cooker: Support for read(), OP_STORE, field-based filters

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

13 files changed, 386 insertions, 231 deletions

diff --git a/common/gluten.h b/common/gluten.h
index 91bc85e..57b94f4 100644
--- a/common/gluten.h
+++ b/common/gluten.h
@@ -68,6 +68,7 @@ enum op_type {
 	OP_FD,
 	OP_RETURN,
 	OP_LOAD,
+	OP_STORE,
 	OP_BITWISE,
 	OP_CMP,
 	OP_RESOLVEDFD,
@@ -185,6 +186,12 @@ struct op_load {
 	size_t size;
 };
 
+struct op_store {
+	struct gluten_offset src;
+	struct gluten_offset dst;
+	struct gluten_offset count;
+};
+
 enum op_cmp_type {
 	CMP_EQ,
 	CMP_NE,
@@ -250,6 +257,7 @@ struct op {
 		struct op_return ret;
 		struct op_fd fd;
 		struct op_load load;
+		struct op_store store;
 		struct op_bitwise bitwise;
 		struct op_cmp cmp;
 		struct op_resolvefd resfd;
diff --git a/cooker/Makefile b/cooker/Makefile
index 64342dc..31b52c9 100644
--- a/cooker/Makefile
+++ b/cooker/Makefile
@@ -32,11 +32,11 @@ CFLAGS += -DSEITAN_AUDIT_ARCH=AUDIT_ARCH_$(AUDIT_ARCH)
 SRCS := call.c calls.c emit.c gluten.c filter.c main.c match.c		\
 	parse.c parson.c						\
         $(COMMON)/util.c						\
-        calls/net.c calls/ioctl.c calls/process.c calls/fs.c
+        calls/net.c calls/ioctl.c calls/process.c calls/fs.c calls/io.c
 HEADERS := call.h calls.h cooker.h emit.h filter.h gluten.h match.h	\
         parse.h parson.h						\
         $(COMMON)/gluten.h $(COMMON)/util.h				\
-        calls/net.h calls/ioctl.h calls/process.h calls/fs.h
+        calls/net.h calls/ioctl.h calls/process.h calls/fs.h calls/io.h
 
 $(BIN): $(SRCS) $(HEADERS)
 	$(CC) $(CFLAGS) -o $(BIN) $(SRCS)
diff --git a/cooker/call.c b/cooker/call.c
index 4e9cb9c..c3f290c 100644
--- a/cooker/call.c
+++ b/cooker/call.c
@@ -100,6 +100,9 @@ static union value parse_field(struct gluten_ctx *g, struct arg *args,
 
 			if (!dry_run)
 				gluten_add_tag_post(g, tag_set, offset);
+
+			if (f->flags & RBUF)
+				return v;
 		}
 
 		if ((tag_get = json_object_get_string(tmp2, "get"))) {
@@ -199,13 +202,13 @@ static union value parse_field(struct gluten_ctx *g, struct arg *args,
 		}
 		break;
 	case STRING:
+		if (dry_run)
+			break;
+
 		v.v_str = json_value_get_string(jvalue);
 		if (strlen(v.v_str) + 1 > f->size)
 			die("   string %s too long for field", v.v_str);
 
-		if (dry_run)
-			break;
-
 		emit_data_at(g, offset, f->type, &v);
 		break;
 	case STRUCT:
@@ -327,7 +330,7 @@ static struct gluten_offset parse_arg(struct gluten_ctx *g, struct arg *args,
 	}
 
 	if (arg_needs_temp(&a->f, a->pos, jvalue, &top_level_tag, 0) ||
-	    multi_field) {
+	    multi_field || (a->f.flags & RBUF)) {
 		if (a->f.size)
 			offset = gluten_rw_alloc(g, a->f.size);
 		else
diff --git a/cooker/calls.c b/cooker/calls.c
index 337ea21..f486777 100644
--- a/cooker/calls.c
+++ b/cooker/calls.c
@@ -15,7 +15,10 @@
 #include "calls/ioctl.h"
 #include "calls/process.h"
 #include "calls/fs.h"
+#include "calls/io.h"
 
 struct call *call_sets[] = {
-	syscalls_net, syscalls_ioctl, syscalls_process, syscalls_fs, NULL,
+	syscalls_net, syscalls_ioctl, syscalls_process, syscalls_fs,
+	syscalls_io,
+	NULL,
 };
diff --git a/cooker/emit.c b/cooker/emit.c
index 57533a1..a257398 100644
--- a/cooker/emit.c
+++ b/cooker/emit.c
@@ -164,6 +164,24 @@ void emit_load(struct gluten_ctx *g, struct gluten_offset dst,
 		die("Too many instructions");
 }
 
+void emit_store(struct gluten_ctx *g, struct gluten_offset dst,
+		struct gluten_offset src, struct gluten_offset count)
+{
+	struct op *op = (struct op *)gluten_ptr(&g->g, g->ip);
+	struct op_store *store = &op->op.store;
+
+	op->type = OP_STORE;
+
+	store->dst = dst;
+	store->src = src;
+	store->count = count;
+
+	debug("   %i: OP_STORE: #%i", g->ip.offset);
+
+	if (++g->ip.offset > INST_MAX)
+		die("Too many instructions");
+}
+
 /**
  * emit_resolved() - Emit OP_RESOLVEFD instruction: resolve file descriptor with path
  * @g:		gluten context
@@ -540,7 +558,7 @@ static void gluten_link(struct gluten_ctx *g, enum jump_type type,
 void emit_bpf_arg(int index, enum type type, union value v, union value mask,
 		  enum op_cmp_type cmp)
 {
-	struct bpf_arg bpf;
+	struct bpf_field bpf;
 
