tracing: probeevent: Add array type support

Add array type support for probe events.
This allows user to get arraied types from memory address.
The array type syntax is

	TYPE[N]

Where TYPE is one of types (u8/16/32/64,s8/16/32/64,
x8/16/32/64, symbol, string) and N is a fixed value less
than 64.

The string array type is a bit different from other types. For
other base types, <base-type>[1] is equal to <base-type>
(e.g. +0(%di):x32[1] is same as +0(%di):x32.) But string[1] is not
equal to string. The string type itself represents "char array",
but string array type represents "char * array". So, for example,
+0(%di):string[1] is equal to +0(+0(%di)):string.

Link: http://lkml.kernel.org/r/152465891533.26224.6150658225601339931.stgit@devbox

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 99 insertions, 31 deletions

diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
index 1e7e0618577d..dfd096031305 100644
--- a/kernel/trace/trace_probe.c
+++ b/kernel/trace/trace_probe.c
@@ -341,9 +341,9 @@ static int __parse_bitfield_probe_arg(const char *bf,
 int traceprobe_parse_probe_arg(char *arg, ssize_t *size,
 		struct probe_arg *parg, bool is_return, bool is_kprobe)
 {
-	struct fetch_insn *code, *tmp = NULL;
-	const char *t;
-	int ret;
+	struct fetch_insn *code, *scode, *tmp = NULL;
+	char *t, *t2;
+	int ret, len;
 
 	if (strlen(arg) > MAX_ARGSTR_LEN) {
 		pr_info("Argument is too long.: %s\n",  arg);
@@ -354,24 +354,42 @@ int traceprobe_parse_probe_arg(char *arg, ssize_t *size,
 		pr_info("Failed to allocate memory for command '%s'.\n", arg);
 		return -ENOMEM;
 	}
-	t = strchr(parg->comm, ':');
+	t = strchr(arg, ':');
 	if (t) {
-		arg[t - parg->comm] = '\0';
-		t++;
+		*t = '\0';
+		t2 = strchr(++t, '[');
+		if (t2) {
+			*t2 = '\0';
+			parg->count = simple_strtoul(t2 + 1, &t2, 0);
+			if (strcmp(t2, "]") || parg->count == 0)
+				return -EINVAL;
+			if (parg->count > MAX_ARRAY_LEN)
+				return -E2BIG;
+		}
 	}
 	/*
 	 * The default type of $comm should be "string", and it can't be
 	 * dereferenced.
 	 */
 	if (!t && strcmp(arg, "$comm") == 0)
-		t = "string";
-	parg->type = find_fetch_type(t);
+		parg->type = find_fetch_type("string");
+	else
+		parg->type = find_fetch_type(t);
 	if (!parg->type) {
 		pr_info("Unsupported type: %s\n", t);
 		return -EINVAL;
 	}
 	parg->offset = *size;
-	*size += parg->type->size;
+	*size += parg->type->size * (parg->count ?: 1);
+
+	if (parg->count) {
+		len = strlen(parg->type->fmttype) + 6;
+		parg->fmt = kmalloc(len, GFP_KERNEL);
+		if (!parg->fmt)
+			return -ENOMEM;
+		snprintf(parg->fmt, len, "%s[%d]", parg->type->fmttype,
+			 parg->count);
+	}
 
 	code = tmp = kzalloc(sizeof(*code) * FETCH_INSN_MAX, GFP_KERNEL);
 	if (!code)
@@ -391,10 +409,20 @@ int traceprobe_parse_probe_arg(char *arg, ssize_t *size,
 			ret = -EINVAL;
 			goto fail;
 		}
-		/* Since IMM or COMM must be the 1st insn, this is safe */
-		if (code->op == FETCH_OP_IMM || code->op == FETCH_OP_COMM)
+		if (code->op != FETCH_OP_DEREF || parg->count) {
+			/*
+			 * IMM and COMM is pointing actual address, those must
+			 * be kept, and if parg->count != 0, this is an array
+			 * of string pointers instead of string address itself.
+			 */
 			code++;
+			if (code->op != FETCH_OP_NOP) {
+				ret = -E2BIG;
+				goto fail;
+			}
+		}
 		code->op = FETCH_OP_ST_STRING;	/* In DEREF case, replace it */
+		code->size = parg->type->size;
 		parg->dynamic = true;
 	} else if (code->op == FETCH_OP_DEREF) {
 		code->op = FETCH_OP_ST_MEM;
@@ -408,12 +436,29 @@ int traceprobe_parse_probe_arg(char *arg, ssize_t *size,
 		code->op = FETCH_OP_ST_RAW;
 		code->size = parg->type->size;
 	}
+	scode = code;
 	/* Modify operation */
 	if (t != NULL) {
 		ret = __parse_bitfield_probe_arg(t, parg->type, &code);
 		if (ret)
 			goto fail;
 	}
+	/* Loop(Array) operation */
+	if (parg->count) {
+		if (scode->op != FETCH_OP_ST_MEM &&
+		    scode->op != FETCH_OP_ST_STRING) {
+			pr_info("array only accepts memory or address\n");
+			ret = -EINVAL;
+			goto fail;
+		}
+		code++;
+		if (code->op != FETCH_OP_NOP) {
+			ret = -E2BIG;
+			goto fail;
+		}
+		code->op = FETCH_OP_LP_ARRAY;
+		code->param = parg->count;
+	}
 	code++;
 	code->op = FETCH_OP_END;
 
