk->pid;
- set_cmdline(idx, tsk->comm);
-
- arch_spin_unlock(&trace_cmdline_lock);
-
- return 1;
-}
-
-static void __trace_find_cmdline(int pid, char comm[])
-{
- unsigned map;
- int tpid;
-
- if (!pid) {
- strcpy(comm, "<idle>");
- return;
- }
-
- if (WARN_ON_ONCE(pid < 0)) {
- strcpy(comm, "<XXX>");
- return;
- }
-
- tpid = pid & (PID_MAX_DEFAULT - 1);
- map = savedcmd->map_pid_to_cmdline[tpid];
- if (map != NO_CMDLINE_MAP) {
- tpid = savedcmd->map_cmdline_to_pid[map];
- if (tpid == pid) {
- strscpy(comm, get_saved_cmdlines(map), TASK_COMM_LEN);
- return;
- }
- }
- strcpy(comm, "<...>");
-}
-
-void trace_find_cmdline(int pid, char comm[])
-{
- preempt_disable();
- arch_spin_lock(&trace_cmdline_lock);
-
- __trace_find_cmdline(pid, comm);
-
- arch_spin_unlock(&trace_cmdline_lock);
- preempt_enable();
-}
-
-static int *trace_find_tgid_ptr(int pid)
-{
- /*
- * Pairs with the smp_store_release in set_tracer_flag() to ensure that
- * if we observe a non-NULL tgid_map then we also observe the correct
- * tgid_map_max.
- */
- int *map = smp_load_acquire(&tgid_map);
-
- if (unlikely(!map || pid > tgid_map_max))
- return NULL;
-
- return &map[pid];
-}
-
-int trace_find_tgid(int pid)
-{
- int *ptr = trace_find_tgid_ptr(pid);
-
- return ptr ? *ptr : 0;
-}
-
-static int trace_save_tgid(struct task_struct *tsk)
-{
- int *ptr;
-
- /* treat recording of idle task as a success */
- if (!tsk->pid)
- return 1;
-
- ptr = trace_find_tgid_ptr(tsk->pid);
- if (!ptr)
- return 0;
-
- *ptr = tsk->tgid;
- return 1;
-}
-
-static bool tracing_record_taskinfo_skip(int flags)
-{
- if (unlikely(!(flags & (TRACE_RECORD_CMDLINE | TRACE_RECORD_TGID))))
- return true;
- if (!__this_cpu_read(trace_taskinfo_save))
- return true;
- return false;
-}
-
-/**
- * tracing_record_taskinfo - record the task info of a task
- *
- * @task: task to record
- * @flags: TRACE_RECORD_CMDLINE for recording comm
- * TRACE_RECORD_TGID for recording tgid
- */
-void tracing_record_taskinfo(struct task_struct *task, int flags)
-{
- bool done;
-
- if (tracing_record_taskinfo_skip(flags))
- return;
-
- /*
- * Record as much task information as possible. If some fail, continue
- * to try to record the others.
- */
- done = !(flags & TRACE_RECORD_CMDLINE) || trace_save_cmdline(task);
- done &= !(flags & TRACE_RECORD_TGID) || trace_save_tgid(task);
-
- /* If recording any information failed, retry again soon. */
- if (!done)
- return;
-
- __this_cpu_write(trace_taskinfo_save, false);
-}
-
-/**
- * tracing_record_taskinfo_sched_switch - record task info for sched_switch
- *
- * @prev: previous task during sched_switch
- * @next: next task during sched_switch
- * @flags: TRACE_RECORD_CMDLINE for recording comm
- * TRACE_RECORD_TGID for recording tgid
- */
-void tracing_record_taskinfo_sched_switch(struct task_struct *prev,
- struct task_struct *next, int flags)
-{
- bool done;
-
- if (tracing_record_taskinfo_skip(flags))
- return;
-
- /*
- * Record as much task information as possible. If some fail, continue
- * to try to record the others.