 	/* gluten uses the comparison to skip to the next match, the BPF filter
 	 * uses it to notify instead.
@@ -550,6 +568,8 @@ void emit_bpf_arg(int index, enum type type, union value v, union value mask,
 	else
 		bpf.cmp = (cmp == CMP_EQ) ? NE : EQ;
 
+	bpf.arg = index;
+
 	if (TYPE_IS_64BIT(type)) {
 		bpf.value.v64 = v.v_num;
 		bpf.op2.v64 = mask.v_num;
@@ -560,7 +580,7 @@ void emit_bpf_arg(int index, enum type type, union value v, union value mask,
 		bpf.type = BPF_U32;
 	}
 
-	filter_add_arg(index, bpf);
+	filter_add_check(&bpf);
 }
 
 void link_block(struct gluten_ctx *g)
diff --git a/cooker/emit.h b/cooker/emit.h
index 1cdadb9..b4f1ae7 100644
--- a/cooker/emit.h
+++ b/cooker/emit.h
@@ -13,6 +13,8 @@ void emit_call(struct gluten_ctx *g, struct context_desc *cdesc, long nr,
 	       struct gluten_offset offset[6], struct gluten_offset ret_offset);
 void emit_load(struct gluten_ctx *g, struct gluten_offset dst,
 	       int index, size_t len);
+void emit_store(struct gluten_ctx *g, struct gluten_offset dst,
+		struct gluten_offset src, struct gluten_offset count);
 struct gluten_offset emit_seccomp_data(int index);
 struct gluten_offset emit_bitwise(struct gluten_ctx *g, enum type type,
 				  enum bitwise_type op_type,
diff --git a/cooker/example.hjson b/cooker/example.hjson
index 458961c..c3dc657 100644
--- a/cooker/example.hjson
+++ b/cooker/example.hjson
@@ -20,26 +20,46 @@
   },
   {
     "match": [ /* CVE-2022-0185-style */
-      { "unshare": { "flags": { "has": { "newuser": true, "newnet": false } } } }
+      { "unshare": { "flags": "CLONE_NEWUSER" } }
     ],
-    "block": { }
+    "return": { "value": 0, "error": -1 }
   },
   {
     "match": [ /* passt */
-      { "unshare": { "flags": { "has": [ "ipc", "mount", "uts", "pid" ] } } }
+      { "unshare": { "flags": { "all": [ "CLONE_NEWIPC", "CLONE_NEWNS", "CLONE_NEWUTS", "CLONE_NEWPID" ] } } }
     ],
-    "block": { }
+    "return": { "value": 0, "error": 0 }
   },
   {
     "match": [ /* Giuseppe's example */
-      { "mknodat": { "path": { "tag": "path" }, "mode": "c", "major": 1, "minor": { "value": { "in": [ 3, 5, 7, 8, 9 ] }, "tag": "minor" } } }
+      { "mknodat":
+        { "path": { "tag": "path" },
+          "mode": { "tag": "mode" },
+          "type": { "tag": "type" },
+          "major": 1,
+          "minor": { "value": { "in": [ 3, 5, 7, 8, 9 ] }, "tag": "minor" }
+        }
+      },
+      { "mknod":
+        { "path": { "tag": "path" },
+          "mode": { "tag": "mode" },
+          "type": { "tag": "type" },
+          "major": 1,
+          "minor": { "value": { "in": [ 3, 5, 7, 8, 9 ] }, "tag": "minor" }
+        }
+      }
     ],
-    "call": {
-      "mknod": { "path": { "tag": { "get": "path" } }, "mode": "c", "major": 1, "minor": { "tag": { "get": "minor" } } },
-      "ret": "x",
-      "context": { "user": "init", "mnt": "caller" }
-    },
-    "return": { "tag": "x" }
+    "call":
+      { "mknod":
+        { "path": { "tag": { "get": "path" } },
+          "mode": { "tag": { "get": "mode" } },
+          "type": { "tag": { "get": "type" } },
+          "major": 1,
+          "minor": { "tag": { "get": "minor" } }
+        },
+        "context": { "mnt": "caller" }
+      },
+    "return": { "value": 0 }
   }
 ]
 
diff --git a/cooker/filter.c b/cooker/filter.c
index 7f1f419..bffdfe4 100644
--- a/cooker/filter.c
+++ b/cooker/filter.c
@@ -17,98 +17,195 @@
 
 #include "filter.h"
 
-struct bpf_entry entries[MAX_ENTRIES];
-static unsigned int index_entries = 0;
+#define N_SYSCALL			512
+#define MAX_ENTRIES_PER_SYSCALL		16
+#define MAX_FIELDS_PER_SYSCALL		16
 
 const char *bpf_cmp_str[] = { "no check", "==", "!=", "<=", "<", ">=", ">",
 			      "==", "!=" };
 
+struct bpf_entry {
+	struct bpf_field field[MAX_FIELDS_PER_SYSCALL];
+};
+
 /**
  * struct filter_call_input - First input stage for cooker notification requests
- * @notify:	Notify on this system call
- * @count:	How many entry for the same syscall
- * @entries:	Index for the arguments for every entry
+ * @notify:		Notify on this syscall
+ * @ignore_args:	Don't filter on arguments for this syscall
+ * @entry:		syscall notification entry with field checks
  */
 struct filter_call_input {
-	bool ignore_args;
 	bool notify;
-	unsigned int count;
-	int entries[MAX_ENTRIES_SYSCALL];
+	bool ignore_args;
+	struct bpf_entry entry[MAX_ENTRIES_PER_SYSCALL];
 } filter_input[N_SYSCALL] = { 0 };
 
 static long current_nr;
 
