Merge tag 'trace-probes-v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull trace probes updates from Steven Rostedt:

 - New "symstr" type for dynamic events that writes the name of the
   function+offset into the ring buffer and not just the address

 - Prevent kernel symbol processing on addresses in user space probes
   (uprobes).

 - And minor fixes and clean ups

* tag 'trace-probes-v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  tracing/probes: Reject symbol/symstr type for uprobe
  tracing/probes: Add symstr type for dynamic events
  kprobes: kretprobe events missing on 2-core KVM guest
  kprobes: Fix check for probe enabled in kill_kprobe()
  test_kprobes: Fix implicit declaration error of test_kprobes
  tracing: Fix race where eprobes can be called before the event

Documentation/trace/kprobes.rst

@@ -131,8 +131,7 @@ For example, if the function is non-recursive and is called with a
 spinlock held, maxactive = 1 should be enough.  If the function is
 non-recursive and can never relinquish the CPU (e.g., via a semaphore
 or preemption), NR_CPUS should be enough.  If maxactive <= 0, it is
-set to a default value.  If CONFIG_PREEMPT is enabled, the default
-is max(10, 2*NR_CPUS).  Otherwise, the default is NR_CPUS.
+set to a default value: max(10, 2*NR_CPUS).
 
 It's not a disaster if you set maxactive too low; you'll just miss
 some probes.  In the kretprobe struct, the nmissed field is set to

Documentation/trace/kprobetrace.rst

@@ -58,8 +58,8 @@ Synopsis of kprobe_events
   NAME=FETCHARG : Set NAME as the argument name of FETCHARG.
   FETCHARG:TYPE : Set TYPE as the type of FETCHARG. Currently, basic types
 		  (u8/u16/u32/u64/s8/s16/s32/s64), hexadecimal types
-		  (x8/x16/x32/x64), "string", "ustring" and bitfield
-		  are supported.
+		  (x8/x16/x32/x64), "string", "ustring", "symbol", "symstr"
+                  and bitfield are supported.
 
   (\*1) only for the probe on function entry (offs == 0).
   (\*2) only for return probe.
@@ -96,6 +96,10 @@ offset, and container-size (usually 32). The syntax is::
 
 Symbol type('symbol') is an alias of u32 or u64 type (depends on BITS_PER_LONG)
 which shows given pointer in "symbol+offset" style.
+On the other hand, symbol-string type ('symstr') converts the given address to
+"symbol+offset/symbolsize" style and stores it as a null-terminated string.
+With 'symstr' type, you can filter the event with wildcard pattern of the
+symbols, and you don't need to solve symbol name by yourself.
 For $comm, the default type is "string"; any other type is invalid.
 
 .. _user_mem_access:

kernel/kprobes.c

@@ -2213,13 +2213,9 @@ int register_kretprobe(struct kretprobe *rp)
 	rp->kp.post_handler = NULL;
 
 	/* Pre-allocate memory for max kretprobe instances */
-	if (rp->maxactive <= 0) {
-#ifdef CONFIG_PREEMPTION
+	if (rp->maxactive <= 0)
 		rp->maxactive = max_t(unsigned int, 10, 2*num_possible_cpus());
-#else
-		rp->maxactive = num_possible_cpus();
-#endif
-	}
+
 #ifdef CONFIG_KRETPROBE_ON_RETHOOK
 	rp->rh = rethook_alloc((void *)rp, kretprobe_rethook_handler);
 	if (!rp->rh)
@@ -2364,6 +2360,14 @@ static void kill_kprobe(struct kprobe *p)
 
 	lockdep_assert_held(&kprobe_mutex);
 
+	/*
+	 * The module is going away. We should disarm the kprobe which
+	 * is using ftrace, because ftrace framework is still available at
+	 * 'MODULE_STATE_GOING' notification.
+	 */
+	if (kprobe_ftrace(p) && !kprobe_disabled(p) && !kprobes_all_disarmed)
+		disarm_kprobe_ftrace(p);
+
 	p->flags |= KPROBE_FLAG_GONE;
 	if (kprobe_aggrprobe(p)) {
 		/*
@@ -2380,14 +2384,6 @@ static void kill_kprobe(struct kprobe *p)
 	 * the original probed function (which will be freed soon) any more.
 	 */
 	arch_remove_kprobe(p);
-
-	/*
-	 * The module is going away. We should disarm the kprobe which
-	 * is using ftrace, because ftrace framework is still available at
-	 * 'MODULE_STATE_GOING' notification.
-	 */
-	if (kprobe_ftrace(p) && !kprobe_disabled(p) && !kprobes_all_disarmed)
-		disarm_kprobe_ftrace(p);
 }
 