@@ -452,14 +497,17 @@ void traceprobe_free_probe_arg(struct probe_arg *arg)
 	kfree(arg->code);
 	kfree(arg->name);
 	kfree(arg->comm);
+	kfree(arg->fmt);
 }
 
+/* When len=0, we just calculate the needed length */
+#define LEN_OR_ZERO (len ? len - pos : 0)
 static int __set_print_fmt(struct trace_probe *tp, char *buf, int len,
 			   bool is_return)
 {
-	int i;
+	struct probe_arg *parg;
+	int i, j;
 	int pos = 0;
-
 	const char *fmt, *arg;
 
 	if (!is_return) {
@@ -470,33 +518,49 @@ static int __set_print_fmt(struct trace_probe *tp, char *buf, int len,
 		arg = "REC->" FIELD_STRING_FUNC ", REC->" FIELD_STRING_RETIP;
 	}
 
-	/* When len=0, we just calculate the needed length */
-#define LEN_OR_ZERO (len ? len - pos : 0)
-
 	pos += snprintf(buf + pos, LEN_OR_ZERO, "\"%s", fmt);
 
 	for (i = 0; i < tp->nr_args; i++) {
-		pos += snprintf(buf + pos, LEN_OR_ZERO, " %s=%s",
-				tp->args[i].name, tp->args[i].type->fmt);
+		parg = tp->args + i;
+		pos += snprintf(buf + pos, LEN_OR_ZERO, " %s=", parg->name);
+		if (parg->count) {
+			pos += snprintf(buf + pos, LEN_OR_ZERO, "{%s",
+					parg->type->fmt);
+			for (j = 1; j < parg->count; j++)
+				pos += snprintf(buf + pos, LEN_OR_ZERO, ",%s",
+						parg->type->fmt);
+			pos += snprintf(buf + pos, LEN_OR_ZERO, "}");
+		} else
+			pos += snprintf(buf + pos, LEN_OR_ZERO, "%s",
+					parg->type->fmt);
 	}
 
 	pos += snprintf(buf + pos, LEN_OR_ZERO, "\", %s", arg);
 
 	for (i = 0; i < tp->nr_args; i++) {
-		if (strcmp(tp->args[i].type->name, "string") == 0)
+		parg = tp->args + i;
+		if (parg->count) {
+			if (strcmp(parg->type->name, "string") == 0)
+				fmt = ", __get_str(%s[%d])";
+			else
+				fmt = ", REC->%s[%d]";
+			for (j = 0; j < parg->count; j++)
+				pos += snprintf(buf + pos, LEN_OR_ZERO,
+						fmt, parg->name, j);
+		} else {
+			if (strcmp(parg->type->name, "string") == 0)
+				fmt = ", __get_str(%s)";
+			else
+				fmt = ", REC->%s";
 			pos += snprintf(buf + pos, LEN_OR_ZERO,
-					", __get_str(%s)",
-					tp->args[i].name);
-		else
-			pos += snprintf(buf + pos, LEN_OR_ZERO, ", REC->%s",
-					tp->args[i].name);
+					fmt, parg->name);
+		}
 	}
 
-#undef LEN_OR_ZERO
-
 	/* return the length of print_fmt */
 	return pos;
 }
+#undef LEN_OR_ZERO
 
 int traceprobe_set_print_fmt(struct trace_probe *tp, bool is_return)
 {
@@ -524,11 +588,15 @@ int traceprobe_define_arg_fields(struct trace_event_call *event_call,
 	/* Set argument names as fields */
 	for (i = 0; i < tp->nr_args; i++) {
 		struct probe_arg *parg = &tp->args[i];
-
-		ret = trace_define_field(event_call, parg->type->fmttype,
-					 parg->name,
-					 offset + parg->offset,
-					 parg->type->size,
+		const char *fmt = parg->type->fmttype;
+		int size = parg->type->size;
+
+		if (parg->fmt)
+			fmt = parg->fmt;
+		if (parg->count)
+			size *= parg->count;
+		ret = trace_define_field(event_call, fmt, parg->name,
+					 offset + parg->offset, size,
 					 parg->type->is_signed,
 					 FILTER_OTHER);
 		if (ret)