-static unsigned int get_number_entries(long nr)
+/**
+ * entry_has_check() - Input stage: does the syscall entry need argument checks?
+ * @entry:	syscall entry with field checks
+ *
+ * Return: true if at least one argument comparison is requested
+ */
+static bool entry_has_check(const struct bpf_entry *entry)
 {
-	struct filter_call_input *call = filter_input + nr;
-	return call->count;
-}
+	unsigned i;
 
-static bool need_check_arg(const struct bpf_entry *entry)
-{
-	for (int i = 0; i < 6; i++)
-		if (entry->args[i].cmp != NO_CHECK)
+	for (i = 0; i < MAX_FIELDS_PER_SYSCALL; i++) {
+		if (entry->field[i].cmp != NO_CHECK)
 			return true;
+	}
+
 	return false;
 }
 
-static bool has_args(long nr)
+/**
+ * call_entry_count() - Input stage: count of entries for the same syscall
+ * @nr:		syscall number
+ *
+ * Return: count of entries for the same syscall
+ */
+static unsigned int call_entry_count(long nr)
 {
 	struct filter_call_input *call = filter_input + nr;
+	unsigned i, count = 0;
 
-	if (call->count < 1)
-		return false;
-	if (call->ignore_args)
-		return false;
+	if (!call->notify || call->ignore_args)
+		return 0;
 
-	/* Check if the first entry has some arguments */
-	return need_check_arg(&entries[call->entries[0]]);
+	for (i = 0; i < MAX_ENTRIES_PER_SYSCALL; i++) {
+		if (entry_has_check(&call->entry[i]))
+			count++;
+		else
+			break;
+	}
+
+	return count;
 }
 
-static unsigned get_args_for_entry(const struct bpf_entry *entry)
+/**
+ * entry_check_count() - Input stage: count of field checks for entry
+ * @entry:	syscall entry with field checks
+ *
+ * Return: count of argument checks
+ */
+static unsigned entry_check_count(const struct bpf_entry *entry)
 {
 	unsigned i, n = 0;
 
-	for (i = 0; i < 6; i++)
-		if (entry->args[i].cmp != NO_CHECK)
+	for (i = 0; i < MAX_FIELDS_PER_SYSCALL; i++)
+		if (entry->field[i].cmp != NO_CHECK)
 			n++;
+
 	return n;
 }
 
+/**
+ * filter_notify() - Start of notification request
+ * @nr:		syscall number
+ */
+void filter_notify(long nr)
+{
+	struct filter_call_input *call = filter_input + nr;
+
+	debug("   BPF: start filter information for #%lu", nr);
+	current_nr = nr;
+	call->notify = true;
+}
+
+/**
+ * filter_add_check() - Add a new field check to the current syscall
+ * @field:	 Field check specification
+ */
+void filter_add_check(struct bpf_field *field)
+{
+	struct filter_call_input *call = filter_input + current_nr;
+	struct bpf_entry *entry;
+	struct bpf_field *check;
+	char buf[BUFSIZ];
+	unsigned n;
+
+	n = snprintf(buf, BUFSIZ, "   BPF: adding #%i %s %lu",
+		     field->arg, bpf_cmp_str[field->cmp],
+		     (field->type == BPF_U32) ? field->value.v32 :
+						field->value.v64);
+
+	if (field->cmp == AND_EQ || field->cmp == AND_NE) {
+		snprintf(buf + n, BUFSIZ - n, " & %lu",
+			 (field->type == BPF_U32) ? field->op2.v32 :
+						    field->op2.v64);
+	}
+
+	debug("%s", buf);
+
+	/* Too many entries or checks: ignore argument checks from now on */
+	if (call_entry_count(current_nr) > MAX_ENTRIES_PER_SYSCALL)
+		call->ignore_args = true;
+
+	entry = &call->entry[call_entry_count(current_nr)];
+	if (entry_check_count(entry) > MAX_FIELDS_PER_SYSCALL)
+		call->ignore_args = true;
+
+	if (call->ignore_args) {
+		debug("   BPF: ignoring fields for syscall #%lu", current_nr);
+		return;
+	}
+
+	check = &entry->field[entry_check_count(entry)];
+
+	debug("   BPF: inserting check at %i for entry %i, syscall %lu",
+	      entry_check_count(entry), call_entry_count(current_nr),
+	      current_nr);
+
+	memcpy(check, field, sizeof(*field));
+}
+
+void filter_needs_deref(void)
+{
+	struct filter_call_input *call = filter_input + current_nr;
+
+	debug("   BPF: arguments for #%lu now ignored", current_nr);
+
+	call->ignore_args = true;
+}
+
 /* Calculate how many instruction for the syscall */
 static unsigned int get_n_args_syscall_instr(long nr)
 {
 	struct filter_call_input *call = filter_input + nr;
-	const struct bpf_entry *entry;
 	unsigned int n = 0, total_instr = 0;
-	unsigned int i, k;
+	unsigned int i, j;
 
