tracing: probeevent: Add $argN for accessing function args
Add $argN special fetch variable for accessing function
arguments. This allows user to trace the Nth argument easily
at the function entry.
Note that this returns most probably assignment of registers
and stacks. In some case, it may not work well. If you need
to access correct registers or stacks you should use perf-probe.
Link: http://lkml.kernel.org/r/152465888632.26224.3412465701570253696.stgit@devbox
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index fdd43f2..3faaadb 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -533,13 +533,15 @@ static int create_trace_kprobe(int argc, char **argv)
long offset = 0;
void *addr = NULL;
char buf[MAX_EVENT_NAME_LEN];
+ unsigned int flags = TPARG_FL_KERNEL;
/* argc must be >= 1 */
if (argv[0][0] == 'p')
is_return = false;
- else if (argv[0][0] == 'r')
+ else if (argv[0][0] == 'r') {
is_return = true;
- else if (argv[0][0] == '-')
+ flags |= TPARG_FL_RETURN;
+ } else if (argv[0][0] == '-')
is_delete = true;
else {
pr_info("Probe definition must be started with 'p', 'r' or"
@@ -625,8 +627,9 @@ static int create_trace_kprobe(int argc, char **argv)
pr_info("Failed to parse either an address or a symbol.\n");
return ret;
}
- if (offset && is_return &&
- !kprobe_on_func_entry(NULL, symbol, offset)) {
+ if (kprobe_on_func_entry(NULL, symbol, offset))
+ flags |= TPARG_FL_FENTRY;
+ if (offset && is_return && !(flags & TPARG_FL_FENTRY)) {
pr_info("Given offset is not valid for return probe.\n");
return -EINVAL;
}
@@ -696,7 +699,7 @@ static int create_trace_kprobe(int argc, char **argv)
/* Parse fetch argument */
ret = traceprobe_parse_probe_arg(arg, &tk->tp.size, parg,
- is_return, true);
+ flags);
if (ret) {
pr_info("Parse error at argument[%d]. (%d)\n", i, ret);
goto error;
@@ -932,6 +935,11 @@ process_fetch_insn(struct fetch_insn *code, struct pt_regs *regs, void *dest,
case FETCH_OP_COMM:
val = (unsigned long)current->comm;
break;
+#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
+ case FETCH_OP_ARG:
+ val = regs_get_kernel_argument(regs, code->param);
+ break;
+#endif
default:
return -EILSEQ;
}
