Commit 18b1e870 authored by Masami Hiramatsu (Google)'s avatar Masami Hiramatsu (Google)
Browse files

tracing/probes: Add $arg* meta argument for all function args 

Add the '$arg*' meta fetch argument for function-entry probe events. This
will be expanded to the all arguments of the function and the tracepoint
using BTF function argument information.

e.g.
 #  echo 'p vfs_read $arg*' >> dynamic_events
 #  echo 'f vfs_write $arg*' >> dynamic_events
 #  echo 't sched_overutilized_tp $arg*' >> dynamic_events
 # cat dynamic_events
p:kprobes/p_vfs_read_0 vfs_read file=file buf=buf count=count pos=pos
f:fprobes/vfs_write__entry vfs_write file=file buf=buf count=count pos=pos
t:tracepoints/sched_overutilized_tp sched_overutilized_tp rd=rd overutilized=overutilized

Also, single '$arg[0-9]*' will be converted to the BTF function argument.

NOTE: This seems like a wildcard, but a fake one at this moment. This
is just for telling user that this can be expanded to several arguments.
And it is not like other $-vars, you can not use this $arg* as a part of
fetch args, e.g. specifying name "foo=$arg*" and using it in dereferences
"+0($arg*)" will lead a parse error.

Link: https://lore.kernel.org/all/168507475126.913472.18329684401466211816.stgit@mhiramat.roam.corp.google.com/



Signed-off-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
parent b576e097

kernel/trace/trace_fprobe.c

+18 −3
Original line number Diff line number Diff line
@@ -925,14 +925,16 @@ static int __trace_fprobe_create(int argc, const char *argv[]) 
	 *  FETCHARG:TYPE : use TYPE instead of unsigned long.

	 */

	struct trace_fprobe *tf = NULL;

	int i, len, ret = 0;

	int i, len, new_argc = 0, ret = 0;

	bool is_return = false;

	char *symbol = NULL, *tmp = NULL;

	const char *event = NULL, *group = FPROBE_EVENT_SYSTEM;

	const char **new_argv = NULL;

	int maxactive = 0;

	char buf[MAX_EVENT_NAME_LEN];

	char gbuf[MAX_EVENT_NAME_LEN];

	char sbuf[KSYM_NAME_LEN];

	char abuf[MAX_BTF_ARGS_LEN];

	bool is_tracepoint = false;

	struct tracepoint *tpoint = NULL;

	struct traceprobe_parse_context ctx = {
@@ -1040,9 +1042,22 @@ static int __trace_fprobe_create(int argc, const char *argv[]) 
	} else

		ctx.funcname = symbol;



	argc -= 2; argv += 2;

	new_argv = traceprobe_expand_meta_args(argc, argv, &new_argc,

					       abuf, MAX_BTF_ARGS_LEN, &ctx);

	if (IS_ERR(new_argv)) {

		ret = PTR_ERR(new_argv);

		new_argv = NULL;

		goto out;

	}

	if (new_argv) {

		argc = new_argc;

		argv = new_argv;

	}



	/* setup a probe */

	tf = alloc_trace_fprobe(group, event, symbol, tpoint, maxactive,

				argc - 2, is_return);

				argc, is_return);

	if (IS_ERR(tf)) {

		ret = PTR_ERR(tf);

		/* This must return -ENOMEM, else there is a bug */
@@ -1054,7 +1069,6 @@ static int __trace_fprobe_create(int argc, const char *argv[]) 
		tf->mod = __module_text_address(

				(unsigned long)tf->tpoint->probestub);



	argc -= 2; argv += 2;

	/* parse arguments */

	for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {

		trace_probe_log_set_index(i + 2);
@@ -1083,6 +1097,7 @@ static int __trace_fprobe_create(int argc, const char *argv[]) 


out:

	trace_probe_log_clear();

	kfree(new_argv);

	kfree(symbol);

	return ret;

kernel/trace/trace_kprobe.c

+19 −4
Original line number Diff line number Diff line
@@ -732,9 +732,10 @@ static int __trace_kprobe_create(int argc, const char *argv[]) 
	 *  FETCHARG:TYPE : use TYPE instead of unsigned long.

	 */

	struct trace_kprobe *tk = NULL;

	int i, len, ret = 0;

	int i, len, new_argc = 0, ret = 0;

	bool is_return = false;

	char *symbol = NULL, *tmp = NULL;

	const char **new_argv = NULL;

	const char *event = NULL, *group = KPROBE_EVENT_SYSTEM;

	enum probe_print_type ptype;

	int maxactive = 0;
@@ -742,6 +743,7 @@ static int __trace_kprobe_create(int argc, const char *argv[]) 
	void *addr = NULL;

	char buf[MAX_EVENT_NAME_LEN];

	char gbuf[MAX_EVENT_NAME_LEN];

	char abuf[MAX_BTF_ARGS_LEN];

	struct traceprobe_parse_context ctx = { .flags = TPARG_FL_KERNEL };



	switch (argv[0][0]) {
@@ -854,19 +856,31 @@ static int __trace_kprobe_create(int argc, const char *argv[]) 
		event = buf;

