[PATCH v7 2/8] Introduce new filtering architecture

Nikolay Marchuk marchuk.nikolay.a at gmail.com
Fri Aug 11 10:43:47 UTC 2017


This change introduces new filtering architecture primitives: filter,
filter_action and bool_expression. Filtering is now done after decoding of
syscall and tcp->qual_flg stores filtering results.

* basic_actions.c: New file.
* basic_filters.c (number_isset): Return bool.
(add_number_to_set): Make static.
(qualify_syscall_number): Rename to parse_syscall_number.
(qualify_syscall_regex): Rename to parse_syscall_regex.
(qualify_syscall_class): Rename to parse_syscall_class.
(qualify_syscall_name): Rename to parse_syscall_name.
(qualify_syscall): Rename to parse_syscall, use renamed functions.
(qualify_syscall_tokens): Rename to parse_syscall_set, make static,
remove "name" argument (assume "system call"), remove 'handle_inversion'
label, remove additional clearing of the sets.
(qualify_tokens): Rename to parse_set, remove 'handle_inversion' label,
remove additional clearing of the set.
(parse_syscall_filter, parse_fd_filter, run_syscall_filter,
run_fd_filter, free_syscall_filter, free_fd_filter): New functions.
* defs.h (struct inject_opts): Add init flag.
(QUAL_READ, QUAL_WRITE): Change description.
(dump_read, dump_write): Add macros for checking QUAL_READ/QUAL_WRITE.
(read_set, write_set): Remove global set variables.
(qualify, qual_flags): Remove old declarations ...
(filter_syscall, parse_qualify_filter, filtering_parsing_finish):
 ... and add new declarations.
* filter.c: New file.
* filter.h: Change declarations.
* filter_action.c: New file.
* filter_expression.c: Likewise.
* filter_qualify.c (read_set, write_set, abbrev_set, inject_set, raw_set,
trace_set, verbose_set): Remove set variables.
(parse_inject_expression): Remove function.
(parse_inject_common_args): New function.
(qualify_read): Rename to parse_read.
(qualify_write): Rename to parse_write.
(qualify_signals): Use parse_set function. Add clearing of the set.
(qualify_trace): Rename to parse_trace.
(qualify_abbrev): Rename to parse_abbrev.
(qualify_verbose): Rename to parse_verbose.
(qualify_raw): Rename to parse_raw.
(qualify_inject_common): Rename to parse_inject_common_qualify, use
new filters.
(qualify_fault): Rename to parse_fault.
(qualify_inject): Rename to parse_inject.
(qualify): Rename to parse_qualify_filter.
(qual_flags): Remove function.
* Makefile.am (strace_SOURCES): Add new files.
* strace.c (init): Use new filtering for -e option.
(trace_syscall): Add filtering after syscall decoding.
* syscall.c (decode_socket_subcall): Remove qual_flags from decoder.
(decode_ipc_subcall): Likewise.
(decode_mips_subcall): Likewise.
(get_scno): Likewise.
(inject_vec, tamper_with_syscall_entering): Remove inject_vec support code.
(dumpio): Check new macros instead of global sets.
* tests/filtering_syscall-syntax.test: Add syscall set syntax testing
of inject and fault.
* tests/qual_fault-syntax.test: Move syscall set syntax testing to
filtering_syscall-syntax.test.
* tests/qual_inject-syntax.test: Likewise.
---
 Makefile.am                         |   4 +
 basic_actions.c                     | 147 ++++++++++++++++++++++
 basic_filters.c                     | 125 +++++++++++++------
 defs.h                              |  14 ++-
 filter.c                            | 146 ++++++++++++++++++++++
 filter.h                            |  37 +++++-
 filter_action.c                     | 230 ++++++++++++++++++++++++++++++++++
 filter_expression.c                 | 235 +++++++++++++++++++++++++++++++++++
 filter_qualify.c                    | 239 ++++++++++++++++--------------------
 strace.c                            |  18 +--
 syscall.c                           |  24 +---
 tests/filtering_syscall-syntax.test |  24 +++-
 tests/qual_fault-syntax.test        |  26 ++--
 tests/qual_inject-syntax.test       |  27 ++--
 14 files changed, 1052 insertions(+), 244 deletions(-)
 create mode 100644 basic_actions.c
 create mode 100644 filter.c
 create mode 100644 filter_action.c
 create mode 100644 filter_expression.c

diff --git a/Makefile.am b/Makefile.am
index 5ec0fa35..84df39a8 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -86,6 +86,7 @@ strace_SOURCES =	\
 	affinity.c	\
 	aio.c		\
 	alpha.c		\
+	basic_actions.c	\
 	basic_filters.c	\
 	bind.c		\
 	bjm.c		\
@@ -133,7 +134,10 @@ strace_SOURCES =	\
 	fetch_struct_statfs.c \
 	file_handle.c	\
 	file_ioctl.c	\
+	filter_action.c	\
+	filter_expression.c \
 	filter_qualify.c \
+	filter.c	\
 	filter.h	\
 	flock.c		\
 	flock.h		\
diff --git a/basic_actions.c b/basic_actions.c
new file mode 100644
index 00000000..5a1ebf8d
--- /dev/null
+++ b/basic_actions.c
@@ -0,0 +1,147 @@
+/*
+ * Copyright (c) 2017 Nikolay Marchuk <marchuk.nikolay.a at gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "defs.h"
+#include "filter.h"
+
+bool
+is_traced(struct tcb *tcp)
+{
+	return (tcp->qual_flg & QUAL_TRACE);
+}
+
+bool
+not_injected(struct tcb *tcp)
+{
+	return !(tcp->qual_flg & QUAL_INJECT);
+}
+
+void *
+parse_null(const char *str)
+{
+	return NULL;
+}
+
+void
+free_null(void *_priv_data)
+{
+	return;
+}
+
+void
+apply_trace(struct tcb *tcp, void *_priv_data)
+{
+	if (!tracing_paths || pathtrace_match(tcp))
+		tcp->qual_flg |= QUAL_TRACE;
+}
+
+void
+apply_inject(struct tcb *tcp, void *_priv_data)
+{
+	struct inject_opts *opts = _priv_data;
+
+	tcp->qual_flg |= QUAL_INJECT;
+	if (!tcp->inject_vec[current_personality])
+		tcp->inject_vec[current_personality] =
+			xcalloc(nsyscalls, sizeof(struct inject_opts));
+	if (scno_in_range(tcp->scno)
+	    && !tcp->inject_vec[current_personality][tcp->scno].init)
+		tcp->inject_vec[current_personality][tcp->scno] = *opts;
+}
+
+static void *
+parse_inject_common(const char *str, bool fault_tokens_only,
+		    const char *description)
+{
+	struct inject_opts *opts = xmalloc(sizeof(struct inject_opts));
+	char *buf = str ? xstrdup(str) : NULL;
+
+	parse_inject_common_args(buf, opts, ";", fault_tokens_only);
+	if (!opts->init)
+		error_msg_and_die("invalid %s '%s'", description, str);
+	free(buf);
+	return opts;
+}
+
+void *
+parse_inject(const char *str)
+{
+	return parse_inject_common(str, false, "inject argument");
+}
+
+void free_inject(void *_priv_data)
+{
+	free(_priv_data);
+}
+
+void
+apply_fault(struct tcb *tcp, void *_priv_data)
+{
+	apply_inject(tcp, _priv_data);
+}
+
+void *
+parse_fault(const char *str)
+{
+	return parse_inject_common(str, true, "fault argument");
+}
+
+void
+free_fault(void *_priv_data)
+{
+	free_inject(_priv_data);
+}
+
+void
+apply_read(struct tcb *tcp, void *_priv_data)
+{
+	tcp->qual_flg |= QUAL_READ;
+}
+
+void
+apply_write(struct tcb *tcp, void *_priv_data)
+{
+	tcp->qual_flg |= QUAL_WRITE;
+}
+
+void
+apply_raw(struct tcb *tcp, void *_priv_data)
+{
+	tcp->qual_flg |= QUAL_RAW;
+}
+
+void
+apply_abbrev(struct tcb *tcp, void *_priv_data)
+{
+	tcp->qual_flg |= QUAL_ABBREV;
+}
+
+void
+apply_verbose(struct tcb *tcp, void *_priv_data)
+{
+	tcp->qual_flg |= QUAL_VERBOSE;
+}
diff --git a/basic_filters.c b/basic_filters.c
index 1dbdeac8..6e2ec39a 100644
--- a/basic_filters.c
+++ b/basic_filters.c
@@ -48,7 +48,8 @@ number_setbit(const unsigned int i, number_slot_t *const vec)
 static bool
 number_isset(const unsigned int i, const number_slot_t *const vec)
 {
-	return vec[i / BITS_PER_SLOT] & ((number_slot_t) 1 << (i % BITS_PER_SLOT));
+	return (vec[i / BITS_PER_SLOT]
+	       & ((number_slot_t) 1 << (i % BITS_PER_SLOT))) ? true : false;
 }
 