- */
- done = !(flags & TRACE_RECORD_CMDLINE) || trace_save_cmdline(prev);
- done &= !(flags & TRACE_RECORD_CMDLINE) || trace_save_cmdline(next);
- done &= !(flags & TRACE_RECORD_TGID) || trace_save_tgid(prev);
- done &= !(flags & TRACE_RECORD_TGID) || trace_save_tgid(next);
-
- /* If recording any information failed, retry again soon. */
- if (!done)
- return;
-
- __this_cpu_write(trace_taskinfo_save, false);
-}
-
-/* Helpers to record a specific task information */
-void tracing_record_cmdline(struct task_struct *task)
-{
- tracing_record_taskinfo(task, TRACE_RECORD_CMDLINE);
-}
-
-void tracing_record_tgid(struct task_struct *task)
-{
- tracing_record_taskinfo(task, TRACE_RECORD_TGID);
-}
-
/*
* Several functions return TRACE_TYPE_PARTIAL_LINE if the trace_seq
* overflowed, and TRACE_TYPE_HANDLED otherwise. This helper function
@@ -5432,29 +5146,6 @@ int trace_keep_overwrite(struct tracer *tracer, u32 mask, int set)
return 0;
}

-static int trace_alloc_tgid_map(void)
-{
- int *map;
-
- if (tgid_map)
- return 0;
-
- tgid_map_max = pid_max;
- map = kvcalloc(tgid_map_max + 1, sizeof(*tgid_map),
- GFP_KERNEL);
- if (!map)
- return -ENOMEM;
-
- /*
- * Pairs with smp_load_acquire() in
- * trace_find_tgid_ptr() to ensure that if it observes
- * the tgid_map we just allocated then it also observes
- * the corresponding tgid_map_max value.
- */
- smp_store_release(&tgid_map, map);
- return 0;
-}
-
int set_tracer_flag(struct trace_array *tr, unsigned int mask, int enabled)
{
if ((mask == TRACE_ITER_RECORD_TGID) ||
@@ -5479,6 +5170,7 @@ int set_tracer_flag(struct trace_array *tr, unsigned int mask, int enabled)
trace_event_enable_cmd_record(enabled);

if (mask == TRACE_ITER_RECORD_TGID) {
+
if (trace_alloc_tgid_map() < 0) {
tr->trace_flags &= ~TRACE_ITER_RECORD_TGID;
return -ENOMEM;
@@ -5924,207 +5616,6 @@ static const struct file_operations tracing_readme_fops = {
.llseek = generic_file_llseek,
};

-static void *saved_tgids_next(struct seq_file *m, void *v, loff_t *pos)
-{
- int pid = ++(*pos);
-
- return trace_find_tgid_ptr(pid);
-}
-
-static void *saved_tgids_start(struct seq_file *m, loff_t *pos)
-{
- int pid = *pos;
-
- return trace_find_tgid_ptr(pid);
-}
-
-static void saved_tgids_stop(struct seq_file *m, void *v)
-{
-}
-
-static int saved_tgids_show(struct seq_file *m, void *v)
-{
- int *entry = (int *)v;
- int pid = entry - tgid_map;
- int tgid = *entry;
-
- if (tgid == 0)
- return SEQ_SKIP;
-
- seq_printf(m, "%d %d\n", pid, tgid);
- return 0;
-}
-
-static const struct seq_operations tracing_saved_tgids_seq_ops = {
- .start = saved_tgids_start,
- .stop = saved_tgids_stop,
- .next = saved_tgids_next,
- .show = saved_tgids_show,
-};
-
-static int tracing_saved_tgids_open(struct inode *inode, struct file *filp)
-{
- int ret;
-
- ret = tracing_check_open_get_tr(NULL);
- if (ret)
- return ret;
-
- return seq_open(filp, &tracing_saved_tgids_seq_ops);
-}
-
-
-static const struct file_operations tracing_saved_tgids_fops = {
- .open = tracing_saved_tgids_open,
- .read = seq_read,
- .llseek = seq_lseek,
- .release = seq_release,
-};
-
-static void *saved_cmdlines_next(struct seq_file *m, void *v, loff_t *pos)
-{
- unsigned int *ptr = v;
-
- if (*pos || m->count)
- ptr++;
-
- (*pos)++;
-
- for (; ptr < &savedcmd->map_cmdline_to_pid[savedcmd->cmdline_num];
- ptr++) {
- if (*ptr == -1 || *ptr == NO_CMDLINE_MAP)
- continue;
-
- return ptr;
- }
-
- return NULL;
-}
-
-static void *saved_cmdlines_start(struct seq_file *m, loff_t *pos)
-{
- void *v;
- loff_t l = 0;
-
- preempt_disable();
- arch_spin_lock(&trace_cmdline_lock);
-
- v = &savedcmd->map_cmdline_to_pid[0];
- while (l <= *pos) {
- v = saved_cmdlines_next(m, v, &l);
- if (!v)
- return NULL;
- }
-
- return v;
-}
-
-static void saved_cmdlines_stop(struct seq_file *m, void *v)
-{
- arch_spin_unlock(&trace_cmdline_lock);
- preempt_enable();
-}
-
-static int saved_cmdlines_show(struct seq_file *m, void *v)
-{
- char buf[TASK_COMM_LEN];
- unsigned int *pid = v;
-
- __trace_find_cmdline(*pid, buf);
- seq_printf(m, "%d %s\n", *pid, buf);