-	for (i = 0; i < call->count; i++) {
-		entry = &entries[call->entries[i]];
+	for (i = 0; i < call_entry_count(nr); i++) {
+		const struct bpf_entry *entry = &call->entry[i];
 		n = 0;
-		for (k = 0; k < 6; k++) {
-			if (entry->args[k].cmp == NO_CHECK)
+
+		for (j = 0; j < entry_check_count(entry); j++) {
+			const struct bpf_field *field = &entry->field[j];
+			enum bpf_cmp cmp = field->cmp;
+
+			if (cmp == NO_CHECK)
 				continue;
-			switch (entry->args[k].type) {
+
+			switch (field->type) {
 			case BPF_U32:
-				/* For 32 bit arguments
+				/* For 32 bit fields
 				 * comparison instructions (2):
 				 *   1 loading the value + 1 for evaluation
 				 * arithemtic instructions (3):
 				 *   1 loading the value + 1 for the operation + 1 for evaluation
 				 */
-				if (entry->args[k].cmp == AND_EQ ||
-				    entry->args[k].cmp == AND_NE)
+				if (cmp == AND_EQ || cmp == AND_NE)
 					n += 3;
 				else
 					n += 2;
 				break;
 			case BPF_U64:
-				/* For 64 bit arguments: 32 instructions * 2
+				/* For 64 bit fields: 32 instructions * 2
 				 * for loading and evaluating the high and low 32 bits chuncks.
 				*/
-				if (entry->args[k].cmp == AND_EQ ||
-				    entry->args[k].cmp == AND_NE)
+				if (cmp == AND_EQ || cmp == AND_NE)
 					n += 6;
 				else
 					n += 4;
@@ -116,87 +213,19 @@ static unsigned int get_n_args_syscall_instr(long nr)
 			}
 		}
 		total_instr += n;
-		/* If there at least an argument, then there is the jump to the
+		/* TODO: rewrite comment: If there at least an argument, then there is the jump to the
 		 * notification */
 		if (n > 0)
 			total_instr++;
 	}
-	/* If there at least an argument for that syscall, then there is the jump to the
+	/* TODO: rewrite comment: If there at least an argument for that syscall, then there is the jump to the
 	* accept */
-	if (has_args(nr))
+	if (call_entry_count(nr))
 		total_instr++;
-	return total_instr;
-}
-
-/**
- * filter_notify() - Start of notification request, check/flush previous one
- * @nr:		System call number, -1 to just flush previous request
- */
-void filter_notify(long nr)
-{
-	struct filter_call_input *call = filter_input + nr;
-
-	if (nr > 0) {
-		debug("   BPF: start filter information for #%lu", nr);
-		current_nr = nr;
-		call->notify = true;
-	}
-}
-
-/**
- * filter_add_arg(): Add a new argument to the current syscall
- * @index:	position of the argument
- * @arg:	the argument to add
- */
-void filter_add_arg(int index, struct bpf_arg arg)
-{
-	struct filter_call_input *call = filter_input + current_nr;
-	struct bpf_entry *entry = &entries[index_entries];
-	char buf[BUFSIZ];
-	unsigned n;
-
-	n = snprintf(buf, BUFSIZ, "   BPF: adding #%i %s %lu",
-		     index, bpf_cmp_str[arg.cmp],
-		     (arg.type == BPF_U32) ? arg.value.v32 : arg.value.v64);
-	if (arg.cmp == AND_EQ || arg.cmp == AND_NE) {
-		snprintf(buf + n, BUFSIZ - n, " & %lu",
-			 (arg.type == BPF_U32) ? arg.op2.v32 : arg.op2.v64);
-	}
-	debug("%s", buf);
-
-	/* If it reaches the maximum number of entries per syscall, then we simply
-	 * notify for all the arguments and ignore the other arguments.
-	 */
-	if (call->count >= MAX_ENTRIES_SYSCALL) {
-		call->ignore_args = true;
-		return;
-	}
-	if (call->ignore_args)
-		return;
-	call->entries[call->count] = index_entries;
-	memcpy(&entry->args[index], &arg, sizeof(arg));
-}
-
-void filter_flush_args()
-{
-	struct filter_call_input *call = filter_input + current_nr;
 
-	debug("   BPF: flush filter information for #%lu", current_nr);
-
-	if (!has_args(current_nr))
-		return;
-	call->count++;
-	index_entries++;
-}
-
-void filter_needs_deref(void)
-{
-	struct filter_call_input *call = filter_input + current_nr;
-
-	debug("   BPF: arguments for #%lu now ignored", current_nr);
+	debug("  BPF: counted %i instructions for syscall %lu", total_instr, nr);
 
-	call->ignore_args = true;
-	call->count = 0;
+	return total_instr;
 }
 
 static int table[N_SYSCALL];
@@ -284,161 +313,161 @@ static void create_lookup_nodes(int jumps[], unsigned int n)
 	}
 }
 
-static unsigned int eq(struct sock_filter filter[], int idx,
-		       const struct bpf_entry *entry, unsigned int jtrue,
+static unsigned int eq(struct sock_filter filter[],
+		       const struct bpf_field *field, unsigned int jtrue,
 		       unsigned int jfalse)
 {
 	unsigned int size = 0;
 	uint32_t hi, lo;
 
-	switch (entry->args[idx].type) {
+	switch (field->type) {
 	case BPF_U64:
-		hi = get_hi((entry->args[idx]).value.v64);
-		lo = get_lo((entry->args[idx]).value.v64);
-		filter[size++] = (struct sock_filter)LOAD(LO_ARG(idx));
+		hi = get_hi(field->value.v64);
+		lo = get_lo(field->value.v64);
+		filter[size++] = (struct sock_filter)LOAD(LO_ARG(field->arg));
 		filter[size++] = (struct sock_filter)EQ(lo, 0, jfalse);
-		filter[size++] = (struct sock_filter)LOAD(HI_ARG(idx));
+		filter[size++] = (struct sock_filter)LOAD(HI_ARG(field->arg));
 		filter[size++] = (struct sock_filter)EQ(hi, jtrue, jfalse);
 		break;
 	case BPF_U32:
-		filter[size++] = (struct sock_filter)LOAD(LO_ARG(idx));
+		filter[size++] = (struct sock_filter)LOAD(LO_ARG(field->arg));
 		filter[size++] = (struct sock_filter)EQ(
-			entry->args[idx].value.v32, jtrue, jfalse);
+			field->value.v32, jtrue, jfalse);
 		break;
 	}
 
 	return size;
 }
 
-static unsigned int gt(struct sock_filter filter[], int idx,
-		       const struct bpf_entry *entry, unsigned int jtrue,
+static unsigned int gt(struct sock_filter filter[],
+		       const struct bpf_field *field, unsigned int jtrue,
 		       unsigned int jfalse)
 {
 	unsigned int size = 0;
 	uint32_t hi, lo;
 