 static void
@@ -62,7 +63,7 @@ reallocate_number_set(struct number_set *const set, const unsigned int new_nslot
 	set->nslots = new_nslots;
 }
 
-void
+static void
 add_number_to_set(const unsigned int number, struct number_set *const set)
 {
 	reallocate_number_set(set, number / BITS_PER_SLOT + 1);
@@ -77,7 +78,7 @@ is_number_in_set(const unsigned int number, const struct number_set *const set)
 }
 
 static bool
-qualify_syscall_number(const char *s, struct number_set *set)
+parse_syscall_number(const char *s, struct number_set *set)
 {
 	int n = string_to_uint(s);
 	if (n < 0)
@@ -108,7 +109,7 @@ regerror_msg_and_die(int errcode, const regex_t *preg,
 }
 
 static bool
-qualify_syscall_regex(const char *s, struct number_set *set)
+parse_syscall_regex(const char *s, struct number_set *set)
 {
 	regex_t preg;
 	int rc;
@@ -180,7 +181,7 @@ lookup_class(const char *s)
 }
 
 static bool
-qualify_syscall_class(const char *s, struct number_set *set)
+parse_syscall_class(const char *s, struct number_set *set)
 {
 	const unsigned int n = lookup_class(s);
 	if (!n)
@@ -203,7 +204,7 @@ qualify_syscall_class(const char *s, struct number_set *set)
 }
 
 static bool
-qualify_syscall_name(const char *s, struct number_set *set)
+parse_syscall_name(const char *s, struct number_set *set)
 {
 	unsigned int p;
 	bool found = false;
@@ -225,7 +226,7 @@ qualify_syscall_name(const char *s, struct number_set *set)
 }
 
 static bool
-qualify_syscall(const char *token, struct number_set *set)
+parse_syscall(const char *token, struct number_set *set)
 {
 	bool ignore_fail = false;
 
@@ -234,11 +235,11 @@ qualify_syscall(const char *token, struct number_set *set)
 		ignore_fail = true;
 	}
 	if (*token >= '0' && *token <= '9')
-		return qualify_syscall_number(token, set) || ignore_fail;
+		return parse_syscall_number(token, set) || ignore_fail;
 	if (*token == '/')
-		return qualify_syscall_regex(token + 1, set) || ignore_fail;
-	return qualify_syscall_class(token, set)
-	       || qualify_syscall_name(token, set)
+		return parse_syscall_regex(token + 1, set) || ignore_fail;
+	return parse_syscall_class(token, set)
+	       || parse_syscall_name(token, set)
 	       || ignore_fail;
 }
 
@@ -247,24 +248,15 @@ qualify_syscall(const char *token, struct number_set *set)
  * according to STR specification.
  */
 void
-qualify_syscall_tokens(const char *const str, struct number_set *const set,
-		       const char *const name)
+parse_syscall_set(const char *const str, struct number_set *const set)
 {
-	/* Clear all sets. */
 	unsigned int p;
-	for (p = 0; p < SUPPORTED_PERSONALITIES; ++p) {
-		if (set[p].nslots)
-			memset(set[p].vec, 0,
-			       sizeof(*set[p].vec) * set[p].nslots);
-		set[p].not = false;
-	}
+	const char *s = str;
 
 	/*
 	 * Each leading ! character means inversion
 	 * of the remaining specification.
 	 */
-	const char *s = str;
-handle_inversion:
 	while (*s == '!') {
 		for (p = 0; p < SUPPORTED_PERSONALITIES; ++p) {
 			set[p].not = !set[p].not;
@@ -280,16 +272,18 @@ handle_inversion:
 		 */
 		return;
 	} else if (strcmp(s, "all") == 0) {
-		s = "!none";
-		goto handle_inversion;
+		for (p = 0; p < SUPPORTED_PERSONALITIES; ++p) {
+			set[p].not = !set[p].not;
+		}
+		return;
 	}
 
 	/*
 	 * Split the string into comma separated tokens.
-	 * For each token, call qualify_syscall that will take care
+	 * For each token, call parse_syscall that will take care
 	 * if adding appropriate syscall numbers to sets.
 	 * The absence of tokens or a negative return code
-	 * from qualify_syscall is a fatal error.
+	 * from parse_syscall is a fatal error.
 	 */
 	char *copy = xstrdup(s);
 	char *saveptr = NULL;
@@ -298,37 +292,62 @@ handle_inversion:
 
 	for (token = strtok_r(copy, ",", &saveptr); token;
 	     token = strtok_r(NULL, ",", &saveptr)) {
-		done = qualify_syscall(token, set);
+		done = parse_syscall(token, set);
 		if (!done) {
-			error_msg_and_die("invalid %s '%s'", name, token);
+			error_msg_and_die("invalid system call '%s'", token);
 		}
 	}
 
 	free(copy);
 
 	if (!done) {
-		error_msg_and_die("invalid %s '%s'", name, str);
+		error_msg_and_die("invalid system call '%s'", str);
+	}
+}
+
+void *
+parse_syscall_filter(const char *str)
+{
+	struct number_set *set = xcalloc(SUPPORTED_PERSONALITIES,
+					 sizeof(struct number_set));
+
+	parse_syscall_set(str, set);
+	return set;
+}
+
+bool
+run_syscall_filter(struct tcb *tcp, void *_priv_data)
+{
+	struct number_set *set = _priv_data;
+
+	return is_number_in_set(tcp->scno, &set[current_personality]);
+}
+
+void
+free_syscall_filter(void *_priv_data)
+{
+	struct number_set *set = _priv_data;
+	unsigned int p;
+
+	for (p = 0; p < SUPPORTED_PERSONALITIES; ++p) {
+		free(set[p].vec);
 	}
+	free(set);
 }
 
 /*
  * Add numbers to SET according to STR specification.
  */
 void
-qualify_tokens(const char *const str, struct number_set *const set,
+parse_set(const char *const str, struct number_set *const set,
 	       string_to_uint_func func, const char *const name)
 {
-	/* Clear the set. */
-	if (set->nslots)
-		memset(set->vec, 0, sizeof(*set->vec) * set->nslots);
-	set->not = false;
+	const char *s = str;
 
 	/*
 	 * Each leading ! character means inversion
 	 * of the remaining specification.
 	 */
-	const char *s = str;
-handle_inversion:
 	while (*s == '!') {
 		set->not = !set->not;
 		++s;
@@ -341,8 +360,8 @@ handle_inversion:
 		 */
 		return;
 	} else if (strcmp(s, "all") == 0) {
-		s = "!none";
-		goto handle_inversion;
+		set->not = !set->not;
+		return;
 	}
 