- return 0;
-}
-
-static const struct seq_operations tracing_saved_cmdlines_seq_ops = {
- .start = saved_cmdlines_start,
- .next = saved_cmdlines_next,
- .stop = saved_cmdlines_stop,
- .show = saved_cmdlines_show,
-};
-
-static int tracing_saved_cmdlines_open(struct inode *inode, struct file *filp)
-{
- int ret;
-
- ret = tracing_check_open_get_tr(NULL);
- if (ret)
- return ret;
-
- return seq_open(filp, &tracing_saved_cmdlines_seq_ops);
-}
-
-static const struct file_operations tracing_saved_cmdlines_fops = {
- .open = tracing_saved_cmdlines_open,
- .read = seq_read,
- .llseek = seq_lseek,
- .release = seq_release,
-};
-
-static ssize_t
-tracing_saved_cmdlines_size_read(struct file *filp, char __user *ubuf,
- size_t cnt, loff_t *ppos)
-{
- char buf[64];
- int r;
-
- preempt_disable();
- arch_spin_lock(&trace_cmdline_lock);
- r = scnprintf(buf, sizeof(buf), "%u\n", savedcmd->cmdline_num);
- arch_spin_unlock(&trace_cmdline_lock);
- preempt_enable();
-
- return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
-}
-
-static int tracing_resize_saved_cmdlines(unsigned int val)
-{
- struct saved_cmdlines_buffer *s, *savedcmd_temp;
-
- s = allocate_cmdlines_buffer(val);
- if (!s)
- return -ENOMEM;
-
- preempt_disable();
- arch_spin_lock(&trace_cmdline_lock);
- savedcmd_temp = savedcmd;
- savedcmd = s;
- arch_spin_unlock(&trace_cmdline_lock);
- preempt_enable();
- free_saved_cmdlines_buffer(savedcmd_temp);
-
- return 0;
-}
-
-static ssize_t
-tracing_saved_cmdlines_size_write(struct file *filp, const char __user *ubuf,
- size_t cnt, loff_t *ppos)
-{
- unsigned long val;
- int ret;
-
- ret = kstrtoul_from_user(ubuf, cnt, 10, &val);
- if (ret)
- return ret;
-
- /* must have at least 1 entry or less than PID_MAX_DEFAULT */
- if (!val || val > PID_MAX_DEFAULT)
- return -EINVAL;
-
- ret = tracing_resize_saved_cmdlines((unsigned int)val);
- if (ret < 0)
- return ret;
-
- *ppos += cnt;
-
- return cnt;
-}
-
-static const struct file_operations tracing_saved_cmdlines_size_fops = {
- .open = tracing_open_generic,
- .read = tracing_saved_cmdlines_size_read,
- .write = tracing_saved_cmdlines_size_write,
-};
-
#ifdef CONFIG_TRACE_EVAL_MAP_FILE
static union trace_eval_map_item *
update_eval_map(union trace_eval_map_item *ptr)
@@ -10693,7 +10184,7 @@ __init static int tracer_alloc_buffers(void)
out_free_pipe_cpumask:
free_cpumask_var(global_trace.pipe_cpumask);
out_free_savedcmd:
- free_saved_cmdlines_buffer(savedcmd);
+ trace_free_saved_cmdlines_buffer();
out_free_temp_buffer:
ring_buffer_free(temp_buffer);
out_rm_hp_state:
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 00f873910c5d..e4f0714d7a49 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1375,6 +1375,16 @@ static inline void trace_buffer_unlock_commit(struct trace_array *tr,
trace_buffer_unlock_commit_regs(tr, buffer, event, trace_ctx, NULL);
}

+DECLARE_PER_CPU(bool, trace_taskinfo_save);
+int trace_save_cmdline(struct task_struct *tsk);
+int trace_create_savedcmd(void);
+int trace_alloc_tgid_map(void);
+void trace_free_saved_cmdlines_buffer(void);
+
+extern const struct file_operations tracing_saved_cmdlines_fops;
+extern const struct file_operations tracing_saved_tgids_fops;
+extern const struct file_operations tracing_saved_cmdlines_size_fops;
+
DECLARE_PER_CPU(struct ring_buffer_event *, trace_buffered_event);
DECLARE_PER_CPU(int, trace_buffered_event_cnt);
void trace_buffered_event_disable(void);
diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c
index c9ffdcfe622e..8a407adb0e1c 100644
--- a/kernel/trace/trace_sched_switch.c
+++ b/kernel/trace/trace_sched_switch.c
@@ -8,6 +8,7 @@
#include <linux/module.h>
#include <linux/kallsyms.h>
#include <linux/uaccess.h>
+#include <linux/kmemleak.h>
#include <linux/ftrace.h>
#include <trace/events/sched.h>

@@ -148,3 +149,517 @@ void tracing_stop_tgid_record(void)
{
tracing_stop_sched_switch(RECORD_TGID);
}
+
+/*
+ * The tgid_map array maps from pid to tgid; i.e. the value stored at index i
+ * is the tgid last observed corresponding to pid=i.
