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tracing: add saved_cmdlines file to show cached task comms 

Export the cached task comms to userspace. This allows user apps to translate
the pids from a trace into their respective task command lines.

[ Impact: let userspace apps reading binary buffer know comm's of pids ]

Signed-off-by: Avadh Patel <avadh4all@gmail.com>
[ added error checking and use of buf pointer to index file_buf ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Avadh Patel 2009-04-10 16:04:48 -04:00 committed by Ingo Molnar
parent d1b182a8d4
commit 69abe6a5d1
1 changed files with 53 additions and 0 deletions
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53
kernel/trace/trace.c
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@ -2421,6 +2421,56 @@ static const struct file_operations tracing_readme_fops = {
.read = tracing_readme_read,
};
static ssize_t
tracing_saved_cmdlines_read(struct file *file, char __user *ubuf,
size_t cnt, loff_t *ppos)
{
char *buf_comm;
char *file_buf;
char *buf;
int len = 0;
int pid;
int i;
file_buf = kmalloc(SAVED_CMDLINES*(16+TASK_COMM_LEN), GFP_KERNEL);
if (!file_buf)
return -ENOMEM;
buf_comm = kmalloc(TASK_COMM_LEN, GFP_KERNEL);
if (!buf_comm) {
kfree(file_buf);
return -ENOMEM;
}
buf = file_buf;
for (i = 0; i < SAVED_CMDLINES; i++) {
int r;
pid = map_cmdline_to_pid[i];
if (pid == -1 || pid == NO_CMDLINE_MAP)
continue;
trace_find_cmdline(pid, buf_comm);
r = sprintf(buf, "%d %s\n", pid, buf_comm);
buf += r;
len += r;
}
len = simple_read_from_buffer(ubuf, cnt, ppos,
file_buf, len);
kfree(file_buf);
kfree(buf_comm);
return len;
}
static const struct file_operations tracing_saved_cmdlines_fops = {
.open = tracing_open_generic,
.read = tracing_saved_cmdlines_read,
};
static ssize_t
tracing_ctrl_read(struct file *filp, char __user *ubuf,
size_t cnt, loff_t *ppos)
@ -3973,6 +4023,9 @@ static __init int tracer_init_debugfs(void)
trace_create_file("trace_marker", 0220, d_tracer,
NULL, &tracing_mark_fops);
trace_create_file("saved_cmdlines", 0444, d_tracer,
NULL, &tracing_saved_cmdlines_fops);
#ifdef CONFIG_DYNAMIC_FTRACE
trace_create_file("dyn_ftrace_total_info", 0444, d_tracer,
&ftrace_update_tot_cnt, &tracing_dyn_info_fops);