 	/*
@@ -373,3 +392,33 @@ handle_inversion:
 		error_msg_and_die("invalid %s '%s'", name, str);
 	}
 }
+
+void *
+parse_fd_filter(const char *str)
+{
+	struct number_set *set = xcalloc(1, sizeof(struct number_set));
+
+	parse_set(str, set, string_to_uint, "descriptor");
+	return set;
+}
+
+bool
+run_fd_filter(struct tcb *tcp, void *_priv_data)
+{
+	int fd = tcp->u_arg[0];
+	struct number_set *set = _priv_data;
+
+	if (fd < 0)
+		return false;
+	return is_number_in_set(fd, set);
+}
+
+void
+free_fd_filter(void *_priv_data)
+{
+	struct number_set *set = _priv_data;
+
+	free(set->vec);
+	free(set);
+	return;
+}
diff --git a/defs.h b/defs.h
index 2efbfa36..69cd765e 100644
--- a/defs.h
+++ b/defs.h
@@ -199,6 +199,7 @@ struct inject_opts {
 	uint16_t step;
 	uint16_t signo;
 	int rval;
+	bool init;
 };
 
 #define MAX_ERRNO_VALUE			4095
@@ -268,8 +269,8 @@ struct tcb {
 #define QUAL_RAW	0x008	/* print all args in hex for this syscall */
 #define QUAL_INJECT	0x010	/* tamper with this system call on purpose */
 #define QUAL_SIGNAL	0x100	/* report events with this signal */
-#define QUAL_READ	0x200	/* dump data read from this file descriptor */
-#define QUAL_WRITE	0x400	/* dump data written to this file descriptor */
+#define QUAL_READ	0x200	/* dump data read in this syscall */
+#define QUAL_WRITE	0x400	/* dump data written in this syscall */
 
 #define DEFAULT_QUAL_FLAGS (QUAL_TRACE | QUAL_ABBREV | QUAL_VERBOSE)
 
@@ -278,6 +279,8 @@ struct tcb {
 #define syserror(tcp)	((tcp)->u_error != 0)
 #define verbose(tcp)	((tcp)->qual_flg & QUAL_VERBOSE)
 #define abbrev(tcp)	((tcp)->qual_flg & QUAL_ABBREV)
+#define dump_read(tcp)	((tcp)->qual_flg & QUAL_READ)
+#define dump_write(tcp)	((tcp)->qual_flg & QUAL_WRITE)
 #define filtered(tcp)	((tcp)->flags & TCB_FILTERED)
 #define hide_log(tcp)	((tcp)->flags & TCB_HIDE_LOG)
 
@@ -662,13 +665,12 @@ print_struct_statfs64(struct tcb *, kernel_ulong_t addr, kernel_ulong_t size);
 extern void print_ifindex(unsigned int);
 
 struct number_set;
-extern struct number_set read_set;
-extern struct number_set write_set;
 extern struct number_set signal_set;
 
 extern bool is_number_in_set(unsigned int number, const struct number_set *);
-extern void qualify(const char *);
-extern unsigned int qual_flags(const unsigned int);
+extern void filtering_parsing_finish(void);
+extern void filter_syscall(struct tcb *);
+extern void parse_qualify_filter(const char *);
 
 #define DECL_IOCTL(name)						\
 extern int								\
diff --git a/filter.c b/filter.c
new file mode 100644
index 00000000..d51b3183
--- /dev/null
+++ b/filter.c
@@ -0,0 +1,146 @@
+/*
+ * Copyright (c) 2017 Nikolay Marchuk <marchuk.nikolay.a at gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "defs.h"
+#include "filter.h"
+
+#define DECL_FILTER(name)						\
+extern void *								\
+parse_ ## name ## _filter(const char *);				\
+extern bool								\
+run_ ## name ## _filter(struct tcb *, void *);				\
+extern void								\
+free_ ## name ## _filter(void *)					\
+/* End of DECL_FILTER definition. */
+
+DECL_FILTER(syscall);
+DECL_FILTER(fd);
+#undef DECL_FILTER
+
+#define FILTER_TYPE(name)						\
+{#name, parse_ ## name ## _filter, run_ ## name ## _filter,		\
+	free_ ## name ## _filter}
+/* End of FILTER_TYPE definition. */
+
+static const struct filter_type {
+	const char *name;
+	void *(*parse_filter)(const char *);
+	bool (*run_filter)(struct tcb *, void *);
+	void (*free_priv_data)(void *);
+} filter_types[] = {
+	FILTER_TYPE(syscall),
+	FILTER_TYPE(fd),
+};
+#undef FILTER_TYPE
+
+struct filter {
+	const struct filter_type *type;
+	void *_priv_data;
+};
+
+static const struct filter_type *
+lookup_filter_type(const char *str)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(filter_types); i++) {
+		if (!strcmp(filter_types[i].name, str))
+			return &filter_types[i];
+	}
+	return NULL;
+}
+
+struct filter *
+add_filter_to_array(struct filter **filters, unsigned int *nfilters,
+		    const char *name)
+{
+	const struct filter_type *type = lookup_filter_type(name);
+	struct filter *filter;
+
+	if (!type)
+		error_msg_and_die("invalid filter '%s'", name);
+	*filters = xreallocarray(*filters, ++(*nfilters),
+				 sizeof(struct filter));
+	filter = &((*filters)[*nfilters - 1]);
+	filter->type = type;
+	return filter;
+}
+
+void
+parse_filter(struct filter *filter, const char *str)
+{
+	filter->_priv_data = filter->type->parse_filter(str);
+}
+
+static bool
+run_filter(struct tcb *tcp, struct filter *filter)
+{
+	return filter->type->run_filter(tcp, filter->_priv_data);
+}
+
+void
+run_filters(struct tcb *tcp, struct filter *filters, unsigned int nfilters,
+	    bool *variables_buf)
+{
+	unsigned int i;
+
+	for (i = 0; i < nfilters; ++i)
+		variables_buf[i] = run_filter(tcp, &filters[i]);
+}
+
+void
+free_filter(struct filter *filter)
+{
+	if (!filter)
+		return;
+	filter->type->free_priv_data(filter->_priv_data);
+}
+
+void *
+get_filter_priv_data(struct filter *filter)
+{
+	return filter ? filter->_priv_data : NULL;
+}
+
+void
+set_filter_priv_data(struct filter *filter, void *_priv_data)
+{
+	if (filter)
+		filter->_priv_data = _priv_data;
+}
+
+void
+set_filters_qualify_mode(struct filter **filters, unsigned int *nfilters)
+{
+	unsigned int i;
+
+	for (i = 0; i < *nfilters - 1; ++i)
+		free_filter(*filters + i);
+	(*filters)[0] = (*filters)[*nfilters - 1];
+	*filters = xreallocarray(*filters, 1, sizeof(struct filter));
+	*nfilters = 1;
+}
diff --git a/filter.h b/filter.h
index eefbd3cb..ec61d0c4 100644
--- a/filter.h
+++ b/filter.h
@@ -29,13 +29,38 @@
 #ifndef STRACE_FILTER_H
 #define STRACE_FILTER_H
 
-struct number_set;
+struct filter;
+
+struct filter_action;
+
+struct bool_expression;
+
 typedef int (*string_to_uint_func)(const char *);
+void parse_set(const char *const, struct number_set *const,
+	       string_to_uint_func, const char *const);
+void parse_inject_common_args(char *, struct inject_opts *, const char *delim,
+			      const bool fault_tokens_only);
+
+/* filter api */
+struct filter* add_filter_to_array(struct filter **, unsigned int *nfilters,
+				   const char *name);
+void parse_filter(struct filter *, const char *str);
+void run_filters(struct tcb *, struct filter *, unsigned int, bool *);
+void free_filter(struct filter *);
+void *get_filter_priv_data(struct filter *);
+void set_filter_priv_data(struct filter *, void *);
+void set_filters_qualify_mode(struct filter **, unsigned int *nfilters);
+
+/* filter action api */
+struct filter *create_filter(struct filter_action *, const char *name);
+struct filter_action *find_or_add_action(const char *);
+void *get_filter_action_priv_data(struct filter_action *);
+void set_filter_action_priv_data(struct filter_action *, void *);
+void set_qualify_mode(struct filter_action *);
 
