Re: [PATCH v9.1 05/11] tracing/probes: Move event parameter fetching code to common parser

Masami Hiramatsu
2023-05-14T04:11:18Z

On Fri, 5 May 2023 17:40:32 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Tue, 2 May 2023 11:18:03 +0900
> "Masami Hiramatsu (Google)" <mhiramat@kernel.org> wrote:
>
> > --- a/kernel/trace/trace_probe.c
> > +++ b/kernel/trace/trace_probe.c
> > @@ -283,27 +283,53 @@ int traceprobe_parse_event_name(const char **pevent, const char **pgroup,
> > return 0;
> > }
> >
> > +static int parse_trace_event_arg(char *arg, struct fetch_insn *code,
> > + struct traceprobe_parse_context *ctx)
> > +{
> > + struct ftrace_event_field *field;
> > + struct list_head *head;
> > +
> > + head = trace_get_fields(ctx->event);
> > + list_for_each_entry(field, head, link) {
> > + if (!strcmp(arg, field->name)) {
> > + code->op = FETCH_OP_TP_ARG;
> > + code->data = field;
> > + return 0;
> > + }
> > + }
> > + return -ENOENT;
> > +}
> > +
> > #define PARAM_MAX_STACK (THREAD_SIZE / sizeof(unsigned long))
> >
> > static int parse_probe_vars(char *arg, const struct fetch_type *t,
> > - struct fetch_insn *code, unsigned int flags, int offs)
> > + struct fetch_insn *code,
> > + struct traceprobe_parse_context *ctx)
> > {
> > unsigned long param;
> > int ret = 0;
> > int len;
> >
> > - if (flags & TPARG_FL_TEVENT) {
> > + if (ctx->flags & TPARG_FL_TEVENT) {
> > if (code->data)
> > return -EFAULT;
> > - code->data = kstrdup(arg, GFP_KERNEL);
> > - if (!code->data)
> > - return -ENOMEM;
> > - code->op = FETCH_OP_TP_ARG;
> > - } else if (strcmp(arg, "retval") == 0) {
> > - if (flags & TPARG_FL_RETURN) {
> > + ret = parse_trace_event_arg(arg, code, ctx);
> > + if (!ret)
> > + return 0;
> > + if (strcmp(arg, "comm") == 0 || strcmp(arg, "COMM") == 0) {
> > + code->op = FETCH_OP_COMM;
> > + return 0;
> > + }
> > + /* backward compatibility */
> > + ctx->offset = 0;
> > + goto inval_var;
> > + }
>
> So this is a bit inconsistent in this function. We have here an if
> statement that returns 0 on success, and jumps to inval_var if it reaches
> the end.

Ah, got it. So it repeating the same pattern in this function.

>
> The rest of the if statements below, also goes to inval_var, or returns
> error, or just falls through the if statement to return ret. It's somewhat
> random.

And here is another pattern.

>
> This should be cleaned up (see patch at the end).

OK, I'll take it.

Thanks!

