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tracing: Place trace_pid_list logic into abstract functions

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[ Upstream commit 6954e415264eeb5ee6be0d22d789ad12c995ee64 ]

Instead of having the logic that does trace_pid_list open coded, wrap it in
abstract functions. This will allow a rewrite of the logic that implements
the trace_pid_list without affecting the users.

Note, this causes a change in behavior. Every time a pid is written into
the set_*_pid file, it creates a new list and uses RCU to update it. If
pid_max is lowered, but there was a pid currently in the list that was
higher than pid_max, those pids will now be removed on updating the list.
The old behavior kept that from happening.

The rewrite of the pid_list logic will no longer depend on pid_max,
and will return the old behavior.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Steven Rostedt (VMware)
2021-09-23 21:03:49 -04:00
committed by Greg Kroah-Hartman
parent 6107b01416
commit d977706172
7 changed files with 217 additions and 61 deletions
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78
kernel/trace/trace.c
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@@ -516,12 +516,6 @@ int call_filter_check_discard(struct trace_event_call *call, void *rec,
return 0;
}
void trace_free_pid_list(struct trace_pid_list *pid_list)
{
vfree(pid_list->pids);
kfree(pid_list);
}
/**
* trace_find_filtered_pid - check if a pid exists in a filtered_pid list
* @filtered_pids: The list of pids to check
@@ -532,14 +526,7 @@ void trace_free_pid_list(struct trace_pid_list *pid_list)
bool
trace_find_filtered_pid(struct trace_pid_list *filtered_pids, pid_t search_pid)
{
/*
* If pid_max changed after filtered_pids was created, we
* by default ignore all pids greater than the previous pid_max.
*/
if (search_pid >= filtered_pids->pid_max)
return false;
return test_bit(search_pid, filtered_pids->pids);
return trace_pid_list_is_set(filtered_pids, search_pid);
}
/**
@@ -596,15 +583,11 @@ void trace_filter_add_remove_task(struct trace_pid_list *pid_list,
return;
}
/* Sorry, but we don't support pid_max changing after setting */
if (task->pid >= pid_list->pid_max)
return;
/* "self" is set for forks, and NULL for exits */
if (self)
set_bit(task->pid, pid_list->pids);
trace_pid_list_set(pid_list, task->pid);
else
clear_bit(task->pid, pid_list->pids);
trace_pid_list_clear(pid_list, task->pid);
}
/**
@@ -621,18 +604,19 @@ void trace_filter_add_remove_task(struct trace_pid_list *pid_list,
*/
void *trace_pid_next(struct trace_pid_list *pid_list, void *v, loff_t *pos)
{
unsigned long pid = (unsigned long)v;
long pid = (unsigned long)v;
unsigned int next;
(*pos)++;
/* pid already is +1 of the actual previous bit */
pid = find_next_bit(pid_list->pids, pid_list->pid_max, pid);
if (trace_pid_list_next(pid_list, pid, &next) < 0)
return NULL;
pid = next;
/* Return pid + 1 to allow zero to be represented */
if (pid < pid_list->pid_max)
return (void *)(pid + 1);
return NULL;
return (void *)(pid + 1);
}
/**
@@ -649,12 +633,14 @@ void *trace_pid_next(struct trace_pid_list *pid_list, void *v, loff_t *pos)
void *trace_pid_start(struct trace_pid_list *pid_list, loff_t *pos)
{
unsigned long pid;
unsigned int first;
loff_t l = 0;
pid = find_first_bit(pid_list->pids, pid_list->pid_max);
if (pid >= pid_list->pid_max)
if (trace_pid_list_first(pid_list, &first) < 0)
return NULL;
pid = first;
/* Return pid + 1 so that zero can be the exit value */
for (pid++; pid && l < *pos;
pid = (unsigned long)trace_pid_next(pid_list, (void *)pid, &l))
@@ -690,7 +676,7 @@ int trace_pid_write(struct trace_pid_list *filtered_pids,
unsigned long val;
int nr_pids = 0;
ssize_t read = 0;
ssize_t ret = 0;
ssize_t ret;
loff_t pos;
pid_t pid;
@@ -703,34 +689,23 @@ int trace_pid_write(struct trace_pid_list *filtered_pids,
* the user. If the operation fails, then the current list is
* not modified.
*/
pid_list = kmalloc(sizeof(*pid_list), GFP_KERNEL);
pid_list = trace_pid_list_alloc();
if (!pid_list) {
trace_parser_put(&parser);
return -ENOMEM;
}
pid_list->pid_max = READ_ONCE(pid_max);
/* Only truncating will shrink pid_max */
if (filtered_pids && filtered_pids->pid_max > pid_list->pid_max)
pid_list->pid_max = filtered_pids->pid_max;
pid_list->pids = vzalloc((pid_list->pid_max + 7) >> 3);
if (!pid_list->pids) {
trace_parser_put(&parser);
kfree(pid_list);
return -ENOMEM;
}
if (filtered_pids) {
/* copy the current bits to the new max */
for_each_set_bit(pid, filtered_pids->pids,
filtered_pids->pid_max) {
set_bit(pid, pid_list->pids);
ret = trace_pid_list_first(filtered_pids, &pid);
while (!ret) {
trace_pid_list_set(pid_list, pid);
ret = trace_pid_list_next(filtered_pids, pid + 1, &pid);
nr_pids++;
}
}
ret = 0;
while (cnt > 0) {
pos = 0;
@@ -746,12 +721,13 @@ int trace_pid_write(struct trace_pid_list *filtered_pids,
ret = -EINVAL;
if (kstrtoul(parser.buffer, 0, &val))
break;
if (val >= pid_list->pid_max)
break;
pid = (pid_t)val;
set_bit(pid, pid_list->pids);
if (trace_pid_list_set(pid_list, pid) < 0) {
ret = -1;
break;
}
nr_pids++;
trace_parser_clear(&parser);
@@ -760,13 +736,13 @@ int trace_pid_write(struct trace_pid_list *filtered_pids,
trace_parser_put(&parser);
if (ret < 0) {
trace_free_pid_list(pid_list);
trace_pid_list_free(pid_list);
return ret;
}
if (!nr_pids) {
/* Cleared the list of pids */
trace_free_pid_list(pid_list);
trace_pid_list_free(pid_list);
read = ret;
pid_list = NULL;
}