-void add_number_to_set(unsigned int number, struct number_set *set);
-void qualify_tokens(const char *str, struct number_set *set,
-		    string_to_uint_func func, const char *name);
-void qualify_syscall_tokens(const char *str, struct number_set *set,
-			    const char *name);
+/* filter expression api */
+struct bool_expression *create_expression();
+bool run_expression(struct bool_expression *, bool *, unsigned int);
+void set_expression_qualify_mode(struct bool_expression *);
 
 #endif /* !STRACE_FILTER_H */
diff --git a/filter_action.c b/filter_action.c
new file mode 100644
index 00000000..c040eda6
--- /dev/null
+++ b/filter_action.c
@@ -0,0 +1,230 @@
+/*
+ * Copyright (c) 2017 Nikolay Marchuk <marchuk.nikolay.a at gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "defs.h"
+#include "filter.h"
+
+#define DECL_FILTER_ACTION(name)					\
+extern void								\
+apply_ ## name(struct tcb *, void *)					\
+/* End of DECL_FILTER_ACTION definition. */
+
+DECL_FILTER_ACTION(trace);
+DECL_FILTER_ACTION(inject);
+DECL_FILTER_ACTION(fault);
+DECL_FILTER_ACTION(read);
+DECL_FILTER_ACTION(write);
+DECL_FILTER_ACTION(raw);
+DECL_FILTER_ACTION(abbrev);
+DECL_FILTER_ACTION(verbose);
+#undef DECL_FILTER_ACTION
+
+extern bool is_traced(struct tcb *);
+extern bool not_injected(struct tcb *);
+
+#define DECL_FILTER_ACTION_PARSER(name)					\
+extern void *								\
+parse_ ## name(const char *);						\
+extern void								\
+free_ ## name(void *)							\
+/* End of DECL_FILTER_ACTION_PARSER definition. */
+
+DECL_FILTER_ACTION_PARSER(null);
+DECL_FILTER_ACTION_PARSER(inject);
+DECL_FILTER_ACTION_PARSER(fault);
+#undef DECL_FILTER_ACTION_PARSER
+
+#define FILTER_ACTION_TYPE(NAME, PRIORITY, FLAG, PARSER, PREFILTER)	\
+{#NAME, PRIORITY, FLAG, parse_ ## PARSER, free_ ## PARSER, PREFILTER,	\
+	apply_ ## NAME}
+/* End of FILTER_ACTION_TYPE definition. */
+
+static const struct filter_action_type {
+	const char *name;
+	/* The highest priority is 0. */
+	unsigned int priority;
+	unsigned int qual_flg;
+	void * (*parse_args)(const char *);
+	void (*free_priv_data)(void *);
+	bool (*prefilter)(struct tcb *);
+	void (*apply)(struct tcb *, void *);
+} action_types[] = {
+	FILTER_ACTION_TYPE(trace,	0, QUAL_TRACE,		null,	NULL),
+	FILTER_ACTION_TYPE(inject,	1, QUAL_INJECT,		inject,	not_injected),
+	FILTER_ACTION_TYPE(fault,	1, QUAL_INJECT,		fault,	not_injected),
+	FILTER_ACTION_TYPE(read,	2, QUAL_READ,		null,	is_traced),
+	FILTER_ACTION_TYPE(write,	2, QUAL_WRITE,		null,	is_traced),
+	FILTER_ACTION_TYPE(raw,		2, QUAL_RAW,		null,	is_traced),
+	FILTER_ACTION_TYPE(abbrev,	2, QUAL_ABBREV,		null,	is_traced),
+	FILTER_ACTION_TYPE(verbose,	2, QUAL_VERBOSE,	null,	is_traced),
+};
+#undef FILTER_ACTION_TYPE
+
+struct filter_action {
+	/* Used to correct order of actions with the same priority. */
+	unsigned int id;
+	const struct filter_action_type *type;
+	struct bool_expression *expr;
+	unsigned int nfilters;
+	struct filter *filters;
+	void *_priv_data;
+};
+
+static struct filter_action *filter_actions;
+static unsigned int nfilter_actions;
+
+static bool *variables_buf;
+
+/*
+ * Compares action priorities. If actions have the same priority,
+ * uses LIFO order.
+ */
+static int
+compare_action_priority(const void *a, const void *b)
+{
+	const struct filter_action *action_a = a;
+	const struct filter_action *action_b = b;
+	unsigned int priority_a = action_a->type->priority;
+	unsigned int priority_b = action_b->type->priority;
+
+	if (priority_a != priority_b) {
+		return (priority_a < priority_b) ? -1 : 1;
+	} else {
+		return (action_a->id > action_b->id) ? -1 : 1;
+	}
+}
+
+void
+filtering_parsing_finish(void)
+{
+	unsigned int maxfilters = 0;
+	unsigned int i;
+
+	/* Sort actions by priority */
+	if (nfilter_actions == 0)
+		return;
+	qsort(filter_actions, nfilter_actions, sizeof(struct filter_action),
+	      &compare_action_priority);
+
+	/* Allocate variables_buf sufficient for any action */
+	for (i = 0; i < nfilter_actions; ++i) {
+		if (filter_actions[i].nfilters > maxfilters)
+			maxfilters = filter_actions[i].nfilters;
+	}
+	variables_buf = xcalloc(maxfilters, sizeof(bool));
+}
+
+static const struct filter_action_type *
+lookup_filter_action_type(const char *str)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(action_types); ++i) {
+		if (!strcmp(action_types[i].name, str))
+			return &action_types[i];
+	}
+	return NULL;
+}
+
+static struct filter_action *
+add_action(const struct filter_action_type *type)
+{
+	struct filter_action *action;
+
+	filter_actions = xreallocarray(filter_actions, ++nfilter_actions,
+				       sizeof(struct filter_action));
+	action = &filter_actions[nfilter_actions - 1];
+	memset(action, 0, sizeof(*action));
+	action->id = nfilter_actions - 1;
+	action->type = type;
+	action->expr = create_expression();
+	return action;
+}
+
+struct filter_action *
+find_or_add_action(const char *name)
+{
+	const struct filter_action_type *type = lookup_filter_action_type(name);
+	unsigned int i;
+
+	if (!type)
+		error_msg_and_die("invalid filter action '%s'", name);
+	/* If action takes arguments, add new action */
+	if (type->parse_args != &parse_null)
+		return add_action(type);
+
+	for (i = 0; i < nfilter_actions; ++i) {
+		if (filter_actions[i].type == type)
+			return &filter_actions[i];
+	}
+	return add_action(type);
+}
+
+static void
+run_filter_action(struct tcb *tcp, struct filter_action *action)
+{
+	if (action->type->prefilter && !action->type->prefilter(tcp))
+		return;
+	run_filters(tcp, action->filters, action->nfilters, variables_buf);
+	if (run_expression(action->expr, variables_buf, action->nfilters))
+		action->type->apply(tcp, action->_priv_data);
+}
+
+struct filter *
+create_filter(struct filter_action *action, const char *name)
+{
+	return add_filter_to_array(&action->filters, &action->nfilters, name);
+}
+
+void
+set_qualify_mode(struct filter_action *action)
+{
+	set_filters_qualify_mode(&action->filters, &action->nfilters);
+	set_expression_qualify_mode(action->expr);
+}
+
+void
+filter_syscall(struct tcb *tcp)
+{
+	unsigned int i;
+
+	for (i = 0; i < nfilter_actions; ++i)
+		run_filter_action(tcp, &filter_actions[i]);
+}
+
+void *
