Re: [RFC][PATCH 08/21] tracing: Make traceprobe parsing code reusable

Steven Rostedt
2017-02-09T20:50:13Z

On Wed, 8 Feb 2017 11:25:04 -0600
Tom Zanussi <tom.zanussi@linux.intel.com> wrote:

> traceprobe_probes_write() and traceprobe_command() actually contain
> nothing that ties them to kprobes - the code is generically useful for
> similar types of parsing elsewhere, so separate it out and move it to
> trace.c/trace.h.
>
> Other than moving it, the only change is in naming:
> traceprobe_probes_write() becomes trace_parse_run_command() and
> traceprobe_command() becomes trace_run_command().
>
> Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
> ---
> kernel/trace/trace.c | 75 +++++++++++++++++++++++++++++++++++++++++++++
> kernel/trace/trace.h | 7 +++++
> kernel/trace/trace_kprobe.c | 18 +++++------
> kernel/trace/trace_probe.c | 75 ---------------------------------------------
> kernel/trace/trace_probe.h | 7 -----
> kernel/trace/trace_uprobe.c | 2 +-
> 6 files changed, 92 insertions(+), 92 deletions(-)
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 5868656..78dff2f 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -7912,6 +7912,81 @@ void ftrace_dump(enum ftrace_dump_mode oops_dump_mode)
> }
> EXPORT_SYMBOL_GPL(ftrace_dump);
>
> +int trace_run_command(const char *buf, int (*createfn)(int, char **))
> +{
> + char **argv;
> + int argc, ret;
> +
> + argc = 0;
> + ret = 0;
> + argv = argv_split(GFP_KERNEL, buf, &argc);
> + if (!argv)
> + return -ENOMEM;
> +
> + if (argc)
> + ret = createfn(argc, argv);
> +
> + argv_free(argv);
> +
> + return ret;
> +}
> +
> +#define WRITE_BUFSIZE 4096
> +
> +ssize_t trace_parse_run_command(struct file *file, const char __user *buffer,
> + size_t count, loff_t *ppos,
> + int (*createfn)(int, char **))
> +{
> + char *kbuf, *tmp;
> + int ret = 0;
> + size_t done = 0;
> + size_t size;
> +
> + kbuf = kmalloc(WRITE_BUFSIZE, GFP_KERNEL);
> + if (!kbuf)
> + return -ENOMEM;
> +
> + while (done < count) {
> + size = count - done;
> +
> + if (size >= WRITE_BUFSIZE)
> + size = WRITE_BUFSIZE - 1;
> +
> + if (copy_from_user(kbuf, buffer + done, size)) {

OK, I'm looking at this code now, and I really dislike how we do a
copy_from_user() at every iteration even when not necessary.

I'm going to fix this in the trace_probe.c file, so giving you a heads
up, that my change will conflict with this patch.