-	switch (entry->args[idx].type) {
+	switch (field->type) {
 	case BPF_U64:
-		hi = get_hi((entry->args[idx]).value.v64);
-		lo = get_lo((entry->args[idx]).value.v64);
-		filter[size++] = (struct sock_filter)LOAD(HI_ARG(idx));
+		hi = get_hi(field->value.v64);
+		lo = get_lo(field->value.v64);
+		filter[size++] = (struct sock_filter)LOAD(HI_ARG(field->arg));
 		filter[size++] = (struct sock_filter)GT(hi, jtrue + 2, 0);
-		filter[size++] = (struct sock_filter)LOAD(LO_ARG(idx));
+		filter[size++] = (struct sock_filter)LOAD(LO_ARG(field->arg));
 		filter[size++] = (struct sock_filter)GT(lo, jtrue, jfalse);
 		break;
 	case BPF_U32:
-		filter[size++] = (struct sock_filter)LOAD(LO_ARG(idx));
+		filter[size++] = (struct sock_filter)LOAD(LO_ARG(field->arg));
 		filter[size++] = (struct sock_filter)GT(
-			entry->args[idx].value.v32, jtrue, jfalse);
+			field->value.v32, jtrue, jfalse);
 		break;
 	}
 
 	return size;
 }
 
-static unsigned int lt(struct sock_filter filter[], int idx,
-		       const struct bpf_entry *entry, unsigned int jtrue,
+static unsigned int lt(struct sock_filter filter[],
+		       const struct bpf_field *field, unsigned int jtrue,
 		       unsigned int jfalse)
 {
 	unsigned int size = 0;
 	uint32_t hi, lo;
 
-	switch (entry->args[idx].type) {
+	switch (field->type) {
 	case BPF_U64:
-		hi = get_hi((entry->args[idx]).value.v64);
-		lo = get_lo((entry->args[idx]).value.v64);
-		filter[size++] = (struct sock_filter)LOAD(HI_ARG(idx));
+		hi = get_hi(field->value.v64);
+		lo = get_lo(field->value.v64);
+		filter[size++] = (struct sock_filter)LOAD(HI_ARG(field->arg));
 		filter[size++] = (struct sock_filter)LT(hi, jtrue + 2, jfalse);
-		filter[size++] = (struct sock_filter)LOAD(LO_ARG(idx));
+		filter[size++] = (struct sock_filter)LOAD(LO_ARG(field->arg));
 		filter[size++] = (struct sock_filter)LT(lo, jtrue, jfalse);
 		break;
 	case BPF_U32:
-		filter[size++] = (struct sock_filter)LOAD(LO_ARG(idx));
+		filter[size++] = (struct sock_filter)LOAD(LO_ARG(field->arg));
 		filter[size++] = (struct sock_filter)LT(
-			entry->args[idx].value.v32, jtrue, jfalse);
+			field->value.v32, jtrue, jfalse);
 		break;
 	}
 
 	return size;
 }
 
-static unsigned int neq(struct sock_filter filter[], int idx,
-			const struct bpf_entry *entry, unsigned int jtrue,
+static unsigned int neq(struct sock_filter filter[],
+			const struct bpf_field *field, unsigned int jtrue,
 			unsigned int jfalse)
 {
-	return eq(filter, idx, entry, jfalse, jtrue);
+	return eq(filter, field, jfalse, jtrue);
 }
 
-static unsigned int ge(struct sock_filter filter[], int idx,
-		       const struct bpf_entry *entry, unsigned int jtrue,
+static unsigned int ge(struct sock_filter filter[],
+		       const struct bpf_field *field, unsigned int jtrue,
 		       unsigned int jfalse)
 {
-	return lt(filter, idx, entry, jfalse, jtrue);
+	return lt(filter, field, jfalse, jtrue);
 }
 
-static unsigned int le(struct sock_filter filter[], int idx,
-		       const struct bpf_entry *entry, unsigned int jtrue,
+static unsigned int le(struct sock_filter filter[],
+		       const struct bpf_field *field, unsigned int jtrue,
 		       unsigned int jfalse)
 {
-	return gt(filter, idx, entry, jfalse, jtrue);
+	return gt(filter, field, jfalse, jtrue);
 }
 
-static unsigned int and_eq (struct sock_filter filter[], int idx,
-			    const struct bpf_entry *entry, unsigned int jtrue,
-			    unsigned int jfalse)
+static unsigned int and_eq(struct sock_filter filter[],
+			   const struct bpf_field *field, unsigned int jtrue,
+			   unsigned int jfalse)
 {
 	unsigned int size = 0;
 