+get_filter_action_priv_data(struct filter_action *action)
+{
+	return action ? action->_priv_data : NULL;
+}
+
+void
+set_filter_action_priv_data(struct filter_action *action, void *_priv_data)
+{
+	if (action)
+		action->_priv_data = _priv_data;
+}
diff --git a/filter_expression.c b/filter_expression.c
new file mode 100644
index 00000000..05f8903e
--- /dev/null
+++ b/filter_expression.c
@@ -0,0 +1,235 @@
+/*
+ * Copyright (c) 2017 Nikolay Marchuk <marchuk.nikolay.a at gmail.com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "defs.h"
+#include <stdarg.h>
+
+struct expression_token {
+	enum token_type {
+		TOK_VARIABLE,
+		TOK_OPERATOR
+	} type;
+	union token_data {
+		unsigned int variable_id;
+		enum operator_type {
+			OP_NOT,
+			OP_AND,
+			OP_OR
+		} operator_id;
+	} data;
+};
+
+struct bool_expression {
+	unsigned int ntokens;
+	struct expression_token *tokens;
+};
+
+struct bool_expression *
+create_expression(void)
+{
+	return xcalloc(1, sizeof(struct bool_expression));
+}
+
+static void
+reallocate_expression(struct bool_expression *const expr,
+		      const unsigned int new_ntokens)
+{
+	if (!expr)
+		error_msg_and_die("invalid expression");
+	expr->tokens = xreallocarray(expr->tokens, new_ntokens,
+				     sizeof(*expr->tokens));
+	if (new_ntokens > expr->ntokens)
+		memset(expr->tokens + expr->ntokens, 0,
+		       sizeof(*expr->tokens) * (new_ntokens - expr->ntokens));
+	expr->ntokens = new_ntokens;
+}
+
+void
+set_expression_qualify_mode(struct bool_expression *expr)
+{
+	if (!expr)
+		error_msg_and_die("invalid expression");
+	reallocate_expression(expr, 1);
+	expr->tokens[0].type = TOK_VARIABLE;
+	expr->tokens[0].data.variable_id = 0;
+}
+
+ATTRIBUTE_FORMAT((printf, 3, 4))
+static int
+printf_append(char **ptr, char *end, const char *fmt, ...)
+	{
+		int ret;
+		va_list args;
+
+		va_start(args, fmt);
+		ret = vsnprintf(*ptr, end - *ptr, fmt, args);
+		va_end(args);
+
+		if (ret < 0)
+			return ret;
+
+		*ptr += MIN(ret, end - *ptr);
+
+		return ret;
+}
+
+/* Print full diagnostics for corrupted expression */
+static void
+handle_corrupted_expression(struct bool_expression *expr, bool *stack,
+			    unsigned int stack_size, unsigned int current_pos,
+			    bool *variables, unsigned int variables_num)
+{
+	char *buf, *pos, *end;
+	unsigned int buf_size;
+	unsigned int i;
+
+	/* Calculate buffer size. */
+	buf_size = sizeof("corrupted filter expression:");
+	buf_size += sizeof("expression (ntokens = ):")
+		    + 3 * sizeof(unsigned int)
+		    + (sizeof("op_") + 3 * sizeof(int)) * expr->ntokens;
+	buf_size += sizeof("variables (nvariables = ):") + 3 * sizeof(int)
+		    + sizeof("false") * variables_num;
+	buf_size += sizeof("current position: ") + 3 * sizeof(int);
+	buf_size += sizeof("stack (stack_size = ):") + 3 * sizeof(int)
+		    + sizeof("false") * stack_size;
+
+	buf = xcalloc(buf_size, 1);
+	pos = buf;
+	end = buf + buf_size;
+
+	printf_append(&pos, end, "corrupted filter expression:\n");
+
+	/* Print expression. */
+	printf_append(&pos, end, "expression (ntokens = %u):", expr->ntokens);
+	for (i = 0; i < expr->ntokens; ++i) {
+		switch (expr->tokens[i].type) {
+		case TOK_VARIABLE:
+			printf_append(&pos, end, " v_%u",
+				      expr->tokens[i].data.variable_id);
+			break;
+		case TOK_OPERATOR:
+			switch (expr->tokens[i].data.operator_id) {
+			case OP_NOT:
+				printf_append(&pos, end, " not");
+				break;
+			case OP_AND:
+				printf_append(&pos, end, " and");
+				break;
+			case OP_OR:
+				printf_append(&pos, end, " or");
+			default:
+				printf_append(&pos, end, " op_%d",
+					      expr->tokens[i].data.operator_id);
+			}
+		default:
+			printf_append(&pos, end, " ?_%d", expr->tokens[i].type);
+		}
+	}
+	printf_append(&pos, end, "\n");
+
+	/* Print variables. */
+	printf_append(&pos, end, "variables (nvariables = %u):", variables_num);
+	for (i = 0; i < variables_num; ++i)
+		printf_append(&pos, end, variables[i] ? " true" : " false");
+	printf_append(&pos, end, "\n");
+
+	printf_append(&pos, end, "current position: %u\n", current_pos);
+
+	/* Print current stack state. */
+	printf_append(&pos, end, "stack (stack_size = %u):", stack_size);
+	for (i = 0; i < stack_size; ++i)
+		printf_append(&pos, end, stack[i] ? " true" : " false");
+
+	error_msg_and_die("%s", buf);
+	free(buf);
+}
+
+#define MAX_STACK_SIZE 32
+
+bool
+run_expression(struct bool_expression *expr, bool *variables,
+	       unsigned int variables_num)
+{
+	bool stack[MAX_STACK_SIZE];
+	unsigned int stack_size = 0;
+	unsigned int i;
+
+	for (i = 0; i < expr->ntokens; ++i) {
+		struct expression_token *tok = &expr->tokens[i];
+
+		switch (tok->type) {
+		case TOK_VARIABLE:
+			if (stack_size == MAX_STACK_SIZE)
+				error_msg_and_die("stack overflow");
+
+			if (tok->data.variable_id >= variables_num)
+				handle_corrupted_expression(expr, stack,
+							    stack_size, i,
+							    variables,
+							    variables_num);
+			stack[stack_size++] = variables[tok->data.variable_id];
+			break;
+		case TOK_OPERATOR:
+			switch (tok->data.operator_id) {
+			case OP_NOT:
+				if (stack_size == 0)
+					handle_corrupted_expression(expr, stack,
+								stack_size, i,
+								variables,
+								variables_num);
+				stack[stack_size - 1] = !stack[stack_size - 1];
+				break;
+			case OP_AND:
+				if (stack_size < 2)
+					handle_corrupted_expression(expr, stack,
+								stack_size, i,
+								variables,
+								variables_num);
+				stack[stack_size - 2] = stack[stack_size - 2]
+						     && stack[stack_size - 1];
+				--stack_size;
+				break;
+			case OP_OR:
+				if (stack_size < 2)
+					handle_corrupted_expression(expr, stack,
+								stack_size, i,
+								variables,
+								variables_num);
+				stack[stack_size - 2] = stack[stack_size - 2]
+						     || stack[stack_size - 1];
+				--stack_size;
+				break;
+			}
+		}
+	}
+
+	if (stack_size != 1)
+		handle_corrupted_expression(expr, stack, stack_size, i,
+					    variables, variables_num);
+	return stack[0];
+}
diff --git a/filter_qualify.c b/filter_qualify.c
index 4283e769..3765f656 100644
--- a/filter_qualify.c
+++ b/filter_qualify.c
@@ -38,16 +38,8 @@ struct number_set {
 	bool not;
 };
 