 /* Disable one kprobe */

kernel/trace/trace.c

@@ -5617,7 +5617,7 @@ static const char readme_msg[] =
 	"\t           +|-[u]<offset>(<fetcharg>), \\imm-value, \\\"imm-string\"\n"
 	"\t     type: s8/16/32/64, u8/16/32/64, x8/16/32/64, string, symbol,\n"
 	"\t           b<bit-width>@<bit-offset>/<container-size>, ustring,\n"
-	"\t           <type>\\[<array-size>\\]\n"
+	"\t           symstr, <type>\\[<array-size>\\]\n"
 #ifdef CONFIG_HIST_TRIGGERS
 	"\t    field: <stype> <name>;\n"
 	"\t    stype: u8/u16/u32/u64, s8/s16/s32/s64, pid_t,\n"

kernel/trace/trace_probe.c

@@ -76,9 +76,11 @@ const char PRINT_TYPE_FMT_NAME(string)[] = "\\\"%s\\\"";
 /* Fetch type information table */
 static const struct fetch_type probe_fetch_types[] = {
 	/* Special types */
-	__ASSIGN_FETCH_TYPE("string", string, string, sizeof(u32), 1,
+	__ASSIGN_FETCH_TYPE("string", string, string, sizeof(u32), 1, 1,
 			    "__data_loc char[]"),
-	__ASSIGN_FETCH_TYPE("ustring", string, string, sizeof(u32), 1,
+	__ASSIGN_FETCH_TYPE("ustring", string, string, sizeof(u32), 1, 1,
+			    "__data_loc char[]"),
+	__ASSIGN_FETCH_TYPE("symstr", string, string, sizeof(u32), 1, 1,
 			    "__data_loc char[]"),
 	/* Basic types */
 	ASSIGN_FETCH_TYPE(u8,  u8,  0),
@@ -98,10 +100,15 @@ static const struct fetch_type probe_fetch_types[] = {
 	ASSIGN_FETCH_TYPE_END
 };
 
-static const struct fetch_type *find_fetch_type(const char *type)
+static const struct fetch_type *find_fetch_type(const char *type, unsigned long flags)
 {
 	int i;
 
+	/* Reject the symbol/symstr for uprobes */
+	if (type && (flags & TPARG_FL_USER) &&
+	    (!strcmp(type, "symbol") || !strcmp(type, "symstr")))
+		return NULL;
+
 	if (!type)
 		type = DEFAULT_FETCH_TYPE_STR;
 
@@ -119,13 +126,13 @@ static const struct fetch_type *find_fetch_type(const char *type)
 
 		switch (bs) {
 		case 8:
-			return find_fetch_type("u8");
+			return find_fetch_type("u8", flags);
 		case 16:
-			return find_fetch_type("u16");
+			return find_fetch_type("u16", flags);
 		case 32:
-			return find_fetch_type("u32");
+			return find_fetch_type("u32", flags);
 		case 64:
-			return find_fetch_type("u64");
+			return find_fetch_type("u64", flags);
 		default:
 			goto fail;
 		}
@@ -478,7 +485,7 @@ parse_probe_arg(char *arg, const struct fetch_type *type,
 					    DEREF_OPEN_BRACE);
 			return -EINVAL;
 		} else {
-			const struct fetch_type *t2 = find_fetch_type(NULL);
+			const struct fetch_type *t2 = find_fetch_type(NULL, flags);
 