+ */
+static int *tgid_map;
+
+/* The maximum valid index into tgid_map. */
+static size_t tgid_map_max;
+
+#define SAVED_CMDLINES_DEFAULT 128
+#define NO_CMDLINE_MAP UINT_MAX
+/*
+ * Preemption must be disabled before acquiring trace_cmdline_lock.
+ * The various trace_arrays' max_lock must be acquired in a context
+ * where interrupt is disabled.
+ */
+static arch_spinlock_t trace_cmdline_lock = __ARCH_SPIN_LOCK_UNLOCKED;
+struct saved_cmdlines_buffer {
+ unsigned map_pid_to_cmdline[PID_MAX_DEFAULT+1];
+ unsigned *map_cmdline_to_pid;
+ unsigned cmdline_num;
+ int cmdline_idx;
+ char saved_cmdlines[];
+};
+static struct saved_cmdlines_buffer *savedcmd;
+
+/* Holds the size of a cmdline and pid element */
+#define SAVED_CMDLINE_MAP_ELEMENT_SIZE(s) \
+ (TASK_COMM_LEN + sizeof((s)->map_cmdline_to_pid[0]))
+
+static inline char *get_saved_cmdlines(int idx)
+{
+ return &savedcmd->saved_cmdlines[idx * TASK_COMM_LEN];
+}
+
+static inline void set_cmdline(int idx, const char *cmdline)
+{
+ strncpy(get_saved_cmdlines(idx), cmdline, TASK_COMM_LEN);
+}
+
+static void free_saved_cmdlines_buffer(struct saved_cmdlines_buffer *s)
+{
+ int order = get_order(sizeof(*s) + s->cmdline_num * TASK_COMM_LEN);
+
+ kmemleak_free(s);
+ free_pages((unsigned long)s, order);
+}
+
+static struct saved_cmdlines_buffer *allocate_cmdlines_buffer(unsigned int val)
+{
+ struct saved_cmdlines_buffer *s;
+ struct page *page;
+ int orig_size, size;
+ int order;
+
+ /* Figure out how much is needed to hold the given number of cmdlines */
+ orig_size = sizeof(*s) + val * SAVED_CMDLINE_MAP_ELEMENT_SIZE(s);
+ order = get_order(orig_size);
+ size = 1 << (order + PAGE_SHIFT);
+ page = alloc_pages(GFP_KERNEL, order);
+ if (!page)
+ return NULL;
+
+ s = page_address(page);
+ kmemleak_alloc(s, size, 1, GFP_KERNEL);
+ memset(s, 0, sizeof(*s));
+
+ /* Round up to actual allocation */
+ val = (size - sizeof(*s)) / SAVED_CMDLINE_MAP_ELEMENT_SIZE(s);
+ s->cmdline_num = val;
+
+ /* Place map_cmdline_to_pid array right after saved_cmdlines */
+ s->map_cmdline_to_pid = (unsigned *)&s->saved_cmdlines[val * TASK_COMM_LEN];
+
+ s->cmdline_idx = 0;
+ memset(&s->map_pid_to_cmdline, NO_CMDLINE_MAP,
+ sizeof(s->map_pid_to_cmdline));
+ memset(s->map_cmdline_to_pid, NO_CMDLINE_MAP,
+ val * sizeof(*s->map_cmdline_to_pid));
+
+ return s;
+}
+
+int trace_create_savedcmd(void)
+{
+ savedcmd = allocate_cmdlines_buffer(SAVED_CMDLINES_DEFAULT);
+
+ return savedcmd ? 0 : -ENOMEM;
+}
+
+int trace_save_cmdline(struct task_struct *tsk)
+{
+ unsigned tpid, idx;
+
+ /* treat recording of idle task as a success */
+ if (!tsk->pid)
+ return 1;
+
+ tpid = tsk->pid & (PID_MAX_DEFAULT - 1);
+
+ /*
+ * It's not the end of the world if we don't get
+ * the lock, but we also don't want to spin
+ * nor do we want to disable interrupts,
+ * so if we miss here, then better luck next time.