-struct number_set read_set;
-struct number_set write_set;
 struct number_set signal_set;
 
-static struct number_set abbrev_set[SUPPORTED_PERSONALITIES];
-static struct number_set inject_set[SUPPORTED_PERSONALITIES];
-static struct number_set raw_set[SUPPORTED_PERSONALITIES];
-static struct number_set trace_set[SUPPORTED_PERSONALITIES];
-static struct number_set verbose_set[SUPPORTED_PERSONALITIES];
-
 static int
 sigstr_to_uint(const char *s)
 {
@@ -156,174 +148,174 @@ parse_inject_token(const char *const token, struct inject_opts *const fopts,
 	return true;
 }
 
-static char *
-parse_inject_expression(const char *const s, char **buf,
-			struct inject_opts *const fopts,
-			const bool fault_tokens_only)
+void
+parse_inject_common_args(char *str, struct inject_opts *const opts,
+			 const char *delim, const bool fault_tokens_only)
 {
 	char *saveptr = NULL;
-	char *name = NULL;
 	char *token;
 
-	*buf = xstrdup(s);
-	for (token = strtok_r(*buf, ":", &saveptr); token;
-	     token = strtok_r(NULL, ":", &saveptr)) {
-		if (!name)
-			name = token;
-		else if (!parse_inject_token(token, fopts, fault_tokens_only))
-			goto parse_error;
-	}
+	opts->first = 1;
+	opts->step = 1;
+	opts->rval = INJECT_OPTS_RVAL_DEFAULT;
+	opts->signo = 0;
+	opts->init = false;
 
-	if (name)
-		return name;
+	for (token = strtok_r(str, delim, &saveptr); token;
+	     token = strtok_r(NULL, delim, &saveptr)) {
+		if (!parse_inject_token(token, opts, fault_tokens_only))
+			return;
+	}
 
-parse_error:
-	free(*buf);
-	return *buf = NULL;
+	/* If neither of retval, error, or signal is specified, then ... */
+	if (opts->rval == INJECT_OPTS_RVAL_DEFAULT && !opts->signo) {
+		if (fault_tokens_only) {
+			/* in fault= syntax the default error code is ENOSYS. */
+			opts->rval = -ENOSYS;
+		} else {
+			/* in inject= syntax this is not allowed. */
+			return;
+		}
+	}
+	opts->init = true;
 }
 
 static void
-qualify_read(const char *const str)
+parse_read(const char *const str)
 {
-	qualify_tokens(str, &read_set, string_to_uint, "descriptor");
+	struct filter_action *action = find_or_add_action("read");
+	struct filter *filter = create_filter(action, "fd");
+
+	parse_filter(filter, str);
+	set_qualify_mode(action);
 }
 
 static void
-qualify_write(const char *const str)
+parse_write(const char *const str)
 {
-	qualify_tokens(str, &write_set, string_to_uint, "descriptor");
+	struct filter_action *action = find_or_add_action("write");
+	struct filter *filter = create_filter(action, "fd");
+
+	parse_filter(filter, str);
+	set_qualify_mode(action);
 }
 
 static void
 qualify_signals(const char *const str)
 {
-	qualify_tokens(str, &signal_set, sigstr_to_uint, "signal");
+	/* Clear the set. */
+	if (signal_set.nslots)
+		memset(signal_set.vec, 0,
+		       sizeof(*signal_set.vec) * signal_set.nslots);
+	signal_set.not = false;
+
+	parse_set(str, &signal_set, sigstr_to_uint, "signal");
 }
 
 static void
-qualify_trace(const char *const str)
+parse_trace(const char *const str)
 {
-	qualify_syscall_tokens(str, trace_set, "system call");
+	struct filter_action *action = find_or_add_action("trace");
+	struct filter *filter = create_filter(action, "syscall");
+
+	parse_filter(filter, str);
+	set_qualify_mode(action);
 }
 
 static void
-qualify_abbrev(const char *const str)
+parse_abbrev(const char *const str)
 {
-	qualify_syscall_tokens(str, abbrev_set, "system call");
+	struct filter_action *action = find_or_add_action("abbrev");
+	struct filter *filter = create_filter(action, "syscall");
+
+	parse_filter(filter, str);
+	set_qualify_mode(action);
 }
 
 static void
-qualify_verbose(const char *const str)
+parse_verbose(const char *const str)
 {
-	qualify_syscall_tokens(str, verbose_set, "system call");
+	struct filter_action *action = find_or_add_action("verbose");
+	struct filter *filter = create_filter(action, "syscall");
+
+	parse_filter(filter, str);
+	set_qualify_mode(action);
 }
 
 static void
-qualify_raw(const char *const str)
+parse_raw(const char *const str)
 {
-	qualify_syscall_tokens(str, raw_set, "system call");
+	struct filter_action *action = find_or_add_action("raw");
+	struct filter *filter = create_filter(action, "syscall");
+
+	parse_filter(filter, str);
+	set_qualify_mode(action);
 }
 
 static void
-qualify_inject_common(const char *const str,
-		      const bool fault_tokens_only,
-		      const char *const description)
+parse_inject_common_qualify(const char *const str, const bool fault_tokens_only,
+			    const char *const description)
 {
-	struct inject_opts opts = {
-		.first = 1,
-		.step = 1,
-		.rval = INJECT_OPTS_RVAL_DEFAULT,
-		.signo = 0
-	};
-	char *buf = NULL;
-	char *name = parse_inject_expression(str, &buf, &opts, fault_tokens_only);
-	if (!name) {
-		error_msg_and_die("invalid %s '%s'", description, str);
-	}
-
-	/* If neither of retval, error, or signal is specified, then ... */
-	if (opts.rval == INJECT_OPTS_RVAL_DEFAULT && !opts.signo) {
-		if (fault_tokens_only) {
-			/* in fault= syntax the default error code is ENOSYS. */
-			opts.rval = -ENOSYS;
-		} else {
-			/* in inject= syntax this is not allowed. */
-			error_msg_and_die("invalid %s '%s'", description, str);
-		}
-	}
-
-	struct number_set tmp_set[SUPPORTED_PERSONALITIES];
-	memset(tmp_set, 0, sizeof(tmp_set));
-	qualify_syscall_tokens(name, tmp_set, description);
-
+	struct inject_opts *opts = xmalloc(sizeof(struct inject_opts));
+	char *buf = xstrdup(str);
+	struct filter_action *action;
+	struct filter *filter;
+	char *args = strchr(buf, ':');
+
+	if (args)
+		*(args++) = '\0';
+
+	action = find_or_add_action(fault_tokens_only ? "fault" : "inject");
+	filter = create_filter(action, "syscall");
+	parse_filter(filter, buf);
+	set_qualify_mode(action);
+	parse_inject_common_args(args, opts, ":", fault_tokens_only);
+	if (!opts->init)
+		error_msg_and_die("invalid %s '%s'", description,
+				  args ? args : "");
 	free(buf);
-
-	/*
-	 * Initialize inject_vec accourding to tmp_set.
-	 * Merge tmp_set into inject_set.
-	 */
-	unsigned int p;
-	for (p = 0; p < SUPPORTED_PERSONALITIES; ++p) {
-		if (!tmp_set[p].nslots && !tmp_set[p].not) {
-			continue;
-		}
-
-		if (!inject_vec[p]) {
-			inject_vec[p] = xcalloc(nsyscall_vec[p],
-					       sizeof(*inject_vec[p]));
-		}
-
-		unsigned int i;
-		for (i = 0; i < nsyscall_vec[p]; ++i) {
-			if (is_number_in_set(i, &tmp_set[p])) {
-				add_number_to_set(i, &inject_set[p]);
-				inject_vec[p][i] = opts;
-			}
-		}
-
-		free(tmp_set[p].vec);
-	}
+	set_filter_action_priv_data(action, opts);
 }
 