-	switch (entry->args[idx].type) {
+	switch (field->type) {
 	case BPF_U64:
-		filter[size++] = (struct sock_filter)LOAD(LO_ARG(idx));
+		filter[size++] = (struct sock_filter)LOAD(LO_ARG(field->arg));
 		filter[size++] = (struct sock_filter)AND(
-			get_lo(entry->args[idx].op2.v64));
+			get_lo(field->op2.v64));
 		filter[size++] = (struct sock_filter)EQ(
-			get_lo((entry->args[idx]).value.v64), 0, jfalse);
-		filter[size++] = (struct sock_filter)LOAD(HI_ARG(idx));
+			get_lo(field->value.v64), 0, jfalse);
+		filter[size++] = (struct sock_filter)LOAD(HI_ARG(field->arg));
 		filter[size++] = (struct sock_filter)AND(
-			get_hi(entry->args[idx].op2.v64));
+			get_hi(field->op2.v64));
 		filter[size++] = (struct sock_filter)EQ(
-			get_hi(entry->args[idx].value.v64), jtrue, jfalse);
+			get_hi(field->value.v64), jtrue, jfalse);
 		break;
 	case BPF_U32:
-		filter[size++] = (struct sock_filter)LOAD(LO_ARG(idx));
+		filter[size++] = (struct sock_filter)LOAD(LO_ARG(field->arg));
 		filter[size++] =
-			(struct sock_filter)AND(entry->args[idx].op2.v32);
+			(struct sock_filter)AND(field->op2.v32);
 		filter[size++] = (struct sock_filter)EQ(
-			entry->args[idx].value.v32, jtrue, jfalse);
+			field->value.v32, jtrue, jfalse);
 		break;
 	}
 
 	return size;
 }
 
-static unsigned int and_ne(struct sock_filter filter[], int idx,
-			   const struct bpf_entry *entry, unsigned int jtrue,
+static unsigned int and_ne(struct sock_filter filter[],
+			   const struct bpf_field *field, unsigned int jtrue,
 			   unsigned int jfalse)
 {
 	unsigned int size = 0;
 
-	switch (entry->args[idx].type) {
+	switch (field->type) {
 	case BPF_U64:
-		filter[size++] = (struct sock_filter)LOAD(LO_ARG(idx));
+		filter[size++] = (struct sock_filter)LOAD(LO_ARG(field->arg));
 		filter[size++] = (struct sock_filter)AND(
-			get_lo(entry->args[idx].op2.v64));
+			get_lo(field->op2.v64));
 		filter[size++] = (struct sock_filter)EQ(
-			get_lo((entry->args[idx]).value.v64), 0, jtrue + 3);
-		filter[size++] = (struct sock_filter)LOAD(HI_ARG(idx));
+			get_lo(field->value.v64), 0, jtrue + 3);
+		filter[size++] = (struct sock_filter)LOAD(HI_ARG(field->arg));
 		filter[size++] = (struct sock_filter)AND(
-			get_hi(entry->args[idx].op2.v64));
+			get_hi(field->op2.v64));
 		filter[size++] = (struct sock_filter)EQ(
-			get_hi(entry->args[idx].value.v64), jfalse, jtrue);
+			get_hi(field->value.v64), jfalse, jtrue);
 		break;
 	case BPF_U32:
-		filter[size++] = (struct sock_filter)LOAD(LO_ARG(idx));
+		filter[size++] = (struct sock_filter)LOAD(LO_ARG(field->arg));
 		filter[size++] =
-			(struct sock_filter)AND(entry->args[idx].op2.v32);
+			(struct sock_filter)AND(field->op2.v32);
 		filter[size++] = (struct sock_filter)EQ(
-			entry->args[idx].value.v32, jfalse, jtrue);
+			field->value.v32, jfalse, jtrue);
 		break;
 	}
 
@@ -449,52 +478,51 @@ static unsigned int insert_args(struct sock_filter filter[], long nr)
 {
 	struct filter_call_input *call = filter_input + nr;
 	unsigned int next_offset, n_checks = 0;
-	unsigned int count = get_number_entries(nr);
+	unsigned int count = call_entry_count(nr);
 	struct bpf_entry *entry;
 	unsigned int offset = 0;
 	unsigned int size = 0;
-	unsigned int i, k;
+	unsigned int i, j;
 
 	for (i = 0; i < count; i++) {
 		n_checks = 0;
-		entry = &entries[call->entries[i]];
+		entry = &call->entry[i];
 		/* If there are multiple entries for the syscall @nr, then the next group
 	         * of arguments to check (i.e. the next offset) is after the number of
 	         * arguments of the current entry. The next_offset is used to
 		 * jump to the next group if the check is false.
 		 */
-		next_offset = get_args_for_entry(entry);
-		for (k = 0; k < 6; k++) {
+		next_offset = entry_check_count(entry);
+		for (j = 0; j < entry_check_count(entry); j++) {
+			struct bpf_field *field = &entry->field[j];
+
 			offset = next_offset - n_checks;
-			switch (entry->args[k].cmp) {
+			switch (field->cmp) {
 			case NO_CHECK:
 				continue;
 			case EQ:
-				size += eq(&filter[size], k, entry, 0, offset);
+				size += eq(&filter[size],     field, 0, offset);
 				break;
 			case NE:
-				size += neq(&filter[size], k, entry, 0, offset);
+				size += neq(&filter[size],    field, 0, offset);
 				break;
 			case GT:
-				size += gt(&filter[size], k, entry, 0, offset);
+				size += gt(&filter[size],     field, 0, offset);
 				break;
 			case LT:
-				size += lt(&filter[size], k, entry, 0, offset);
+				size += lt(&filter[size],     field, 0, offset);
 				break;
 			case GE:
-				size += ge(&filter[size], k, entry, 0, offset);
+				size += ge(&filter[size],     field, 0, offset);
 				break;
 			case LE:
-				size += le(&filter[size], k, entry, 0, offset);
+				size += le(&filter[size],     field, 0, offset);
 				break;
 			case AND_EQ:
-				size += and_eq
-					(&filter[size], k, entry, 0, offset);
+				size += and_eq(&filter[size], field, 0, offset);
 				break;
 			case AND_NE:
-				size += and_ne(&filter[size], k, entry, 0,
-					       offset);
-
+				size += and_ne(&filter[size], field, 0, offset);
 				break;
 			}
 			n_checks++;
@@ -503,7 +531,7 @@ static unsigned int insert_args(struct sock_filter filter[], long nr)
 		 * to add the notification */
 		if (n_checks > 0)
 			filter[size++] = (struct sock_filter)BPF_STMT(
-				BPF_RET | BPF_K, SECCOMP_RET_USER_NOTIF);
+				BPF_RET | BPF_K, SECCOMP_RET_ALLOW);
 	}
 