 			*tmp = '\0';
 			ret = parse_probe_arg(arg, t2, &code, end, flags, offs);
@@ -630,9 +637,9 @@ static int traceprobe_parse_probe_arg_body(const char *argv, ssize_t *size,
 		/* The type of $comm must be "string", and not an array. */
 		if (parg->count || (t && strcmp(t, "string")))
 			goto out;
-		parg->type = find_fetch_type("string");
+		parg->type = find_fetch_type("string", flags);
 	} else
-		parg->type = find_fetch_type(t);
+		parg->type = find_fetch_type(t, flags);
 	if (!parg->type) {
 		trace_probe_log_err(offset + (t ? (t - arg) : 0), BAD_TYPE);
 		goto out;
@@ -662,8 +669,16 @@ static int traceprobe_parse_probe_arg_body(const char *argv, ssize_t *size,
 
 	ret = -EINVAL;
 	/* Store operation */
-	if (!strcmp(parg->type->name, "string") ||
-	    !strcmp(parg->type->name, "ustring")) {
+	if (parg->type->is_string) {
+		if (!strcmp(parg->type->name, "symstr")) {
+			if (code->op != FETCH_OP_REG && code->op != FETCH_OP_STACK &&
+			    code->op != FETCH_OP_RETVAL && code->op != FETCH_OP_ARG &&
+			    code->op != FETCH_OP_DEREF && code->op != FETCH_OP_TP_ARG) {
+				trace_probe_log_err(offset + (t ? (t - arg) : 0),
+						    BAD_SYMSTRING);
+				goto fail;
+			}
+		} else {
 			if (code->op != FETCH_OP_DEREF && code->op != FETCH_OP_UDEREF &&
 			    code->op != FETCH_OP_IMM && code->op != FETCH_OP_COMM &&
 			    code->op != FETCH_OP_DATA && code->op != FETCH_OP_TP_ARG) {
@@ -671,7 +686,9 @@ static int traceprobe_parse_probe_arg_body(const char *argv, ssize_t *size,
 						    BAD_STRING);
 				goto fail;
 			}
-		if ((code->op == FETCH_OP_IMM || code->op == FETCH_OP_COMM ||
+		}
+		if (!strcmp(parg->type->name, "symstr") ||
+		    (code->op == FETCH_OP_IMM || code->op == FETCH_OP_COMM ||
 		     code->op == FETCH_OP_DATA) || code->op == FETCH_OP_TP_ARG ||
 		     parg->count) {
 			/*
@@ -679,6 +696,8 @@ static int traceprobe_parse_probe_arg_body(const char *argv, ssize_t *size,
 			 * must be kept, and if parg->count != 0, this is an
 			 * array of string pointers instead of string address
 			 * itself.
+			 * For the symstr, it doesn't need to dereference, thus
+			 * it just get the value.
 			 */
 			code++;
 			if (code->op != FETCH_OP_NOP) {
@@ -690,6 +709,8 @@ static int traceprobe_parse_probe_arg_body(const char *argv, ssize_t *size,
 		if (!strcmp(parg->type->name, "ustring") ||
 		    code->op == FETCH_OP_UDEREF)
 			code->op = FETCH_OP_ST_USTRING;
+		else if (!strcmp(parg->type->name, "symstr"))
+			code->op = FETCH_OP_ST_SYMSTR;
 		else
 			code->op = FETCH_OP_ST_STRING;
 		code->size = parg->type->size;
@@ -919,8 +940,7 @@ static int __set_print_fmt(struct trace_probe *tp, char *buf, int len,
 	for (i = 0; i < tp->nr_args; i++) {
 		parg = tp->args + i;
 		if (parg->count) {
-			if ((strcmp(parg->type->name, "string") == 0) ||
-			    (strcmp(parg->type->name, "ustring") == 0))
+			if (parg->type->is_string)
 				fmt = ", __get_str(%s[%d])";
 			else
 				fmt = ", REC->%s[%d]";
@@ -928,8 +948,7 @@ static int __set_print_fmt(struct trace_probe *tp, char *buf, int len,
 				pos += snprintf(buf + pos, LEN_OR_ZERO,
 						fmt, parg->name, j);
 		} else {
-			if ((strcmp(parg->type->name, "string") == 0) ||
-			    (strcmp(parg->type->name, "ustring") == 0))
+			if (parg->type->is_string)
 				fmt = ", __get_str(%s)";
 			else
 				fmt = ", REC->%s";

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)	\
+#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)
 