+ *
+ * This is called within the scheduler and wake up, so interrupts
+ * had better been disabled and run queue lock been held.
+ */
+ lockdep_assert_preemption_disabled();
+ if (!arch_spin_trylock(&trace_cmdline_lock))
+ return 0;
+
+ idx = savedcmd->map_pid_to_cmdline[tpid];
+ if (idx == NO_CMDLINE_MAP) {
+ idx = (savedcmd->cmdline_idx + 1) % savedcmd->cmdline_num;
+
+ savedcmd->map_pid_to_cmdline[tpid] = idx;
+ savedcmd->cmdline_idx = idx;
+ }
+
+ savedcmd->map_cmdline_to_pid[idx] = tsk->pid;
+ set_cmdline(idx, tsk->comm);
+
+ arch_spin_unlock(&trace_cmdline_lock);
+
+ return 1;
+}
+
+static void __trace_find_cmdline(int pid, char comm[])
+{
+ unsigned map;
+ int tpid;
+
+ if (!pid) {
+ strcpy(comm, "<idle>");
+ return;
+ }
+
+ if (WARN_ON_ONCE(pid < 0)) {
+ strcpy(comm, "<XXX>");
+ return;
+ }
+
+ tpid = pid & (PID_MAX_DEFAULT - 1);
+ map = savedcmd->map_pid_to_cmdline[tpid];
+ if (map != NO_CMDLINE_MAP) {
+ tpid = savedcmd->map_cmdline_to_pid[map];
+ if (tpid == pid) {
+ strscpy(comm, get_saved_cmdlines(map), TASK_COMM_LEN);
+ return;
+ }
+ }
+ strcpy(comm, "<...>");
+}
+
+void trace_find_cmdline(int pid, char comm[])
+{
+ preempt_disable();
+ arch_spin_lock(&trace_cmdline_lock);
+
+ __trace_find_cmdline(pid, comm);
+
+ arch_spin_unlock(&trace_cmdline_lock);
+ preempt_enable();
+}
+
+static int *trace_find_tgid_ptr(int pid)
+{
+ /*
+ * Pairs with the smp_store_release in set_tracer_flag() to ensure that
+ * if we observe a non-NULL tgid_map then we also observe the correct
+ * tgid_map_max.
+ */
+ int *map = smp_load_acquire(&tgid_map);
+
+ if (unlikely(!map || pid > tgid_map_max))
+ return NULL;
+
+ return &map[pid];
+}
+
+int trace_find_tgid(int pid)
+{
+ int *ptr = trace_find_tgid_ptr(pid);
+
+ return ptr ? *ptr : 0;
+}
+
+static int trace_save_tgid(struct task_struct *tsk)
+{
+ int *ptr;
+
+ /* treat recording of idle task as a success */
+ if (!tsk->pid)
+ return 1;
+
+ ptr = trace_find_tgid_ptr(tsk->pid);
+ if (!ptr)
+ return 0;
+
+ *ptr = tsk->tgid;
+ return 1;
+}
+
+static bool tracing_record_taskinfo_skip(int flags)
+{
+ if (unlikely(!(flags & (TRACE_RECORD_CMDLINE | TRACE_RECORD_TGID))))
+ return true;
+ if (!__this_cpu_read(trace_taskinfo_save))
+ return true;
+ return false;
+}
+
+/**
+ * tracing_record_taskinfo - record the task info of a task
+ *
+ * @task: task to record
+ * @flags: TRACE_RECORD_CMDLINE for recording comm
+ * TRACE_RECORD_TGID for recording tgid
+ */
+void tracing_record_taskinfo(struct task_struct *task, int flags)
+{
+ bool done;
+
+ if (tracing_record_taskinfo_skip(flags))
+ return;
+
+ /*
+ * Record as much task information as possible. If some fail, continue
+ * to try to record the others.
