tracing/probes: Add symstr type for dynamic events

Add 'symstr' type for storing the kernel symbol as a string data
instead of the symbol address. This allows us to filter the
events by wildcard symbol name.

e.g.
  # echo 'e:wqfunc workqueue.workqueue_execute_start symname=$function:symstr' >> dynamic_events
  # cat events/eprobes/wqfunc/format
  name: wqfunc
  ID: 2110
  format:
  	field:unsigned short common_type;	offset:0;	size:2;	signed:0;
  	field:unsigned char common_flags;	offset:2;	size:1;	signed:0;
  	field:unsigned char common_preempt_count;	offset:3;	size:1;	signed:0;
  	field:int common_pid;	offset:4;	size:4;	signed:1;

  	field:__data_loc char[] symname;	offset:8;	size:4;	signed:1;

  print fmt: " symname=\"%s\"", __get_str(symname)

Note that there is already 'symbol' type which just change the
print format (so it still stores the symbol address in the tracing
ring buffer.) On the other hand, 'symstr' type stores the actual
"symbol+offset/size" data as a string.

Link: https://lore.kernel.org/all/166679930847.1528100.4124308529180235965.stgit@devnote3/

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

1 files changed, 11 insertions, 5 deletions

diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
index de38f1c03776..0838b74f403b 100644
--- a/kernel/trace/trace_probe.h
+++ b/kernel/trace/trace_probe.h
@@ -98,6 +98,7 @@ enum fetch_op {
 	FETCH_OP_ST_UMEM,	/* Mem: .offset, .size */
 	FETCH_OP_ST_STRING,	/* String: .offset, .size */
 	FETCH_OP_ST_USTRING,	/* User String: .offset, .size */
+	FETCH_OP_ST_SYMSTR,	/* Kernel Symbol String: .offset, .size */
 	// Stage 4 (modify) op
 	FETCH_OP_MOD_BF,	/* Bitfield: .basesize, .lshift, .rshift */
 	// Stage 5 (loop) op
@@ -133,7 +134,8 @@ struct fetch_insn {
 struct fetch_type {
 	const char		*name;		/* Name of type */
 	size_t			size;		/* Byte size of type */
-	int			is_signed;	/* Signed flag */
+	bool			is_signed;	/* Signed flag */
+	bool			is_string;	/* String flag */
 	print_type_func_t	print;		/* Print functions */
 	const char		*fmt;		/* Format string */
 	const char		*fmttype;	/* Name in format file */
@@ -177,16 +179,19 @@ DECLARE_BASIC_PRINT_TYPE_FUNC(symbol);
 #define _ADDR_FETCH_TYPE(t) __ADDR_FETCH_TYPE(t)
 #define ADDR_FETCH_TYPE _ADDR_FETCH_TYPE(BITS_PER_LONG)
 
-#define __ASSIGN_FETCH_TYPE(_name, ptype, ftype, _size, sign, _fmttype)	\
-	{.name = _name,				\
+#define __ASSIGN_FETCH_TYPE(_name, ptype, ftype, _size, sign, str, _fmttype)	\
+	{.name = _name,					\
 	 .size = _size,					\
-	 .is_signed = sign,				\
+	 .is_signed = (bool)sign,			\
+	 .is_string = (bool)str,			\
 	 .print = PRINT_TYPE_FUNC_NAME(ptype),		\
 	 .fmt = PRINT_TYPE_FMT_NAME(ptype),		\
 	 .fmttype = _fmttype,				\
 	}
+
+/* Non string types can use these macros */
 #define _ASSIGN_FETCH_TYPE(_name, ptype, ftype, _size, sign, _fmttype)	\
-	__ASSIGN_FETCH_TYPE(_name, ptype, ftype, _size, sign, #_fmttype)
+	__ASSIGN_FETCH_TYPE(_name, ptype, ftype, _size, sign, 0, #_fmttype)
 #define ASSIGN_FETCH_TYPE(ptype, ftype, sign)			\
 	_ASSIGN_FETCH_TYPE(#ptype, ptype, ftype, sizeof(ftype), sign, ptype)
 
@@ -431,6 +436,7 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call,
 	C(ARRAY_TOO_BIG,	"Array number is too big"),		\
 	C(BAD_TYPE,		"Unknown type is specified"),		\
 	C(BAD_STRING,		"String accepts only memory argument"),	\
+	C(BAD_SYMSTRING,	"Symbol String doesn't accept data/userdata"),	\
 	C(BAD_BITFIELD,		"Invalid bitfield"),			\
 	C(ARG_NAME_TOO_LONG,	"Argument name is too long"),		\
 	C(NO_ARG_NAME,		"Argument name is not specified"),	\