 	return size;
@@ -524,6 +552,8 @@ unsigned int filter_build(struct sock_filter filter[], unsigned n)
 	/* No nodes if there is a single syscall */
 	n_nodes = (1 << count_shift_right(n - 1)) - 1;
 
+	debug("  BPF: tree has %i nodes", n_nodes);
+
 	/* Pre */
 	/* cppcheck-suppress badBitmaskCheck */
 	filter[size++] = (struct sock_filter)BPF_STMT(
@@ -559,8 +589,8 @@ unsigned int filter_build(struct sock_filter filter[], unsigned n)
 	/* Insert leaves */
 	for (i = 0; i < n; i++) {
 		nr = get_syscall(i);
-		if (get_number_entries(nr) > 0) {
-			offset = next_offset;
+		if (call_entry_count(nr) > 0) {
+			offset = next_offset - 1;
 		} else {
 			/* If the syscall doesn't have any arguments, then notify */
 			offset = notify - size - 1;
@@ -573,10 +603,12 @@ unsigned int filter_build(struct sock_filter filter[], unsigned n)
 		next_offset += get_n_args_syscall_instr(nr) - 1;
 	}
 	/* Seccomp accept and notify instruction */
-	filter[size++] = (struct sock_filter)BPF_STMT(BPF_RET | BPF_K,
+		filter[size++] = (struct sock_filter)BPF_STMT(BPF_RET | BPF_K,
 						      SECCOMP_RET_ALLOW);
-	filter[size++] = (struct sock_filter)BPF_STMT(BPF_RET | BPF_K,
-						      SECCOMP_RET_USER_NOTIF);
+	if (!call_entry_count(nr))
+		filter[size++] = (struct sock_filter)BPF_STMT(BPF_RET | BPF_K,
+						     SECCOMP_RET_USER_NOTIF);
+
 
 	/*
 	 * Insert args. It sequentially checks all the arguments for a syscall
@@ -584,13 +616,15 @@ unsigned int filter_build(struct sock_filter filter[], unsigned n)
 	 * check the following entry of the syscall and its arguments.
 	 */
 	for (i = 0; i < n; i++) {
-		nr = get_syscall(i);
 		size += insert_args(&filter[size], nr);
-		if (has_args(nr))
+		if (call_entry_count(nr))
 			filter[size++] = (struct sock_filter)BPF_STMT(
-				BPF_RET | BPF_K, SECCOMP_RET_ALLOW);
+				BPF_RET | BPF_K, SECCOMP_RET_USER_NOTIF);
 	}
 
+	debug("  BPF: filter with %i call%s has %i instructions",
+	      n, n != 1 ? "s" : "", size);
+
 	return size;
 }
 
diff --git a/cooker/match.c b/cooker/match.c
index 374f277..776823d 100644
--- a/cooker/match.c
+++ b/cooker/match.c
@@ -41,7 +41,7 @@ static struct gluten_offset arg_load(struct gluten_ctx *g, struct arg *a)
 		size = a->f.size;
 	}
 
-	if (!size) {
+	if (!size || (a->f.flags & RBUF)) {
 		g->match_dst[index].offset.type = OFFSET_SECCOMP_DATA;
 		g->match_dst[index].offset.offset = index;
 		g->match_dst[index].len = 0;
@@ -152,7 +152,7 @@ xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx  xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx
 	}
 
 	/* Nothing to match on: just store as reference */
-	if (!jvalue)
+	if (!jvalue || (f->flags & RBUF))
 		return v;
 
 	offset.offset += f->offset;
@@ -381,7 +381,6 @@ void handle_matches(struct gluten_ctx *g, JSON_Value *value)
 
 				filter_notify(call->number);
 				parse_match(g, args, call->args);
-				filter_flush_args();
 
 				break;
 			}
diff --git a/cooker/parse.c b/cooker/parse.c
index 7cac43f..8dc89f9 100644
--- a/cooker/parse.c
+++ b/cooker/parse.c
@@ -72,9 +72,32 @@ static void handle_limit(struct gluten_ctx *g, JSON_Value *value)
 	(void)value;
 }
 
+static void handle_write(struct gluten_ctx *g, JSON_Value *value)
+{
+	JSON_Object *obj = json_value_get_object(value);
+	struct gluten_offset src, dst, count;
+	const char *tag;
+
+	if (!(tag = json_object_get_string(obj, "src")))
+		die("invalid tag specification");
+	src = gluten_get_tag(g, tag);
+
+	if (!(tag = json_object_get_string(obj, "dst")))
+		die("invalid tag specification");
+	dst = gluten_get_tag(g, tag);
+
+	if (!(tag = json_object_get_string(obj, "count")))
+		die("invalid tag specification");
+	count = gluten_get_tag(g, tag);
+
+	emit_store(g, dst, src, count);
+}
+
 static void handle_return(struct gluten_ctx *g, JSON_Value *value)
 {
 	JSON_Object *obj = json_value_get_object(value);
+	struct gluten_offset data = NULL_OFFSET;
+	const char *tag;
 	JSON_Value *jvalue;
 	union value v = { .v_u64 = 0 };
 	int32_t error = 0;
@@ -83,14 +106,16 @@ static void handle_return(struct gluten_ctx *g, JSON_Value *value)
 	debug("  Parsing \"return\"");
 