-- Steve

> + ret = -EFAULT;
> + goto out;
> + }
> + kbuf[size] = '\0';
> + tmp = strchr(kbuf, '\n');
> +
> + if (tmp) {
> + *tmp = '\0';
> + size = tmp - kbuf + 1;
> + } else if (done + size < count) {
> + pr_warn("Line length is too long: Should be less than %d\n",
> + WRITE_BUFSIZE);
> + ret = -EINVAL;
> + goto out;
> + }
> + done += size;
> + /* Remove comments */
> + tmp = strchr(kbuf, '#');
> +
> + if (tmp)
> + *tmp = '\0';
> +
> + ret = trace_run_command(kbuf, createfn);
> + if (ret)
> + goto out;
> + }
> + ret = done;
> +
> +out:
> + kfree(kbuf);
> +
> + return ret;
> +}
> +
> __init static int tracer_alloc_buffers(void)
> {
> int ring_buf_size;
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index ac55fa1..f2af21b 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -1647,6 +1647,13 @@ extern int trace_event_enable_disable(struct trace_event_file *file,
> int trace_keep_overwrite(struct tracer *tracer, u32 mask, int set);
> int set_tracer_flag(struct trace_array *tr, unsigned int mask, int enabled);
>
> +#define MAX_EVENT_NAME_LEN 64
> +
> +extern int trace_run_command(const char *buf, int (*createfn)(int, char**));
> +extern ssize_t trace_parse_run_command(struct file *file,
> + const char __user *buffer, size_t count, loff_t *ppos,
> + int (*createfn)(int, char**));
> +
> /*
> * Normal trace_printk() and friends allocates special buffers
> * to do the manipulation, as well as saves the print formats
> diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> index a133ecd..8f3b4d9 100644
> --- a/kernel/trace/trace_kprobe.c
> +++ b/kernel/trace/trace_kprobe.c
> @@ -876,8 +876,8 @@ static int probes_open(struct inode *inode, struct file *file)
> static ssize_t probes_write(struct file *file, const char __user *buffer,
> size_t count, loff_t *ppos)
> {
> - return traceprobe_probes_write(file, buffer, count, ppos,
> - create_trace_kprobe);
> + return trace_parse_run_command(file, buffer, count, ppos,
> + create_trace_kprobe);
> }
>
> static const struct file_operations kprobe_events_ops = {
> @@ -1402,9 +1402,9 @@ static __init int kprobe_trace_self_tests_init(void)
>
> pr_info("Testing kprobe tracing: ");
>
> - ret = traceprobe_command("p:testprobe kprobe_trace_selftest_target "
> - "$stack $stack0 +0($stack)",
> - create_trace_kprobe);
> + ret = trace_run_command("p:testprobe kprobe_trace_selftest_target "
> + "$stack $stack0 +0($stack)",
> + create_trace_kprobe);
> if (WARN_ON_ONCE(ret)) {
> pr_warn("error on probing function entry.\n");
> warn++;
> @@ -1424,8 +1424,8 @@ static __init int kprobe_trace_self_tests_init(void)
> }
> }
>
> - ret = traceprobe_command("r:testprobe2 kprobe_trace_selftest_target "
> - "$retval", create_trace_kprobe);
> + ret = trace_run_command("r:testprobe2 kprobe_trace_selftest_target "
> + "$retval", create_trace_kprobe);
> if (WARN_ON_ONCE(ret)) {
> pr_warn("error on probing function return.\n");
> warn++;
> @@ -1495,13 +1495,13 @@ static __init int kprobe_trace_self_tests_init(void)
> disable_trace_kprobe(tk, file);
> }
>
> - ret = traceprobe_command("-:testprobe", create_trace_kprobe);
> + ret = trace_run_command("-:testprobe", create_trace_kprobe);
> if (WARN_ON_ONCE(ret)) {
> pr_warn("error on deleting a probe.\n");
> warn++;
> }
>
> - ret = traceprobe_command("-:testprobe2", create_trace_kprobe);
> + ret = trace_run_command("-:testprobe2", create_trace_kprobe);
> if (WARN_ON_ONCE(ret)) {
> pr_warn("error on deleting a probe.\n");
> warn++;
> diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> index 8c0553d..b7de026 100644
> --- a/kernel/trace/trace_probe.c
> +++ b/kernel/trace/trace_probe.c
> @@ -622,81 +622,6 @@ void traceprobe_free_probe_arg(struct probe_arg *arg)
> kfree(arg->comm);
> }
>
> -int traceprobe_command(const char *buf, int (*createfn)(int, char **))
> -{
> - char **argv;
> - int argc, ret;
> -
> - argc = 0;
> - ret = 0;
> - argv = argv_split(GFP_KERNEL, buf, &argc);
> - if (!argv)
> - return -ENOMEM;
> -
> - if (argc)
> - ret = createfn(argc, argv);
> -
> - argv_free(argv);
> -
> - return ret;
> -}
> -
> -#define WRITE_BUFSIZE 4096
> -
> -ssize_t traceprobe_probes_write(struct file *file, const char __user *buffer,
> - size_t count, loff_t *ppos,
> - int (*createfn)(int, char **))
> -{
> - char *kbuf, *tmp;
> - int ret = 0;
> - size_t done = 0;
> - size_t size;
> -
> - kbuf = kmalloc(WRITE_BUFSIZE, GFP_KERNEL);
> - if (!kbuf)
> - return -ENOMEM;
> -
> - while (done < count) {
> - size = count - done;
> -
> - if (size >= WRITE_BUFSIZE)
> - size = WRITE_BUFSIZE - 1;
> -
> - if (copy_from_user(kbuf, buffer + done, size)) {
> - ret = -EFAULT;
> - goto out;
> - }
> - kbuf[size] = '\0';
> - tmp = strchr(kbuf, '\n');
> -
> - if (tmp) {
> - *tmp = '\0';
> - size = tmp - kbuf + 1;
> - } else if (done + size < count) {
> - pr_warn("Line length is too long: Should be less than %d\n",
> - WRITE_BUFSIZE);
> - ret = -EINVAL;
> - goto out;
> - }
> - done += size;
> - /* Remove comments */
> - tmp = strchr(kbuf, '#');
> -
> - if (tmp)
> - *tmp = '\0';
> -
> - ret = traceprobe_command(kbuf, createfn);
> - if (ret)
> - goto out;
> - }
> - ret = done;
> -
> -out:
> - kfree(kbuf);
> -
> - return ret;
> -}
> -
> static int __set_print_fmt(struct trace_probe *tp, char *buf, int len,
> bool is_return)
> {
> diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
> index 0c0ae54..37ab38c 100644
> --- a/kernel/trace/trace_probe.h
> +++ b/kernel/trace/trace_probe.h
> @@ -42,7 +42,6 @@
>
> #define MAX_TRACE_ARGS 128
> #define MAX_ARGSTR_LEN 63
> -#define MAX_EVENT_NAME_LEN 64
> #define MAX_STRING_SIZE PATH_MAX
>
> /* Reserved field names */
> @@ -356,12 +355,6 @@ extern int traceprobe_conflict_field_name(const char *name,
>
> extern int traceprobe_split_symbol_offset(char *symbol, unsigned long *offset);
>
> -extern ssize_t traceprobe_probes_write(struct file *file,
> - const char __user *buffer, size_t count, loff_t *ppos,
> - int (*createfn)(int, char**));
> -
> -extern int traceprobe_command(const char *buf, int (*createfn)(int, char**));
> -
> /* Sum up total data length for dynamic arraies (strings) */
> static nokprobe_inline int
> __get_data_size(struct trace_probe *tp, struct pt_regs *regs)
> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
> index 4f2ba2b..10e3ec8 100644
> --- a/kernel/trace/trace_uprobe.c
> +++ b/kernel/trace/trace_uprobe.c
> @@ -649,7 +649,7 @@ static int probes_open(struct inode *inode, struct file *file)
> static ssize_t probes_write(struct file *file, const char __user *buffer,
> size_t count, loff_t *ppos)
> {
> - return traceprobe_probes_write(file, buffer, count, ppos, create_trace_uprobe);
> + return trace_parse_run_command(file, buffer, count, ppos, create_trace_uprobe);
> }
>
> static const struct file_operations uprobe_events_ops = {