@@ -353,7 +358,8 @@ int trace_probe_create(const char *raw_command, int (*createfn)(int, const char
 #define TPARG_FL_KERNEL BIT(1)
 #define TPARG_FL_FENTRY BIT(2)
 #define TPARG_FL_TPOINT BIT(3)
-#define TPARG_FL_MASK	GENMASK(3, 0)
+#define TPARG_FL_USER   BIT(4)
+#define TPARG_FL_MASK	GENMASK(4, 0)
 
 extern int traceprobe_parse_probe_arg(struct trace_probe *tp, int i,
 				const char *argv, unsigned int flags);
@@ -431,6 +437,7 @@ 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"),	\

kernel/trace/trace_probe_tmpl.h

@@ -67,6 +67,37 @@ probe_mem_read(void *dest, void *src, size_t size);
 static nokprobe_inline int
 probe_mem_read_user(void *dest, void *src, size_t size);
 
+static nokprobe_inline int
+fetch_store_symstrlen(unsigned long addr)
+{
+	char namebuf[KSYM_SYMBOL_LEN];
+	int ret;
+
+	ret = sprint_symbol(namebuf, addr);
+	if (ret < 0)
+		return 0;
+
+	return ret + 1;
+}
+
+/*
+ * Fetch a null-terminated symbol string + offset. Caller MUST set *(u32 *)buf
+ * with max length and relative data location.
+ */
+static nokprobe_inline int
+fetch_store_symstring(unsigned long addr, void *dest, void *base)
+{
+	int maxlen = get_loc_len(*(u32 *)dest);
+	void *__dest;
+
+	if (unlikely(!maxlen))
+		return -ENOMEM;
+
+	__dest = get_loc_data(dest, base);
+
+	return sprint_symbol(__dest, addr);
+}
+
 /* From the 2nd stage, routine is same */
 static nokprobe_inline int
 process_fetch_insn_bottom(struct fetch_insn *code, unsigned long val,
@@ -99,17 +130,23 @@ process_fetch_insn_bottom(struct fetch_insn *code, unsigned long val,
 stage3:
 	/* 3rd stage: store value to buffer */
 	if (unlikely(!dest)) {
-		if (code->op == FETCH_OP_ST_STRING) {
+		switch (code->op) {
+		case FETCH_OP_ST_STRING:
 			ret = fetch_store_strlen(val + code->offset);
 			code++;
 			goto array;
-		} else if (code->op == FETCH_OP_ST_USTRING) {
+		case FETCH_OP_ST_USTRING:
 			ret += fetch_store_strlen_user(val + code->offset);
 			code++;
 			goto array;
-		} else
+		case FETCH_OP_ST_SYMSTR:
+			ret += fetch_store_symstrlen(val + code->offset);
+			code++;
+			goto array;
+		default:
 			return -EILSEQ;
 		}
+	}
 
 	switch (code->op) {
 	case FETCH_OP_ST_RAW:
@@ -129,6 +166,10 @@ process_fetch_insn_bottom(struct fetch_insn *code, unsigned long val,
 		loc = *(u32 *)dest;
 		ret = fetch_store_string_user(val + code->offset, dest, base);
 		break;
+	case FETCH_OP_ST_SYMSTR:
+		loc = *(u32 *)dest;
+		ret = fetch_store_symstring(val + code->offset, dest, base);
+		break;
 	default:
 		return -EILSEQ;
 	}

kernel/trace/trace_uprobe.c

@@ -691,7 +691,8 @@ static int __trace_uprobe_create(int argc, const char **argv)
 	for (i = 0; i < argc && i < MAX_TRACE_ARGS; i++) {
 		trace_probe_log_set_index(i + 2);
 		ret = traceprobe_parse_probe_arg(&tu->tp, i, argv[i],
-					is_return ? TPARG_FL_RETURN : 0);
+					(is_return ? TPARG_FL_RETURN : 0) |
+					TPARG_FL_USER);
 		if (ret)
 			goto error;
 	}

tools/testing/selftests/ftrace/test.d/kprobe/uprobe_syntax_errors.tc

@@ -23,4 +23,9 @@ check_error 'p /bin/sh:10^%hoge'	# BAD_ADDR_SUFFIX
 check_error 'p /bin/sh:10(10)^%return'	# BAD_REFCNT_SUFFIX
 fi
 
+# symstr is not supported by uprobe
+if grep -q ".*symstr.*" README; then
+check_error 'p /bin/sh:10 $stack0:^symstr'	# BAD_TYPE
+fi
+
 exit 0