[PATCH v8 02/10] tracing/probes: Allow eprobe to use variable without $ prefix

["Masami Hiramatsu (Google)" <mhiramat@kernel.org>]

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

The commit 69efd863a785 ("tracing/eprobes: Allow use of BTF names
to dereference pointers") allows eprobe to use event field without
"$" prefix when it is used with typecast, it is natual to allow it
without typecast.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 Changes in v8:
  - Newly added.
---
 kernel/trace/trace_probe.c                         |   12 +++++++++++-
 kernel/trace/trace_probe.h                         |    1 +
 .../test.d/dynevent/eprobes_syntax_errors.tc       |    3 +--
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 0da7c0b53ba7..2ce7d62471cb 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -1341,7 +1341,17 @@ parse_probe_arg(char *arg, const struct fetch_type *type,
 		ret = handle_typecast(arg, pcode, end, ctx);
 		break;
 	default:
-		if (isalpha(arg[0]) || arg[0] == '_') {	/* BTF variable */
+		if (isalpha(arg[0]) || arg[0] == '_') {
+			/* BTF variable or event field*/
+			if (ctx->flags & TPARG_FL_TEVENT) {
+				ret = parse_trace_event(arg, *pcode, ctx);
+				if (ret < 0) {
+					trace_probe_log_err(ctx->offset,
+							    NO_EVENT_FIELD);
+					return -EINVAL;
+				}
+				break;
+			}
 			if (!tparg_is_function_entry(ctx->flags) &&
 			    !tparg_is_function_return(ctx->flags)) {
 				trace_probe_log_err(ctx->offset, NOSUP_BTFARG);
diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index 40b53b5b58a9..2e0d8384ee5c 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -559,6 +559,7 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call,
 	C(NO_PTR_STRCT,		"This is not a pointer to union/structure."),	\
 	C(NOSUP_DAT_ARG,	"Non pointer structure/union argument is not supported."),\
 	C(BAD_HYPHEN,		"Failed to parse single hyphen. Forgot '>'?"),	\
+	C(NO_EVENT_FIELD,	"This event field is not found."),	\
 	C(NO_BTF_FIELD,		"This field is not found."),	\
 	C(BAD_BTF_TID,		"Failed to get BTF type info."),\
 	C(BAD_TYPE4STR,		"This type does not fit for string."),\
diff --git a/tools/testing/selftests/ftrace/test.d/dynevent/eprobes_syntax_errors.tc b/tools/testing/selftests/ftrace/test.d/dynevent/eprobes_syntax_errors.tc
index 2a680c086047..0e65e787e426 100644
--- a/tools/testing/selftests/ftrace/test.d/dynevent/eprobes_syntax_errors.tc
+++ b/tools/testing/selftests/ftrace/test.d/dynevent/eprobes_syntax_errors.tc
@@ -10,7 +10,7 @@ check_error() { # command-with-error-pos-by-^
 check_error 'e ^a.'			# NO_EVENT_INFO
 check_error 'e ^.b'			# NO_EVENT_INFO
 check_error 'e ^a.b'			# BAD_ATTACH_EVENT
-check_error 'e syscalls/sys_enter_openat ^foo'	# BAD_ATTACH_ARG
+check_error 'e syscalls/sys_enter_openat ^foo'	# NO_EVENT_FIELD
 check_error 'e:^/bar syscalls/sys_enter_openat'	# NO_GROUP_NAME
 check_error 'e:^12345678901234567890123456789012345678901234567890123456789012345/bar syscalls/sys_enter_openat'	# GROUP_TOO_LONG
 
@@ -19,7 +19,6 @@ check_error 'e:^ syscalls/sys_enter_openat'		# NO_EVENT_NAME
 check_error 'e:foo/^12345678901234567890123456789012345678901234567890123456789012345 syscalls/sys_enter_openat'	# EVENT_TOO_LONG
 check_error 'e:foo/^bar.1 syscalls/sys_enter_openat'	# BAD_EVENT_NAME
 
-check_error 'e:foo/bar syscalls/sys_enter_openat arg=^dfd'	# BAD_FETCH_ARG
 check_error 'e:foo/bar syscalls/sys_enter_openat arg=^$foo'	# BAD_ATTACH_ARG
 
 if grep -q '<attached-group>\.<attached-event>.*\[if <filter>\]' README; then