	}



	argc -= 2; argv += 2;

	ctx.funcname = symbol;

	new_argv = traceprobe_expand_meta_args(argc, argv, &new_argc,

					       abuf, MAX_BTF_ARGS_LEN, &ctx);

	if (IS_ERR(new_argv)) {

		ret = PTR_ERR(new_argv);

		new_argv = NULL;

		goto out;

	}

	if (new_argv) {

		argc = new_argc;

		argv = new_argv;

	}



	/* setup a probe */

	tk = alloc_trace_kprobe(group, event, addr, symbol, offset, maxactive,

				argc - 2, is_return);

				argc, is_return);

	if (IS_ERR(tk)) {

		ret = PTR_ERR(tk);

		/* This must return -ENOMEM, else there is a bug */

		WARN_ON_ONCE(ret != -ENOMEM);

		goto out;	/* We know tk is not allocated */

	}

	argc -= 2; argv += 2;



	/* parse arguments */

	ctx.funcname = symbol;

	for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {

		trace_probe_log_set_index(i + 2);

		ctx.offset = 0;
@@ -894,6 +908,7 @@ static int __trace_kprobe_create(int argc, const char *argv[]) 


out:

	trace_probe_log_clear();

	kfree(new_argv);

	kfree(symbol);

	return ret;

kernel/trace/trace_probe.c

+165 −4
Original line number Diff line number Diff line
@@ -371,9 +371,11 @@ static const char *type_from_btf_id(struct btf *btf, s32 id) 
	return NULL;

}



static const struct btf_param *find_btf_func_param(const char *funcname, s32 *nr)

static const struct btf_param *find_btf_func_param(const char *funcname, s32 *nr,

						   bool tracepoint)

{

	struct btf *btf = traceprobe_get_btf();

	const struct btf_param *param;

	const struct btf_type *t;

	s32 id;
@@ -395,9 +397,16 @@ static const struct btf_param *find_btf_func_param(const char *funcname, s32 *nr 
		return ERR_PTR(-ENOENT);



	*nr = btf_type_vlen(t);

	param = (const struct btf_param *)(t + 1);



	if (*nr)

		return (const struct btf_param *)(t + 1);

	/* Hide the first 'data' argument of tracepoint */

	if (tracepoint) {

		(*nr)--;

		param++;

	}



	if (*nr > 0)

		return param;

	else

		return NULL;

}
@@ -418,7 +427,8 @@ static int parse_btf_arg(const char *varname, struct fetch_insn *code, 
		return -EINVAL;



	if (!ctx->params) {

		params = find_btf_func_param(ctx->funcname, &ctx->nr_params);

		params = find_btf_func_param(ctx->funcname, &ctx->nr_params,

					     ctx->flags & TPARG_FL_TPOINT);

		if (IS_ERR(params)) {

			trace_probe_log_err(ctx->offset, NO_BTF_ENTRY);

			return PTR_ERR(params);
@@ -451,12 +461,19 @@ static const struct fetch_type *parse_btf_arg_type(int arg_idx, 


	return find_fetch_type(typestr, ctx->flags);

}



#else

static struct btf *traceprobe_get_btf(void)

{

	return NULL;

}



static const struct btf_param *find_btf_func_param(const char *funcname, s32 *nr,

						   bool tracepoint)

{

	return ERR_PTR(-EOPNOTSUPP);

}



static int parse_btf_arg(const char *varname, struct fetch_insn *code,

			 struct traceprobe_parse_context *ctx)

{
@@ -1114,6 +1131,150 @@ void traceprobe_free_probe_arg(struct probe_arg *arg) 
	kfree(arg->fmt);

}



static int argv_has_var_arg(int argc, const char *argv[], int *args_idx,

			    struct traceprobe_parse_context *ctx)

{

	int i, found = 0;



	for (i = 0; i < argc; i++)

		if (str_has_prefix(argv[i], "$arg")) {

			trace_probe_log_set_index(i + 2);



			if (!tparg_is_function_entry(ctx->flags)) {

				trace_probe_log_err(0, NOFENTRY_ARGS);

				return -EINVAL;

			}



			if (isdigit(argv[i][4])) {

				found = 1;

				continue;

			}



			if (argv[i][4] != '*') {

				trace_probe_log_err(0, BAD_VAR);

				return -EINVAL;

			}



			if (*args_idx >= 0 && *args_idx < argc) {

				trace_probe_log_err(0, DOUBLE_ARGS);

				return -EINVAL;

			}

			found = 1;

			*args_idx = i;

		}



	return found;

}



static int sprint_nth_btf_arg(int idx, const char *type,

			      char *buf, int bufsize,

			      struct traceprobe_parse_context *ctx)

{

	struct btf *btf = traceprobe_get_btf();

	const char *name;

	int ret;



	if (idx >= ctx->nr_params) {

		trace_probe_log_err(0, NO_BTFARG);

		return -ENOENT;