 	jvalue = json_object_get_value(obj, "error");
-        if (json_value_get_type(jvalue) == JSONNumber) {
-		error = json_value_get_number(jvalue);
-	}
+        if (json_value_get_type(jvalue) == JSONNumber)
+		data = emit_data(g, U64, sizeof(v.v_u64), &v);
+	else if ((tag = json_object_get_string(obj, "error")))
+		data = gluten_get_tag(g, tag);
 
 	jvalue = json_object_get_value(obj, "value");
-        if (json_value_get_type(jvalue) == JSONNumber) {
-		v.v_u64 = json_value_get_number(jvalue);
-	}
+        if (json_value_get_type(jvalue) == JSONNumber)
+		data = emit_data(g, U64, sizeof(v.v_u64), &v);
+	else if ((tag = json_object_get_string(obj, "value")))
+		data = gluten_get_tag(g, tag);
 
 	jvalue = json_object_get_value(obj, "continue");
         if (json_value_get_type(jvalue) == JSONBoolean) {
@@ -101,7 +126,8 @@ static void handle_return(struct gluten_ctx *g, JSON_Value *value)
 
 	debug("  emit return: val=%ld errno=%d cont=%s", v.v_u64, error,
 	      cont ? "true" : "false");
-	emit_return(g, emit_data(g, U64, sizeof(v.v_u64), &v), error, cont);
+
+	emit_return(g, data, error, cont);
 }
 
 static void handle_context(struct gluten_ctx *g, JSON_Value *value)
@@ -121,6 +147,7 @@ struct rule_parser {
 } parsers[] = {
 	{ "match",	handle_matches },
 	{ "call",	handle_calls },
+	{ "write",	handle_write },
 	{ "fd",		handle_fd },
 	{ "limit",	handle_limit },
 	{ "return",	handle_return },
diff --git a/demo/socket.hjson b/demo/socket.hjson
index 7a16ccc..d9a3345 100644
--- a/demo/socket.hjson
+++ b/demo/socket.hjson
@@ -1,7 +1,7 @@
 [
   {
     "match": [
-      { "socket": { "family": "unix", "type": "stream", "flags": 0, "protocol": 0 } }
+      { "socket": { "family": "unix", "type": "stream", "flags": "cloexec", "protocol": 0 } }
     ],
     "call": [
       { "socket": { "family": "unix", "type": "stream", "flags": [ "cloexec", "nonblock" ], "protocol": 0 }, "ret": "new_fd" }
diff --git a/operations.c b/operations.c
index e1132d5..70c8f08 100644
--- a/operations.c
+++ b/operations.c
@@ -292,6 +292,45 @@ out:
 	return ret;
 }
 
+int op_store(const struct seccomp_notif *req, int notifier, struct gluten *g,
+	     struct op_store *store)
+{
+	const long unsigned int *dst = gluten_ptr(&req->data, g, store->dst);
+	const size_t *count = gluten_ptr(&req->data, g, store->count);
+	const void *src = gluten_ptr(&req->data, g, store->src);
+	char path[PATH_MAX];
+	int fd, ret = 0;
+
+	debug("  op_store: argument (%s %d) in (%s %d) size=%d",
+	      gluten_offset_name[store->src.type], store->src.offset,
+	      gluten_offset_name[store->dst.type], store->dst.offset);
+
+	if (dst == NULL)
+		ret_err(-1, "  op_store: empty destination");
+
+	snprintf(path, sizeof(path), "/proc/%d/mem", req->pid);
+	if ((fd = open(path, O_WRONLY | O_CLOEXEC)) < 0)
+		ret_err(-1, "error opening mem for %d", req->pid);
+	/*
+         * Avoid the TOCTOU and check if the read mappings are still valid
+         */
+	if (!is_cookie_valid(notifier, req->id)) {
+		err("the seccomp request isn't valid anymore");
+		ret = -1;
+		goto out;
+	}
+
+	if (pwrite(fd, src, *count, *dst) < 0) {
+		err("pwrite");
+		ret = -1;
+		goto out;
+	}
+
+out:
+	close(fd);
+	return ret;
+}
+
 int op_return(const struct seccomp_notif *req, int notifier, struct gluten *g,
 	      struct op_return *op)
 {
@@ -503,6 +542,7 @@ int eval(struct gluten *g, const struct seccomp_notif *req,
 			HANDLE_OP(OP_RETURN, op_return, ret, g);
 			HANDLE_OP(OP_FD, op_fd, fd, g);
 			HANDLE_OP(OP_LOAD, op_load, load, g);
+			HANDLE_OP(OP_STORE, op_store, store, g);
 			HANDLE_OP(OP_BITWISE, op_bitwise, bitwise, g);
 			HANDLE_OP(OP_CMP, op_cmp, cmp, g);
 			HANDLE_OP(OP_RESOLVEDFD, op_resolve_fd, resfd, g);
diff --git a/seitan.c b/seitan.c
index a18e3ea..bd1a7e2 100644
--- a/seitan.c
+++ b/seitan.c
@@ -217,7 +217,6 @@ int main(int argc, char **argv)
 		if ((notifier = recvfd(fd)) < 0)
 			die("  failed recieving the notifier fd");
 	}
-	sleep(1);
 
 	if ((epollfd = epoll_create1(0)) < 0)
 		die("  epoll_create");