 static void
-qualify_fault(const char *const str)
+parse_fault(const char *const str)
 {
-	qualify_inject_common(str, true, "fault argument");
+	parse_inject_common_qualify(str, true, "fault argument");
 }
 
 static void
-qualify_inject(const char *const str)
+parse_inject(const char *const str)
 {
-	qualify_inject_common(str, false, "inject argument");
+	parse_inject_common_qualify(str, false, "inject argument");
 }
 
 static const struct qual_options {
 	const char *name;
 	void (*qualify)(const char *);
 } qual_options[] = {
-	{ "trace",	qualify_trace	},
-	{ "t",		qualify_trace	},
-	{ "abbrev",	qualify_abbrev	},
-	{ "a",		qualify_abbrev	},
-	{ "verbose",	qualify_verbose	},
-	{ "v",		qualify_verbose	},
-	{ "raw",	qualify_raw	},
-	{ "x",		qualify_raw	},
+	{ "trace",	parse_trace	},
+	{ "t",		parse_trace	},
+	{ "abbrev",	parse_abbrev	},
+	{ "a",		parse_abbrev	},
+	{ "verbose",	parse_verbose	},
+	{ "v",		parse_verbose	},
+	{ "raw",	parse_raw	},
+	{ "x",		parse_raw	},
 	{ "signal",	qualify_signals	},
 	{ "signals",	qualify_signals	},
 	{ "s",		qualify_signals	},
-	{ "read",	qualify_read	},
-	{ "reads",	qualify_read	},
-	{ "r",		qualify_read	},
-	{ "write",	qualify_write	},
-	{ "writes",	qualify_write	},
-	{ "w",		qualify_write	},
-	{ "fault",	qualify_fault	},
-	{ "inject",	qualify_inject	},
+	{ "read",	parse_read	},
+	{ "reads",	parse_read	},
+	{ "r",		parse_read	},
+	{ "write",	parse_write	},
+	{ "writes",	parse_write	},
+	{ "w",		parse_write	},
+	{ "fault",	parse_fault	},
+	{ "inject",	parse_inject	},
 };
 
 void
-qualify(const char *str)
+parse_qualify_filter(const char *str)
 {
 	const struct qual_options *opt = qual_options;
 	unsigned int i;
@@ -342,18 +334,3 @@ qualify(const char *str)
 
 	opt->qualify(str);
 }
-
-unsigned int
-qual_flags(const unsigned int scno)
-{
-	return	(is_number_in_set(scno, &trace_set[current_personality])
-		   ? QUAL_TRACE : 0)
-		| (is_number_in_set(scno, &abbrev_set[current_personality])
-		   ? QUAL_ABBREV : 0)
-		| (is_number_in_set(scno, &verbose_set[current_personality])
-		   ? QUAL_VERBOSE : 0)
-		| (is_number_in_set(scno, &raw_set[current_personality])
-		   ? QUAL_RAW : 0)
-		| (is_number_in_set(scno, &inject_set[current_personality])
-		   ? QUAL_INJECT : 0);
-}
diff --git a/strace.c b/strace.c
index ae93f923..88f7168e 100644
--- a/strace.c
+++ b/strace.c
@@ -770,7 +770,8 @@ droptcb(struct tcb *tcp)
 
 	int p;
 	for (p = 0; p < SUPPORTED_PERSONALITIES; ++p)
-		free(tcp->inject_vec[p]);
+		if (tcp->inject_vec[p])
+			free(tcp->inject_vec[p]);
 
 	free_tcb_priv_data(tcp);
 
@@ -1576,13 +1577,13 @@ init(int argc, char *argv[])
 	shared_log = stderr;
 	set_sortby(DEFAULT_SORTBY);
 	set_personality(DEFAULT_PERSONALITY);
-	qualify("trace=all");
-	qualify("abbrev=all");
-	qualify("verbose=all");
+	parse_qualify_filter("trace=all");
+	parse_qualify_filter("abbrev=all");
+	parse_qualify_filter("verbose=all");
 #if DEFAULT_QUAL_FLAGS != (QUAL_TRACE | QUAL_ABBREV | QUAL_VERBOSE)
 # error Bug in DEFAULT_QUAL_FLAGS
 #endif
-	qualify("signal=all");
+	parse_qualify_filter("signal=all");
 	while ((c = getopt(argc, argv,
 		"+b:cCdfFhiqrtTvVwxyz"
 #ifdef USE_LIBUNWIND
@@ -1649,7 +1650,7 @@ init(int argc, char *argv[])
 			show_fd_path++;
 			break;
 		case 'v':
-			qualify("abbrev=none");
+			parse_qualify_filter("abbrev=none");
 			break;
 		case 'V':
 			print_version();
@@ -1664,7 +1665,7 @@ init(int argc, char *argv[])
 				error_opt_arg(c, optarg);
 			break;
 		case 'e':
-			qualify(optarg);
+			parse_qualify_filter(optarg);
 			break;
 		case 'o':
 			outfname = optarg;
@@ -1712,6 +1713,7 @@ init(int argc, char *argv[])
 			break;
 		}
 	}
+	filtering_parsing_finish();
 
 	argv += optind;
 	argc -= optind;
@@ -2414,6 +2416,8 @@ trace_syscall(struct tcb *tcp, unsigned int *sig)
 		case 0:
 			return 0;
 		case 1:
+			if (!tcp->qual_flg)
+				filter_syscall(tcp);
 			res = syscall_entering_trace(tcp, sig);
 		}
 		syscall_entering_finish(tcp, res);
diff --git a/syscall.c b/syscall.c
index a0c649ea..b740dadb 100644
--- a/syscall.c
+++ b/syscall.c
@@ -345,7 +345,6 @@ decode_socket_subcall(struct tcb *tcp)
 		return;
 
 	tcp->scno = scno;
-	tcp->qual_flg = qual_flags(scno);
 	tcp->s_ent = &sysent[scno];
 
 	unsigned int i;
@@ -385,7 +384,6 @@ decode_ipc_subcall(struct tcb *tcp)
 	}
 
 	tcp->scno = SYS_ipc_subcall + call;
-	tcp->qual_flg = qual_flags(tcp->scno);
 	tcp->s_ent = &sysent[tcp->scno];
 
 	const unsigned int n = tcp->s_ent->nargs;
@@ -402,7 +400,6 @@ decode_mips_subcall(struct tcb *tcp)
 	if (!scno_is_valid(tcp->u_arg[0]))
 		return;
 	tcp->scno = tcp->u_arg[0];
-	tcp->qual_flg = qual_flags(tcp->scno);
 	tcp->s_ent = &sysent[tcp->scno];
 	memmove(&tcp->u_arg[0], &tcp->u_arg[1],
 		sizeof(tcp->u_arg) - sizeof(tcp->u_arg[0]));
@@ -431,7 +428,7 @@ dumpio(struct tcb *tcp)
 	if (fd < 0)
 		return;
 
-	if (is_number_in_set(fd, &read_set)) {
+	if (dump_read(tcp)) {
 		switch (tcp->s_ent->sen) {
 		case SEN_read:
 		case SEN_pread:
@@ -454,7 +451,7 @@ dumpio(struct tcb *tcp)
 			return;
 		}
 	}
-	if (is_number_in_set(fd, &write_set)) {
+	if (dump_write(tcp)) {
 		switch (tcp->s_ent->sen) {
 		case SEN_write:
 		case SEN_pwrite:
@@ -540,8 +537,6 @@ static void get_error(struct tcb *, const bool);
 static int arch_set_error(struct tcb *);
 static int arch_set_success(struct tcb *);
 