	}

	name = btf_name_by_offset(btf, ctx->params[idx].name_off);

	if (!name) {

		trace_probe_log_err(0, NO_BTF_ENTRY);

		return -ENOENT;

	}

	ret = snprintf(buf, bufsize, "%s%s", name, type);

	if (ret >= bufsize) {

		trace_probe_log_err(0, ARGS_2LONG);

		return -E2BIG;

	}

	return ret;

}



/* Return new_argv which must be freed after use */

const char **traceprobe_expand_meta_args(int argc, const char *argv[],

					 int *new_argc, char *buf, int bufsize,

					 struct traceprobe_parse_context *ctx)

{

	const struct btf_param *params = NULL;

	int i, j, n, used, ret, args_idx = -1;

	const char **new_argv = NULL;

	int nr_params;



	ret = argv_has_var_arg(argc, argv, &args_idx, ctx);

	if (ret < 0)

		return ERR_PTR(ret);



	if (!ret) {

		*new_argc = argc;

		return NULL;

	}



	params = find_btf_func_param(ctx->funcname, &nr_params,

				     ctx->flags & TPARG_FL_TPOINT);

	if (IS_ERR(params)) {

		if (args_idx != -1) {

			/* $arg* requires BTF info */

			trace_probe_log_err(0, NOSUP_BTFARG);

			return (const char **)params;

		}

		return 0;

	}

	ctx->params = params;

	ctx->nr_params = nr_params;



	if (args_idx >= 0)

		*new_argc = argc + ctx->nr_params - 1;

	else

		*new_argc = argc;



	new_argv = kcalloc(*new_argc, sizeof(char *), GFP_KERNEL);

	if (!new_argv)

		return ERR_PTR(-ENOMEM);



	used = 0;

	for (i = 0, j = 0; i < argc; i++) {

		trace_probe_log_set_index(i + 2);

		if (i == args_idx) {

			for (n = 0; n < nr_params; n++) {

				ret = sprint_nth_btf_arg(n, "", buf + used,

							 bufsize - used, ctx);

				if (ret < 0)

					goto error;



				new_argv[j++] = buf + used;

				used += ret + 1;

			}

			continue;

		}



		if (str_has_prefix(argv[i], "$arg")) {

			char *type = NULL;



			n = simple_strtoul(argv[i] + 4, &type, 10);

			if (type && !(*type == ':' || *type == '\0')) {

				trace_probe_log_err(0, BAD_VAR);

				ret = -ENOENT;

				goto error;

			}

			/* Note: $argN starts from $arg1 */

			ret = sprint_nth_btf_arg(n - 1, type, buf + used,

						 bufsize - used, ctx);

			if (ret < 0)

				goto error;

			new_argv[j++] = buf + used;

			used += ret + 1;

		} else

			new_argv[j++] = argv[i];

	}



	return new_argv;



error:

	kfree(new_argv);

	return ERR_PTR(ret);

}



int traceprobe_update_arg(struct probe_arg *arg)

{

	struct fetch_insn *code = arg->code;

kernel/trace/trace_probe.h

+10 −1
Original line number Diff line number Diff line
@@ -33,7 +33,9 @@ 
#define MAX_ARGSTR_LEN		63

#define MAX_ARRAY_LEN		64

#define MAX_ARG_NAME_LEN	32

#define MAX_BTF_ARGS_LEN	128

#define MAX_STRING_SIZE		PATH_MAX

#define MAX_ARG_BUF_LEN		(MAX_TRACE_ARGS * MAX_ARG_NAME_LEN)



/* Reserved field names */

#define FIELD_STRING_IP		"__probe_ip"
@@ -391,6 +393,9 @@ struct traceprobe_parse_context { 
extern int traceprobe_parse_probe_arg(struct trace_probe *tp, int i,

				      const char *argv,

				      struct traceprobe_parse_context *ctx);

const char **traceprobe_expand_meta_args(int argc, const char *argv[],

					 int *new_argc, char *buf, int bufsize,

					 struct traceprobe_parse_context *ctx);



extern int traceprobe_update_arg(struct probe_arg *arg);

extern void traceprobe_free_probe_arg(struct probe_arg *arg);
@@ -485,7 +490,11 @@ extern int traceprobe_define_arg_fields(struct trace_event_call *event_call, 
	C(NO_EP_FILTER,		"No filter rule after 'if'"),		\

	C(NOSUP_BTFARG,		"BTF is not available or not supported"),	\

	C(NO_BTFARG,		"This variable is not found at this probe point"),\

	C(NO_BTF_ENTRY,		"No BTF entry for this probe point"),

	C(NO_BTF_ENTRY,		"No BTF entry for this probe point"),	\

	C(BAD_VAR_ARGS,		"$arg* must be an independent parameter without name etc."),\

	C(NOFENTRY_ARGS,	"$arg* can be used only on function entry"),	\

	C(DOUBLE_ARGS,		"$arg* can be used only once in the parameters"),	\

	C(ARGS_2LONG,		"$arg* failed because the argument list is too long"),



#undef C

#define C(a, b)		TP_ERR_##a