+ */
+ done = !(flags & TRACE_RECORD_CMDLINE) || trace_save_cmdline(task);
+ done &= !(flags & TRACE_RECORD_TGID) || trace_save_tgid(task);
+
+ /* If recording any information failed, retry again soon. */
+ if (!done)
+ return;
+
+ __this_cpu_write(trace_taskinfo_save, false);
+}
+
+/**
+ * tracing_record_taskinfo_sched_switch - record task info for sched_switch
+ *
+ * @prev: previous task during sched_switch
+ * @next: next task during sched_switch
+ * @flags: TRACE_RECORD_CMDLINE for recording comm
+ * TRACE_RECORD_TGID for recording tgid
+ */
+void tracing_record_taskinfo_sched_switch(struct task_struct *prev,
+ struct task_struct *next, int flags)
+{
+ bool done;
+
+ if (tracing_record_taskinfo_skip(flags))
+ return;
+
+ /*
+ * Record as much task information as possible. If some fail, continue
+ * to try to record the others.
+ */
+ done = !(flags & TRACE_RECORD_CMDLINE) || trace_save_cmdline(prev);
+ done &= !(flags & TRACE_RECORD_CMDLINE) || trace_save_cmdline(next);
+ done &= !(flags & TRACE_RECORD_TGID) || trace_save_tgid(prev);
+ done &= !(flags & TRACE_RECORD_TGID) || trace_save_tgid(next);
+
+ /* If recording any information failed, retry again soon. */
+ if (!done)
+ return;
+
+ __this_cpu_write(trace_taskinfo_save, false);
+}
+
+/* Helpers to record a specific task information */
+void tracing_record_cmdline(struct task_struct *task)
+{
+ tracing_record_taskinfo(task, TRACE_RECORD_CMDLINE);
+}
+
+void tracing_record_tgid(struct task_struct *task)
+{
+ tracing_record_taskinfo(task, TRACE_RECORD_TGID);
+}
+
+int trace_alloc_tgid_map(void)
+{
+ int *map;
+
+ if (tgid_map)
+ return 0;
+
+ tgid_map_max = pid_max;
+ map = kvcalloc(tgid_map_max + 1, sizeof(*tgid_map),
+ GFP_KERNEL);
+ if (!map)
+ return -ENOMEM;
+
+ /*
+ * Pairs with smp_load_acquire() in
+ * trace_find_tgid_ptr() to ensure that if it observes
+ * the tgid_map we just allocated then it also observes
+ * the corresponding tgid_map_max value.
+ */
+ smp_store_release(&tgid_map, map);
+ return 0;
+}
+
+static void *saved_tgids_next(struct seq_file *m, void *v, loff_t *pos)
+{
+ int pid = ++(*pos);
+
+ return trace_find_tgid_ptr(pid);
+}
+
+static void *saved_tgids_start(struct seq_file *m, loff_t *pos)
+{
+ int pid = *pos;
+
+ return trace_find_tgid_ptr(pid);
+}
+
+static void saved_tgids_stop(struct seq_file *m, void *v)
+{
+}
+
+static int saved_tgids_show(struct seq_file *m, void *v)
+{
+ int *entry = (int *)v;
+ int pid = entry - tgid_map;
+ int tgid = *entry;
+
+ if (tgid == 0)
+ return SEQ_SKIP;
+
+ seq_printf(m, "%d %d\n", pid, tgid);
+ return 0;
+}
+
+static const struct seq_operations tracing_saved_tgids_seq_ops = {
+ .start = saved_tgids_start,
+ .stop = saved_tgids_stop,
+ .next = saved_tgids_next,
+ .show = saved_tgids_show,
+};
+
+static int tracing_saved_tgids_open(struct inode *inode, struct file *filp)
+{
+ int ret;
+
+ ret = tracing_check_open_get_tr(NULL);
+ if (ret)
+ return ret;
+
+ return seq_open(filp, &tracing_saved_tgids_seq_ops);
+}
+
+
+const struct file_operations tracing_saved_tgids_fops = {
+ .open = tracing_saved_tgids_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