-struct inject_opts *inject_vec[SUPPORTED_PERSONALITIES];
-
 static struct inject_opts *
 tcb_inject_opts(struct tcb *tcp)
 {
@@ -553,14 +548,6 @@ tcb_inject_opts(struct tcb *tcp)
 static long
 tamper_with_syscall_entering(struct tcb *tcp, unsigned int *signo)
 {
-	if (!tcp->inject_vec[current_personality]) {
-		tcp->inject_vec[current_personality] =
-			xcalloc(nsyscalls, sizeof(**inject_vec));
-		memcpy(tcp->inject_vec[current_personality],
-		       inject_vec[current_personality],
-		       nsyscalls * sizeof(**inject_vec));
-	}
-
 	struct inject_opts *opts = tcb_inject_opts(tcp);
 
 	if (!opts || opts->first == 0)
@@ -680,9 +667,7 @@ syscall_entering_trace(struct tcb *tcp, unsigned int *sig)
 			break;
 	}
 
-	if (!(tcp->qual_flg & QUAL_TRACE)
-	 || (tracing_paths && !pathtrace_match(tcp))
-	) {
+	if (!(tcp->qual_flg & QUAL_TRACE)) {
 		tcp->flags |= TCB_FILTERED;
 		return 0;
 	}
@@ -1201,7 +1186,8 @@ get_scno(struct tcb *tcp)
 
 	if (scno_is_valid(tcp->scno)) {
 		tcp->s_ent = &sysent[tcp->scno];
-		tcp->qual_flg = qual_flags(tcp->scno);
+		/* Clear qual_flg to differ valid syscall from printargs */
+		tcp->qual_flg = 0;
 	} else {
 		struct sysent_buf *s = xcalloc(1, sizeof(*s));
 
diff --git a/tests/filtering_syscall-syntax.test b/tests/filtering_syscall-syntax.test
index 698a894c..2a4125ae 100755
--- a/tests/filtering_syscall-syntax.test
+++ b/tests/filtering_syscall-syntax.test
@@ -35,10 +35,12 @@ check_syscall()
 	check_e "invalid system call '$1'" -e abbrev="$2"
 	check_e "invalid system call '$1'" -e verbose="$2"
 	check_e "invalid system call '$1'" -e raw="$2"
+	check_e "invalid system call '$1'" -e inject="$2"
+	check_e "invalid system call '$1'" -e fault="$2"
 }
 
 # invalid syscall
-for arg in '' , ,, ,,, : :: ::: \! \!, \
+for arg in '' , ,, ,,, \! \!, \
 	   invalid_syscall_name \
 	   -1 -2 -3 -4 -5 \
 	   32767 \
@@ -52,6 +54,25 @@ for arg in '' , ,, ,,, : :: ::: \! \!, \
 	check_syscall "$arg" "$arg"
 done
 
+# Temporary workaround
+for arg in : :: ::: \
+	   ; do
+	check_e "invalid system call '$arg'" -e trace="$arg"
+	check_e "invalid system call '$arg'" -e abbrev="$arg"
+	check_e "invalid system call '$arg'" -e verbose="$arg"
+	check_e "invalid system call '$arg'" -e raw="$arg"
+	check_e "invalid system call ''" -e inject="$arg"
+	check_e "invalid system call ''" -e fault="$arg"
+done
+
+# Temporary workaround for '!:' check
+check_e "invalid system call ':'" -e trace=\!:
+check_e "invalid system call ':'" -e abbrev=\!:
+check_e "invalid system call ':'" -e verbose=\!:
+check_e "invalid system call ':'" -e raw=\!:
+check_e "invalid system call '!'" -e inject=\!:
+check_e "invalid system call '!'" -e fault=\!:
+
 # invalid syscall with inversion
 for arg in -1 -2 -3 -4 -5 \
 	   invalid_syscall_name \
@@ -78,7 +99,6 @@ for arg in file,nonsense \
 done
 
 # special cases
-check_syscall ":"	\!:
 check_syscall "!"	1,\!
 check_syscall "!open"	1,\!open
 check_syscall "none"	1,none
diff --git a/tests/qual_fault-syntax.test b/tests/qual_fault-syntax.test
index 0cce539a..5bc58194 100755
--- a/tests/qual_fault-syntax.test
+++ b/tests/qual_fault-syntax.test
@@ -27,7 +27,7 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 # THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-. "${srcdir=.}/init.sh"
+. "${srcdir=.}/syntax.sh"
 
 #
 # F
@@ -40,16 +40,7 @@ fail_with()
 		"strace -e fault=$* failed to handle an argument error properly"
 }
 
-for arg in '' , ,, ,,, : :: ::: \! \!, \!: \
-	   invalid_syscall_name \
-	   invalid_syscall_name:when=3 \
-	   -1 \!-1 \
-	   -1:when=4 \
-	   -2 \
-	   -2:when=5 \
-	   32767 \!32767 \
-	   32767:when=6 \
-	   chdir:42 \!chdir:42 \
+for arg in chdir:42 \!chdir:42 \
 	   chdir:42:when=7 \
 	   chdir:invalid \
 	   chdir:invalid:when=8 \
@@ -92,12 +83,6 @@ for arg in '' , ,, ,,, : :: ::: \! \!, \!: \
 	   chdir:when=65536:error=30 \
 	   chdir:when=1+65536 \
 	   chdir:when=1+65536:error=31 \
-	   file,nonsense \
-	   \!desc,nonsense \
-	   chdir,nonsense \
-	   \!chdir,nonsense \
-	   1,nonsense \
-	   \!1,nonsense \
 	   chdir:retval=0 \
 	   chdir:signal=1 \
 	   chdir:error=1:error=2 \
@@ -108,4 +93,11 @@ for arg in '' , ,, ,,, : :: ::: \! \!, \!: \
 		fail_with "$arg"
 done
 
+# check syscall syntax with fault args
+for arg in invalid_syscall_name \
+	   -1 -2 32767 \
+	   ; do
+	check_e "invalid system call '$arg'" -e fault="$arg:when=1"
+done
+
 exit 0
diff --git a/tests/qual_inject-syntax.test b/tests/qual_inject-syntax.test
index a9e44d74..7859d825 100755
--- a/tests/qual_inject-syntax.test
+++ b/tests/qual_inject-syntax.test
@@ -27,7 +27,7 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 # THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-. "${srcdir=.}/init.sh"
+. "${srcdir=.}/syntax.sh"
 
 #
 # F
@@ -40,17 +40,7 @@ fail_with()
 		"strace -e inject=$* failed to handle an argument error properly"
 }
 
-for arg in '' , ,, ,,, : :: ::: \! \!, \!: \
-	   invalid_syscall_name \
-	   invalid_syscall_name:when=3 \
-	   -1 \!-1 \
-	   -1:when=4 \
-	   -2 \
-	   -2:when=5 \
-	   32767 \!32767 \
-	   32767:when=6 \
-	   42 \
-	   chdir \
+for arg in 42 chdir \
 	   chdir:42 \!chdir:42 \
 	   chdir:42:when=7 \
 	   chdir:invalid \
@@ -94,12 +84,6 @@ for arg in '' , ,, ,,, : :: ::: \! \!, \!: \
 	   chdir:when=65536:error=30 \
 	   chdir:when=1+65536 \
 	   chdir:when=1+65536:error=31 \
-	   file,nonsense \
-	   \!desc,nonsense \
-	   chdir,nonsense \
-	   \!chdir,nonsense \
-	   1,nonsense \
-	   \!1,nonsense \
 	   chdir:retval=-1 \
 	   chdir:signal=0 \
 	   chdir:signal=129 \
@@ -115,4 +99,11 @@ for arg in '' , ,, ,,, : :: ::: \! \!, \!: \
 		fail_with "$arg"
 done
 
+# check syscall syntax with inject args
+for arg in invalid_syscall_name \
+	   -1 -2 32767 \
+	   ; do
+	check_e "invalid system call '$arg'" -e inject="$arg:when=1"
+done
+
 exit 0
-- 
2.11.0





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