>
> > +
> > + if (strcmp(arg, "retval") == 0) {
> > + if (ctx->flags & TPARG_FL_RETURN) {
> > code->op = FETCH_OP_RETVAL;
> > } else {
> > - trace_probe_log_err(offs, RETVAL_ON_PROBE);
> > + trace_probe_log_err(ctx->offset, RETVAL_ON_PROBE);
> > ret = -EINVAL;
> > }
> > } else if ((len = str_has_prefix(arg, "stack"))) {
> > @@ -313,9 +339,9 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t,
> > ret = kstrtoul(arg + len, 10, &param);
> > if (ret) {
> > goto inval_var;
> > - } else if ((flags & TPARG_FL_KERNEL) &&
> > + } else if ((ctx->flags & TPARG_FL_KERNEL) &&
> > param > PARAM_MAX_STACK) {
> > - trace_probe_log_err(offs, BAD_STACK_NUM);
> > + trace_probe_log_err(ctx->offset, BAD_STACK_NUM);
> > ret = -EINVAL;
> > } else {
> > code->op = FETCH_OP_STACK;
> > @@ -326,13 +352,13 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t,
> > } else if (strcmp(arg, "comm") == 0 || strcmp(arg, "COMM") == 0) {
> > code->op = FETCH_OP_COMM;
> > #ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
> > - } else if (tparg_is_function_entry(flags) &&
> > + } else if (tparg_is_function_entry(ctx->flags) &&
> > (len = str_has_prefix(arg, "arg"))) {
> > ret = kstrtoul(arg + len, 10, &param);
> > if (ret) {
> > goto inval_var;
> > } else if (!param || param > PARAM_MAX_STACK) {
> > - trace_probe_log_err(offs, BAD_ARG_NUM);
> > + trace_probe_log_err(ctx->offset, BAD_ARG_NUM);
> > return -EINVAL;
> > }
> > code->op = FETCH_OP_ARG;
> > @@ -341,7 +367,7 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t,
> > * The tracepoint probe will probe a stub function, and the
> > * first parameter of the stub is a dummy and should be ignored.
> > */
> > - if (flags & TPARG_FL_TPOINT)
> > + if (ctx->flags & TPARG_FL_TPOINT)
> > code->param++;
> > #endif
> > } else
> > @@ -350,7 +376,7 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t,
> > return ret;
> >
> > inval_var:
> > - trace_probe_log_err(offs, BAD_VAR);
> > + trace_probe_log_err(ctx->offset, BAD_VAR);
> > return -EINVAL;
> > }
> >
>
>
> diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> index 84a9f0446390..a30aab8cef7f 100644
> --- a/kernel/trace/trace_probe.c
> +++ b/kernel/trace/trace_probe.c
> @@ -307,6 +307,7 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t,
> struct traceprobe_parse_context *ctx)
> {
> unsigned long param;
> + int err = BAD_VAR;
> int ret = 0;
> int len;
>
> @@ -322,45 +323,61 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t,
> }
> /* backward compatibility */
> ctx->offset = 0;
> - goto inval_var;
> + goto inval;
> }
>
> if (strcmp(arg, "retval") == 0) {
> if (ctx->flags & TPARG_FL_RETURN) {
> code->op = FETCH_OP_RETVAL;
> - } else {
> - trace_probe_log_err(ctx->offset, RETVAL_ON_PROBE);
> - ret = -EINVAL;
> + return 0;
> }
> - } else if ((len = str_has_prefix(arg, "stack"))) {
> + err = RETVAL_ON_PROBE;
> + ret = -EINVAL;
> + goto inval;
> + }
> +
> + if ((len = str_has_prefix(arg, "stack"))) {
> +
> if (arg[len] == '\0') {
> code->op = FETCH_OP_STACKP;
> - } else if (isdigit(arg[len])) {
> + return 0;
> + }
> +
> + if (isdigit(arg[len])) {
> ret = kstrtoul(arg + len, 10, &param);
> - if (ret) {
> - goto inval_var;
> - } else if ((ctx->flags & TPARG_FL_KERNEL) &&
> - param > PARAM_MAX_STACK) {
> - trace_probe_log_err(ctx->offset, BAD_STACK_NUM);
> + if (ret)
> + goto inval;
> +
> + if ((ctx->flags & TPARG_FL_KERNEL) &&
> + param > PARAM_MAX_STACK) {
> + err = BAD_STACK_NUM;
> ret = -EINVAL;
> - } else {
> - code->op = FETCH_OP_STACK;
> - code->param = (unsigned int)param;
> + goto inval;
> }
> - } else
> - goto inval_var;
> - } else if (strcmp(arg, "comm") == 0 || strcmp(arg, "COMM") == 0) {
> + code->op = FETCH_OP_STACK;
> + code->param = (unsigned int)param;
> + return 0;
> + }
> + goto inval;
> + }
> +
> + if (strcmp(arg, "comm") == 0 || strcmp(arg, "COMM") == 0) {
> code->op = FETCH_OP_COMM;
> + return 0;
> + }
> +
> #ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
> - } else if (tparg_is_function_entry(ctx->flags) &&
> - (len = str_has_prefix(arg, "arg"))) {
> + if (tparg_is_function_entry(ctx->flags) &&
> + (len = str_has_prefix(arg, "arg"))) {
> ret = kstrtoul(arg + len, 10, &param);
> - if (ret) {
> - goto inval_var;
> - } else if (!param || param > PARAM_MAX_STACK) {
> - trace_probe_log_err(ctx->offset, BAD_ARG_NUM);
> - return -EINVAL;
> + if (ret)
> + goto inval;
> +
> + if (!param || param > PARAM_MAX_STACK) {
> + err = BAD_ARG_NUM;
> + goto inval;
> }
> +
> code->op = FETCH_OP_ARG;
> code->param = (unsigned int)param - 1;
> /*
> @@ -369,14 +386,11 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t,
> */
> if (ctx->flags & TPARG_FL_TPOINT)
> code->param++;
> + return 0;
> #endif
> - } else
> - goto inval_var;
> -
> - return ret;
>
> -inval_var:
> - trace_probe_log_err(ctx->offset, BAD_VAR);
> +inval:
> + trace_probe_log_err(ctx->offset, err);
> return -EINVAL;
> }
>

--
Masami Hiramatsu (Google) <mhiramat@kernel.org>