+static void *saved_cmdlines_next(struct seq_file *m, void *v, loff_t *pos)
+{
+ unsigned int *ptr = v;
+
+ if (*pos || m->count)
+ ptr++;
+
+ (*pos)++;
+
+ for (; ptr < &savedcmd->map_cmdline_to_pid[savedcmd->cmdline_num];
+ ptr++) {
+ if (*ptr == -1 || *ptr == NO_CMDLINE_MAP)
+ continue;
+
+ return ptr;
+ }
+
+ return NULL;
+}
+
+static void *saved_cmdlines_start(struct seq_file *m, loff_t *pos)
+{
+ void *v;
+ loff_t l = 0;
+
+ preempt_disable();
+ arch_spin_lock(&trace_cmdline_lock);
+
+ v = &savedcmd->map_cmdline_to_pid[0];
+ while (l <= *pos) {
+ v = saved_cmdlines_next(m, v, &l);
+ if (!v)
+ return NULL;
+ }
+
+ return v;
+}
+
+static void saved_cmdlines_stop(struct seq_file *m, void *v)
+{
+ arch_spin_unlock(&trace_cmdline_lock);
+ preempt_enable();
+}
+
+static int saved_cmdlines_show(struct seq_file *m, void *v)
+{
+ char buf[TASK_COMM_LEN];
+ unsigned int *pid = v;
+
+ __trace_find_cmdline(*pid, buf);
+ seq_printf(m, "%d %s\n", *pid, buf);
+ return 0;
+}
+
+static const struct seq_operations tracing_saved_cmdlines_seq_ops = {
+ .start = saved_cmdlines_start,
+ .next = saved_cmdlines_next,
+ .stop = saved_cmdlines_stop,
+ .show = saved_cmdlines_show,
+};
+
+static int tracing_saved_cmdlines_open(struct inode *inode, struct file *filp)
+{
+ int ret;
+
+ ret = tracing_check_open_get_tr(NULL);
+ if (ret)
+ return ret;
+
+ return seq_open(filp, &tracing_saved_cmdlines_seq_ops);
+}
+
+const struct file_operations tracing_saved_cmdlines_fops = {
+ .open = tracing_saved_cmdlines_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
+static ssize_t
+tracing_saved_cmdlines_size_read(struct file *filp, char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ char buf[64];
+ int r;
+
+ preempt_disable();
+ arch_spin_lock(&trace_cmdline_lock);
+ r = scnprintf(buf, sizeof(buf), "%u\n", savedcmd->cmdline_num);
+ arch_spin_unlock(&trace_cmdline_lock);
+ preempt_enable();
+
+ return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
+}
+
+void trace_free_saved_cmdlines_buffer(void)
+{
+ free_saved_cmdlines_buffer(savedcmd);
+}
+
+static int tracing_resize_saved_cmdlines(unsigned int val)
+{
+ struct saved_cmdlines_buffer *s, *savedcmd_temp;
+
+ s = allocate_cmdlines_buffer(val);
+ if (!s)
+ return -ENOMEM;
+
+ preempt_disable();
+ arch_spin_lock(&trace_cmdline_lock);
+ savedcmd_temp = savedcmd;
+ savedcmd = s;
+ arch_spin_unlock(&trace_cmdline_lock);
+ preempt_enable();
+ free_saved_cmdlines_buffer(savedcmd_temp);
+
+ return 0;
+}
+
+static ssize_t
+tracing_saved_cmdlines_size_write(struct file *filp, const char __user *ubuf,
+ size_t cnt, loff_t *ppos)
+{
+ unsigned long val;
+ int ret;
+
+ ret = kstrtoul_from_user(ubuf, cnt, 10, &val);
+ if (ret)
+ return ret;
+
+ /* must have at least 1 entry or less than PID_MAX_DEFAULT */
+ if (!val || val > PID_MAX_DEFAULT)
+ return -EINVAL;
+
+ ret = tracing_resize_saved_cmdlines((unsigned int)val);
+ if (ret < 0)
+ return ret;
+
+ *ppos += cnt;
+
+ return cnt;
+}
+
+const struct file_operations tracing_saved_cmdlines_size_fops = {
+ .open = tracing_open_generic,
+ .read = tracing_saved_cmdlines_size_read,
+ .write = tracing_saved_cmdlines_size_write,
+};
--
2.43.0